Abstract
Brain development is a tightly regulated and highly complex process. Disruption can lead to neurodevelopmental disorders (NDDs), such as autism spectrum disorder, developmental delay, and intellectual disability. ELAV-like 2 (ELAVL2) is an RNA-binding protein involved in the regulation of RNA metabolism, particularly in the brain, but has not yet been associated with NDDs. We report an international cohort of 15 individuals with non-inherited (de novo) variants in ELAVL2, all of whom present with overlapping neurodevelopmental clinical features. This study aimed to investigate ELAVL2 as a novel neurodevelopmental disorder gene by functionally characterising candidate variants identified in our patient cohort.
Five truncating variants introducing premature stop codons, together with two larger-scale gene disruptions, support haploinsufficiency of ELAVL2 as the likely disease mechanism. However, seven missense variants (single amino acid substitutions) and one truncating variant in the final exon of ELAVL2 required further investigation, as their impact on protein function was unknown. To assess the effect of these variants on protein stability, a cycloheximide chase assay was performed. Co-immunoprecipitation was then used to examine the effects of select patient variants on ELAVL2 dimerisation.
Our results showed that several patient variants reduced ELAVL2 protein stability, supporting our haploinsufficiency hypothesis and confirming that these variants are likely pathogenic (n = 4; one-way ANOVA, P = <0.033). In addition, one variant, located close to the AlphaFold-modelled dimerisation interface, shows a decrease in dimerisation, indicating an additional mechanism by which variants can impair protein function.
These findings support that loss-of-function variants in ELAVL2 cause a novel neurodevelopmental disorder, connecting this well-established neuronal RNA-binding protein with the clinical phenotypes observed in our cohort. Future experiments studying specific ELAVL2 target RNAs will provide further insight into the pathophysiological mechanism of this novel disorder.