Functional analyses of a seven transmembrane receptor essential for osteoclast differentiation

破骨细胞是骨吸收的多核巨细胞，是骨重建所必需的，由单核前体细胞融合而成。我们先前通过差减的方法分离到了编码七个跨膜受体DC-STAMP的cDNA克隆，它在破骨细胞的发生中起着重要作用(Kukita et al.J.Exp.地中海医院。200：941,2004)。为了揭示DC-STAMP的功能，我们尝试用多种方法和一种在刺激下分化为破骨细胞样细胞的小鼠细胞系来鉴定它的配体。由于斑马鱼草案基因组序列中不包含DC-STAMP基因序列，因此无法进行基因敲除实验。然而，我们通过数据库搜索发现了一个与DC-STAMP基因部分序列同源的新基因。斑马鱼基因组中有3个基因含有这个DC-STAMP基序。根据EST数据，我们克隆了其中一个基因的cdna。该基因含有跨膜区，可能与DC-STAMP一样参与细胞融合。最近，果蝇Snky和线虫SPE-42蛋白被证明具有DC-STAMP基序，尽管与斑马鱼基因的同源关系尚不清楚。这些跨膜蛋白被证明是卵子-精子膜融合所必需的。因此，对带有DC-STAMP基序的斑马鱼基因的分析将为膜融合的机制提供更多的见解。

Osteoclasts are bone-resorbing, multinucleated giant cells that are essential for bone remodeling and are formed through cell fusion of mononuclear precursor cells. By cDNA subtraction, we previously isolated a cDNA clone coding for seven-transmembrane receptor DC-STAMP which plays an important role in ostc oclastogenesis (Kukita et al. J. Exp. Med. 200:941, 2004). In order to reveal the function of DC-STAMP, we have tried to identify its ligand using several methods and a mouse cell line which differentiates into osteoclast-like cells upon stimulation. However, positive results have not been obtained so far.Since the zebrafish draft genome sequence does not contain the DC-STAMP gene sequence, we have not been able to do the knock-down experiment. However, we found by database search a novel gene with sequence homology to a portion of the DC-STAMP gene. There are 3 genes containing this DC-STAMP motif in the zebrafish genome. We isolated a cDNA for one of the genes based on the EST data. This gene contains transmembrane regions and may be involved in the cell fusion like DC-STAMP. Recently Drosophila Snky and C. elegans Spe-42 proteins have been shown to have the DC-STAMP motif, although the orthologous relationships with the zebrafish gene are unclear. These transmembrane proteins are shown to be required in egg-sperm membrane fusion. Therefore analyses of the zebrafish genes with the DC-STAMP motifs will provide additional insights into the mechanisms involved in the membrane fusion.