Deletion of the X gene, Kdm6a, in microglia reverses the disease-associated microglia transcriptome

Multiple sclerosis (MS) exhibits a sex difference with the female to male bias nearly 3:1. This may be due to differences in sex hormones, sex chromosomes, or both. Kdm6a is an X chromosome gene that escapes X-inactivation and encodes for a histone demethylase which can modulate autosomal gene expression. Females have two copies of Kdm6a, while males have one copy. Microglia play a key role in the neuropathology of MS. Thus, Kdm6a was selectively deleted in microglia in the MS model, experimental autoimmune encephalomyelitis (EAE), to determine the effect on microglia, neuropathology, and clinical disease. Deletion of the X chromosome gene Kdm6a in microglia ameliorated EAE in females. The transcriptome in microglia Kdm6a knockout mice compared to wild type showed downregulation of disease-associated microglia (DAM) markers and upregulation of resting microglia markers. Gene ontology analyses demonstrated that selective deletion of Kdm6a in microglia caused reversal of the transcriptome changes induced by EAE. In contrast to effects in female mice, selective deletion of Kdm6a in microglia of male mice had no effect on EAE. To complement findings using genetic knockouts, pharmacologic blocking of Kdm6a was done using metformin. Metformin treatment, compared to vehicle, ameliorated EAE in females, with microglia histologically and transcriptionally similar to those from healthy controls. Further in translation, analyses of microglia transcriptomes in MS and healthy controls suggested that blocking Kdm6a may be a novel strategy to target disease-associated microglia in MS women. Overall design: Microglia RNAs were isolated from RiboTag mice with Tmem119-Cre/ERT2. For cKO, Kdm6a gene was deleted using Tmem119-Cre/ERT2.