Objective: To analysis variants of COL4A5 gene in two Chinese pedigrees affected with Alport syndrome (AS) and provide prenatal diagnosis for them.
Methods: Two unrelated ethnic Han Chinese pedigrees who had visited the First Affiliated Hospital of Zhengzhou University respectively in September 2018 and January 2020 were selected as the study subjects. Clinical data were collected, and genomic DNA was extracted from peripheral venous blood and amniotic fluid samples for genetic testing. Following next generation sequencing, candidate variants of the COL4A5 gene were verified by Sanger sequencing and bioinformatic analysis. The gender of the fetuses was determined by the presence of sex-determining region on Y (SRY).
Results: Genetic testing revealed that the proband and a fetus from pedigree 1 had both harbored a c.2723G>A (p.Gly908Glu) variant in exon 32 of the COL4A5 gene, whilst the proband and a fetus from pedigree 2 had both harbored a c.3817G>A (p.Gly1273Asp) variant in exon 44 of the COL4A5 gene. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), both variants were classified as likely pathogenic (PP2+PM2_Supporting). Following exclusion of maternal contamination, PCR amplification of the SRY region indicated that both fetuses were males.
Conclusion: The c.2723G>A (p.Gly908Glu) and c.3817G>A (p.Gly1273Asp) variants of the COL4A5 gene probably underlay the AS in the two pedigrees. Detection of the SRY region can reliably identify the fetal sex, which is conducive to the prenatal diagnosis. Above results have also enriched the mutational spectrum of the COL4A5 gene and provided a reference for correlating the genotype and phenotype of the AS.