Titus, E. | Search bioRxiv

bioRxiv2023

Cell type specificity of mosaic chromosome 1q gain resolved by snRNA-seq in a case of epilepsy with hyaline protoplasmic astrocytopathy

STRUCTURED ABSTRACTO_ST_ABSIntroductionC_ST_ABSMosaic gain of chromosome 1q (chr1q) has been associated with malformation of cortical development (MCD) and epilepsy. Hyaline protoplasmic astrocytopathy (HPA) is a rare neuropathological finding seen in cases of epilepsy with MCD. The cell-type specificity of mosaic chr1q gain in the brain and the molecular signatures of HPA are unknown. MethodsWe present a child with pharmacoresistant epilepsy who underwent epileptic focus resections at age 3 and 5 years and was found to have mosaic chr1q gain and HPA. We performed single-nuclei RNA-sequencing (snRNA-seq) of brain tissue from the second resection. ResultssnRNA-seq showed increased expression of chr1q genes specifically in subsets of neurons and astrocytes. Differentially expressed genes associated with inferred chr1q gain included AKT3 and genes associated with cell adhesion or migration. A subpopulation of astrocytes demonstrated marked enrichment for synapse-associated transcripts, possibly linked to the astrocytic inclusions observed in HPA. DiscussionsnRNA-seq may be used to infer the cell type-specificity of mosaic chromosomal copy number changes and identify associated gene expression alterations, which in the case of chr1q gain may involve aberrations in cell migration. Future studies using spatial profiling could yield further insights on the molecular signatures of HPA.

neuroscience↗

bioRxiv2019

The crystal structure of a cardiac calsequestrin filament reveals an atomic mechanism of calsequestrin-associated catecholaminergic polymorphic ventricular tachycardia

Mutations in the calcium-binding protein calsequestrin cause a highly lethal familial arrhythmia, catecholaminergic polymorphic ventricular tachycardia (CPVT). In vivo, calsequestrin multimerizes into filaments, but a compelling atomic-resolution structure of a calsequestrin filament is lacking. We report a crystal structure of a cardiac calsequestrin filament with supporting mutation analysis provided by an in vitro fomentation assay. We also report and characterize a novel disease-associated calsequestrin mutation, S173I, which localizes to the filament-forming interface. In addition, we show that a previously reported dominant disease mutation, K180R, maps to the same multimerization surface. Both mutations disrupt filamentation, suggesting that dominant disease arises from defects in multimer formation. A ytterbium-derivatized structure pinpoints multiple credible calcium sites at filament-forming interfaces, explaining the atomic basis of calsequestrin filamentation in the presence of calcium. This work advances our understanding of calsequestrin biochemistry and provides a unifying structure-function molecular mechanism by which dominant-acting calsequestrin mutations provoke lethal arrhythmias.

biochemistry↗