A novel splice-acceptor site mutation (IVS13-2A>T) of polycystic kidney disease 1 (PKD1) gene resulting in an RNA processing defect with a 74-nucleotide deletion in exon 14 of the mRNA transcript.

Autosomal dominant polycystic kidney disease (ADPKD) occurs mainly from mutations of polycystic kidney disease 1 (PKD1) gene. A novel mutation of the PKD1 gene due to a nucleotide substitution in splice-acceptor site of IVS13 (AG->TG) was identified by analyses of PKD1-cDNA and genomic DNA. The IVS13-2A>T substitution resulted in an inactivation of this splice site and utilization of cryptic splice acceptor site in exon 14, causing a 74-nucleotide deletion of this exon in the PKD1-mRNA transcript. The abnormal transcript was present ectopically in the patients' lymphocytes. The partial deletion of PKD1-mRNA leads to frameshift translation and introduces a termination signal at codon 1075. The truncated protein with about one quarter of the full-length polycystin-1 is most likely inactive. Thus, the effect of this mutation would be "loss-of-function" type. Allele specific amplification (ASA) was developed to detect the mutation in DNA samples of other family members. The mutation was present in 11 affected but absent in 13 unaffected family members, corresponding to the results of linkage analysis. In addition, it was not observed in DNA samples of 57 unrelated healthy individuals. Hum Mutat 15:115, 2000.

Medical genetics in Thailand.

The development of medical genetics as a discipline in Thailand is relatively recent. It originated through interest in hematological disorders which occur in high frequency, namely the thalassemias and hemoglobinopathies, together with glucose-6-phosphate dehydrogenase deficiency. Although a complete registry of genetic diseases in Thailand has not yet been established, considerable data has accumulated through special interest groups.

Molecular defect of PKD1 gene resulting in abnormal RNA processing in a Thai family.

Autosomal dominant polycystic kidney disease (ADPKD) is a common human autosomal disorder caused mainly by mutations of the PKD1 gene. In analysis of PKD1 transcripts by long RT-PCR and nested PCR procedures, we observed PKD1-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 PKD1 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 PKD1 region. Molecular diagnosis of PKD1 in this family could, therefore, be carried out by genomic DNA amplification to directly detect the PKD1 intronic deletion.

Dyskeratosis congenita: clinical features and genetic aspects. Report of a family and review of the literature.

A large family with dyskeratosis congenita is reported. There were nine affected males, the findings in five of who are reported. We review 46 cases selected from the literature. The cardinal findings of this inherited multisystem disorder are delineated from these 51 cases. The complications of the disease, including opportunistic infection, are described. The parallel is made between dyskeratosis congenita and Fanconi's anaemia. The X-linked transmission of dyskeratosis congenita is confirmed by the family pedigree in this report. From the analysis of the families reported in the literature, there appears to be genetic heterogeneity in this disease. This study in our family indicates absence of close linkage between the Xga locus and the X-linked recessive form of dyskeratosis congenita.

Dyskeratosis congenita: hematologic evaluation of a sibship and review of the literature.

Dyskeratosis congenita is a rare genodermatosis whose hematologic complications include pancytopenia of variable time of onset, a propensity for opportunistic infections, and neoplasia. A family in which the disorder segregated in 3 generations and involved 9 members is reported, and the hematologic data of the 46 previously reported cases are reviewed.

Digital clubbing, hyperhidrosis, acro-osteolysis and osteoporosis. A case resembling pachydermoperiostosis.

We report a Cambodian girl with digital clubbing, profuse hyperhidrosis, and joint and leg pain and swelling. She also had extensive acro-osteolysis of distal phalanges as well as generalized osteoporosis. There was no other affected person in the family, but her parents were first cousins. Although the X-ray changes are unusual, this patient probably represents a case of pachydermoperiostosis, either occurring as a new mutation or inherited as an autosomal recessive syndrome.

Autosomal dominant cerebellar ataxia with dementia: evidence for a fourth disease locus.

The autosomal dominant cerebellar ataxias have proved particularly difficult to classify due to the lack of phenotypic concordance both within and between families. Genetic heterogeneity has been established, and disease loci for spinal cerebellar ataxia have been assigned to chromosomes 6 (SCA1), 12 (SCA2) and 14 (Machado Joseph disease (MJD)). Genetic analysis performed on a large Thai kindred with autosomal dominant cerebellar ataxia, in which frontal lobe signs and dementia are commonly observed in affected family members, exclude linkage to the SCA1, SCA2 and MJD loci. This demonstrates that mutation in at least one further locus can cause spinal cerebellar ataxia, indicating the need for caution in the use of markers for predictive testing or prenatal diagnosis these disorders.