Vitamin D modulates cortical transcriptome and behavioral phenotypes in an Mecp2 heterozygous Rett syndrome mouse model

Rett syndrome (RTT) is an X-linked neurological disorder caused by mutations in the transcriptional regulator MECP2 . Mecp2 loss-of-function leads to the disruption of many cellular pathways, including aberrant activation of the NF-κB pathway. Genetically attenuating the NF-κB pathway in Mecp2 -null mice ameliorates hallmark phenotypes of RTT, including reduced dendritic complexity, raising the question of whether NF-κB pathway inhibitors could provide a therapeutic avenue for RTT. Vitamin D is a known inhibitor of NF-κB signaling; further, vitamin D deficiency is prevalent in RTT patients and male Mecp2 -null mice. We previously demonstrated that vitamin D rescues the aberrant NF-κB activity and reduced neurite outgrowth of Mecp2 -knockdown cortical neurons in vitro , and that dietary vitamin D supplementation rescues decreased dendritic complexity and soma size of neocortical projection neurons in both male hemizygous Mecp2 -null and female heterozygous mice in vivo . Here, we have identified over 200 genes whose dysregulated expression in the Mecp2 +/- cortex is modulated by dietary vitamin D. Genes normalized with vitamin D supplementation are involved in dendritic complexity, synapses, and neuronal projections, suggesting that the rescue of their expression could underpin the rescue of neuronal morphology. Further, motor and anxiety-like behavioral phenotypes in Mecp2 +/- mice correlate with circulating vitamin D levels, and there is a disruption in the homeostasis of the vitamin D synthesis pathway in Mecp2 +/- mice. Thus, our data indicate that vitamin D modulates RTT pathology and its supplementation could provide a simple and cost-effective partial therapeutic for RTT.