Comparative analysis of osr1 function in nephrogenesis

描述(申请人提供)：奇数跳过相关基因1(Osr1)是已知最早在中间中胚层(IM)形成过程中表达的基因，中间中胚层是所有脊椎动物肾脏组织的胚胎组织。在斑马鱼、鸡和小鼠胚胎中，osr1在未分化的IM中表达，并在肾管启动和小管形成时下调。在斑马鱼的osr1中注射吗啉可导致早期肾脏标记的几乎完全丧失，背侧和腹侧标记的扩张，以及类似于Bmp2b突变体漩涡的超收敛延伸表型。OSR1纯合子缺失的小鼠在肾脏形成方面存在严重缺陷。Osr1在鸡胚胎中的错误表达导致肾脏基因在体节中的异位表达。最后，在斑马鱼漩涡突变体中，osr1的表达缺失。根据这些数据，可以推测关于osr1在肾脏形成过程中的功能和调控的几个不相互排斥的假设：(1)osr1在早期胚胎模式中发挥作用，抑制背侧和腹侧模式，并建立一条有能力形成IM的组织带；(2)osr1直接促进早期肾脏基因的表达；以及(3)osr1维持早期谱系中的肾脏前体细胞，并抑制上皮结构的末端分化。这些假说将通过在斑马鱼、鸡和小鼠胚胎中进行osr1功能获得和丧失的实验，通过研究其他肾脏调控基因的错误表达对osr1表达的影响，以及通过检测斑马鱼背腹图案突变体中osr1的表达来验证。通过对三个不同脊椎动物胚胎中osr1的研究，应该会出现一个全面的图像，了解osr1在肾脏形成中的作用，这将大大增加我们对肾脏发育调节的理解。这些研究还可能增加对先天性肾脏异常的了解，并可能产生重要的信息，可用于生成用于治疗目的的肾组织。

DESCRIPTION (provided by applicant): Odd-skipped related 1 (osr1) is the earliest gene known to be expressed during the formation of the intermediate mesoderm (IM), the embryonic tissue which gives rise to all vertebrate kidney tissue. In zebrafish, chicken, and mouse embryos, osr1 is expressed in undifferentiated IM, and is down regulated upon initiation of kidney duct and tubule formation. Injection of morpholinos to osr1 in zebrafish leads to almost complete loss of early kidney markers, expansion of both dorsal and ventral markers, and a hyperconvergent extension phenotype similar to the Bmp2b mutant swirl. Mice with homozygous deletions in osr1 have severe defects in kidney formation. Misexpression of osr1 in chicken embryos results in ectopic expression of kidney genes in the somite. Finally, osr1 expression is lost in zebrafish swirl mutants. From these data, several, not mutually exclusive hypotheses regarding the function and regulation of osr1 during kidney formation can be postulated: (1) osr1 functions during early embryonic patterning to inhibit dorsal and ventral patterning and establish a band of tissue competent to form IM; (2) osr1 directly promotes early kidney gene expression; and (3) osr1 maintains kidney precursor cells in an early lineage compartment and inhibits terminal differentiation of epithelial structures. These hypothesis will be tested by conducting osr1 gain and loss of function experiments in zebrafish, chicken, and mouse embryos, by studying the effects of the misexpression of other kidney regulatory genes on osr1 expression, and by examining osr1 expression in zebrafish dorso-ventral patterning mutants. By studying osr1 in three diverse vertebrate embryos, a comprehensive picture should emerge of the roles of osr1 during kidney formation, which should add significantly to our understanding of the regulation of kidney development. The studies may also lead to increased understanding of congenital kidney anomalies and may yield important information that can be used to generate kidney tissue for therapeutic purposes.