Molecular Defect of PK.Dl Gene Resulting in Abnormal RNA Processing in a Thai Family
NANYAWAN RUNGROJ,M.Sc.*, KRIENGSAK VAREESANGTHIP, M.D., Ph.D.**, PRAPON WILAIRAT, Ph.D.****, WANNA THONGNOPPAKHUN, Ph.D.*, CHINTANA SIRINAVIN, M.D.*,***, PA-THAI YENCHITSOMANUS, Ph.D.*,*****
Affiliation : * Division of Molecular Genetics, Department of Research and Development, Faculty of Medicine Siriraj Hospital, ** Division of Nephrology, Department of Medicine, Faculty of Medicine Siriraj Hospital, *** Division of Medical Genetics, Department of Medicine, Faculty of Medicine Siriraj Hospital, **** Department of Biochemistry, Faculty of Science, ***** Division of Medical Molecuiar Biology, Department of Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
Autosomal dominant polycystic kidney disease (ADPKD) is a common human autosomal disorder caused mainly by mutations of the PKDJ gene. In analysis of PKDJ transcripts by long RT-PCR and nested PCR procedures, we observed PKDJ-cDNA fragments from three ADPKD siblings from the same family with a size approximately 250 base pairs (bp) shorter than normal. Further investigations showed that the PKDJ transcripts from these patients had been abnormally processed, the nucleotide sequence of exon 43 containing 291 nt was missing from the transcripts, which would result in an abnormal polycystin-1 with an in-frame deletion of 97 amino acids. This splicing defect did not result from a mutation that disrupted the splice donor or acceptor sites adjacent to exon 43 or the branch sites in flanking introns but was most likely due to 20-bp deletion observed in intron 43. The intronic deletion was present in 8 affected members but absent in 11 unaffected members, corresponding with the results of genetic linkage analysis using 5 polymorphic markers in the PKDJ region. Molecular diagnosis of PKDJ in this family could, therefore, be carried out by genomic DNA amplification to directly detect the PKDJ intronic deletion.
Keywords : Polycystic Kidney Disease 1 (PKDJ), PKDJ Mutation, Intronic Deletion, Exon Skipping, RNA Processing Defect, Abnormal Splicing
