For a better understanding of the cause of this disorder, we searched for mutations in the PKD2 gene in two PKD2-linked families characterized by different clinical phenotypes.
Refining the localization of the PKD2 locus on chromosome 4q by linkage analysis in Spanish families with autosomal dominant polycystic kidney disease type 2.
Linkage studies have shown that the majority (approximately 85%) of ADPKD cases are due to mutations in PKD1 on chromosome 16p13.3, while mutations in PKD2 on chromosome 4q21-q23 are thought to account for most of the remaining cases.
The PKD1 children had, in comparison with those with PKD2, significantly greater total of renal cysts (13.3 +/- 12.5 vs 3.0 +/- 2.1, P = 0.004), larger kidneys [right/left kidney length 0.89 +/- 1.22 standard deviation score (SDS) vs 0.17 +/- 1.03 SDS, P = 0.045, and 1.19 +/- 1.42 SDS vs 0.12 +/- 1.09 SDS, P = 0.014, successively] and higher ambulatory day-time and night-time systolic BP (day-time/night-time BP index 0.93 +/- 0.10 vs 0.86 +/- 0.05, P = 0.021 and 0.94 +/- 0.07 vs 0.89 +/- 0.04, P = 0.037, successively).
Locus heterogeneity in ADPKD is known to contribute to differences in disease severity, with PKD1-linked families having earlier onset of end-stage renal disease (ESRD) than PKD2-linked families (mean age at ESRD: 56 versus 70, respectively).
ICSNPathway analysis identified 14 candidate causal SNPs, five genes, and two candidate causal pathways, which provided two hypothetical biologic mechanisms: (1) rs2728121 (regulatory region) to polycystic kidney disease 2 (PKD2) to ion transmembrane transporter activity; (2) rs942377, rs3799346, rs3799344, rs2762353, rs13197601, rs3757131, rs1165215, rs1165196 to SLC17A1 to ion transmembrane transporter activity and secondary active transmembrane transporter activity.