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

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.

PRC2 Acts as a Critical Timer That Drives Oligodendrocyte Fate over Astrocyte Identity by Repressing the Notch Pathway.

PRC2 creates the repressive mark histone H3 Lys27 trimethylation. Although PRC2 is involved in various biological processes, its role in glial development remains ambiguous. Here, we show that PRC2 is required for oligodendrocyte (OL) differentiation and myelination, but not for OL precursor formation. PRC2-deficient OL lineage cells differentiate into OL precursors, but they fail to trigger the molecular program for myelination, highlighting that PRC2 is essential for directing the differentiation timing of OL precursors. PRC2 null OL lineage cells aberrantly induce Notch pathway genes and acquire astrocytic features. The repression of the Notch pathway restores the myelination program and inhibits abnormal astrocytic differentiation in the PRC2-deficient OL lineage, indicating that Notch is a major target of PRC2. Altogether, our studies propose a specific action of PRC2 as a novel gatekeeper that determines the glial fate choice and the timing of OL lineage progression and myelination by impinging on the Notch pathway.

Author Correction: Single cell transcriptome analysis of developing arcuate nucleus neurons uncovers their key developmental regulators.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Single cell transcriptome analysis of developing arcuate nucleus neurons uncovers their key developmental regulators.

Despite the crucial physiological processes governed by neurons in the hypothalamic arcuate nucleus (ARC), such as growth, reproduction and energy homeostasis, the developmental pathways and regulators for ARC neurons remain understudied. Our single cell RNA-seq analyses of mouse embryonic ARC revealed many cell type-specific markers for developing ARC neurons. These markers include transcription factors whose expression is enriched in specific neuronal types and often depleted in other closely-related neuronal types, raising the possibility that these transcription factors play important roles in the fate commitment or differentiation of specific ARC neuronal types. We validated this idea with the two transcription factors, Foxp2 enriched for Ghrh-neurons and Sox14 enriched for Kisspeptin-neurons, using Foxp2- and Sox14-deficient mouse models. Taken together, our single cell transcriptome analyses for the developing ARC uncovered a panel of transcription factors that are likely to form a gene regulatory network to orchestrate fate specification and differentiation of ARC neurons.

Inter-individual variability in OCT1 expression and its relationship with OCT1 genotype in liver samples from a Korean population.

To clarify inter-individual variation in the expression of organic cation transporter 1 (OCT1), the levels of OCT1 mRNA and protein from 65 human liver samples were examined by real-time PCR and Western blot analysis and were associated with OCT1 genotypes. The expression levels of OCT1 mRNA and protein in 65 liver samples of Korean origin were not normally distributed and varied by 23.6- and 15.9-fold, respectively. OCT1 mRNA expression was correlated with OCT1 protein expression with a correlation coefficient of 0.641 (p < 0.0001). However, non-genetic factors, such as age, gender, and cholestasis, were not significantly associated with OCT1 expression. When quantitative expression levels were compared in relation to OCT1 promoter SNPs, there was no significant difference in OCT1 expression levels among the -1795 GG, GA, and AA genotypes. Moreover, expression levels of OCT1 were not changed in relation to the -1756 genotypes. Inter-individual variation in OCT1 mRNA and protein expression levels in the liver did not correlate with OCT1 genotypes or non-genetic factors, such as age, gender, and cholestasis. These results suggest that genetic and non-genetic factors may not be a significant contributing factor of variations in OCT1 expression from liver samples of Korean origin.

Genetic polymorphisms in Na+-taurocholate co-transporting polypeptide (NTCP) and ileal apical sodium-dependent bile acid transporter (ASBT) and ethnic comparisons of functional variants of NTCP among Asian populations.

Genetic variants of Na(+)-taurocholate co-transporting polypeptide (NTCP; SLC10A1) and ileal apical sodium-dependent bile acid transporter (ASBT; SLC10A2), which greatly contribute to bile acid homeostasis, were extensively explored in the Korean population and functional variants of NTCP were compared among Asian populations. From direct DNA sequencing, six SNPs were identified in the SLC10A1 gene and 14 SNPs in the SLC10A2 gene. Three of seven coding variants were non-synonymous SNPs: two variants from SLC10A1 (A64T, S267F) and one from SLC10A2 (A171S). No linkage was analysed in the SLC10A1 gene because of low frequencies of genetic variants, and the SLC10A2 gene was composed of two separated linkage disequilibrium blocks contrary to the white population. The stably transfected NTCP-A64T variant showed significantly decreased uptakes of taurocholate and rosuvastatin compared with wild-type NTCP. The decreased taurocholate uptake and increased rosuvastatin uptake were shown in the NTCP-S267F variant. The allele frequencies of these functional variants were 1.0% and 3.1%, respectively, in a Korean population. However, NTCP-A64T was not found in Chinese and Vietnamese subjects. The frequency distribution of NTCP-S267F in Koreans was significantly lower than those in Chinese and Vietnamese populations. Our data suggest that NTCP-A64T and -S267F variants cause substrate-dependent functional change in vitro, and show ethnic difference in their allelic frequencies among Asian populations although the clinical relevance of these variants is remained to be evaluated.