Life science
Healthcare, Gene therapy, Drug devlopment

A human isogenic iPSC-derived cell line panel identifies major
regulators of aberrant astrocyte proliferation in Down syndrome
Center for Maternal, Fetal and Neonatal Medicine, Osaka University Hospital
Associate Professor Yasuji Kitabatake
Researchmap https://researchmap.jp/kyasujiLife science

Abstract
Astrocytes exert adverse effects on the brains of individuals withDown syndrome (DS). Although a neurogenic-to-gliogenic shift in
the fate-specification step has been reported, the mechanisms andkey regulators underlying the accelerated proliferation of astrocyte
precursor cells (APCs) in DS remain elusive. Here, we establisheda human isogenic cell line panel based on DS-specific induced
pluripotent stem cells, the XIST-mediated transcriptional silencing
system in trisomic chromosome 21, and genome/chromosome-editing technologies to eliminate phenotypic fluctuations caused bygenetic variation. The transcriptional responses of genes observed
upon XIST induction and/or downregulation are not uniform, andonly a small subset of genes show a characteristic expression
pattern, which is consistent with the proliferative phenotypes of DS
APCs. Comparative analysis and experimental verification using
gene modification reveal dose-dependent proliferation-promoting
activity of DYRK1A and PIGP on DS APCs. Our collection of humanisogenic cell lines provides a comprehensive set of cellular models
for further DS investigations.

▍ Significance of the research and Future perspective
DS astrocytes exert toxic effects on the formation and maturationof neural networks and neuron survival by reducing neuronal activity, inducing morphological alterations, and promoting neuronal
apoptosis. In the DS brain, astrocytes may act as important modulators in DS pathophysiology. Thus, identifying critical regulators for
astrocyte overpopulation may be a critical first step for investigating disease mechanisms and developing new therapeutic strategies for DS.

▍ Background & Results
Down syndrome (DS; trisomy 21) is the most common form ofchromosomal aberration, which results from an extra copy of human chromosome 21. All individuals with DS exhibit various typesof clinical features, including intellectual disability and cognitivedeficits. Although the healthy human brain contains almost equalnumbers of neuronal and glial cells, studies with DS brains showeda significantly reduced number of neurons and nearly twice as
many astrocytes compared with that of age-matched controls.
To eliminate biological ‘noise’, which can result from genetic
variability, we established an isogenic iPSC panel where all celllines share a single genetic background by combining DS-specific iPSCs, XIST-induced chromosome silencing, and genome/
chromosome-editing technologies. These cell lines were subjected
to astrocytic differentiation, and comparative analysis between
their gene-expression profiles and proliferative phenotypes (with acommon genetic background) was performed. Once XIST-induced
silencing was stabilized, the transcriptional levels of most genes
were continuously suppressed after the removal of doxycycline(Dox). However, the enhanced proliferative phenotype of APCs inDS, which was suppressed by chromosome silencing, returned
to aberrantly accelerated conditions by Dox removal. Carefulanalysis of this discrepancy between transcriptional and phenotypic responses enabled us to narrow down the causative genes
responsible for astrocyte overproliferation. We further establishedvarious types of systematically designed partial trisomy 21 iPSCs(Partial-Tri21 iPSCs), leading to the identification of two responsible
genes, namely dual-specificity tyrosine-phosphorylation-regulated
kinase 1A (DYRK1A) and phosphatidylinositol glycan anchor biosynthesis, class P (PIGP).

Fig1. Modeling Down syndrome with patient-specific iPS cells

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were differentiated into the neural lineage for the elucidation of pathological mechanism

in Down syndrome.

in Down syndrome.

Fig. 2 Generation of an isogenic iPSC panel for disease modelling of DS.
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P a t e n t
Kawatani, Keiji; Nambara, Toshihiko; Kitabatake Yasuji et al. A human isogenic iPSC-derived cell line panel identifies major regulators of aberrant astrocyte proliferation in Down syndrome. Commun Biol. 2021; 4(1): 730. doi: 10.1038/s42003-021-02242-7
UR
L https://www.nature.com/articles/s42003-021-02242-7
K e y w o r d down syndrome, iPS cell, genome editing, astrocyte
Tr e a t i s e