Signaling during mammalian urogenital-anorectal develop

胚胎发育过程中的泌尿生殖-肛门直肠结构畸形是人类常见的出生缺陷。例如，大约每320名男性新生儿中就有一人发生由于尿路上皮细胞未能管状形成的尿道下裂。控制泌尿生殖和肛门直肠结构发育的基因、蛋白质和细胞信号网络还知之甚少。Eph受体酪氨酸激酶家族和它们的膜锚定的ePhin配体是高度保守的分子，在不同的细胞-细胞识别事件中发挥作用，包括神经系统中轴突路径寻找所需的那些事件，神经脊细胞的迁移和血管组织中的那些。提供的初步数据显示，某些Eph受体和肾上腺素基因靶向突变的小鼠表现出尿道下裂和泄殖腔和泄殖腔膜延迟分离，这是泌尿生殖器-肛门直肠发育异常的中线融合特征中的两个常见故障。为了更详细地探索这些初步发现，我们提出了三个具体目标：1)全面表征在Eph和eaffin突变小鼠中观察到的异常的泌尿生殖-肛门发育；2)通过开发体外和体内检测方法，研究和干扰Eph/eaffin信号在泌尿生殖系统中的活动；以及3)通过记录Eph受体和eaffin在人类泌尿生殖-肛门发育中的表达，并通过筛选出生时患有尿道下裂和其他后肠异常的个体，来阐明这些分子在人类泌尿生殖-肛门发育中的重要性。通过结合小鼠分子遗传学、生化分析和临床研究的力量，这一合作研究项目的总体目标是详细描述哺乳动物泌尿生殖-肛门直肠发育过程中使用的细胞-细胞信号转导事件。

Malformations of urogenital-anorectal structures during embryonic development are frequently observed birth defects in humans. For instance, hypospadias, which is due to a failure of the urethral epithelial cells to tubularize, occurs in approximately 1 out of every 320 male births. The genes, proteins, and cell signaling networks that control development of urogenital and anorectal structures are poorly understood. The Eph family of receptor tyrosine kinases and their membrane- anchored ephrin ligands are highly conserved molecules that function in diverse cell-cell recognition events, including those required for axon pathfinding in the nervous system, in migration of neural crest cells and in vascular organization. Preliminary data is provided that show gene-targeted mice mutant for certain Eph receptors and ephrins display hypospadias and delayed septation of the cloaca and cloacal membrane, two common failures in midline fusion characteristic of abnormal urogenital-anorectal development. To explore these preliminary findings in greater detail, three specific aims are proposed: 1) To fully characterize the abnormal urogenital-anorectal development observed in the Eph and ephrin mutant mice; 2) To study and perturb the activities of Eph/ephrin signals in the urogenital system by developing in vitro and in vivo assays; and 3) To delineate the importance of Eph receptors and ephrins in human urogenital-anorectal development by documenting the expression of these molecules and by screening for mutations in ephrin genes in individuals born with hypospadias and other hindgut abnormalities. By combining the powers of mouse molecular genetics, biochemical analysis and clinical-based studies, the overall goal of this collaborative research project is to characterize in detail the cell-cell signal transduction events that are utilized in mammalian urogenital-anorectal development.