Association Between Endometriosis And Polymorphisms Of Galactose-1-phosphate Uridyl Transferase

BACKGROUNDEndometriosis is a common benign disease whose etiology is still unknown. However, there is mounting evidence that genetic susceptibility is a risk factor in the development of the disease. It is generally accepted that endometriosis may be a complex trait, like diabetes or asthma, in which multiple gene loci interact with each other and environment to produce the disease phenotype. Some studies using genetic polymorphism and linkage analysis, implicate genes that encode for metabolic and detoxification enzymes, such as galactose 1-phosphate uridyl transferase (GALT) , glutathione s-transferase Ml (GSTM1) , glutathione s-transferase T1 (GSTT1) and N-acetyltransferase 2 (NAT2), in the pathogenesis of the disease.Cramer et al (1996) , reported an association between the N314D polymorphism of the galactose-1-phosphate uridyl transferase (GALT)enzyme and endometriosis in a North American population. However, Morland (1998), Hadfield (1999) and Stefansson (2001) have failed to reproduce this finding in samples drawn from the Caucasion, UK and Iceland population respectively.GALT is responsible for catalyzing the production of glucose-1-phosphate and uridyl diphosphate-galacotose from glactose-1-phosphate and uridyl diphosphate-glucose and constitutes the main pathway of galactose metabolism in humans. There are more than 100 kinds of polymorphism of the GALT gene, two of the most common being Q188R, where arginine is substituted for glutamine at codon 188, and N314D, where aspartate is substituted for asparagine at condon314.The homozygotes of Q188R have no enzyme activity in human erythrocytes and this allele has a prevalence of 60-70% in Caucasians with galactosemia. The N314D polymorphism results from an A to G transition in exon 10 of the GALT gene. Previous studies suggested that the polymorphism has been associated with infertility, premature ovarian failure, Mullerian anomalies and ovarian cancer.Reduced GALT activity associated with N314D may be an aetiological factor in endometriosis or the polymorphism may be in linkage disequilibrium with this disease susceptibility allele. The GALT gene locus has been mapped to the short arm of chromosome 9P21, aregion where loss of heterozygosity at candidate ovarian tumour suppressor loci has been reported in endometriotic tissue. Another possibility is that maternal GALT deficiency could increase the risk of endometriosis in female offspring. It has been postulated that genetically caused errors of galactose metabolism could lead to abnormal intrauterine exposure to galactose and in the offspring to a defect in canalization of the cervix, with cervical stenosis and increased risk of retrograde menstruation and subsequent endometriosis as a result.In this study we aimed to determine whether the polymorphism N314D and another important polymorphism Q188R are associate with endometriosis in Han nationality population. Therefore, we may regard these mutations as the candidate diagnostic markers of endometriosis. MATERIALS AND METHODS1. Clinical specimen and DNA isolationGenomic DNA was obtained from blood lymphocytes of 96 Han nationality women undergoing laproscopy and laprorectomy for endometriosis in Zhejiang women's hospital. The control group consisted of 86 women confirmed no pelvic endometriosis by laproscopy or laprorectomy for ectopic pregnancy or leiomyoma2. Polymerase chain reactionsPolymerase chain reactions (PCRs) were performed in a total volume of 50 μ1 containing 200 ng of DNA and primers specific for exon 6 and exon 10 of GALT in a multiplex reaction. PCR consisted of: one cycle of 8 min at 94℃ followed by 36 cycles of 94℃ for 1 min, 65℃ for 1 min, and 72℃ for 1 min, one cycle of 72℃ for 10 min.3. Detection of the Q188R and N314D polymorphismSamples were assessed for the Q188R and N314D mutations based on the previous observation that Q188R creates an Hpall site in exon 6 and the N314D mutation creates a SinI site in exon 10. PCR products were digested with Hpa II and Sin I and separated by...