Novel cause of hereditary obstructive azoospermia: a T2 allele in the CFTR gene

Haplotype analysis of the CFTR gene on normal and mutant CFTR genes

BACKGROUND

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene are responsible for Cystic Fibrosis (CF) disease. Since the distribution of polymorphisms varies among populations, a comparison between the frequency of CFTR polymorphisms in patients and healthy population may further identify their role in CF disease. The results obtained from this research may facilitate the prediction of disease phenotype in prenatal diagnosis or newborn screening program as well as determine the possible associations between haplotypes and specific mutations.

METHODS

Blood samples collected from 27 unrelated West Iranian families contain at least one CF patient and 55 control families with no history of CF. Samples were analyzed for c.1210-12 T [5-9], c.1242-35-1242-12GT [8-10], c.744-33GATT [6-8] and c.869 + 11C > T polymorphisms by automated direct DNA sequencing following DNA extraction.

RESULTS

Our results showed that the T7 allele is the most common allele in normal and non-ΔF508 CF chromosomes with the frequencies of 93.6% and 100%, respectively. Conversely, T9 was the only allele detected in ΔF508 chromosomes. Moreover, the c.1242-35-1242-12GT analysis showed that (TG)11 repeat was the most common dinucleotide repeat in both, non-ΔF508 and normal chromosomes with the frequencies of 91% and 71%, respectively. The c.744-33GATT and c.869 + 11C > T polymorphism analyses indicated that (GATT)6 and T allele are only found in ΔF508 CF chromosomes. Besides, the [T7-TG11-GATT7-C] haplotype was the most common haplotype in both, normal and non-ΔF508 CF subjects while the [T9-TG10- GATT6-T] haplotype was only detected in CF patients carrying ΔF508 mutation.

CONCLUSIONS

Our findings identified an informative haplotype that could be used in genetic counseling, prenatal diagnosis and future screening of CF in Iran.

Congenital bilateral absence of the vas deferens as an atypical form of cystic fibrosis: reproductive implications and genetic counseling

Congenital bilateral absence of the vas deferens (CBAVD) is found in 1% to 2% of males with infertility and is present in 6% of obstructive azoospermia cases. Nearly 95% of men with cystic fibrosis (CF, an autosomal recessive disorder) have CBAVD. There are genetic links between CBAVD and CF. Some mutations in the gene encoding cystic fibrosis transmembrane conductance regulator (CFTR) can lead to CBAVD as a monosymptomatic form of CF. With the use of assisted reproductive techniques (ART), especially testicular or epididymal sperm aspiration, intracytoplasmic sperm injection, and in vitro fertilization, it is possible that men with CBAVD can produce offspring. Therefore, genetic counseling should be offered to couples undergoing ART to discuss the probability of having offspring that carry CFTR gene mutations. The aim of this review was to present the main cause of CBAVD, to call attention to its implications for assisted reproduction, and to show the importance of genetic counseling for couples where men have CBAVD, as they can have offspring with a lethal disease.

Association of cystic fibrosis genetic modifiers with congenital bilateral absence of the vas deferens

OBJECTIVE

To investigate whether genetic modifiers of cystic fibrosis (CF) lung disease also predispose to congenital bilateral absence of the vas deferens (CBAVD) in association with cystic fibrosis transmembrane conductance regulator (CFTR) mutations. We tested the hypothesis that polymorphisms of transforming growth factor (TGF)-β1 (rs 1982073, rs 1800471) and endothelin receptor type A (EDNRA) (rs 5335, rs 1801708) are associated with the CBAVD phenotype.

DESIGN

Genotyping of subjects with clinical CBAVD.

SETTING

Outpatient and hospital-based clinical evaluation.

PATIENT(S)

DNA samples from 80 subjects with CBAVD and 51 healthy male controls from various regions of Europe. This is one of the largest genetic studies of this disease to date.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Genotype analysis.

RESULT(S)

For single nucleotide polymorphism (SNP) rs 5335, we found increased frequency of the CC genotype among subjects with CBAVD. The difference was significant among Turkish patients versus controls (45.2% vs. 19.4%), and between all cases versus controls (36% vs. 15.7%). No associations between CBAVD penetrance and polymorphisms rs 1982073, rs 1800471, or rs 1801708 were observed.

CONCLUSION(S)

Our findings indicate that endothelin receptor type A polymorphism rs 5335 may be associated with CBAVD penetrance. To our knowledge, this is the first study to investigate genetic modifiers relevant to CBAVD.