The histone H3-lysine 4-methyltransferase Mll4 governs the development of growth hormone-releasing hormone-producing neurons

In humans, inactivating mutations in MLL4, which encodes a histone H3-lysine 4-methyltrasferase, lead to Kabuki syndrome (KS). While dwarfism is a cardinal feature of KS, the underlying etiology remains unclear. Here we report that Mll4 is a critical regulator of the development of growth hormone-releasing hormone (GHRH)-producing neurons in the hypothalamus. The two distinct Mll4 mutant mouse models exhibited dwarfism, accompanied by impairment of developmental programs for GHRH-neurons. Our genome-wide studies revealed that, in the developing hypothalamus, Mll4 collaborates mainly with the transcription factor Nrf1 to trigger the expression of GHRH-neuronal genes. Interestingly, the deficiency of Mll4 resulted in a marked reduction of transcriptionally active histone marks in the embryonic hypothalamus, which was rescued by treatment with the histone deacetylase inhibitor AR-42. Further, AR-42 treatment restored GHRH-neuronal production in Mll4 mutant mice. Together, our results suggest that the dysregulation of MLL4-directed epigenetic control of GHRH-neuronal genes is a substantial contributing factor to dwarfism in human KS. ChIP-seq samples from wild-type hypothalamus were prepared for sequencing according to the Illumina protocol, and sequenced on the Illumina Hiseq 2500. We will then identified that Mll4 and Nrf1 cooperate to regulate the gene transcription in the development of GHRH-neurons in the hypothalamic arcuate nucleus.