Haploinsufficiency of Pkd2 is associated with increased tubular cell proliferation and interstitial fibrosis in two murine Pkd2 models.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited human kidney disease and is caused by germline mutations in PKD1 (85%) or PKD2 (15%). It has been estimated that around 1% of tubular cells give rise to cysts, and cell hyperproliferation has been noted to be a cardinal feature of cystic epithelium. Nevertheless, it is uncertain whether the increase in proliferative index observed is an early or late feature of the cystic ADPKD kidney. METHODS: Two Pkd2 mouse mutants (WS25 and WS183) have been recently generated as orthologous models of PKD2. To determine the effect of Pkd2 dosage on cell proliferation, cyst formation and renal fibrosis, we studied renal tissue from Pkd2(WS25/WS25) and Pkd2(+/-) mice by histological analysis. We also examined the proliferative index in archival nephrectomy tissue obtained from patients with ADPKD and normal controls. RESULTS: The proliferative index of non-cystic tubules in Pkd2 mutant mice as assessed by proliferating cell nuclear antigen and Ki67-positive nuclei was between 1-2%, values 5-10 times higher than control tissue. Similarly, the proliferative index of non-cystic tubules in human ADPKD kidneys was 40 times higher than corresponding controls. In Pkd2 mutant mice, significant correlations were found between the fibrosis score and the mean cyst area as well as with the proliferative index. Of significance, proliferating tubular cells were uniformly positive for polycystin-2 expression in Pkd2(+/-) kidney. CONCLUSION: These results suggest that an increase in cell proliferation is an early event preceding cyst formation and can result from haploinsufficiency at Pkd2. The possible pathogenic link between tubular cell proliferation, interstitial fibrosis and cyst formation is discussed.     

Genotypes of autosomal dominant polycystic kidney disease in Japanese

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common hereditary disorders. The prevalence of the ADPKD genotype in the Caucasian and Latin populations has been reported. Here, we used linkage analysis to demonstrate the prevalence of the genotype and the correlation between phenotypes and genotypes among 21 Japanese ADPKD families consisting of 96 individuals and including 57 affected members. Six polymorphic markers, each linked to either the polycystic kidney disease 1 (PKD1) or polycystic kidney disease 2 (PKD2) gene, were used for polymerase chain reaction analysis. Seventeen families (81%) showed linkage to PKD1, two families (10%) showed linkage to PKD2, and two families did not show linkage to either PKD1 or PKD2. One of the PKD1-linked families was indicated to have different mutations of PKD1 gene in the same family. PKD2-linked families did not have milder symptoms than PKD1-linked families. Received: October 9, 2001 / Accepted: November 9, 2001     

Transient receptor potential polycystin-2 (TRPP2) regulates motility and intracellular calcium of porcine sperm

Polycystin-2, also known as transient receptor potential polycystin-2 (TRPP2), is a membrane protein that regulates calcium homeostasis in renal epithelial cells. Mutations in PKD2, the gene encoding human TRPP2, cause enlarged cystic kidneys and contribute to polycystic kidney disease (PKD). Male Drosophila melanogaster with mutations in amo, the homolog of PKD2, display a mild decrease in sperm motility but have a drastic reduction in fertility due to failed sperm migration and storage within the female tract. Although TRPP2 has critical roles for Drosophila sperm function, the protein has not been described in mammalian sperm. Herein, we report the localization of TRPP2 in porcine sperm and identify functions of TRPP2 in regulating intracellular Ca²⁺ and motility. Porcine sperm treated with an antibody to TRPP2 in capacitating medium had reduced average path velocity and curvilinear velocity (p < .05). Blocking TRPP2 also increased sperm tail beat-cross frequency (p < .05). After 90 min of capacitation, sperm incubated with TRPP2 antibody had decreased intracellular Ca²⁺ concentration compared to controls (p < .05), consistent with TRPP2 function as a plasma membrane cation channel. This is the first report that mammalian sperm contain TRPP2, which appears to regulate intracellular Ca²⁺ and motility patterns in porcine sperm.     

Nueva mutación asociada a poliquistosis renal autosómica dominante con efecto fundador localizada en la Alpujarra de Granada

ObjectiveTo demonstrate that the variant not described in PKD1 gene c.7292T> A, identified in four families from the Alpujarra in Granada, is the cause of autosomal dominant polycystic kidney disease (ADPKD). This variant consists of a transversion of thymine (T) by adenine (A) that at the level of the Polycystin 1 protein produces a change of leucine (Leu / L) by Glutamine (Gln / Q) in position 2431 (p.Leu2431Gln).MethodSociodemographic and clinical variables were registered using clinical histories, genealogical trees, ultrasounds and genetic analysis to ADPKD and healthy individuals belonging to these families in the context of segregation study.ResultsAll PKD individuals carried the c.7292T>A variant in heterozygosis, whereas healthy ones did not. Among all ADPKD patients, 62.9% were women. ADPKD diagnosis was made at 29.3 ± 15.82 years, after having the first child in 64.8%. The main reasons for diagnosis were family history and hematuria episodes. The onset of renal replacement therapy (RRT) occurred at 55.8 ± 7.62 years (range 44-67), and death at 63 ± 92.2 years (range 48-76), being the cause unknown, cardiovascular and insufficiency kidney the most frequent; the median of renal survival was established at 58.5 ± 0.77 years and the median survival of patients at 67.2 ± 3.54 years. No differences in kidney and patient survivals were observed according to sex. Among deceased patients, 52.2% required RRT and 94.4% suffered from renal failure.ConclusionsThe variant c.7292T>A in PKD1 gene is responsible for the disease, and its distribution in the Alpujarra region of Granada suggests a founder effect. In ADPKD it is necessary to perform segregation studies that help us to reclassify genetic variants, in this case from indeterminate to pathogenic.     

一个多囊肾家系的PKD2基因变异分析及蛋白定位研究

目的检测一个常染色体显性多囊肾家系的基因变异位点,并进行致病性功能验证。方法采集先证者及其家属的外周血标本,提取血液基因组DNA,运用全外显子组测序手段对先证者进行基因变异分析,筛选候选基因变异位点,再用Sanger测序技术对所有家系成员进行验证,并在健康人群中筛查该变异。同时构建PKD2基因的野生型和变异型真核表达载体,转染HEK293T和HeLa细胞,观察蛋白表达及细胞定位情况。结果先证者存在PKD2基因c.2051dupA(p.Tyr684Ter)移码变异,该变异使cDNA序列第2051位碱基A重复,导致终止密码子的形成,产生截短蛋白。免疫荧光实验显示,与野生型相比,变异型蛋白在细胞内的定位发生了改变,这种改变可能由PKD2编码蛋白C端缺失引起。结论PKD2基因c.2051dupA(p.Tyr684Ter)变异可能是该家系患者的致病原因。     

2型常染色体显性遗传性多囊肾病致病基因突变研究

目的建立检测2型常染色体显性遗传性多囊肾病致病基因PKD2突变的方法,分析中国汉族人PKD2基因的突变。方法收集临床确诊的中国汉族人常染色体显性遗传性多囊肾病(ADPKD)患者48例,用试剂盒提取外周血白细胞DNA,利用聚合酶链反应-单链构象多态性分析(PCR-SSCP)技术进行突变分析,对异常条带的PCR产物进行核苷酸序列测定,明确突变位点和方式。结果从48例中成功检测到4种突变,包括1种无义突变、1种移码突变、2种错义突变。第1种为外显子5的1249C→T,417位编码氨基酸发生无义突变。第2种为外显子13的第2401位碱基A缺失,造成编码氨基酸移码突变。第3种突变为外显子1的568G→A,编码氨基酸改变为190Ala→Thr;第4种为外显子5的1168G→A,编码氨基酸改变为390Gly→Ser。结论PCR-SSCP技术可用于PKD2的直接基因诊断,并从本组患者中检测到4种突变,丰富了PKD2基因突变谱,为今后开展ADPKD的直接基因诊断、产前诊断和囊肿前诊断提供了一种有用方法。     

A role for phospholipase D in angiotensin II-induced protein kinase D activation in adrenal glomerulosa cell models

The mineralocorticoid aldosterone plays an important role in regulating blood pressure, with excess causing hypertension and exacerbating cardiovascular disease. Previous studies have indicated a role for both phospholipase D (PLD) and protein kinase D (PKD) in angiotensin II (AngII)-regulated aldosterone production in adrenal glomerulosa cells. Therefore, the relationship between AngII-activated PLD and PKD was determined in two glomerulosa cell models, primary bovine zona glomerulosa (ZG) and HAC15 human adrenocortical carcinoma cells, using two inhibitors, 1-butanol and the reported PLD inhibitor, fluoro-2-indolyl des-chlorohalopemide (FIPI). FIPI was first confirmed to decrease PLD activation in response to AngII in the two glomerulosa cell models. Subsequently, it was shown that both 1-butanol and FIPI inhibited AngII-elicited PKD activation and aldosterone production. These results indicate that PKD is downstream of PLD and suggest that PKD is one of the mechanisms through which PLD promotes aldosterone production in response to AngII in adrenal glomerulosa cells.     

Preimplantation genetic diagnosis for polycystic kidney disease

OBJECTIVE: To use preimplantation genetic diagnosis for achieving a polycystic kidney disease (PKD)-free pregnancy for a couple in which the female partner was affected by PKD but whose PKD1 or PKD2 carrier status was not established. DESIGN: Case report. SETTING: The IVF program of Reproductive Genetics Institute, Chicago, Illinois. PATIENT(S): An at-risk couple with the female partner affected by PKD, whose PKD1 or PKD2 carrier status was not established. INTERVENTION(S): Removal of PB1 and PB2 and testing for three closely linked markers to PKD1 (Kg8, D16S664, and SM7) and four closely linked markers to PKD2 (D4S2922, D4S2458, D4S423, and D4S1557) after standard IVF. MAIN OUTCOME MEASURE(S): Deoxyribonucleic acid analysis of PB1 and PB2 indicating whether corresponding oocytes were PKD1 or PKD2 allele free, for the purpose of transferring only embryos resulting from mutation-free oocytes. RESULT(S): Of 11 oocytes tested by PB1 and PB2 DNA analysis, 7 were predicted to contain PKD1 or PKD2, with the remaining 4 free of both mutations. Three embryos resulting from these oocytes were transferred, yielding a twin pregnancy and the birth of two unaffected children. CONCLUSION(S): This is the first preimplantation genetic diagnosis for PKD, which resulted in the birth of healthy twins confirmed to be free of PKD1 and PKD2. Preimplantation genetic diagnosis based on linked marker analysis provides an alternative for avoiding the pregnancy and birth of children with PKD, even in at-risk couples without exact PKD1 or PKD2 carrier information.