MECP2 and autism spectrum disorder: Whether or how this increased length has any functional significance for the regulation of these genes is unclear from our studies, but it is intriguing that these long genes are disrupted in forms of autism spectrum disorder (Zylka et al., 2015; Wei et al., 2016) and in the related developmental disorder Rett Syndrome (Sugino et al., 2014; Gabel et al., 2015), where loss of the chromatin protein Mecp2 leads to selective upregulation of long neuronal genes in a highly cell-type-specific fashion.