The transcription factor Lc-Maf participates in Col27a1 regulation during chondrocyte maturation.
The transcription factor Lc-Maf, which is a splice variant of c-Maf, is expressed in cartilage undergoing endochondral ossification and participates in the regulation of type II collagen through a cartilage-specific Col2a1 enhancer element. Type XXVII and type XI collagens are also expressed in cartilage during endochondral ossification, and so enhancer/reporter assays were used to determine whether Lc-Maf could regulate cartilage-specific enhancers from the Col27a1 and Col11a2 genes. The Col27a1 enhancer was upregulated over 4-fold by Lc-Maf, while the Col11a2 enhancer was downregulated slightly. To confirm the results of these reporter assays, rat chondrosarcoma (RCS) cells were transiently transfected with an Lc-Maf expression plasmid, and quantitative RT-PCR was performed to measure the expression of endogenous Col27a1 and Col11a2 genes. Endogenous Col27a1 was upregulated 6-fold by Lc-Maf overexpression, while endogenous Col11a2 was unchanged. Finally, in situ hybridization and immunohistochemistry were performed in the radius and ulna of embryonic day 17 mouse forelimbs undergoing endochondral ossification. Results demonstrated that Lc-Maf and Col27a1 mRNAs are coexpressed in proliferating and prehypertrophic regions, as would be predicted if Lc-Maf regulates Col27a1 expression. Type XXVII collagen protein was also most abundant in prehypertrophic and proliferating chondrocytes. Others have shown that mice that are null for Lc-Maf and c-Maf have expanded hypertrophic regions with reduced ossification and delayed vascularization. Separate studies have indicated that Col27a1 may serve as a scaffold for ossification and vascularization. The work presented here suggests that Lc-Maf may affect the process of endochondral ossification by participating in the regulation of Col27a1 expression.
Department of Microbiology and Molecular Biology, Brigham Young University, 591 WIDB, Provo, UT 84602, USA.
Jaime L
JL
Mayo
Devin N
DN
Holden
Jeffery R
JR
Barrow
Laura C
LC
Bridgewater
D000818:Animals; D001483:Base Sequence; D001842:Bone and Bones / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D019902:Chondrocytes / Q000166:cytology / Q000502:physiology*; D024161:Collagen Type XI / Q000235:genetics / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D024022:Fibrillar Collagens / Q000235:genetics / Q000378:metabolism*; D005552:Forelimb / Q000033:anatomy & histology / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D051379:Mice; D008969:Molecular Sequence Data; D010012:Osteogenesis / Q000502:physiology*; D011401:Promoter Regions, Genetic; D051257:Proto-Oncogene Proteins c-maf / Q000235:genetics / Q000378:metabolism*; D051381:Rats
C497046:Col11a2 protein, mouse; C480972:Col27a1 protein, mouse; D024161:Collagen Type XI; D024022:Fibrillar Collagens; C495608:Maf protein, mouse; D051257:Proto-Oncogene Proteins c-maf