The histone H3 lysine-27 demethylase Jmjd3 plays a critical role in specific regulation of Th17 cell differentiation

Interleukin(IL)17-producing T helper(Th17)cells play critical roles in the clearance of extracellular bacteria and fungi as well as the pathogenesis of various autoimmune diseases,such as multiple sclerosis,psoriasis,and ulcerative colitis.Although a global transcriptional regulatory network of Th17 cell differentiation has been mapped recently,the participation of epigenetic modifications in the differentiation process has yet to be elucidated.We demonstrated here that histone H3 lysine-27(H3K27)demethylation,predominantly mediated by the H3K27 demethylase Jmjd3,crucially regulated Th17 cell differentiation.Activation of naı¨ve CD41 T cells immediately induced high expression of Jmjd3.Genetic depletion of Jmjd3 in CD41 T cells specifically impaired Th17 cell differentiation both in vitro and in vivo.Ectopic expression of Jmjd3 largely rescued the impaired differentiation of Th17 cells in vitro in Jmjd3-deficientCD41 T cells.Importantly,Jmjd3-deficient mice were resistant to the induction of experimental autoimmune encephalomyelitis(EAE).Furthermore,inhibition of the H3K27 demethylase activity with the specific inhibitor GSK-J4 dramatically suppressed Th17 cell differentiation in vitro.At the molecular level,Jmjd3 directly bound to and reduced the level of H3K27 trimethylation(me3)at the genomic sites ofRorc,which encodes the masterTh17 transcription factorRorgt,and Th17 cytokine genes such as Il17,Il17f,and Il22.Therefore,our studies established acritical role of Jmjd3-mediatedH3K27demethylation inTh17 cell differentiation andsuggest that Jmjd3 can be a novel therapeutic target for suppressing autoimmune responses.

JMJD3 promotes chondrocyte proliferation and hypertrophy during endochondral bone formation in mice

JMJD3(KDM6B)is an H3K27me3 demethylase and counteracts polycomb-mediated transcription repression.However,the function of JMJD3 in vivo is not well understood.Here we show that JMJD3 is highly expressed in cells of the chondrocyte lineage,especially in prehypertrophic and hypertrophic chondrocytes,during endochondral ossification.Homozygous deletion of Jmjd3 results in severely decreased proliferation and delayed hypertrophy of chondrocytes,and thereby marked retardation of endochondral ossification in mice.Genetically,JMJD3 associates with RUNX2 to promote proliferation and hypertrophy of chondrocytes.Biochemically,JMJD3 associates with and enhances RUNX2 activity by derepression of Runx2 and Ihh transcription throughits H3K27me3 demethylase activity.These results demonstrate that JMJD3 is a key epigenetic regulator in the process of cartilage maturation during endochondral bone formation.