Transdifferentiation of vascular smooth muscle cells (VSMC) into chondrogenic cells contributes significantly to vascular calcification during the pathogenesis of atherosclerosis. However, the transcriptional mechanisms that control such phenotypic switch remain unclear. This process is characterized by the induction of Sox9 and Col2a1 genes accompanied by the repression of myocardin (Myocd) and SMC differentiation markers such as SM22, SM α-actin and SM-MHC. Here we explore the regulatory role of SOX9, the master regulator for chondrogenesis, in modulating SMC marker gene expression. qRT-PCR and luciferase assays show that over-expression of SOX9 inhibits SMC gene transcription and promoter activities induced by myocardin, the master regulator of smooth muscle differentiation. Such suppression is independent of the CArG box in the SMC promoters but dependent on myocardin. EMSA assay further shows that SOX9 neither participates in SRF (serum response factor) binding to the CArG box nor interacts with SRF, while co-immunoprecipitation demonstrates an association of SOX9 with myocardin. Conversely, myocardin suppresses SOX9-mediated chondrogenic gene Col2a1 expression. These findings provide the first mechanistic insights into the important regulatory role of SOX9 and myocardin in controlling the transcription program during SMC transdifferentiation into chondrocytes.
Amphioxus belongs to the Cephalochordata, which is the most basal subphylum of the chordates. Despite many studies on the endocrine system of amphioxus, key information about its regulation remains ambiguous. Here we clearly demonstrate the presence of a functional kisspeptin/kisspeptin receptor (Kiss-Kissr) system, which is involved in the regulation of reproduction in amphioxus. Evolutionary analyses revealed large expansion of Kiss and Kissr (gpr54) genes in amphioxus, and they might represent the ancestral type of the Kiss/gpr54 genes in chordates. Amphioxus Kiss was obviously expression at the cerebral vesicle and the Hatschek pit, whereas amphioxus gpr54 messenger RNA (mRNA) was abundantly present in nerve cord, ovary, and testes. Amphioxus GPR54-Like1 (GPR54L-1) was shown to be located on the cell membrane. The synthetic amphioxus Kiss-like (KissL) peptides were capable of activating the amphioxus GPR54L-1 with different potencies, hinting the interaction between Kiss and GPR54. Moreover, the expression of amphioxus gpr54 mRNA was significantly decreased during low or high temperature extremes. Importantly, the injection of amphioxus KissL could cause an elevation of zebrafish blood luteinizing hormone level and induce the expression of amphioxus gpb5, a gene encoding the ancestral type of vertebrate pituitary glycoprotein hormones. Also, the expression levels of BjkissL-2 or Bjgpr54L-1 were downregulated after spermiation or spawning. Collectively, the amphioxus Kiss-Kissr system has a correlation with the regulation of reproduction. Our studies provide insights into the functional roles and evolutionary history of the Kiss-Kissr system, as well as the origin of the vertebrate neuroendocrine axis for controlling reproduction.
The role of bone morphogenetic proteins (BMPs) in regulating adipose has recently become a field of interest. However, the underlying mechanism of this effect has not been elucidated. Here we show that the anti-fat effect of Bmp8a is mediated by promoting fatty acid oxidation and inhibiting adipocyte differentiation. Knocking out the bmp8a gene in zebrafish results in weight gain, fatty liver, and increased fat production. The bmp8a-/- zebrafish exhibits decreased phosphorylation levels of AMPK and ACC in the liver and adipose tissues, indicating reduced fatty acid oxidation. Also, Bmp8a inhibits the differentiation of 3T3-L1 preadipocytes into mature adipocytes by activating the Smad2/3 signaling pathway, in which Smad2/3 binds to the central adipogenic factor PPARγ promoter to inhibit its transcription. In addition, lentivirus-mediated overexpression of Bmp8a in 3T3-L1 cells significantly increases NOD-like receptor, TNF, and NF-κB signaling pathways. Furthermore, NF-κB interacts with PPARγ, blocking PPARγ’s activation of its target gene Fabp4, thereby inhibiting adipocyte differentiation. These data bring a signal bridge between immune regulation and adipocyte differentiation. Collectively, our findings indicate that Bmp8a plays a critical role in regulating lipid metabolism and adipogenesis, potentially providing a therapeutic approach for obesity and its comorbidities.
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