Elizabeth Hai-Yen Chu

The brain is exquisitely sensitive to methyl-CpG-binding protein 2 (MeCP2) abundance. Too little causes Rett syndrome (RTT), too much causes MECP2 duplication syndrome (MDS), and in both, severity tracks with the amount of functional MeCP2. Even modest deviations are detrimental, yet how MeCP2 abundance is controlled remains poorly understood. Using genome-wide CRISPR knockout screens, we identified hundreds of proteins regulating MeCP2, revealing a casein kinase 2 alpha 1 (CSNK2A1)-driven regulatory axis stabilizing MeCP2. We show this axis is druggable and therapeutically relevant, using a novel CSNK2A1 inhibitor in human cells and targeting Csnk2a1 in an MDS mouse model. We further connect CSNK2A1-MeCP2 regulatory disruption to Okur-Chung neurodevelopmental syndrome (OCNDS), caused by mutations in CSNK2A1 , finding ∼50% less hippocampal MeCP2 in an OCNDS mouse model. Together, these data identify a druggable regulatory axis modulating MeCP2 and implicate MeCP2 dysregulation in the molecular pathogenesis of OCNDS and potentially other neurodevelopmental disorders.

Many neurological diseases impact specific brain regions despite widespread expression of the disease-related protein. Spinocerebellar ataxia type 1 (SCA1) primarily affects the cerebellum, though Ataxin-1 (ATXN1) is widely expressed. We previously showed that intensified interaction between mutant ATXN1 and Capicua (CIC) drives SCA1 pathogenesis in the cerebellum, whereas ATXN1 loss augments amyloid β production in the hippocampus and cortex. CIC, however, forms a complex with ATXN1 and its paralog, Ataxin-1-like (ATXN1L), yet knockout of either yields completely different phenotypes. To determine whether this could be due to CIC having two isoforms, we generated mice bearing either the long (CIC-L) or short (CIC-S) isoform. Loss of CIC-L led to cognitive deficits, whereas loss of CIC-S caused early postnatal lethality, phenocopying ATXN1 and ATXN1L knockout mice, respectively. Furthermore, CIC-L preferentially interacts with ATXN1, and CIC-S with ATXN1L. Our data underscore the importance of isoform–paralog interplay in studying regional vulnerability in neurodegenerative diseases.

Many neurological diseases impact specific brain regions despite widespread expression of the disease-related protein. Spinocerebellar ataxia type 1 (SCA1) primarily affects the cerebellum, though Ataxin-1 (ATXN1) is widely expressed. We previously showed that intensified interaction between mutant ATXN1 and Capicua (CIC) drives SCA1 pathogenesis in the cerebellum, whereas ATXN1 loss augments amyloid beta production in the hippocampus and cortex. CIC, however, forms a complex with ATXN1 and its paralog, Ataxin-1-like (ATXN1L)—yet knockout of either yields completely different phenotypes. To determine whether this could be due to CIC having two isoforms, we generated mice bearing either the long (CIC-L) or short (CIC-S) isoform. Loss of CIC-L led to cognitive deficits, whereas loss of CIC-S caused perinatal lethality, phenocopying, ATXN1 and ATXN1L knockout mice, respectively. Furthermore, CIC-L preferentially interacts with ATXN1, and CIC-S with ATXN1L. Our data underscore the importance of isoform–paralog interplay in studying regional vulnerability in neurodegenerative diseases.

Voltage‐gated calcium channels (VGCCs) are multi‐subunit ion channel proteins that control and regulate a wide array of physiological processes. Their dysfunction has been implicated in several neurological, cardiac, psychiatric, endocrine, oncogenic, and muscular disorders. The diverse and specialized cellular functions involving VGCC‐mediated calcium signaling stem from two primary mechanisms: differential and cell‐specific expression of pore‐forming (α1) and auxiliary subunit genes, and extensive alternative splicing of their pre‐mRNA. All the 10 α1‐encoding genes undergo alternative splicing to generate a wide array of cell‐specific CaV variants with distinct biophysical, pharmacological, and protein–protein interaction properties. This proteomic diversity and the associated cell‐specific expression signature of CaV splice variants are tightly regulated by trans‐acting splicing factors—RNA‐binding proteins that control the inclusion or skipping of alternatively spliced exons during post‐transcriptional pre‐mRNA processing. The discovery that several channelopathies are caused by aberrant splicing due to genetic mutations in either cis‐acting binding elements on the pre‐mRNA or in core splicing machinery components highlights the crucial role of alternative splicing in VGCC‐related pathologies. These insights have opened new therapeutic avenues, as targeting the alternative splicing of disease‐associated specific exons has recently emerged as a novel, promising treatment for neurodevelopmental disorders and channelopathies associated with splicing dysfunction.