Homozygous 5T alleles, clinical presentation and genetic analysis within a family with congenital bilateral absence of the vas deferens

Abstract

Objective: To study the cystic fibrosis transmembrane regulator(CFTR) genotypes and genetic characteristics of a Chinese family with Congenital bilateral absence of vas deferens(CBAVD). Methods: Two 33/29-years-old brothers presented with CBAVD-caused obstructive azoospermia were diagnosed on the basis of scrotal palpation, analysis of semen and ultrasound tests. We extracted their genomic DNA as well as their healthy parents' from the peripheral blood leukocytes. To identify CFTR mutations, each of the 27 exons of the CFTR gene and their flanking splice sites sequences were amplified by polymerase chain reaction(PCR) and subsequently studied with Sanger sequencing. Mutations/variations were identified and compared with the control sequence searched in the NCBI database. Results: Homozygous 5T mutation at the splicing site ahead of exon 10 of the CFTR gene was identified in both brothers in association with 13TG and 12TG alleles(13TG-5T/12TG-5T), one of those was inherited from the mother(13TG-5T/11TG-7T), the other was from the father(12TG-5T/12TG-7T). All of the results above had been excluded the presence of other mutations. Genetic study of this family supports that homozygous 5T mutation is associated with CBAVD. Individuals with homozygous 5T alleles are 20 times more possible to transmit this deleterious variant to the next generation than general population. Conclusions: This family we analysed agrees with the previous conclusion that 5T allele is a deleterious and heritable mutation which could cause CBAVD. Considering better genetic counseling, CFTR gene detection and Preimplantation genetic diagnosis(PGD) are suggested for CBAVD couples who seek for reproductive assistance.