Wada Hiroshi
School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8572, Japan.
Zoolog Sci. 2010 Feb;27(2):119-23. doi: 10.2108/zsj.27.119.
The current understanding of the origin and evolution of the genetic cassette for the vertebrate skeletal system is reviewed. Molecular phylogenetic analyses of fibrillar collagen genes, which encode the main component of both cartilage and mineralized bone, suggest that genome duplications in vertebrate ancestors were essential for producing distinct collagen fibers for cartilage and mineralized bone. Several data Indicate co-expression of the ancestral copy of fibrillar collagen with the SoxE and Runx transcription factors. Therefore, the genetic cassette may have already existed in protochordate ancestors, and may operate in the development of the pharyngeal gill skeleton. Accompanied by genome duplications in vertebrate ancestors, this genetic cassette may have also been duplicated and co-opted for cartilage and bone. Subsequently, the genetic cassette for cartilage recruited novel genetic material via domain shuffling. Aggrecan, acquired by means of domain shuffling, performs an essential role in cartilage as a shock absorber. In contrast, the cassette for bone recruited new genetic material produced by tandem duplication of the SPARC/osteonectin genes. Some of the duplicated copies of SPARC/osteonectin became secretory Cabinding phosphoproteins (SCPPs) performing a central role in mineralization by regulating the calcium phosphate concentration. Comparative genome analysis revealed similar molecular evolutionary histories for the genetic cassettes for cartilage and bone, namely duplication of the ancestral genetic cassette and recruitment of novel genetic material.
本文综述了目前对脊椎动物骨骼系统遗传盒起源与进化的理解。对编码软骨和矿化骨主要成分的纤维状胶原蛋白基因进行的分子系统发育分析表明，脊椎动物祖先的基因组复制对于产生用于软骨和矿化骨的不同胶原纤维至关重要。多项数据表明，纤维状胶原蛋白的原始拷贝与SoxE和Runx转录因子共表达。因此，该遗传盒可能在原索动物祖先中就已存在，并可能在咽鳃骨骼的发育中发挥作用。伴随着脊椎动物祖先的基因组复制，这个遗传盒可能也被复制并被用于软骨和骨骼的发育。随后，软骨的遗传盒通过结构域洗牌招募了新的遗传物质。通过结构域洗牌获得的聚集蛋白聚糖在软骨中作为减震器发挥着重要作用。相比之下，骨骼的遗传盒招募了由SPARC/骨连接蛋白基因串联重复产生的新遗传物质。SPARC/骨连接蛋白的一些重复拷贝成为分泌性钙结合磷蛋白（SCPPs），通过调节磷酸钙浓度在矿化过程中发挥核心作用。比较基因组分析揭示了软骨和骨骼遗传盒相似的分子进化历史，即原始遗传盒的复制和新遗传物质的招募。
