H3K36 methyltransferase NSD1 regulates chondrocyte differentiation for skeletal development and fracture repair

Rui Shao,Matthew Greenblatt,Weiguo Zou,Huiling Ouyang,Xi Chen,Lijun Wang,Hongwei Ouyang,Zhong Zhang,Zhan Xu

doi:10.1038/s41413-021-00148-y

Abstract

Chondrocyte differentiation is a critical process for endochondral ossification, which is responsible for long bone development and fracture repair. Considerable progress has been made in understanding the transcriptional control of chondrocyte differentiation; however, epigenetic regulation of chondrocyte differentiation remains to be further studied. NSD1 is a H3K36 (histone H3 at lysine 36) methyltransferase. Here, we showed that mice with Nsd1 deficiency in Prx1+ mesenchymal progenitors but not in Col2+ chondrocytes showed impaired skeletal growth and fracture healing accompanied by decreased chondrogenic differentiation. Via combined RNA sequencing (RNA-seq) and chromatin immunoprecipitation sequencing (ChIP-seq) analysis, we identified sex determining region Y box 9 (Sox9), the key transcription factor of chondrogenic differentiation, as a functional target gene of NSD1. Mechanistically, NSD1 regulates Sox9 expression by modulating H3K36me1 and H3K36me2 levels in the Sox9 promoter region, constituting a novel epigenetic regulatory mechanism of chondrogenesis. Moreover, we found that NSD1 can directly activate the expression of hypoxia-inducible factor 1α (HIF1α), which plays a vital role in chondrogenic differentiation through its regulation of Sox9 expression. Collectively, the results of our study reveal crucial roles of NSD1 in regulating chondrogenic differentiation, skeletal growth, and fracture repair and expand our understanding of the function of epigenetic regulation in chondrogenesis and skeletal biology.

Highlights

Human stature depends mainly on the growth of long bones.Chondrocyte differentiation in the growth plate is a major factor for bone growth and is involved in endochondral ossification, the process that vertebrates use mainly to form the skeleton.[1]
When RNA sequencing (RNA-seq) data were analyzed separately, we found that the levels of Hif1α and its target genes were decreased after Nsd[1] deletion (Figs. 6a and S7A)
In this study, we found that the histone methyltransferase Nuclear receptor binding SET domain-containing protein 1 (NSD1) plays a key role in chondrogenic differentiation

Summary

RESULTS

Explore whether the absence of NSD1 affects fracture repair. X-ray scan results showed that Nsd1f/f;Prx1-Cre mice had less callus. Impaired cartilage development To explore the functions of NSD1 and histone methylation in chondrogenic differentiation and skeletal growth, we first examined the expression levels of H3K36 methyltransferases in Histological assessments showed that cartilage formation was delayed in Nsd1f/f;Prx1-Cre mice (Fig. 3c, d). In Nsd1f/f;Prx1-Cre mice, chondrogenesis lagged behind that in wildformed in the callus showed no difference from that in control mice (Fig. 3n) These findings suggest that Nsd[1] deletion in Prx1+ mesenchymal progenitors leads to impaired fracture healing in mice. In Nsd1f/f;Col2-Cre mice, chondrogenesis and ossification center formation were normal (Fig. 1g–j) These data indicate that NSD1 deletion in Prx1+ mesenchymal. Nsd[1] deletion in mesenchymal progenitors led to skeletal growth decreased in micromasses formed by chondroprogenitor cells from Nsd1f/f;Prx1-Cre mice (Fig. 4c, d). Since Sox[9] is a well-known target gene regulated by HIF1α, these data indicate that NSD1 directly regulates Hif1α and that the regulation of Sox[9] by NSD1 can be achieved indirectly through Hif1α (Fig. 6g)

DISCUSSION

Findings

MATERIALS AND METHODS