Progressive polycystic renal disease in an aged horse

Identification of porcine polycystic kidney disease 1 (PKD1) gene: molecular cloning, expression profile, and implication in disease model

The polycystic kidney disease 1 (PKD1) gene, which accounts for ~85% of human autosomal dominant polycystic kidney disease (ADPKD) cases, has been extensively studied in human and mouse. Much information about the pathogenesis of and treatments for ADPKD has been gained from the use of mouse models. However, because mouse models pose some limitations, further studies in other model systems are needed to investigate the biological basis of ADPKD. The pig is regarded as an important biomedical model. Thus, we isolated a pig PKD1 homolog and characterized its cDNA sequence, genomic structure, expression profile, alternative splicing, methylation status, protein characteristics, and immunohistochemical features in both neonatal and adult pigs. The pig PKD1 cDNA is 14,209bp long and encodes a 4305-residue polypeptide. The genomic sequence of PKD1 is ~50kb with 46 exons. An alternative splice acceptor site was identified in intron 9. PKD1 is expressed in all tissues tested in both neonatal and adult pigs and exhibits a developmentally regulated expression pattern. Western blotting revealed that the molecular mass of polycystin-1 is ~460kDa, but its expression level is relatively low. Immunohistochemical study of the kidneys shows that polycystin-1 is mainly expressed in the tubular epithelia. Bisulfite methylation analysis of CpG islands in the promoter region does not show a direct correlation between methylation status and expression level among different tissues/cells. The cloning and characterization of pig PKD1 indicates that the pig and human genes are highly similar in length of genomic and cDNA sequences, genomic structure and context, expression patterns, conserved transcription factor binding sites, and the molecular mass of the encoded polycystin-1. These data support our current understanding of PKD1, and suggest that the pig is an ideal candidate for development of an ADPKD disease model.

Polycystic kidney disease in adult Brazilian agoutis (Dasyprocta leporina)

During the last 21 years, 7 adult captive Brazilian agoutis (Dasyprocta leporina) from 4 different zoologic gardens were necropsied and histologically examined at the Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany. All animals had polycystic kidney disease as the major pathologic change. Except in 1 case, no clinical signs were recognized prior to death. The animals had macroscopic bilateral alterations of the kidneys ranging from granulated surfaces to severe polycystic changes. Microscopic examination revealed multifocal to generalized, moderate to severe cystic dilatations of Bowman's capsules and renal tubules, moderate mesangial and capsular proliferation of the renal corpuscles, mild interstitial fibrosis, and mild to moderate interstitial lympho-plasmacytic infiltrations. Little information is known about the genetic relationships of these animals, but breeding practice indicates a high possibility of inbred agouti zoo populations in Germany. This is the first report on polycystic kidney disease in Brazilian agoutis with possible genetic background.