# Joint genome-wide association study of progressive supranuclear palsy identifies novel susceptibility loci and genetic correlation to neurodegenerative diseases

Jason A. Chen, Zongbo Chen, Hyejung Won, Alden Y. Huang, Jennifer K.

Lowe, Kevin Wojta, Jennifer S. Yokoyama, Gilbert Bensimon, P. Nigel Leigh, Christine Payan, et al.

► To cite this version:

Jason A. Chen, Zongbo Chen, Hyejung Won, Alden Y. Huang, Jennifer K. Lowe, et al. Joint genome-wide association study of progressive supranuclear palsy identifies novel susceptibility loci and genetic correlation to neurodegenerative diseases. Molecular Neurodegeneration, 2018, 13 (1), pp.41. 10.1186/s13024-018-0270-8 . hal-03164802

HAL Id: hal-03164802

https://hal.science/hal-03164802

Submitted on 10 Mar 2021

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>
RESEARCH ARTICLE

Open Access

<figure><img src="image_2.png" /></figure>

CrossMark

# Joint genome-wide association study of progressive supranuclear palsy identifies novel susceptibility loci and genetic correlation to neurodegenerative diseases

Jason A. Chen¹, Zhongbo Chen², Hyejung Won<fnref n="3" />, Alden Y. Huang¹, Jennifer K. Lowe<fnref n="3" />, Kevin Wojta⁴, Jennifer S. Yokoyama⁵, Gilbert Bensimon⁶,⁷,⁸, P. Nigel Leigh⁹, Christine Payan⁶,⁷, Aleksey Shatunov², Ashley R. Jones², Kathryn M. Lewis¹⁰, Panagiotis Deloukas¹¹, Philippe Amouyel¹², Christophe Tzourio¹³, Jean-Francois Dartigues¹³, Albert Ludolph¹⁴, Adam L. Boxer⁵, Jeff M. Bronstein<fnref n="3" />, Ammar Al-Chalabi², Daniel H. Geschwind¹,<fnref n="3" /> and Giovanni Coppola¹,<fnref n="3" />,⁴,¹⁵*

<figure><img src="image_3.png" /></figure>

**Abstract**

**Background:** Progressive supranuclear palsy (PSP) is a rare neurodegenerative disease for which the genetic contribution is incompletely understood.

**Methods:** We conducted a joint analysis of 5,523,934 imputed SNPs in two newly-genotyped progressive supranuclear palsy cohorts, primarily derived from two clinical trials (Allon davunetide and NNIPPS riluzole trials in PSP) and a previously published genome-wide association study (GWAS), in total comprising 1646 cases and 10,662 controls of European ancestry.

**Results:** We identified 5 associated loci at a genome-wide significance threshold $P < 5 \times 10^{-8}$, including replication of 3 loci from previous studies and 2 novel loci at 6p21.1 and 12p12.1 (near *RUNX2* and *SLCO1A2*, respectively). At the 17q21.31 locus, stepwise regression analysis confirmed the presence of multiple independent loci (localized near *MAPT* and *KANSL1*). An additional 4 loci were highly suggestive of association ($P < 1 \times 10^{-6}$). We analyzed the genetic correlation with multiple neurodegenerative diseases, and found that PSP had shared polygenic heritability with Parkinson's disease and amyotrophic lateral sclerosis.

**Conclusions:** In total, we identified 6 additional significant or suggestive SNP associations with PSP, and discovered genetic overlap with other neurodegenerative diseases. These findings clarify the pathogenesis and genetic architecture of PSP.

**Keywords:** Genome-wide association study, Progressive supranuclear palsy, Neurodegeneration

**Background**

Tau pathology is a prominent hallmark of neurodegenerative diseases, including Alzheimer's disease (AD) and frontotemporal dementia (FTD). Progressive supranuclear palsy (PSP) is a relatively pure tauopathy associated with parkinsonism -

dementia, characterized by pathological tau aggregation and a clinical syndrome of postural instability, falls, and supranuclear ophthalmoplegia [1]. It shares symptomatic and neuropathologic overlap with a large group of diseases, that are collectivity known as “tauopathies” due to characteristic tau deposits; however, compared to these diseases, PSP appears to be more clinically, neuropathologically, and genetically homogenous [2–4]. Notably, the clinical syndrome has high correlation with the neuropathology [5]. These characteristics have thrust PSP into a central role for studying

<figure><img src="image_4.png" /></figure>

<footnote>* Correspondence: gcoppola@ucla.edu
¹Interdepartmental Program in Bioinformatics, University of California, Los Angeles, CA 90095, USA</footnote>

<footnote n="3">³Program in Neurogenetics, Department of Neurology and Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
Full list of author information is available at the end of the article</footnote>
neurodegeneration, enabling clinical trials of a relatively
homogenous patient population with potentially more uni-
form response to treatment. Therefore, PSP has become a
target of intense clinical research [6, 7]. While the disease
shares neuropathological overlap with other tauopathies, the
polygenic genetic correlation with other neurodegenerative
diseases remains to be clarified.

The major known genetic risk factor is an extended
H1 haplotype on chromosome 17q21.31, which includes
MAPT (the gene encoding the tau protein), and is
homozygous in almost all PSP patients [2]. Other risk
factors identified include genome wide significant associ-
ations at loci near MAPT, MOBP, STX6, and EIF2AK3,
suggesting a strong contribution of common variation in
its genetic architecture [8]. We reasoned that the inclu-
sion of additional cases and controls could increase the
statistical power for genome-wide association, potentially
yielding novel loci that could provide insight into the
molecular mechanisms of PSP and other more common
tauopathies.

**Methods**

Cohort

Three cohorts of primarily European ancestry were in-
cluded in the study – “UCLA”, a combination of 349
PSP patients and 130 controls from the UCSF Memory
and Aging Center [2, 9] and the Allon Therapeutics
Davunetide trial [6]; “NNIPPS”, a group of 341 PSP pa-
tients from the Neuroprotection and Natural History in
Parkinson Plus Syndromes (NNIPPS) trial [7] and the
Blood Brain Barrier in Parkinson Plus syndromes
(BBBIPPS) study; and “Hoglinger”, 1112 PSP patients
from a previously published GWAS [8]. The UCLA co-
hort was divided into two, because of differences in
genotyping platform: “UCLA Omni 2.5” and “UCLA
HumanCore”. Further details are available in the Supple-
mentary Methods.

Genotyping

Genotyping in the UCLA study cohort was performed as
a prelude to whole-genome sequencing, and was per-
formed by Illumina (using the Illumina HumanOmni 2.5
Array) and the New York Genome Center (using the
Illumina HumanCore Array). Genotyping calls were
made using the Illumina GenomeStudio software.

Public datasets

Genotypes from the Hoglinger et al. GWAS [8] (cases
only – no controls) were obtained from the NIAGADS
database. Out-of-sample controls were obtained from
dbGAP Authorized Access to match each genotyping
platform. In total, for the HumanOmni 2.5 M platform, we
obtained 2364 subjects; for the OmniExpress platform, 870
subjects; and for the HumanQuad 660 W platform, 8756

subjects. For the Illumina HumanQuad 660 W Array
(Hoglinger et al. study), we used phs000103.v1.p1 "Genome--
Wide Association Studies of Prematurity and Its Complica-
tions", phs000289.v1.p1 "National Human Genome Research
Institute (NHGRI) GENEVA Genome-Wide Association
Study of Venous Thrombosis", phs000188.v1.p1 "Vanderbilt
Genome-Electronic Records (VGER) Project: QRS Dur-
ation", phs000203.v1.p1 "A Genome-Wide Association Study
of Peripheral Arterial Disease", phs000237.v1.p1 "Northwest-
ern NUGene Project: Type 2 Diabetes", phs000234.v1.p1
"Group Health/UW Aging and Dementia eMERGE study",
and phs000170.v1.p1 "A Genome-Wide Association Study
on Cataract and HDL in the Personalized Medicine Research
Project Cohort". For the Illumina HumanOmni 2.5 Array
(UCLA – this study, and NNIPPS study), we used
phs000371.v1.p1 "Genetic Modifiers of Huntington's Dis-
ease", phs000429.v1.p1 "NEI Age-Related Eye Disease Study
(AREDS) - Genetic Variation in Refractive Error Substudy",
and phs000421.v1.p1 "A Genome-Wide Association Study
of Fuchs' Endothelial Corneal Dystrophy (FECD)". For the
Illumina HumanCore Array (UCLA – this study), we used
the WTCCC2 cohort, which was typed on the related Illu-
mina OmniExpress Array. Subjects with an ascertained
phenotype (e.g., disease) were removed. More detailed in-
formation regarding these datasets is available in Add-
itional file 1: Table S1.

Data preprocessing

Genotypes for all datasets were converted to the forward
strand, and converted into coordinates based on the hg19
reference sequence using UCSC liftOver [10]. The genotypes
were then merged and pre-processed according to platform.
Determination of cryptic relatedness (pairwise proportion
IBD, PI-HAT > 0.2), sample missingness (> 0.05), genotype
missingness (> 0.05), Hardy-Weinberg equilibrium *p*-value
(< 10⁻⁵), and sex-matching was performed in PLINK
v1.90b3.28 [11] and used to quality-control (QC) samples
using standard parameters [12]. Ancestry was predicted by
multidimensional scaling based on raw Hamming distances,
implemented in PLINK. Only samples of presumed
European ancestry that clustered with known Europeans
from the HapMap3 cohort [13] were included. Preprocessing
steps are further elaborated in Additional file 2: Figure S1.

Imputation

Imputation was performed separately for each geno-
typing platform using the IMPUTE v2.3.2 algorithm
[14]. Prephasing of chromosomes using the Segmented
HAPlotype Estimation & Imputation Tool (SHAPEIT)
v2.r837 was performed as previously described [15, 16].
IMPUTE2 was run on the prephased haplotypes using the
1000 Genomes Project Phase 3 reference in non-overlapping
5 megabase chunks with a 250 kilobase buffer and an effect-
ive population size of 20,000. Imputed variants with an
imputation genotype probability < 0.9, missingness > 0.05, or
minor allele frequency < 0.01 were removed, and genotypes
across platforms were merged. Cryptic relatedness across co-
horts was assessed, and related/duplicated samples were
removed.

Association

Association was performed using a linear mixed model to correct for population structure, using BOLT-LMM [17]. The genotyping platform was used as a categorical covariate. The standard infinitesimal model *p*-values were chosen for downstream anaylsis. Odds ratios were calculated as exp. (beta). Because some of the individual cohort sizes violate the large sample size assumptions of BOLT-LMM, odds ratios for association (for individual cohorts) were computed using a logistic regression model in PLINK, using the first 5 eigenvectors, derived from Principal Component Analysis (PCA), as covariates. Power calculations were performed using the Genetic Power Calculator [18], assuming a variant with risk allele frequency of 0.5 and relative risk of 1.3 in an additive genetic model, a disease with a prevalence of 10 in 100,000, and a p-value threshold of 5 × 10<sup>-8</sup>, using a genotypic, 2 df case-control test. QQ and Manhattan plots were constructed using the R package “qqman” [19]. Forest plots were constructed using the R package “metafor” [20]. The genomic inflation factor λ was computed with PLINK. Correction of the genomic inflation factor to an equivalent sample size of 1000 cases and 1000 controls was performed as previously described [21]. To control for the extended haplotype on chr17q21 and to identify independent association signals, we performed association as before, but including the haplotype (tagged by the SNP rs1560310) [22] as a covariate.

Proportion variance in liability explained

The explained variance in liability at each of the
genome-wide significant loci was calculated according to
the method of So et al., which requires the frequency of
the risk allele, the relative risk of the heterozygous geno-
type, the relative risk of the homozygous risk genotype,
and the prevalence of the disease in the population [23].
The allele frequencies were calculated from the control
population of the joint genotyping cohort. Relative risks
were approximated with the corresponding odds ratios,
which converges to relative risk when the prevalence of
disease is rare. Genotypic odds ratios were estimated by
assuming an additive model. The prevalence of PSP was
estimated at 6.5 per 100,000 in accordance with prior
epidemiological studies [24, 25]. The genome-wide poly-
genic variance in liability explained was calculated using
GCTA v1.24.7 [26]. The genetic relationship matrix was
calculated chromosome-by-chromosome and then
re-combined. The first 5 principal components were

calculated and used as covariates for restricted max-
imum likelihood (REML) analysis.

Prediction of gene expression differences associated with
PSP-associated SNPs

Genetic associations with PSP may be due to genetic
control of gene expression. We used TWAS to pre-
dict differential gene expression in PSP from the joint
analysis summary statistics, integrating paired geno-
typing and gene expression data from the GTEx
Consortium [27]. Correcting for approximately 5000
effective independent tests per brain region (taking
into account 5483 genes with significantly heritable
weights and the interdependence of gene expression,
particularly across tissues), the significance threshold
was set at P < 1 × 10⁻⁵.

Credible set of causal variants at PSP GWAS loci

A credible set (potential causal variants) was identified at each of total of seven genome-wide significant loci identified in this study using the CAusal Variants Identification in Associated Regions (CAVIAR) software package [28]. Because of the extended linkage disequilibrium patterns in the chromosome 17q21.31 haplotype region, causal variants were not identified at this associated locus. Within each of the selected loci, the SNP with the minimum joint association *p*-value was chosen as the index SNP, and variants with *p*-value < 10<sup>-5</sup> and in LD (r<sup>2</sup> > 0.6) with the index SNP were input into CAVIAR. The CAVIAR-identified credible set contains potential causal variants (with a confidence level of 95% under the statistical model) that could explain the association at each locus.

Identification of genes linked to credible SNPs with
chromatin interaction data

Genetic variation can result in changes to the coding se-
quence of a gene (e.g., nonsense and missense variants)
or can regulate the gene's expression (e.g., by affecting
transcription factor binding in promoter or enhancer
regions). We first identified credible SNPs as "func-
tional" (stopgain variant, frameshift variant, splice donor
variant, nonsense-mediated decay transcript variant, or
missense variant). Of the remaining credible SNPs, we
identified those in the promoter region of a gene, de-
fined as the range 2 kb upstream to 1 kb downstream
relative to the transcription start site (TSS). Finally, the
remaining credible SNPs were considered possible regu-
latory variants and tested for short- or long- range inter-
action with other regions of chromatin to identify
potential downstream target genes. The interactions
were determined by Hi-C experiments in IMR90 and
embryonic stem cells from public data [29, 30], and fetal
brain germinal zone (ventricular and subventricular
zone) and cortical plate (intermediate zone and marginal zone) from our group [31].

## Genetic correlation with neurodegenerative diseases

Genetic correlation was assessed from GWAS summary statistics using the Linkage Disequilibrium Score Regression method (LDSC) [32]. Summary statistics were filtered by only considering SNPs that overlap with the HapMap3 reference panel. Refer to the Supplementary Methods for further details.

## Data availability

Full and imputed genotyping results from the UCLA and NNIPPS cohorts will be made available on the NIAGADS database.

## Results

We analyzed subjects from three GWAS cohorts, including 1) a multi-center cohort [2, 6] in whom we performed genotyping using the Illumina HumanOmni2.5 BeadChip and the Illumina HumanCore BeadChip (“UCLA”); 2) patients from centers in France, Germany, and the United Kingdom as part of the Neuroprotection and Natural History in Parkinson Plus Syndromes (NNIPPS) study, a double-blind randomized placebo-controlled clinical trial of riluzole [7], genotyped with the Illumina HumanOmni2.5 BeadChip (“NNIPPS”), and 3) a cohort of autopsy-proven cases from a previously published [8] GWAS (“Hoglinger”). A more detailed description of the cohorts is provided in Additional file 1: Table S1. We combined each cohort with platform-matched, out-of-sample controls from dbGAP (Additional file 1: Table S1). Stringent QC – excluding SNPs that had low genotype call rates (< 0.95) or did not follow Hardy-Weinberg equilibrium, and excluding subjects with low sample call rate (< 0.95), non-European ancestry, incompatible sex, cryptic relatedness, or duplication across cohorts (Additional file 2: Figure S1) – was applied to each cohort (including platform-matched controls). We then imputed variants implementing IMPUTE2 [14] using the 1000 Genomes Phase 3 Reference Panel to estimate genotypes at more than 77,000,000 SNPs. Imputed variants with imputation quality scores ($r^2 < 0.9$) or low minor allele frequency (< 0.01) were filtered, and genotypes across all cohorts were combined in a joint analysis. In total, we examined 6,419,662 SNPs in 1646 PSP cases and 10,662 controls.

Association was initially performed using the 616 cases represented from the UCLA and NNIPPS cohorts. Genome-wide significant association was detected at loci near MAPT and largely corresponded to the haplotype region (lead SNP rs79730878, $p = 5.4 \times 10^{-45}$; Additional file 1: Table S2). Other top associations were found at loci near MOBP, STX6, SEMA4D, DDX27, and SP1, though these did not reach genome-wide significance.

To increase statistical power, we combined all three cohorts in a joint analysis framework. We estimated that this combined cohort had 90% power to detect association of a variant with allele frequency of 0.5 and relative risk of 1.3. For a cohort of the sample size of that in a previous PSP GWAS from Hoglinger et al., the power to detect association was only 33%. In the primary analysis, we assessed the genome-wide association between the genotype at each SNP and case-control status using a linear mixed model to correct for population stratification. The genomic inflation factor $\lambda$ for the joint analysis was 1.05; for the UCLA-Omni2.5, UCLA-HumanCore, NNIPPS, and Hoglinger cohorts, $\lambda$ was 1.03, 1.02, 1.11, and 1.11, respectively (Fig. 1, Additional file 2: Figure S2 and S3). We considered the joint inflation factor to be acceptable in the setting of a relatively large joint analysis sample size [33]. Scaled for sample size, the adjusted genomic inflation factor $\lambda_{1000}$ was 1.02.

The results of the joint analysis genome-wide association are shown in Fig. 1 and Additional file 2: Figure S4. SNPs at 5 loci, in cytobands 17q21.31 (in an extended haplotype containing MAPT, lead SNP rs71920662, odds ratio OR = 0.19, $p = 3.9 \times 10^{-113}$), 3p22.1 (within MOBP, rs10675541, OR = 0.71, $p = 7.2 \times 10^{-19}$), 1q25.3 (within STX6, rs57113693, OR = 1.3, $p = 8.7 \times 10^{-16}$), 6p21.1 (within RUNX2, rs35740963, OR = 0.77, $p = 1.8 \times 10^{-8}$), and 12p12.1 (within SLCO1A2, rs7966334, OR = 1.5, $p = 3.2 \times 10^{-8}$), reached genome-wide significance ($p < 5 \times 10^{-8}$) (Additional file 1: Table S2, Additional file 2: Figure S5). An additional SNP reported in a previous GWAS [8], rs7571971, was also analyzed. Although this SNP did not reach genome-wide significance in the joint analysis (OR = 1.18, $p = 2.7 \times 10^{-5}$), the direction of the association was consistent with the previous association in each cohort. In order to decrease the likelihood that the results were influenced by population stratification, we assessed association at the loci in each of the study cohorts (Fig. 2). Associations at the lead SNPs in each of the regions were consistent across the three most well-powered study cohorts (Hoglinger, NNIPPS, and UCLA Omni2.5) while in general, the HumanCore subset of the UCLA cohort was underpowered to detect association. An additional 4 loci demonstrated suggestive association ($1 \times 10^{-6} < P < 5 \times 10^{-8}$), in 1q41 (intergenic, near DUSP10, rs12125383, OR = 1.28, $p = 5.3 \times 10^{-8}$), 12q13.13 (within SP1, rs147124286, OR = 0.74, $p = 4.1 \times 10^{-7}$), 8q24.21 (within ASAP1, rs2045091, OR = 1.25, $p = 4.7 \times 10^{-7}$), and 1p22.3 (near WDR63 and MIR4423, rs114573015, OR = 2.1, $p = 5.9 \times 10^{-7}$) (Additional file 1: Table S3). Overall, the genome-wide significant loci explained a combined 5.9% of the variance in heritable liability of PSP (Additional file 1: Table S4). The locus tagging the chr17q21 haplotype surrounding MAPT contributed the majority (5.0%), while new loci contributed an additional 0.2% of the total liability. Using a polygenic model implemented in GCTA [26], the
<figure><img src="image_5.png" /></figure>

entire set of genotyped SNPs explains 9.4 ± 0.8% (estimate ±standard error) of the variance on the liability scale, suggesting that many loci are yet to be found.

The association between PSP and the chr17q21 haplotype (H1/H2) has been widely characterized, but independent SNPs in the chr17q21 region may also contribute to disease susceptibility. To test this, we performed linear regression, taking haplotype as a covariate. Additionally, we identified subjects that were homozygous for the risk allele (H1/H1), and performed association in this subset of patients. Both approaches identified similar independent associations from the H1 haplotype in the 17q21.31 region, with the most significant SNPs at rs8078967 (P = 1.9 × 10⁻¹⁴) and rs9904290 (P = 8.9 × 10⁻¹²) in the haplotype-regressed and H1/H1 only datasets, respectively (Additional file 2: Figure S5). These SNPs did not appear to be in strong linkage disequilibrium with a previously reported SNP association, rs242557 [8] (r² = 0.008 and 0.007 in the 1000 Genomes Project data – EUR super-population, respectively) that was filtered from this dataset in variant QC; however, they were highly correlated with each other (r² = 0.996). Additionally, both variants and rs242557 are within the first intron of the MAPT gene.

To further understand how variation at each of the loci contributes to disease risk, we assessed the functional consequences of significant SNPs. We first identified a set of potential causal SNPs using the CAVIAR method, which identifies a “credible set” of SNPs that encompasses those likely to be causal [28]. The 17q21.31 locus was excluded from the analysis because of its unusual, long-range linkage disequilibrium pattern. In some loci, potentially causal coding variants were identified (in genome-wide significant loci, at 6p21.1, in RUNX2, and at 12p12.1, in SLCO1A2; and in suggestive loci, at 8q24.21, in ASAP1, and at 12q13.13, in AMHR2; Additional file 1: Table S5). Other SNPs in the credible set fell within regulatory regions; we identified the gene associated with each SNP using data from Hi-C experiments, mapping chromosome conformation patterns on a genome-wide scale from four human cell types (IMR-90 fetal lung fibroblasts, embryonic stem cells, fetal brain, and fetal brain germinal zone). Each potential regulatory SNP in the credible set was then associated with genes in close proximity by chromosomal conformation, yielding potential downstream causal genes (Additional file 1: Table S5).

To supplement the mapping information from Hi-C, we also identified the functional consequences of GWAS
<figure><img src="image_6.png" /><figcaption>Fig. 2 (See legend on next page.)</figcaption></figure>
(See figure on previous page.)

**Fig. 2** Forest plots showing association across each individual cohort for selected SNPs. A total of six genome-wide significant loci were identified, with representative SNPs: a rs71920662 in 17q21.31, near MAPT; b rs57113693 in 1q25.3, near STX6; c rs10675541 in 3p22.1, near MOBP; d rs35740963 in 6p21.1, near RUNX2; and e rs7966334 in 12p12.1, near SLCO1A2. An additional four suggestive loci were also identified: f rs12125383 in 1q41, near DUSP10 in an intergenic region; g rs147124286 in 12q13.13, near SP1; h rs2045091 in 8q24.21, near ASAP1; and i rs114573015 in 1p22.3, near WDR63. j Additionally, a previously reported GWAS SNP rs7571971 in 2p11.2, near EIF2AK3, was not identified as genome-wide significant in the joint analysis

hits using the TWAS method to predict genes that may be affected by risk alleles [27]. TWAS estimates gene expression values using paired reference transcriptome/ genotyping datasets (e.g., for expression quantitative trait loci - eQTL studies) and genotype information from summary statistics, and predicts differential expression between cases and controls. Using reference data from the GTEx Consortium, TWAS predicted the effect of gene expression from the risk haplotypes in multiple tissues. At a threshold of $P < 1 \times 10^{-5}$, we identified a number of genes that were called as differentially expressed (Additional file 1: Table S6). As expected due to the length and lack of recombination in the region, most of these genes (17) clustered around the chromosome 17 haplotype. Notably, *MAPT* (within the associated 17q21.31 locus) was among the genes predicted to be differentially expressed, as well as *STX6* (within the associated 1q24 locus), *SP1* (within the suggestive 12q13.13 locus), *SKIV2L* (within 6p21.33, nearby the associated 6p21.1 locus), and *RPSA* (within the associated 3p22.1 locus). Other genes that were pinpointed outside of association regions were *CEP57* (in 11q21) and *RPS6KL1* (in 14q24.3).

The strong neuropathological overlap of PSP with other tauopathies suggests that genetic overlap may exist. Using the LDSC software [32], we assessed genetic overlap of PSP with other neurodegenerative diseases, including AD, behavioral variant FTD (bvFTD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), by using GWAS summary statistics. As controls, we included summary statistics from GWAS for heritable, non-neurodegenerative diseases of brain (schizophrenia and bipolar disorder), a quantitative trait (height), and a non-brain disease (type 2 diabetes) (for further details, refer to the Supplementary Methods). Each of these traits was shown to be heritable. Statistically significant genetic correlations were identified for PD ($P = 9.7 \times 10^{-5}$) and ALS ($P = 1.8 \times 10^{-3}$), but not for non-neurodegenerative disease control GWAS (Fig. 3).

## Discussion

As a prototypical tauopathy, insight into PSP susceptibility alleles can help to illuminate the downstream molecular effects of tau pathology, which is a major component of

many common neurodegenerative diseases. Altogether, from a joint analysis of three disease cohorts, we have found 2 novel genome-wide significant susceptibility loci in PSP and replicated 3 previously reported loci. Of the loci identified in this study, three (within *MAPT*, *MOBP*, and *STX6*) were reported significant in a previous GWAS [8].

In the *MAPT* region, a third independent association was identified, also in *MAPT* intron 1, speculatively suggesting important regulatory functions in this region; however, no effects in differential expression have been uncovered. Overall, the mechanisms of the *MAPT* associations have been unclear. The larger H1/H2 haplotype appears to affect splicing at *MAPT* exon 3 but not overall tau expression [34]; while other *MAPT* variants, such as rs242557, may affect tau expression in some tissues [35], the effect is not robust in brain tissue. The additional association identified here may provide an orthogonal point of investigation into this curious region.

An additional locus near the *EIF2AK3* gene (encoding PERK, a key component of the unfolded protein response) was also previously identified; however, the reported SNP did not reach genome-wide significance in this joint analysis or in the new “Hoglinger” cohort (using different controls).

We also identified 2 novel genome-wide significant susceptibility loci at 6p21.1 and 12p12.1 (near *RUNX2* and *SLCO1A2*, respectively). At 6p21.1, we identified a lead SNP as well as several coding SNPs in the credible set within *RUNX2*, a gene thought to be a transcriptional factor involved in regulation of osteoblastic differentiation [36]. While seemingly unrelated to PSP, a curious number of neurodegeneration-related genes are also involved in bone diseases (e.g. *TREM2*, which has been linked to AD and Nasu-Hakola disease [37, 38], and *VCP*, linked to amyotrophic lateral sclerosis and Paget's disease of bone [39, 40]). At 12p12.1, we identified a lead SNP and credible set coding SNPs within *SLCO1A2*, a transporter present (among other places) at the blood-brain barrier, where it regulates solute trafficking [41]. An additional four loci (near the genes *DUSP10*, *SP1*, *ASAP1*, and *WDR63/MIR4423*) were suggestive of association, but did not reach genome-wide significance. While this study raises the possibility of involvement of these genes in PSP pathogenesis, further fine-mapping and functional studies are needed to confirm their possible roles.
<figure><img src="image_7.png" /><figcaption>**Fig. 3** Heatmap of genetic correlation between GWAS summary statistics for neurodegenerative diseases (PSP – progressive supranuclear palsy, ALS – amyotrophic lateral sclerosis, AD – Alzheimer's disease, bvFTD – behavioral variant frontotemporal dementia, PD – Parkinson's disease), calculated by LDSC. GWAS for non-neurodegenerative phenotypes (SCZ – schizophrenia, BIP – bipolar disorder, height, and T2D- type 2 diabetes mellitus) are also included for comparison. In each cell, the genetic correlation coefficient (and *P* value in parentheses) is shown. Phenotypes that share a common polygenic background are positively correlated</figcaption></figure>

Our results also implicate possible alternative causal genes in previously reported genome-wide significant loci. At 3p22.1, the gene closest to the GWAS lead SNP was reported as *MOBP*. This locus has previously been implicated in differential expression of the SLC25A38/ appoptosin gene, which may regulate tau cleavage [42]. Using Hi-C, we have identified chromatin interactions with *MYRIP* and *EIF1B* that could also explain this association. Similarly, at 1q25.3, the gene closest to the GWAS lead SNP was *STX6*; by Hi-C, we have also identified *XPR1* as a possible candidate gene. Interestingly, our group has previously demonstrated *XPR1* mutations in primary familial brain calcification [43], though any mechanistic overlap with PSP is unclear. Analysis of eQTL datasets (in GTEx) suggests that *RPSA* at 3p22.1 and *SKIV2L* near 6p21.1 may also be the causal genes but the tissue-relevant datasets were relatively underpowered.

Aside from identifying additional associated loci and highlighting potential PSP susceptibility genes, we analyzed the polygenic overlap between neurodegenerative diseases, identifying shared heritability with PD and ALS. Curiously, these diseases do not have predominant tau neuropathology, as PSP and other tauopathies do. Typically, PD is associated with aggregation of α-synuclein, and ALS with aggregation of TDP43 and other proteins, while tau pathology is prominent in AD. However, there are known shared genetic risk factors among these diseases. The 17q21.31 haplotype is highly associated with PD, in the same direction as in PSP [44], and SNPs near the *MOBP* gene have been recently associated with ALS [45]. Our results indicate the existence of common neurodegenerative disease pathways even across traditional protein aggregate-based subdivisions, and could potentially lead to effective treatment strategies.
A limitation of the study includes the case-control matching design. While this design allows for matching by array platforms and avoids stratification due to technical artifacts, stratification based on the ancestral differences may be present. The potential for stratification was reduced by strict filtering based on multidimensional scaling to limit the sample to subjects of European ancestry, and linear mixed model methods to further reduce confounding. Combining multiple cohorts as we have done may also reduce the degree of population stratification in the joint sample. Overall, the genomic inflation factor (λ = 1.05) suggested an acceptable level of population stratification. The validity of the results and replication of the original GWAS are further reinforced by the consistency of the identified associations across the multiple platform-matched sub-cohorts.

## Conclusion

Here, we have increased the number of significant genetic risk locus for PSP, an important advance for understanding its pathophysiology. The power of this study to identify novel loci at genome wide significance and a large unexplained heritability suggests that PSP may be highly amenable to genetic association studies in larger sample cohorts using next generation sequencing. Overall, by establishing the genetic correlations of PSP with PD and ALS and identifying novel genome-wide significant and suggestive associations, we shed insight into the mechanisms of neurodegenerative disease.

## Additional files

**Additional file 1:** Supplementary Tables S1-S5 (XLSX 636 kb)

**Additional file 2:** Supplementary Figures S1-S5, Supplementary Methods. (DOCX 8021 kb)

### Abbreviations

AD: Alzheimer's disease; ALS: Amyotrophic lateral sclerosis; bvFTD: Behavioral variant frontotemporal dementia; eQTL: Expression quantitative trait loci; FTD: Frontotemporal dementia; GWAS: Genome-wide association study; PCA: Principal component analysis; PD: Parkinson's disease; PSP: Progressive supranuclear palsy; QC: Quality control; SNP: Single nucleotide polymorphism

### Acknowledgements

We acknowledge the contributions of Alice Zhang, who has helped with acquiring controls genotyping; Margaret Chu, for administrative support; and all of the patients and their families, to whom this work is dedicated.

### Funding

This work was funded by grants from the Tau Consortium (D.H.G. and G.C.); the National Institutes of Health, F31 NS084556 (J.A.C.) UG3 NS104095 and P30 NS062691 from the National Institute of Neurological Disorders and Stroke (Informatics Center for Neurogenetics and Neurogenomics to G.C.); and the Fu-Hsing and Jyu-Yuan Chen family. Z.C. was supported by funding from the NIHR Academic Clinical Fellowship. Three academic institutions (Institute of Psychiatry, Psychology and Neuroscience, King's College London; Assistance Publique-Hôpitaux de Paris and University of Ulm) were sponsors of the NNIPPS study in each country, and jointly own the data. The BBBIPPS

study was supported by the French Health Ministry, Programme Hospitalier de Recherche Clinique (AOM04035). The Assistance Publique - Hôpitaux de Paris (France) was the sponsor of the study. The protocol and amendments were reviewed and approved by the Comité de Protection des Personnes de Pitié-Salpêtrière Hospital (France). The NNIPPS genotyping and analysis was supported under the aegis of JPND - (www.jpnd.eu, United Kingdom), Medical Research Council (MR/L501529/1; MR/R024804/1) and Economic and Social Research Council (ES/L008238/1). A.A.C. receives salary support from the National Institute for Health Research (NIHR) Dementia Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King's College London. The work leading up to this publication was funded by the European Community's Health Seventh Framework Programme (FP7/2007-2013; grant agreement number 259867) and Horizon 2020 Programme (H2020-PHC-2014-two-stage; grant agreement number 633413). We thank the UCLA Neuroscience Genomics Core (www.semel.ucla.edu/ungc) for assistance with genotyping data generation. Samples from the National Cell Repository for Alzheimer's Disease (NCRAD), which receives government support under a cooperative agreement grant (U24 AG021886) awarded by the National Institute on Aging (NIA), were used in this study. We thank contributors who collected samples used in this study, as well as patients and their families, whose help and participation made this work possible.

### Availability of data and materials

Summary measures will be made available in the NIAGADS database (https://www.niagads.org/). Additional data obtained from the NIAGADS and dbGAP databases are available with access restrictions from the corresponding databases.

### URLs

CAVIAR, http://genetics.cs.ucla.edu/caviar/index.html;
dbGAP, http://www.ncbi.nlm.nih.gov/gap;
GCTA, http://cnsgenomics.com/software/gcta/index.html;
Genetic Power Calculator, http://zzz.bwh.harvard.edu/gpc/;
HapMap, ftp://ftp.ncbi.nlm.nih.gov/hapmap/;
IMPUTE2, https://mathgen.stats.ox.ac.uk/impute/impute_v2.html;
LocusZoom, http://locuszoom.sph.umich.edu/locuszoom/;
MetaXcan, https://github.com/hakyimlab/MetaXcan;
NIAGADS, https://www.niagads.org/;
PLINK2, https://www.cog-genomics.org/plink2;
SHAPEIT, https://mathgen.stats.ox.ac.uk/genetics_software/shapeit/shapeit.html;
UCSC Genome Browser, https://genome.ucsc.edu/cgi-bin/hgGateway;

### Authors' contributions

JAC contributed to study design, data collection, experimental design, statistical analysis, and drafting and revision of the manuscript. ZC contributed to data collection, statistical analysis, and drafting of the manuscript. HW contributed to data collection and statistical analysis. AYH contributed to study design and statistical analysis. JKL, KW, GB, PNL, CP, AS, ARJ, CML, WL, PD, PA, CT, J-FD, AL, ALB, and JMB contributed to subject recruitment, data collection, experimental design, and revision of the manuscript. JSY contributed to data collection and statistical analysis. AA-C and DHG contributed to supervision of the project, subject recruitment, data collection, statistical analysis, experimental design, and revision of the manuscript. GC contributed to supervision of the project, subject recruitment, data collection, statistical analysis, experimental design, and drafting and revision of the manuscript. All authors read and approved the final manuscript.

### Ethics approval and consent to participate

Written informed consent was obtained for all patients participating in the Allon Therapeutics davunetide trial and the NNIPPS trial, and IRB approval was obtained from the corresponding Institutional Review Boards. For the NNIPPS study, The protocol and amendments were reviewed and approved by the Comité de Protection des Personnes de Pitié-Salpêtrière Hospital (France), the UK Multicentre Research Ethics Committee (MREC) (UK), Ethikkommission of the University of Ulm (Germany) and by local Institutional Review Boards (Ethics Committees) where appropriate (UK, Germany). For the BBBIPPS study, the protocol and amendments were reviewed and approved by the Comité de Protection des Personnes de Pitié-Salpêtrière Hospital (France). Additional data was obtained via NIAGADS and dbGAP in accordance with data access policies. The Institutional Review
Board at the University of California, Los Angeles, approved the joint study design, including review of outside consent forms.

**Consent for publication**

Not applicable.

**Competing interests**

J.A.C. is founder of Verge Genomics, a biotechnology company, and holds an equity stake. P.A. is a member of the Scientific Advisory Board of Genoscreen, a biotechnology company, and Director of the Fondation Plan Alzheimer, a non-profit organization. J-F.G. has received research grant funding from Roche.

**Publisher's Note**

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Author details**

¹Interdepartmental Program in Bioinformatics, University of California, Los Angeles, CA 90095, USA. ²Maurice Wohl Clinical Neuroscience Institute, Department of Basic and Clinical Neuroscience, King's College London, London SE5 9RX, UK. ³Program in Neurogenetics, Department of Neurology and Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA. ⁴Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, CA 90095, USA. ⁵Memory and Aging Center, Department of Neurology, University of California, San Francisco, CA 94158, USA. ⁶BESPIM, CHU-Nîmes, Nîmes, France. ⁷Dept Pharmacologie Clinique, Pitié-Salpêtrière Hospital, AP-PH, Paris, France. ⁸Pharmacology UPMC-Paris VI, Université Paris-Sorbonne, Paris, France. ⁹Trafford Centre for Biomedical Research, Brighton and Sussex Medical School, University of Sussex, Falmer, Brighton, UK. ¹⁰Medical Research Council Social, Genetic and Developmental Psychiatry Centre, and Department of Medical and Molecular Genetics, King's College London, London SE5 8AF, UK. ¹¹William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK. ¹²Univ. Lille, Inserm, CHU Lille, Institut Pasteur de Lille, U1167 - RID-AGE - Risk Factor and molecular determinants of aging diseases, Labex-Distalz, F-59000 Lille, France. ¹³Univ. Bordeaux, Inserm, Bordeaux Population Health Research Center, UMR 1219, CHU Bordeaux, F-33000 Bordeaux, France. ¹⁴Department of Neurology, University of Ulm, Oberer Eselsberg, Ulm, Germany. ¹⁵Departments of Psychiatry and Neurology, David Geffen School of Medicine, University of California, Los Angeles, 695 Charles E Young Dr. South, Gonda Bldg, Rm 1524, Los Angeles, CA 90095, USA.

Received: 16 May 2018 Accepted: 29 June 2018

Published online: 08 August 2018

**References**

1. Respondek G, Roeber S, Kretzschmar H, Troakes C, Al-Sarraj S, Gelpi E, Gaig C, Chiu WZ, van Swieten JC, Oertel WH, et al. Accuracy of the national institute for neurological disorders and stroke/society for progressive supranuclear palsy and neuroprotection and natural history in Parkinson plus syndromes criteria for the diagnosis of progressive supranuclear palsy. Mov Disord. 2013;28(4):504-9.

2. Chen JA, Wang Q, Davis-Turak J, et al. A multiancestral genome-wide exome array study of alzheimer disease, frontotemporal dementia, and progressive supranuclear palsy. JAMA Neurol. 2015;72(4):414-22.

3. Williams DR, de Silva R, Paviour DC, Pittman A, Watt HC, Kilford L, Holton JL, Revesz T, Lees AJ. Characteristics of two distinct clinical phenotypes in pathologically proven progressive supranuclear palsy: Richardson's syndrome and PSP-parkinsonism. Brain. 2005;128(6):1247-58.

4. Josephs KA, Petersen RC, Knopman DS, Boeve BF, Whitwell J, Duffy JR, Parisi JE, Dickson DW. Clinicopathologic analysis of frontotemporal and corticobasal degenerations and PSP. Neurology. 2006;66(1):41-8.

5. Osaki Y, Ben-Shlomo Y, Lees AJ, Daniel SE, Colosimo C, Wenning G, Quinn N. Accuracy of clinical diagnosis of progressive supranuclear palsy. Mov Disord. 2004;19(2):181-9.

6. Boxer AL, Lang AE, Grossman M, Knopman DS, Miller BL, Schneider LS, Doody RS, Lees A, Golbe LI, Williams DR, et al. Davunetide in patients with progressive supranuclear palsy: a randomised, double-blind, placebo-controlled phase 2/3 trial. Lancet Neurol. 2014;13(7):676-85.

7. Bensimon G, Ludolph A, Agid Y, Vidailhet M, Payan C, Leigh PN. Riluzole treatment, survival and diagnostic criteria in Parkinson plus disorders: the NNIPPS study. Brain. 2009;132(1):156-71.

8. Hoglinger GU, Melhem NM, Dickson DW, Sleiman PMA, Wang L-S, Klei L, Rademakers R, de Silva R, Litvan I, Riley DE, et al. Identification of common variants influencing risk of the tauopathy progressive supranuclear palsy. Nat Genet. 2011;43(7):699-705.

9. Li Y, Chen JA, Sears RL, Gao F, Klein ED, Karydas A, Geschwind MD, Rosen HJ, Boxer AL, Guo W, et al. An epigenetic signature in peripheral blood associated with the haplotype on 17q21.31, a risk factor for neurodegenerative Tauopathy. PLoS Genet. 2014;10(3):e1004211.

10. Rosenbloom KR, Armstrong J, Barber GP, Casper J, Clawson H, Diekhans M, Dreszer TR, Fujita PA, Guruvadoo L, Haeussler M, et al. The UCSC genome browser database: 2015 update. Nucleic Acids Res. 2015;43(D1):D670-81.

11. Chang CC, Chow CC, Tellier LC, Vattikuti S, Purcell SM, Lee JJ. Second-generation PLINK: rising to the challenge of larger and richer datasets. GigaScience. 2015;4(1):1-16.

12. Evangelou E, Ioannidis JPA. Meta-analysis methods for genome-wide association studies and beyond. Nat Rev Genet. 2013;14(6):379-89.

13. The International HapMap 3 Consortium. Integrating common and rare genetic variation in diverse human populations. Nature. 2010;467(7311):52-8.

14. Howie BN, Donnelly P, Marchini J. A flexible and accurate genotype imputation method for the next generation of genome-wide association studies. PLoS Genet. 2009;5(6):e1000529.

15. O'Connell J, Gurdasani D, Delaneau O, Pirastu N, Ulliv S, Cocca M, Traglia M, Huang J, Huffman JE, Rudan I, et al. A general approach for haplotype phasing across the full Spectrum of relatedness. PLoS Genet. 2014;10(4):e1004234.

16. Delaneau O, Marchini J. The genomes project C: integrating sequence and array data to create an improved 1000 genomes project haplotype reference panel. Nat Commun. 2014;5:3934.

17. Loh P-R, Tucker G, Bulik-Sullivan BK, Vilhjalmsson BJ, Finucane HK, Salem RM, Chasman DI, Ridker PM, Neale BM, Berger B, et al. Efficient Bayesian mixed-model analysis increases association power in large cohorts. Nat Genet. 2015;47(3):284-90.

18. Purcell S, Cherny SS, Sham PC. Genetic power calculator: design of linkage and association genetic mapping studies of complex traits. Bioinformatics. 2003;19(1):149-50.

19. Turner SD. qqman: an R package for visualizing GWAS results using Q-Q and manhattan plots. In: bioRxiv; 2014. p. 005165. https://doi.org/10.1101/005165.

20. Viechtbauer W. Conducting meta-analyses in R with the metafor package. J Stat Softw. 2010;36(3):48.

21. Freedman ML, Reich D, Penney KL, McDonald GJ, Mignault AA, Patterson N, Gabriel SB, Topol EJ, Smoller JW, Pato CN, et al. Assessing the impact of population stratification on genetic association studies. Nat Genet. 2004; 36(4):388-93.

22. Coppola G, Chinnathambi S, Lee JJ, Dombroski BA, Baker MC, Soto-Ortolaza AI, Lee SE, Klein E, Huang AY, Sears R, et al. Evidence for a role of the rare p. A152T variant in MAPT in increasing the risk for FTD-spectrum and Alzheimer's diseases. Hum Mol Genet. 2012;21(15):3500-12.

23. So H-C, Gui AHS, Cherny SS, Sham PC. Evaluating the heritability explained by known susceptibility variants: a survey of ten complex diseases. Genet Epidemiol. 2011;35(5):310-7.

24. Schrag A, Ben-Shlomo Y, Quinn NP. Prevalence of progressive supranuclear palsy and multiple system atrophy: a cross-sectional study. Lancet. 1999; 354(9192):1771-5.

25. Nath U, Ben-Shlomo Y, Thomson RG, Morris HR, Wood NW, Lees AJ, Burn DJ. The prevalence of progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome) in the UK. Brain. 2001;124(7):1438-49.

26. Yang J, Lee SH, Goddard ME, Visscher PM. GCTA: a tool for genome-wide complex trait analysis. Am J Hum Genet. 2011;88(1):76-82.

27. Gusev A, Ko A, Shi H, Bhatia G, Chung W, Penninx BWJH, Jansen R, de Geus EJC, Boomsma DI, Wright FA, et al. Integrative approaches for large-scale transcriptome-wide association studies. Nat Genet. 2016;48(3):245-52.

28. Homozdiari F, Kostem E, Kang EY, Pasaniuc B, Eskin E. Identifying causal variants at loci with multiple signals of association. Genetics. 2014;198(2):497-508.

29. Dixon JR, Jung I, Selvaraj S, Shen Y, Antosiewicz-Bourget JE, Lee AY, Ye Z, Kim A, Rajagopal N, Xie W, et al. Chromatin architecture reorganization during stem cell differentiation. Nature. 2015;518(7539):331-6.

30. Dixon JR, Selvaraj S, Yue F, Kim A, Li Y, Shen Y, Hu M, Liu JS, Ren B. Topological domains in mammalian genomes identified by analysis of chromatin interactions. Nature. 2012;485(7398):376-80.
31. Won H, de la Torre-Ubieta L, Stein JL, Parikshak NN, Huang J, Opland CK, Gandal MJ, Sutton GJ, Hormozdiari F, Lu D, et al. Chromosome conformation elucidates regulatory relationships in developing human brain. Nature. 2016;538(7626):523-7.

32. Bulik-Sullivan BK, Loh P-R, Finucane HK, Ripke S, Yang J. Schizophrenia working Group of the Psychiatric Genomics C, Patterson N, Daly MJ, price AL, Neale BM: LD score regression distinguishes confounding from polygenicity in genome-wide association studies. Nat Genet. 2015;47(3):291-5.

33. Yang J, Weedon MN, Purcell S, Lettre G, Estrada K, Willer CJ, Smith AV, Ingelsson E, O'Connell JR, Mangino M, et al. Genomic inflation factors under polygenic inheritance. Eur J Hum Genet. 2011;19(7):807-12.

34. Trabzuni D, Wray S, Vandrovcova J, Ramasamy A, Walker R, Smith C, Luk C, Gibbs JR, Dillman A, Hernandez DG, et al. MAPT expression and splicing is differentially regulated by brain region: relation to genotype and implication for tauopathies. Hum Mol Genet. 2012;21(18):4094-103.

35. Chen J, Yu J-T, Wojta K, Wang H-F, Zetterberg H, Blennow K, Yokoyama JS, Weiner MW, Kramer JH, Rosen H, et al. Genome-wide association study identifies MAPT locus influencing human plasma tau levels. Neurology. 2017;88(7):669-76.

36. Komori T. Regulation of bone development and extracellular matrix protein genes by RUNX2. Cell Tissue Res. 2009;339(1):189-95.

37. Jonsson T, Stefansson H, Steinberg S, Jonsdottir I, Jonsson PV, Snaedal J, Bjornsson S, Huttenlocher J, Levey AI, Lah JJ, et al. Variant of TREM2 associated with the risk of Alzheimer's disease. N Engl J Med. 2013;368(2):107-16.

38. Guerreiro R, Wojtas A, Bras J, Carrasquillo M, Rogaeva E, Majounie E, Cruchaga C, Sassi C, Kauwe JSK, Younkin S, et al. TREM2 variants in Alzheimer's disease. N Engl J Med. 2013;368(2):117-27.

39. Johnson JO, Mandrioli J, Benatar M, Abramzon Y, Van Deerlin VM, Trojanowski JQ, Gibbs JR, Brunetti M, Gronka S, Wuu J, et al. Exome sequencing reveals VCP mutations as a cause of familial ALS. Neuron. 2010;68(5):857-64.

40. Watts GDJ, Wymer J, Kovach MJ, Mehta SG, Mumm S, Darvish D, Pestronk A, Whyte MP, Kimonis VE. Inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia is caused by mutant valosin-containing protein. Nat Genet. 2004;36(4):377-81.

41. Urquhart BL, Kim RB. Blood-brain barrier transporters and response to CNS-active drugs. Eur J Clin Pharmacol. 2009;65(11):1063-70.

42. Zhao Y, Tseng IC, Heyser Charles J, Rockenstein E, Mante M, Adame A, Zheng Q, Huang T, Wang X, Arslan Pharhad E, et al. Appoptosin-mediated caspase cleavage of tau contributes to progressive Supranuclear palsy pathogenesis. Neuron. 2015;87(5):963-75.

43. Legati A, Giovannini D, Nicolas G, Lopez-Sanchez U, Quintans B, Oliveira JRM, Sears RL, Ramos EM, Spiteri E, Sobrido M-J, et al. Mutations in XPR1 cause primary familial brain calcification associated with altered phosphate export. Nat Genet. 2015;47(6):579-81.

44. Nalls MA, Keller MF, Hernandez DG, Chen L, Stone DJ, Singleton AB. On behalf of the Parkinson's progression marker initiative i: baseline genetic associations in the Parkinson's progression markers initiative (PPMI). Mov Disord. 2016;31(1):79-85.

45. van Rheenen W, Shatunov A, Dekker AM, McLaughlin RL, Diekstra FP, Pulit SL, van der Spek RAA, Vosa U, de Jong S, Robinson MR, et al. Genome-wide association analyses identify new risk variants and the genetic architecture of amyotrophic lateral sclerosis. Nat Genet. 2016;48(9):1043-8.

Ready to submit your research? Choose BMC and benefit from:

* fast, convenient online submission

* thorough peer review by experienced researchers in your field

* rapid publication on acceptance

* support for research data, including large and complex data types

* gold Open Access which fosters wider collaboration and increased citations

* maximum visibility for your research: over 100M website views per year

At BMC, research is always in progress.

Learn more biomedcentral.com/submissions

<figure><img src="image_8.png" /></figure>