The histone H3-lysine 4-methyltransferase Mll4 regulates the development of growth hormone-releasing hormone-producing neurons in the mouse hypothalamus

Abstract

In humans, inactivating mutations in MLL4, which encodes a histone H3-lysine 4-methyltransferase, lead to Kabuki syndrome (KS). While dwarfism is a cardinal feature of KS, the underlying etiology remains unclear. Here we report that Mll4 regulates the development of growth hormone-releasing hormone (GHRH)-producing neurons in the mouse hypothalamus. Our two Mll4 mutant mouse models exhibit dwarfism phenotype and impairment of the developmental programs for GHRH-neurons. Our ChIP-seq analysis reveals that, in the developing mouse hypothalamus, Mll4 interacts with the transcription factor Nrf1 to trigger the expression of GHRH-neuronal genes. Interestingly, the deficiency of Mll4 results in a marked reduction of histone marks of active transcription, while treatment with the histone deacetylase inhibitor AR-42 rescues the histone mark signature and restores GHRH-neuronal production in Mll4 mutant mice. Our results suggest that the developmental dysregulation of Mll4-directed epigenetic control of transcription plays a role in the development of GHRH-neurons and dwarfism phenotype in mice.

Selective requirement for polycomb repressor complex 2 in the generation of specific hypothalamic neuronal subtypes

“…Similarly, the non-overlapping sets of upstream regulators, Dlx1, Otp, Sim1, Satb2 and Arnt2 for DA neurons ( Biran et al, 2015 ; Orquera et al, 2016 ; Yee et al, 2009 ; Zhang et al, 2021a ), and Dbx1, Ebf2 and Lhx9 for Hcrt neurons ( Dalal et al, 2013 ; De La Herran-Arita et al, 2011 ; Liu et al, 2015 ; Sokolowski et al, 2015 ), also argue against a common origin, as well as against a common genetic pathway. Interestingly, knockout of the H3K4-methyltransferase Mll4 ( Kmt2d ) gene in the developing hypothalamic arcuate nucleus also resulted in highly selective effects on neuronal subtype specification ( Huisman et al, 2021 ).…”

Critical changes in hypothalamic gene networks in response to pancreatic cancer as found by single-cell RNA sequencing

“…Mice were intraperitoneally injected with a ketamine cocktail before performing perfusion with PBS and 4% PFA. ISH was then performed as previously described [ 48 ]. Brains were fixed in PBS + 4% PFA overnight, cryoprotected with sucrose gradients (5%, 10%, 15%, and 30% sucrose), and frozen in OCT blocks, followed by sectioning with cryostat (15 μm per section), and subsequently frozen again.…”

Characterizing the molecular impact ofKMT2Dvariants on the epigenetic and transcriptional landscapes in Kabuki Syndrome

“…It is notable that the reported roles of KMT2D in literature are somewhat inconsistent, as some studies describe KMT2D as a methyltransferase specifically acting on a single mark (e.g., H3K4me3 or H3K4me1), while others describe KMT2D to act on enhancer marks (H3K4me1/2) or all forms of H3K4me. (Fahrner et al 2019;Carosso et al 2019;Huisman et al 2021;Zhang et al 2015;Ortega-Molina et al 2015) Despite the variations and discrepancies in the literature, most studies report greater changes in H3K4me1/2 than H3K4me3. In line with the reported literature, our results show that KMT2D haploinsufficiency has a greater impact on H3K4me1/2, thus enhancer states.…”

“…There have been recent advances in understanding the specific role of KMT2D in the KS disease process. (Fahrner et al 2019; Carosso et al 2019; Huisman et al 2021; Bjornsson et al 2014) Previous studies largely focusing on human blood DNA methylation profiles showed that the DNA methylation profiles differ between KS and unaffected controls. (Aref-Eshghi et al 2017, 2018; Sobreira et al 2017) While differentially methylated regions may be useful as future biomarkers, they are of limited use for elucidating regulatory mechanisms in KS pathology as KMT2D mutations primarily affect histone modifications and only subsequently exert their effect on DNA methylation.…”