A Germline Variant in the TERT Gene Is a Novel Predisposition Allele Associated with Myeloproliferative Neoplasms
Authors: Hinds David A. , Barnholt Kimberly E. , Zehnder James L. , Kiefer Amy K. , Do Chuong B. , Eriksson Nicholas , Mountain Joanna L. , Francke Uta , Tung Joyce A. , Nguyen Huong (Marie) , Levine Ross L. , Mesa Ruben A. , Gotlib Jason 
Published: October 2019

Abstract
Abstract 707

Background:
Myeloproliferative neoplasms (MPNs) are disorders that result in unregulated overproduction of one or more myeloid blood cell types by the bone marrow. Polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) comprise the three classic MPNs. The somatic JAK2 V617F mutation is present in 95% of PV patients, and 50–60% of ET and PMF patients. Past work has identified a germline haplotype in JAK2 associated with risk of developing a V617F-positive MPN (Kilpivaara et al; Olcaydu et al; Jones et al, Nat. Genet., 2009).

Methods:
We recruited a web-based participatory cohort of individuals with MPNs to better understand the genetic basis of these conditions. Participation in this MPN research initiative included free genotyping, and participants provided informed consent and responses to surveys online, under a protocol approved by the external AAHRPP-accredited IRB, Ethical & Independent Review Services. We enrolled and collected saliva samples from more than 700 participants with the following self-reported diagnoses: systemic mastocytosis (n=142), ET (n=145), PV (n=137), PMF (n=50), chronic myelogenous leukemia (n=108), and 97 with overlapping diagnoses (e.g. ET or PV with PMF). Participants were genotyped using a derivative of the Illumina HumanOmniExpress BeadChip with additional custom content, including probes for the JAK2 V617F variant. We performed a genome-wide association study (GWAS) of classic MPN diagnoses (at least one of ET, PV, or MF), using 407 cases from this MPN research initiative and 94,037 controls drawn from the broader 23andMe research participant community. Association was assessed by logistic regression adjusted for age, gender, and 5 principal components to model ancestry.

Results:
We replicated the known association between germline variation in JAK2 and classic MPNs (rs12340895: odds ratio=2.5, P=7.4 × 10−35). We also identified a novel genome-wide-significant association in TERT, or telomerase reverse transcriptase (rs2853677: odds ratio=1.6 per G allele, P=6.3 × 10−11). The association is consistent with an additive model on the logistic scale (odds ratio=2.6 for 2 versus 0 G alleles). Another variant in TERT, rs2736100, has previously been associated with several non-hematological cancers and with red blood cell count, and our lead SNP is in linkage disequilibrium with TERT variant rs2736100 (r2=0.54). While no other loci reached the threshold of genome-wide significance (P<5.0 × 10−8), we saw a suggestive association with a germline missense variant (F858L) in ATM, or ataxia telangiectasia mutated gene (rs1800056: odds ratio=2.6 per C allele, P=1.4 × 10−5). This variant has also been reported to be associated with breast cancer and chronic lymphocytic leukemia.
The rs2853677 TERT variant was associated with each of ET, PV, and PMF, with similar effect sizes. It was not associated with JAK2 V617F mutation status within the MPN cohort (odds ratio=1.0, P=1.0), while the germline JAK2 variant was preferentially associated with V617F-positive MPNs (odds ratio=2.1, P=3.0 × 10−6). The high-risk allele of rs2853677 was also predictive of V617F status among 23andMe participants who had not been recruited into the MPN community (odds ratio=1.6, P=0.0012). These results suggest that while variation in TERT facilitates either acquisition or proliferation of V617F-positive myeloid cells, it also predisposes to MPNs through a V617F-independent mechanism.

Conclusion:
We have identified a germline variant in TERT which is a new predisposition allele for classic MPNs. These results demonstrate the potential for web-based recruitment methods to contribute to genetic research for uncommon diseases.

Disclosures:
Hinds: 23andMe: Employment, Equity Ownership, Patents & Royalties. Barnholt:23andMe, Inc.: Employment. Zehnder:23andMe, Inc.: Unpaid advisor and collaborator Other. Kiefer:23andMe, Inc.: Employment. Do:23andMe, Inc.: Employment, Equity Ownership, Patents & Royalties. Eriksson:23andMe, Inc.: Employment, Equity Ownership, Patents & Royalties. Mountain:23andMe, Inc.: Consultancy, Employment, Honoraria, Patents & Royalties, Research Funding. Francke:23andMe, Inc.: Employment, Honoraria, Research Funding; Locus Development: Consultancy, Membership on an entity's Board of Directors or advisory committees. Tung:23andMe, Inc.: Employment. Mesa:23andMe, Inc: Unpaid advisor and collaborator Other. Gotlib:23andMe, Inc.: Unpaid advisor and collaborator Other.