Histone Variants and Their Chaperones: An Emerging Epigenetic Mechanism in Neurodevelopment and Neurodevelopmental Disorders.

Neurodevelopment is a highly regulated process that relies on the precise regulation of gene expression. Numerous epigenetic mechanisms contribute and cooperate to ensure the proper execution of developmental gene expression programs. Indeed, disruption of the molecular machinery regulating the deposition or removal of epigenetics markers is associated with numerous neurodevelopmental disorders, including autism spectrum disorder and intellectual disabilities. Among the various epigenetic marks that are fundamental for brain development, research has recently begun to focus on the role of histone variants and their associated chaperone proteins. Replication-independent histone variants can replace replication-dependent canonical histones in neuronal chromatin, giving nucleosomes unique properties that allow them to influence transcription. The deposition and removal of histone variants into neuronal chromatin are controlled by chaperone proteins that are integrated into chromatin remodelling complexes. Several studies report that the deposition and removal of histone variants by chaperone proteins from genes during development is pivotal for the regulation of gene expression, suggesting they are fundamental for neurodevelopment. This review will focus on the histone variants H2A.Z and H3.3, and the exclusive chaperones that regulate their dynamics, in gene expression during neurodevelopment and the progression of neurodevelopmental disorders.