Martinek Nathalie, Zou Rong, Berg Marina, Sodek Jaro, Ringuette Maurice
Department of Zoology, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada M5S 3G5.
Dev Genes Evol. 2002 Apr;212(3):124-33. doi: 10.1007/s00427-002-0220-9. Epub 2002 Mar 13.
SPARC (secreted protein, acidic, rich in cysteine, also called BM40 and osteonectin) is a multifunctional calcium-binding glycoprotein whose modular organization has been highly conserved between invertebrates and vertebrates, indicating a conservation of function during metazoan evolution. Genome analysis has revealed a single copy of the DrosophilaSPARC ( dSPARC) gene. As a first step towards investigating the function of SPARC in Drosophila, we examined its spatiotemporal distribution during development. During embryogenesis, dSPARC mRNA transcripts are restricted to mesoderm derivatives, hemocytes, and the fat body. Immunostaining with anti- DrosophilaSPARC antibodies indicates that dSPARC secreted by the hemocytes and fat body cells is concentrated in basal laminae surrounding internal organs. During oogenesis, dSPARC transcripts are restricted to the somatic cells of the germarium and follicles. Consistent with embryonic development, the resultant protein is concentrated in basal laminae. Mutations in type IV collagen are associated with a dramatic decrease in dSPARC protein immunostaining in hemocytes. The data suggest that the production and assembly of dSPARC in the basal lamina is dependent on type IV collagen, and raise the possibility that dSPARC and type IV collagen interactions are a prerequisite to the assembly and structural integrity of basal laminae in Drosophila.
SPARC（分泌性蛋白质，酸性，富含半胱氨酸，也称为BM40和骨连接蛋白）是一种多功能钙结合糖蛋白，其模块结构在无脊椎动物和脊椎动物之间高度保守，这表明后生动物进化过程中功能的保守性。基因组分析显示果蝇SPARC（dSPARC）基因只有一个拷贝。作为研究SPARC在果蝇中功能的第一步，我们研究了其在发育过程中的时空分布。在胚胎发生过程中，dSPARC mRNA转录本局限于中胚层衍生物、血细胞和脂肪体。用抗果蝇SPARC抗体进行免疫染色表明，血细胞和脂肪体细胞分泌的dSPARC集中在内脏周围的基膜中。在卵子发生过程中，dSPARC转录本局限于生殖腺和卵泡的体细胞。与胚胎发育一致，产生的蛋白质集中在基膜中。IV型胶原的突变与血细胞中dSPARC蛋白免疫染色的显著降低有关。数据表明，基膜中dSPARC的产生和组装依赖于IV型胶原，并增加了dSPARC与IV型胶原相互作用是果蝇基膜组装和结构完整性的先决条件的可能性。
