Heterogenous spectrum of CFTR gene mutations in Indian patients with congenital absence of vas deferens (original) (raw)
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Molecular human reproduction, 2014
Cystic fibrosis (CF) is usually considered a rare disease in the Indian population. Two studies have reported on the frequency of cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations in Indian males with congenital absence of the vas deferens (CAVD), however, data on the spectrum of CFTR gene mutations are still lacking. Therefore, the present study was designed to identify the spectrum of CFTR gene mutations as well as to investigate an association of CF genetic modifiers in the penetrance of CAVD in infertile Indian men. A total of 60 consecutive infertile males with a diagnosis of CAVD were subjected to CFTR gene analysis which revealed 13 different CFTR gene mutations and 1 intronic variant that led to aberrant splicing. p.Phe508del (n = 16) and p.Arg117His (n = 4) were among the most common severe forms of CFTR mutations identified. The IVS8-T5 allele, which is considered as a mild form of CFTR mutation, was found with an allelic frequency of 28.3%. Eight n...
Human Reproduction, 2005
BACKGROUND: Clinically affected cystic fibrosis (CF) patients present a spectrum of genital phenotypes ranging from normal fertility to moderately impaired spermatogenesis and congenital bilateral absence of vas deferens (CBAVD). Little is known about the CF incidence in the Taiwanese population. It has been shown that the CBAVD in men without clinical evidence of CF is associated with a high incidence of mutated CFTR (cystic fibrosis transmembrane conductance regulator) alleles. In order to understand the involvement of the CFTR gene in the aetiology of Asian/Taiwanese male infertility, we screened the entirety of the CFTR gene in 36 infertile males with CBAVD. METHODS: Temporal temperature gradient gel electrophoresis (TTGE) followed by direct DNA sequencing was used. RESULTS: Five mutations, p.V201M, p.N287K, c.-8G > C (125G > C), p.M469I and p.S895N, were found in five of the patients. p.N287K occurred in the first transmembrane-spanning domain, p.M469I in the first ATP-binding domain and p.S895N in the second transmembrane-spanning domain, were novel. In addition, seven homozygous and seven heterozygous 5T alleles in the intron 8 poly(T) tract were found. The overall frequency of CFTR mutant alleles in Taiwanese CBAVD males was 26 out of 72 5 36%. This finding was lower than the published frequency of CFTR mutations in other ethnic CBAVD patients (ranging from 50 to 74%). The frequency of p.M470V in Taiwanese CBAVD patients is not significantly different from that in the general population (P 5 0.12). CONCLUSIONS: The results of this study add to the short list of Taiwanese/Asian CFTR mutations. Unlike Caucasian patients, the CFTR mutations cannot account for the majority of Taiwanese CBAVD. This is consistent with the low incidence of CF in the Asian/Taiwanese population. Furthermore, the mutation spectrum of CFTR in CBAVD patients does not overlap with the Caucasian CFTR mutation spectrum.
2004
BACKGROUND: Cystic fibrosis conductance transmembrane regulator (CFTR) gene mutations and IVS8 poly(T) variants in Portuguese patients with bilateral (CBAVD) and unilateral (CUAVD) congenital absence of the vas deferens remain to be evaluated. METHODS: Patient screening was carried out by PCR, denaturing gradient gel electrophoresis and DNA sequencing. RESULTS: CFTR mutations were found in 18 out of 31 (58.1%) CBAVD and in three of four (75%) CUAVD patients. The most frequent mutations were F508del and R334W in CBAVD and G542X in CUAVD, with the allelic frequencies of R334W (6.5%) and G542X (25%) being particular to the Portuguese population. The 5T allelic frequency was 3.5% in the fertile male population, 25% in CUAVD and 27.4% in CBAVD patients. The combined frequency of mutations (CFTR 1 5T) was increased in CBAVD to 22 out of 31 (71%). The frequency of CFTR mutations was compared with that of patients with secondary obstructive azoospermia (OAZ; one out of 16, 6.3%) and non-obstructive azoospermia (NOAZ; two out of 22, 9.1%) with conserved spermatogenesis, which were similar to the general population. However, whereas the 5T allelic frequency in OAZ was similar to that of the general population (3.1%), it was increased in NOAZ cases (14.3%). CONCLUSIONS: Data confirm that CFTR 1 5T mutations represent the most common genetic abnormality in CAVD, and suggest that cases of NOAZ may be associated with the 5T allele.
Molecular Human Reproduction, 2006
Congenital bilateral absence of the vas deferens (CBAVD) is a frequent cause of obstructive azoospermia. Nearly 75% of men with CBAVD have at least one detectable common cystic fibrosis (CF) transmembrane conductance regulator (CFTR) mutation. To study the involvement of CFTR mutations in the Iranian population with presumed low CF frequency, we analysed 112 Iranian CBAVD males. Three Iranian CBAVD males with no clinical CF phenotype indicated by a normal karyotype, normal pancreatic function and sweat chloride concentration and no Y chromosome microdeletions were studied for CFTR mutations, IVS8-5T mutations and M470V exon 10 missense polymorphism. The entire coding sequence of each gene was analysed using a combination of the denaturing gradient-gel electrophoresis or by single-strand conformation analysis and direct DNA sequencing. Also, 52 fertile males were tested as controls to rule out polymorphism. This approach allowed us to detect one novel nonsense mutation (K536X) in the nucleotide-binding domain 1 (NBD1) region and two novel missense mutations (Y122H and T338A) in the M2 and M6 regions of CFTR gene in our studied population, which were not reported previously. Also, the conservation of changed nucleotide and amino acid in mutated regions was analysed by aligning with nine different species. K536X nonsense mutation (transversion) was found in the first NBD (NBF1), which plays an important regulatory role in CFTR function. It was, therefore, considered as a severe allele responsible for elevated sweat chloride levels and obstructive azoospermia. Because Y122H and T338A mutations were compound heterozygote with the IVS8-5T, it is difficult to judge the severity of these mutations and their role in the CBAVD phenotype. Figure 4. cDNA sequence alignment results of nine different species for exons 4, 7 and 11 find conserved mutated nucleotides in different species.
Asian Journal of Andrology, 2010
Congenital bilateral absence of vas deferens (CBAVD) is a manifestation of the mildest form of cystic fibrosis (CF) and is characterized by obstructive azoospermia in otherwise healthy patients. Owing to the availability of assisted reproductive technology, CBAVD patients can father children. These fathers are at risk of transmitting a mutated allele of the CF transmembrane conductance regulator (CFTR) gene, responsible for CF, to their offspring. The identification of mutations in both CFTR alleles in CBAVD patients is a crucial requirement for calculating the risk of producing a child with full-blown CF if the female partner is a healthy CF carrier. However, in the majority of CBAVD patients, conventional mutation screening is not able to detect mutations in both CFTR alleles, and this difficulty hampers the execution of correct genetic counselling. To obtain information about the most represented CFTR mutations in CBAVD patients, we analysed 23 CBAVD patients, 15 of whom had a single CFTR mutation after screening for 36 mutations and the 5T allele. The search for the second CFTR mutation in these cases was performed by using a triplex approach: (i) first, a reverse dot-blot analysis was performed to detect mutations with regional impact; (ii) next, multiple ligation-dependent probe amplification assays were conducted to search for large rearrangements; and (iii) finally, denaturing high-performance liquid chromatography was used to search for point mutations in the entire coding region. Using these approaches, the second CFTR mutation was detected in six patients, which increased the final detection rate to 60.8%.
Human Reproduction, 2007
BACKGROUND: Mutations in the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene have been widely detected in infertile men with congenital bilateral absence of the vas deferens (CBAVD). Despite extensive analysis of the CFTR gene using varied screening methods, a number of cases remain unsolved and could be attributable to the presence of large gene rearrangements, as recently shown for CF patients. METHODS: We carried out a complete CFTR gene study in a group of 222 CBAVD patients with strict diagnosis criteria and without renal anomaly, and searched for rearrangements using a semi-quantitative assay in a subgroup of 61 patients. RESULTS: The overall mutation detection rate was 87.8%, and 82% of patients carried two mutations. Ten out of the 99 different mutations accounted for 74.6% of identified alleles. Four large rearrangements were found in patients who already carried a mild mutation: two known partial deletions (exons 17a to 18 and 22 to 23), a complete deletion and a new partial duplication (exons 11 to 13). The rearrangements accounted for 7% of the previously unknown alleles and 1% of all identified alleles. CONCLUSIONS: Screening for rearrangements should be part of comprehensive CFTR gene studies in CBAVD patients and may have impacts on genetic counselling for the patients and their families.
Mutations of the CFTR gene in Turkish patients with congenital bilateral absence of the vas deferens
Human Reproduction, 2004
BACKGROUND: Mutations of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) can cause congenital bilateral absence of the vas deferens (CBAVD) as a primarily genital form of cystic ®brosis. The spectrum and frequency of CFTR mutations in Turkish males with CBAVD is largely unknown. METHODS: We investigated 51 Turkish males who had been diagnosed with CBAVD at the Hacettepe University, Ankara, for the presence of CFTR gene mutations by direct sequencing of the coding region and exon/intron boundaries. RESULTS: We identi®ed 27 different mutations on 72.5% of the investigated alleles. Two-thirds of the patients harboured CFTR gene mutations on both chromosomes. Two predominant mutations, IVS8-5T and D1152H, accounted for more than one-third of the alleles. Five mutations are described for the ®rst time. With one exception, all identi®ed patients harboured at least one mutation of the missense or splicing type. Presently available mutation panels would have uncovered only 7±12% of CFTR alleles in this population cohort. CONCLUSIONS: Although cystic ®brosis is relatively rare in Turkey, CFTR mutations are responsible for the majority of CBAVD in Turkish males. Because of a speci®c mutation pro®le, a population-speci®c panel should be recommended for targeted populations such as CBAVD in Turkey or elsewhere.
Fertility and Sterility, 2005
Objective: To report a novel cystic fibrosis transmembrane conductance regulator (CFTR) gene missense mutation in a compound heterozygote with congenital bilateral absence of the vas deferens (CBAVD). Design: Descriptive, controlled study. Setting: Tertiary academic hospital genetics laboratory and private in vitro fertilization (IVF) clinic. Patient(s): One 46-year-old man with CBAVD and no clinical cystic fibrosis (CF) phenotype as indicated by the advanced age at diagnosis, absence of chronic airways and gastrointestinal disease, and normal pancreatic function and sweat chloride concentration. Genomic blood DNA from the patient's parents was analyzed to perform family studies, and 109 fertile men, 32 patients with CBAVD, 15 children carriers of one CFTR mutation, and 5 patients with CF were used to rule out polymorphism.
Diversity of the basic defect of homozygous CFTR mutation genotypes in humans
Journal of Medical Genetics, 2007
Background: Knowledge of how CFTR mutations other than F508del translate into the basic defect in cystic fibrosis (CF) is scarce due to the low incidence of homozygous index cases. Methods: 17 individuals who are homozygous for deletions, missense, stop or splice site mutations in the CFTR gene were investigated for clinical symptoms of CF and assessed in CFTR function by sweat test, nasal potential difference and intestinal current measurement. Results: CFTR activity in sweat gland, upper airways and distal intestine was normal for homozygous carriers of G314E or L997F and in the range of F508del homozygotes for homozygous carriers of E92K, W1098L, R553X, R1162X, CFTRdele2(ins186) or CFTRdele2,3(21 kb). Homozygotes for M1101K, 1898+3 A-G or 3849+10 kb C-T were not consistent CF or non-CF in the three bioassays. 14 individuals exhibited some chloride conductance in the airways and/or in the intestine which was identified by the differential response to cAMP and DIDS as being caused by CFTR or at least two other chloride conductances. Discussion: CFTR mutations may lead to unusual electrophysiological or clinical manifestations. In vivo and ex vivo functional assessment of CFTR function and indepth clinical examination of the index cases are indicated to classify yet uncharacterised CFTR mutations as either disease-causing lesions, risk factors, modifiers or neutral variants.