[Prenatal diagnosis and genetic counseling of X-linked Alport syndrome in China].

Objective: Alport syndrome (AS) is a progressive renal disease characterized by hematuria and progressive renal failure. X-linked dominance is the major inheritance form of the syndrome, accounting for almost 80% of the cases, caused by mutations in COL4A5 genes. There is currently no effective treatment that has been shown to favorably affect the outcome of AS, so early diagnosis and even prenatal diagnosis is very important.
Methods: In this study mutation of COL4A5 was detected by amplifying the entire coding sequence mRNA of peripheral blood lymphocytes using nested PCR in two Chinese X-linked dominant Alport syndrome (XLAS) families, then the first prenatal diagnosis of XLAS in China was performed. Mutation analysis of the fetus was performed on both cDNA-based level and DNA-based level of amniocytes. Fetus sex was determined by PCR amplification of SRY as well as karyotypes analysis. Maternal cells contamination was excluded by linkage analysis.
Results: There was a deletion mutation in the proband of the first family, 2696 - 2705 del gtatgatggg in the 32 exon of COL4A5, but the mother did not carry the mutation (de novo). There was a G to A substitution at position 4271 in exon 46 of COL4A5 gene (c.G4271A) in the second family, the mother also carried this mutation. After genetic counselling, only the second family accepted prenatal diagnosis. Both amniocytes cDNA level and amniocytes genomic DNA level based prenatal diagnosis showed that the fetus did not carry the same mutation as the mother. PCR amplification of SRY and karyotypes analysis showed a male fetus. Linkage analysis of X chromosome polymorphic microsatellite markers showed that there was no MCC in amniocytes.
Conclusion: Both cDNA level and DNA level analysis could enhance the accuracy and reliability of prenatal diagnosis. PCR amplification of SRY was faster than karyotypes analysis in the fetal sex determination. Linkage analysis was useful in the detection of maternal cells contamination in amniocytes.