Cancela M L, Ohresser M C, Reia J P, Viegas C S, Williamson M K, Price P A
Centro de Ciências do Mar, Universidade do Algarve, Faro, Portugal.
J Bone Miner Res. 2001 Sep;16(9):1611-21. doi: 10.1359/jbmr.2001.16.9.1611.
Matrix Gla protein (MGP) belongs to the family of vitamin K-dependent, Gla-containing proteins and in higher vertebrates, is found in the extracellular matrix of mineralized tissues and soft tissues. MGP synthesis is highly regulated at the transcription and posttranscription levels and is now known to be involved in the regulation of extracellular matrix calcification and maintenance of cartilage and soft tissue integrity during growth and development. However, its mode of action at the molecular level remains unknown. Because there is a large degree of conservation between amino acid sequences of shark and human MGP, the function of MGP probably has been conserved throughout evolution. Given the complexity of the mammalian system, the study of MGP in a lower vertebrate might be advantageous to relate the onset of MGP expression with specific events during development. Toward this goal, MGP was purified from Xenopus long bones and its N-terminal amino acid sequence was determined and used to clone the Xenopus MGP complementary DNA (cDNA) by a mixture of reverse-transcription (RT)- and 5'- rapid amplification of cDNA ends (RACE)-polymerase chain reaction (PCR). MGP messenger RNA (mRNA) was present in all tissues analyzed although predominantly expressed in Xenopus bone and heart and its presence was detected early in development at the onset of chondrocranium development and long before the appearance of the first calcified structures and metamorphosis. These results show that in this system, as in mammals, MGP may be required to delay or prevent mineralization of cartilage and soft tissues during the early stages of development and indicate that Xenopus is an adequate model organism to further study MGP function during growth and development.
基质γ-羧基谷氨酸蛋白（MGP）属于维生素K依赖的含γ-羧基谷氨酸蛋白家族，在高等脊椎动物中，存在于矿化组织和软组织的细胞外基质中。MGP的合成在转录和转录后水平受到高度调控，目前已知其参与细胞外基质钙化的调节以及生长发育过程中软骨和软组织完整性的维持。然而，其在分子水平的作用模式仍不清楚。由于鲨鱼和人类MGP的氨基酸序列有很大程度的保守性，MGP的功能可能在整个进化过程中得以保留。鉴于哺乳动物系统的复杂性，在低等脊椎动物中研究MGP可能有利于将MGP表达的起始与发育过程中的特定事件联系起来。为了实现这一目标，从非洲爪蟾的长骨中纯化出MGP，并测定其N端氨基酸序列，然后通过逆转录（RT）和5'- cDNA末端快速扩增（RACE）-聚合酶链反应（PCR）混合物克隆非洲爪蟾MGP互补DNA（cDNA）。在所有分析的组织中均存在MGP信使RNA（mRNA），尽管在非洲爪蟾的骨骼和心脏中表达最为显著，并且在软骨颅发育开始时的发育早期就检测到其存在，远早于第一个钙化结构出现和变态之前。这些结果表明，在这个系统中，与哺乳动物一样，在发育早期可能需要MGP来延迟或防止软骨和软组织的矿化，并且表明非洲爪蟾是进一步研究生长发育过程中MGP功能的合适模式生物。
