Genetic Etilogy of Renal Agenesis in the ACI Rat

描述(由申请人提供)：单侧肾发育不全(URA)是人类常见的发育缺陷，大约每500-1000名活产儿中就有1例发生。患病个体后代中URA频率明显高于一般人群，提示遗传因素参与了URA的发生。ACI大鼠自发出现URA的发生率约为15%。在ACI品系与两个未受影响的大鼠品系哥本哈根(COP)和棕色挪威(BN)之间的一系列遗传杂交中，我们将一个遗传位点定位于大鼠14号染色体(RNO14)，命名为Renag1(肾脏发育不全1)，MAT是这些杂交中URA的主要(如果不是唯一的)决定因素。Renag1的ACI等位基因以不完全显性和不完全穿透的方式传递URA。这项拟议研究的总体目标是充分确定ACI大鼠肾脏发育不全的遗传学和胚胎学基础。具体目标1是精细定位大鼠14号染色体上的Renag1的位置。我们已经将Renag1定位到RNO14上大约15 centiMorgan(Cm)的间隔。为了将Renag1的位置定义为接近0.5厘米的分辨率，我们将生成多达400个受URA影响的(BN X ACI)F2后代，并在Renag1区域以高密度放置的标记上确定这些大鼠的基因类型。标记上BN等位基因的纯合性将排除该标记驻留在Renag1内。目的2明确ACI大鼠肾脏发育不全的胚胎学基础，在交配后的特定时间点处死ACI雌性大鼠，收集发育中的胚胎，进行切片和显微镜检查。了解ACI大鼠何时出现第一个可识别的肾脏发育缺陷，将为何时何地出现与Renag1相关的分子缺陷提供新的和潜在的重要见解。具体目的3是比较Pax2、GDNF和Ret在ACI和BN大鼠肾脏发育过程中的表达。正常的肾脏发育需要Pax2、GDNF和Ret的协调表达。我们推测，在ACI大鼠中，导致URA的Renag1相关缺陷可能导致与BN大鼠相比，Pax2、GDNF和/或Ret在质量和/或数量上的差异。这些基因在肾脏发育过程中的表达将在蛋白和mRNA水平上在ACI和BN大鼠品系中进行评估。完成这些目标后，我们将更好地了解ACI大鼠肾脏发育不全的遗传学基础，并将能够评估该动物模型与人类肾脏发育不全的相关性。

DESCRIPTION (provided by applicant): Unilateral renal agenesis (URA) is a common developmental defect in humans, occurring at a frequency of approximately 1 in 500-1000 live births. The frequency of URA in offspring of affected individuals is markedly higher than in the general population, indicating that genetic factors contribute to the genesis of URA. ACI rats spontaneously exhibit URA at an incidence of approximately 15%. In a series of genetic crosses between the ACI strain and two unaffected rat strains, Copenhagen (COP) and Brown Norway (BN), we have mapped to rat chromosome 14 (RNO14) a genetic locus, designated Renag1 (Renal agenesis 1), mat serves as the major, if not sole, determinant of URA in these crosses. The ACI allele of Renag 1 acts in an incompletely dominant and incompletely penetrant manner to confer URA. The overall goals of this proposed research are to define fully the genetic and embryologic bases of renal agenesis in the ACI rat. Specific Aim 1 is to fine map the location of Renagl on rat chromosome 14. We have mapped Renag1 to an approximate 15 centiMorgan (cM) interval on RNO14. To define the location of Renag1 to a resolution approaching 0.5 cM, we will generate up to 400 URA-affected (BN x ACI)F2 progeny and determine the genotypes of these rats at markers placed at a high density across the Renag1 region. Homozygosity for the BN allele at a marker will exclude that marker from residing within Renag1. Specific Aim 2 is to define the embryologic bases of renal agenesis in the ACI rat ACI females will be sacrificed at defined time points after mating and the developing embryos will be harvested, sectioned and examined microscopically. Knowledge of when the first discernable defect in renal development occurs in the ACI rat will provide novel and potentially important insights into when and where the molecular defect associated with Renag1 is manifested. Specific Aim 3 is to compare expression of Pax2, Gdnf and Ret during renal development in the ACI and BN rat strains. Proper renal development requires coordinated expression of Pax2, Gdnf and Ret. We hypothesize that Renag1-associated defect leading to URA in the ACI rat may result in qualitative and/or quantitative differences in Pax2, Gdnf and/or Ret expression relative to the BN rat. Expression of these genes during renal development will be evaluated at the protein and mRNA levels in both the ACI and BN rat strains. Upon completion of these Aims, we will better understand the genetic bases of renal agenesis in the ACI rat and will be able to assess the relevance of this animal model to renal agenesis in humans.