Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene have been implicated in the onset of cystic fibrosis and other clinical respiratory disorders. In the present study, we investigated the role of CFTR variations, poly-T, TG-repeats, and M470V in susceptibility to bronchial asthma and chronic bronchitis in a Chinese population in Jiangsu province, China. A total of 72 bronchial asthma patients, 68 chronic bronchitis patients, and 117 healthy subjects were included in this study. The Tn-TGm haplotype was sequenced and the CFTR variant M470V was detected using restriction fragment length polymorphism (RFLP). We found that the frequency of T5-TG12-V470 in chronic bronchitis patients was 0.07%, which was notably higher than that in healthy subjects (0.01%) and bronchial asthma patients (0.04%). Thus, the presence of the T5-TG12 haplotype of the CFTR gene is likely to play a role in the development and progression of respiratory conditions, such as chronic bronchitis.

Huang Q, Ding W, Wei MX. Comparative analysis of common CFTR polymorphisms poly-T, TG-repeats and M470V in a healthy Chinese population. World J Gastroenterol 2008; 14(12): 1925-1930 INTRODUCTIONThe cystic fibrosis transmembrane conductance regulator (CFTR) gene on chromosome 7q31 spans approximately 250 kb of DNA and encodes 27 exons encodes [1] . The CFTR gene encodes a cAMP-and ATP-dependent chloride channel that is present in the apical membrane of the epithelial cells that line most exocrine glands [2] . Phosphorylation of the regulatory domain by protein kinase A, followed by binding and hydrolysis of ATP at both nucleotide-binding domains, regulates the transport of chloride ions through the channel [3] . Absence, reduced levels, or malfunction of the CFTR protein results in cystic fibrosis (CF), and CF-like diseases such as congenital bilateral absence of the vas deferens (CBAVD) [4,5] , bronchiectasis [6] and chronic pancreatitis [7] . Since the discovery of the CFTR gene, more than 1000 mutations and 200 polymorphisms have been identified [8] . CF is one of the most common autosomal recessive disorders in Caucasians, with an incidence of approximately 1 in 2500 Caucasian births and a carrier frequency of approximately 1 in 25. However, in Asians, the prevalence of CF is very low, with an incidence of approximately 1 in 100 000, and in particular, the severe mutations, such as ∆F508, G542X and N1303K, are rarely found in Asians. Previous studies have demonstrated that polymorphisms outside the CFTR gene [9,10] , as well as within the gene, may affect transcription or function of the CFTR protein and modify the phenotype of some CF mutations. It has been mentioned that poly-T, TG-repeats and M470V polymorphisms play a role in the development of CF-like diseases. The poly-T tract located at the junction of intron Abstract AIM: To investigate the three important cystic fibrosis transmembrane conductance regulator (CFTR ) haplotypes poly-T, TG-repeats and the M470V polymorphisms in the Chinese population, and to compare their distribution with that in Caucasians and other Asian populations. RAPID COMMUNICATION METHODS:Genomic DNA was extracted from blood leukocytes. Exons 9 and 10 of the CFTR gene were obtained through polymerase chain reaction (PCR). Exon 9 DNA sequences were directly detected by an automated sequencer and poly-T and TG-repeats were identified by direct sequence analysis. Pure exon 10 PCRamplified products were digested by Hph Ⅰ restriction enzyme and the M470V mutation was detected by the AGE photos of digestion products.RESULTS: T7 was the most common (93.6%) haplotype and the (TG)11 frequency of 57.2% and (TG)12 frequency of 40.9% were dominant haplotypes in the junction of intron 8 (IVS-8) and exon 9. The frequency of T5 was 3.8% and all T5 allele tracts (10 alleles) were joined with (TG)12. Four new alleles of T6 (1.5%) were found in three healthy individuals. In exon 10, the V allele (56.1%) was slightly more frequent than the M allele (43.9%), and the M/V (45.5%) was the dominan...