SEARCH FOR NOVEL GENES AND MUTATIONS IN THE RP3 INTERVAL

XLPRA是一种X连锁视网膜变性，相当于犬类的人类RP3。RP3映射到OTC和DXS1110之间的520 kb间隔。RPGR是唯一已知的RP3原因突变的基因，然而大多数RP3患者似乎没有RPGR突变。尚未确定的RPGR突变可能解释了RP3患者的平衡。如果不是，那么位于这个区间的其他基因肯定是原因。XLPRA的两个不同模式，XLPRA1和XLPRA2，与RPGR共分离，两者的RPGR cDNA序列都是正常的。我们的目标是使用XLPRA犬来确定1)RPGR突变是否导致疾病(S)，或2)该区域的新疾病基因是否与视网膜退行性变表型有关？XLPRA致病基因(S)和突变(S)的鉴定将有助于研究这些疾病的分子机制，并为临床前研究和治疗提供新的大型动物模型。我们将首先通过连锁、重组和物理作图来提炼XLPRA1和XLPRA2的最小区域。如果这些区域重叠，我们还将在XLPRA1和XLPRA2代表由同一基因的不同突变引起的疾病的假设下定义它们共同的最小零重组间隔。在这一假设下，组合的家系产生了更大的力量，将搜索区域显著减少到1Mb以下。如果RPGR落在任何一种或两种疾病的零重组区域内，我们将详细检查RPGR基因组序列，以寻找相应疾病的缺失或重排(S)。在没有这种RPGR基因组改变的情况下，将从RPGR特定的犬BAC中对野生型犬RPGR进行完整的基因组测序，然后对XLPRA1和XLPRA2的基因进行基因组测序。如果这些分析排除了RPGR，我们将从XLPRA零重组区间对犬BAC和Cosmids进行最小平铺路径，并评估其中确定的其他基因、EST和保守序列。

XLPRA, an X-linked retinal degeneration, is the canine equivalent of human RP3. RP3 maps to a 520 kb interval between OTC and DXS1110. RPGR is the only gene for which RP3-causal mutations are known, yet most RP3 patients do not appear to have RPGR mutations. RPGR mutations yet to be identified might account for the balance of RP3 patients. If not, then other genes located in this interval must be responsible. Two distinct models of XLPRA, XLPRA1 and XLPRA2, cosegregate with RPGR and, in both, the RPGR cDNA sequence is normal. Our objective is to use XLPRA dogs to determine 1) do RPGR mutations cause the disease(s), or 2) can novel disease genes in this region be incriminated for either retinal degeneration phenotype? Identification of the gene(s) and mutation(s) responsible for XLPRA will allow for studies of the molecular mechanisms of these diseases, and provide new large animal models for pre-clinical studies and therapy. We will first refine the XLPRA1 and XLPRA2 minimal regions by linkage, recombination and physical mapping. If these regions overlap, we will also define their minimum common zero- recombination interval under the hypothesis that XLPRA1 and XLPRA2 represent diseases caused by different mutations in the same gene. Under this hypothesis, the combined pedigrees yields much greater power to reduce the search area to significantly less than 1 Mb. If RPGR falls within the zero recombination region for either or both diseases, we will examine RPGR genomic sequence in detail for deletions or rearrangements in the appropriate disease(s). In the absence of such RPGR genomic alterations, full genomic sequencing of wild type canine RPGR will be done from RPGR-specific canine BACs, followed by genomic sequencing of the gene for both XLPRA1 and XLPRA2. If RPGR is excluded by these analyses for either disease, we will make a minimal tiling path of canine BACs and cosmids from the XLPRA zero-recombination interval, and evaluate other genes, ESTs and conserved sequences identified therein.