ASSESSING THE ROLE OF BAF SUBUNIT VARIANTS IMPLICATED IN NEURODEVELOPMENTAL DISORDERS USING DROSOPHILA-BASED FUNCTIONAL ASSAYS

Abstract

Neurodevelopmental disorders (NDDs) are frequently caused by variants in genes associated with chromatin regulation, interfering with transcriptional programs that support normal neurodevelopment. These genes include subunits of the Brahma-associated factor (BAF) chromatin-remodelling complex. Functional assays in the model organism Drosophila can inform whether an NDD-associated variant alters the function of the encoded protein. Here, I employed a Drosophila assay to assess variants in the BAF subunit SMARCD1. Knockout of Bap60, the fly orthologue of SMARCD1, is lethal. The expression of human SMARCD1 rescues lethality, forming the basis for a ‘humanised rescue’ assay. I screened 22 SMARCD1 variants of uncertain significance and found a deleterious effect in seven, providing functional evidence that reclassifies the variants to likely pathogenic. Additionally, I developed alternative assays for the BAF subunits ACTL6A/B and SMARCA2/4. Overall, this work provides novel insight on the functional impact of NDD-associated BAF subunit variants, assisting in their clinical classification.