Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas;
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas;
Am J Physiol Renal Physiol. 2014 Aug 1;307(3):F356-68. doi: 10.1152/ajprenal.00422.2013. Epub 2014 Jun 4.
Autosomal recessive polycystic kidney disease, an inherited disorder characterized by the formation of cysts in renal collecting ducts and biliary dysgenesis, is caused by mutations of the polycystic kidney and hepatic disease 1 (PKHD1) gene. Expression of PKHD1 is tissue specific and developmentally regulated. Here, we show that a 2.0-kb genomic fragment containing the proximal promoter of mouse Pkhd1 directs tissue-specific expression of a lacZ reporter gene in transgenic mice. LacZ is expressed in renal collecting ducts beginning during embryonic development but is not expressed in extrarenal tissues. The Pkhd1 promoter contains a binding site for the transcription factor hepatocyte nuclear factor (HNF)-1β, which is required for activity in transfected cells. Mutation of the HNF-1β-binding site abolishes the expression of the lacZ reporter gene in renal collecting ducts. Transgenes containing the 2.0-kb promoter and 2.7 kb of additional genomic sequence extending downstream to the second exon are expressed in the kidney, intrahepatic bile ducts, and male reproductive tract. This pattern overlaps with the endogenous expression of Pkhd1 and coincides with sites of expression of HNF-1β. We conclude that the proximal 2.0-kb promoter is sufficient for tissue-specific expression of Pkhd1 in renal collecting ducts in vivo and that HNF-1β is required for Pkhd1 promoter activity in collecting ducts. Additional genomic sequences located from exons 1-2 or elsewhere in the gene locus are required for expression in extrarenal tissues.
常染色体隐性多囊肾病是一种遗传性疾病,其特征是肾集合管中的囊肿形成和胆道发育不良,由多囊肾病和肝病 1 (PKHD1) 基因突变引起。PKHD1 的表达具有组织特异性和发育调控性。在这里,我们展示了一个包含近端启动子的 2.0kb 基因组片段 mouse Pkhd1 ,在转基因小鼠中指导 lacZ 报告基因的组织特异性表达。LacZ 在胚胎发育过程中开始在肾集合管中表达,但不在肾脏外组织中表达。Pkhd1 启动子包含转录因子肝细胞核因子 (HNF)-1β的结合位点,该位点对于转染细胞的活性是必需的。HNF-1β 结合位点的突变会使 lacZ 报告基因在肾集合管中的表达消失。包含 2.0kb 启动子和 2.7kb 额外基因组序列的转基因,该序列延伸到第二个外显子下游,在肾脏、肝内胆管和男性生殖道中表达。这种模式与内源性 Pkhd1 的表达重叠,并与 HNF-1β 的表达部位一致。我们得出结论,近端 2.0kb 启动子足以在体内肾集合管中特异性表达 Pkhd1,并且 HNF-1β是集合管中 Pkhd1 启动子活性所必需的。位于外显子 1-2 或基因座其他部位的额外基因组序列对于肾脏外组织的表达是必需的。