A family with autosomal dominant polycystic kidney disease not linked to chromosome 16p13.3

Jeffery S, Saggar-Malik AK, Morgan S, MacGregor GA. A family with autosomal dominant polycystic kidney disease not linked to chromosome 16p13.3.
Clin Genet 1993: 44: 173–176. © Munksgaard, 1993
A family of Sicilian origin with autosomal dominant polycystic kidney disease (APKD) has been shown to be unlinked to chromosome 16 markers. LOD scores for the polymorphic markers 3'HVR and SM7 flanking the PKD 1 locus, were -1.4 and -2.33 respectively, and θ_max was 0.5 for each marker. The clinical phenotype of this family is consistent with that of the other non-linked families with APKD reported in the literature, all outside the United Kingdom, which have a milder progression than those linked to 16p13.3. Assuming that a clinic population represents the most severe forms of a disease and non PKD-1 is a less aggressive phenotype, the degree of genetic heterogeneity for APKD in the population may well be much greater than at present suggested.     

Genes homologous to the autosomal dominant polycystic kidney disease genes (PKD1 and PKD2)

Autosomal Dominant Polycystic Kidney Disease (ADPKD), a common inherited disease leading to progressive renal failure, can be caused by a mutation in either the PKD1 or PKD2 gene. Both genes encode for putative transmembrane proteins, polycystin-1 and polycystin-2, which show significant homology to each other and are believed to interact at their carboxy termini. To identify genes that code for related proteins we searched for homologous sequences in several databases and identified one partial cDNA and two genomic sequences with significant homology to both polycystin-1 and - 2. Further analysis revealed one novel gene, PKD2L2, located on chromosome band 5q31, and two recently described genes, PKD2L and PKDREJ, located on chromosome bands 10q31 and 22q13.3, respectively. PKD2L2 and PKD2L, which encode proteins of 613 and 805 amino acids, are approximately 65% similar to polycystin-2. The third gene, PKDREJ, encodes a putative 2253 amino acid protein and shows about 35% similarity to both polycystin-1 and polycystin-2. For all the genes expression was found in testis. Additional expression of PKD2L was observed in retina, brain, liver and spleen by RT-PCR. Analyses of five ADPKD families without clear linkage to either the PKD1 or PKD2 locus showed no linkage to any of the novel loci, excluding these genes as the cause of ADPKD in these families. Although these genes may not be involved in renal cystic diseases, their striking homology to PKD2 and PKD1 implies similar roles and may contribute to elucidating the function of both polycystin-1 and polycystin-2.     

一个可能与PKD2基因连锁的常染色体显性多囊肾病家系

目的 研究常染色体显性多囊肾病（autosomal dominant polycystic kidney disease,ADPKD）在中国人中的遗传异质性。方法 采用聚合酶链反应 （polymerase chain reaction, PCR）、非变性聚丙烯酰胺凝胶电泳,检测了1个ADPKD家系各成员中与PKD1基因连锁的4种和与PKD2连锁的4种微卫星标记的基因分型。然后以软件辅助构建单倍型,并推测疾病单倍型。结果 发现该ADPKD家系中,与PKD1紧密连锁的4个微卫星KG8、SM6、CW4和CW2是有信息的;与PKD2基因紧密连锁的3种微卫星DNAIMS1563、D4S414和D4S423是有信息的。推定的单倍型提示,在这个家系中疾病可能与PKD2连锁,而不与PKD1连锁。结论 在此家系中,受累成员间存在表型异质性,并且有一个早发的儿童患者。与PKD2连锁的家系较少,这个家系的报道表明中国人中存在ADPKD的遗传异质性,PKD2的异常也可能会引起中国人ADPKD的发生。另外,发现有遗传早现现象存在,且疾病通过母亲传递。这提示在与PKD1不连锁的家系中后代可能早发病。     

Multipoint mapping of adult onset polycystic kidney disease (PKD1) on chromosome 16.

Analysis of genetic linkage data in 33 adult onset polycystic kidney (ADPKD) families was carried out using probes for the D16S85, D16S84, and D16S94 loci. The data set of 33 families shows no evidence of genetic heterogeneity since one unlinked family was previously excluded. Two point linkage analysis showed maximum likelihood values of the recombination fraction of 0.07 for ADPKD and D16S85 (lod score 18.78), 0.02 for ADPKD and D16S84 (lod score 7.55), and 0.00 for ADPKD and D16S94 (lod score 6.73). Multipoint analysis showed a maximum likelihood order of tel-D16S85-0.06-D16S84-0.02-(PKD1, D16S94)-cen with a multipoint lod score of 32.16. Analysis of rare recombinants lying close to PKD1 gave results consistent with this order.     

常染色体显性成人多囊肾病两家系PKD1、PKD2基因的突变鉴定

目的 鉴定两个常染色体显性成人多囊肾病家系的致病突变.方法 采用酚氯仿法提取家系成员及无亲缘关系的100名健康对照个体的外周血白细胞DNA,PCR扩增先证者致病基因PKD1、PKD2的所有外显子序列及其侧翼内含子剪切区域,直接测序确定DNA序列的变异.通过家系和正常对照的比较分析,对检测到的变异是否与疾病相关进行了初步探讨.结果 在两个家系中共检测到5个序列变异:PKD1:c.2469G＞A,PKD1:c.5014_5015 delAG,PKD1:c.10529C＞T,PKD2:c.568G＞A和PKD2:c.2020-1_2020 delAG.其中PKD1:c.2469G＞A和PKD2:c.2020-1_2020 delAG为新发现的变异.此外,检测到的移码突变和剪切突变未见于家系中健康成员及无亲缘关系的正常对照.结论 PKD1:c.5014_5015 delAG和PKD2:c.2020-1_2020 delAG分别为家系A和B的致病突变,且PKD2:c.2020-1_2020 delAG为先证者新发生的突变.     

Mutational analysis of PKD1 gene in a Chinese family with autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a hereditary disease and common renal disease. Mutations of PKD genes are responsible for this disease. We analyzed a large Chinese family with ADPKD using Sanger sequencing to identify the mutation responsible for this disease. The family comprised 27 individuals including 10 ADPKD patients. These ADPKD patients had severe renal disease and most of them died very young. We analyzed 6 survival patients gene and found they all had C10529T mutation in exon 35 of PKD1 gene. We did not found gene mutation in any unaffected relatives or 300 unrelated controls. These findings suggested that the C10529T mutation in PKD1 gene might be the pathogenic mutation responsible for the disease in this family.     

Autosomal dominant polycystic kidney disease (ADPKD, MIM 173900, PKD1 and PKD2 genes, protein products known as polycystin-1 and polycystin-2)

Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited nephropathy affecting over 1:1000 of the worldwide population. It is a systemic condition with frequent hepatic and cardiovascular manifestations in addition to the progressive development of renal cysts that eventually result in loss of renal function in the majority of affected individuals. The diagnosis of ADPKD is typically made using renal imaging despite the identification of mutations in PKD1 and PKD2 that account for virtually all cases. Mutations in PKD1 are associated with more severe clinical disease and earlier onset of renal failure. Most PKD gene mutations are loss of function and a 'two-hit' mechanism has been demonstrated underlying focal cyst formation. The protein products of the PKD genes, the polycystins, form a calcium-permeable ion channel complex that regulates the cell cycle and the function of the renal primary cilium. Abnormal cilial function is now thought to be the primary defect in several types of PKD including autosomal recessive polycystic kidney disease and represents a novel and exciting mechanism underlying a range of human diseases.     

Co-inheritance of pathogenic variants in PKD1 and PKD2 genes presenting as severe antenatal phenotype of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is caused by pathogenic variants in either PKD1 or PKD2 genes. Disease severity is dependent on various factors including the presence of modifier genes. We describe a family with recurrent foetal presentation of ADPKD due to co-inheritance of pathogenic variants in both PKD1 [c.3860T > C; p.(Leu1287Pro)] and PKD2 [(c.1000C > A; p.(Pro334Thr)] genes. Familial segregation studies revealed the mother and the father to be heterozygous for the same variants in the PKD1 and PKD2 genes, respectively, as found in the foetus. Renal ultrasonography detected evidence of cystic disease in the mother and two of her family members. No cysts were detected in the father, however the paternal grandfather died of renal cystic disease. The absence of disease in the father can be explained by the phenomenon of incomplete penetrance, or Knudson's two-hit hypothesis of cystogenesis in the grandfather. This case underscores the importance of sequencing PKD2 gene even in the presence of a familial PKD1 variant, as well as genetic testing of the cysts for evidence of the second hit.     

Apparent normalisation of fetal renal size in autosomal dominant polycystic kidney disease (PKD1)

We present a family with adult onset autosomal dominant polycystic kidney disease (ADPKD) in two generations, linked to the PKD1 locus and with paternal transmission to the fetus. The fetus carried the PKD1 haplotype and was, therefore a gene carrier. Progressive hyperechogenic renal enlargement, but no cysts, was documented by serial fetal ultrasounds at 21, 23 and 34 weeks of gestation. Surprisingly, the newborn renal scan showed normal sized kidneys with apparently normal corticomedullary differentiation. However, at 11 months of age, the evolution of cysts in one kidney, and then in the other kidney at 20 months, was documented by ultrasound in the absence of clinical symptoms or signs. The observed normalisation of fetal renal ultrasound appearances at birth has not previously been described in fetuses presenting with PKD1.     

A comprehensive search for mutations in the PKD1 and PKD2 in Japanese subjects with autosomal dominant polycystic kidney disease

To elucidate the genotypic and phenotypic characteristics of autosomal dominant polycystic kidney disease (ADPKD) in Japanese populations, we performed a comprehensive search for mutations in PKD1 and PKD2 in 180 Japanese ADPKD patients from 161 unrelated families. We identified 112 (89 PKD1 and 23 PKD2) mutations within 135 families. Patients with PKD2 mutations account for 23.6% of all Japanese ADPKD families in this study. Seventy‐five out of the 112 mutations have not been reported previously. The estimated glomerular filtration rate (eGFR) decline was significantly faster in patients with PKD1 mutations than in those with PKD2 mutations (?3.25 and ?2.08 ml min^?1 year^?1 for PKD1 and PKD2, respectively, p < 0.01). These results indicate that mutations within PKD1 and PKD2 can be linked to most of the cases of Japanese ADPKD, and the renal function decline was faster in patients with PKD1 mutations than in those with PKD2 mutations also in the Japanese ADPKD. We also found that PKD2 mutations were more frequent in Japanese ADPKD than that in European or American ADPKD.     

Autosomal dominant polycystic kidney disease: comprehensive mutation analysis of PKD1 and PKD2 in 700 unrelated patients

Autosomal dominant polycystic kidney disease (ADPKD), the most common inherited kidney disorder, is caused by mutations in PKD1 or PKD2. The molecular diagnosis of ADPKD is complicated by extensive allelic heterogeneity and particularly by the presence of six highly homologous sequences of PKD1 exons 1-33. Here, we screened PKD1 and PKD2 for both conventional mutations and gross genomic rearrangements in up to 700 unrelated ADPKD patients--the largest patient cohort to date--by means of direct sequencing, followed by quantitative fluorescent multiplex polymerase chain reaction or array-comparative genomic hybridization. This resulted in the identification of the largest number of new pathogenic mutations (n = 351) in a single publication, expanded the spectrum of known ADPKD pathogenic mutations by 41.8% for PKD1 and by 23.8% for PKD2, and provided new insights into several issues, such as the population-dependent distribution of recurrent mutations compared with founder mutations and the relative paucity of pathogenic missense mutations in the PKD2 gene. Our study, together with others, highlights the importance of developing novel approaches for both mutation detection and functional validation of nondefinite pathogenic mutations to increase the diagnostic value of molecular testing for ADPKD.     

Presymptomatic molecular diagnosis of autosomal dominant polycystic kidney disease using PKD1-and PKD2-linked markers in Cypriot families

Autosomal dominant polycystic kidney disease (ADPKD), is a heterogeneous disorder, primarily characterized by the formation of cysts in the kidneys, and the late development in life of progressive chronic kidney failure. Three genes are implicated in causing ADPKD. One on chromosome 16, PKD1, accounts for 85–90% of all cases, and the PKD2 gene on chromosome 4 accounts for the remainder. A very rare third locus is still of unknown location. We used PKD1-and PKD2-linked polymorphic markers to make the diagnosis of ADPKD in young presymptomatic members in affected families. We showed that in young members of families where clinical diagnosis cannot be definitively established, molecular linkage analysis can assist clinicians in the diagnosis. In one family a 24-year old had one cyst on the right kidney; however, molecular analysis showed clearly that he had inherited the normal haplotype. In another family, in one part of the pedigree there was co-inheritance of the disease with a PKD1-linked haplotype which originated in a non-affected 78-year-old father. Analysis with PKD2-linked markers excluded this locus. The data can be explained in one of two ways. Either this family phenotype is linked to a third locus, or the proband was the first affected person, most probably because of a novel mutation in one of her father's chromosomes. In conclusion, the combined use of markers around the PKD1 and the PKD2 locus provides more definitive answers in cases where presymptomatic diagnosis is requested by concerned families.