The transcription factor Lc‐Maf participates in Col27a1 regulation during chrondrocyte maturation

Abstract

The transcription factor Lc‐Maf has previously been shown to play an important role in endochondral ossification. In this study, enhancer/reporter assays were used to determine whether Lc‐Maf could regulate cartilage‐specific enhancers from the Col27a1 and Col11a2 genes, which are both expressed in chondrocytes during endochondral ossification. The Col27a1 enhancer was upregulated over 4‐fold, while the Col11a2 enhancer was affected very little by Lc‐Maf. To confirm these reporter assays, rat chondrosarcoma (RCS) cells were transiently transfected with an Lc‐Maf expression plasmid, and quantitative RT‐PCR was performed to measure expression of endogenous Col27a1 and Col11a2 genes. Endogenous Col27a1 was found to be upregulated approximately 5‐fold by Lc‐Maf overexpression, while endogenous Col11a2 was unchanged. Finally, in situ hybridization and immunohistochemistry were performed in embryonic mouse limbs undergoing endochondral ossification. Results demonstrated that Lc‐Maf and Col27a1 mRNAs were most prominent in prehypertrophic and proliferating chondrocytes, and that type XXVII collagen protein was similarly most abundant in prehypertrophic and proliferating chondrocytes in these samples. This work suggests that Lc‐Maf may affect endochondral ossification by participating in the regulation of Col27a1 expression. Supported by NIH grant AR4883 and by the Fulton Family Foundation.