Loss of astrocytic markers and impaired metabolic function in spinocerebellar ataxia type 7 patient-derived neural cultures.

Spinocerebellar ataxia type 7 (SCA7) is a rare neurodegenerative disorder caused by a CAG repeat expansion in the ATXN7 gene. This repeat expansion results in an abnormally long polyglutamine (PolyQ) tract in the Ataxin-7 protein. This ultimately leads to the degeneration of most notably Purkinje cells and retinal cells. Because no treatment exist that can halt or slow disease progression, there is a critical need for patient-specific disease models to uncover new pathogenic mechanisms and enable therapeutic testing. In this study, induced human pluripotent stem cells (hiPSCs) derived from healthy controls and individuals with SCA7 were differentiated into a mixed neural cell population consisting of neurons and astrocytes. Although control and SCA7 neurons appeared morphologically similar, SCA7-derived astrocytes exhibited a pronounced loss of the astrocyte-specific markers GFAP and S100B. Transcriptome analysis revealed substantial alterations in genes related to glial differentiation, cellular metabolism and oxygen handling, protein homeostasis, and neuronal differentiation and neuronal signalling. Mitochondrial stress assays further confirmed a mitochondrial phenotype in SCA7 neural cells. Together, these findings demonstrate that hiPSC-derived neural cells provide a robust platform that can be used for studying disease mechanisms and testing potential therapies for SCA7.