Lack of association between the TGF-beta1 gene polymorphisms and recurrent spontaneous abortion.

Transforming growth factor-beta1 (TGF-beta1) is produced by T regulatory lymphocytes (Treg), which play an important role in the physiology of pregnancy. Several polymorphisms of the TGF-beta1 gene (TGFB1) have been reported, some with an important correlation with TGF-beta1 production and disease severity. We performed an association study between TGFB1 polymorphisms and recurrent spontaneous abortion (RSA). We first used a PCR-RFLP method to detect three known TGFB1 cSNPs (coding single nucleotide polymorphisms) among 111 RSA and 110 normal control women from Southern Iran, such as 29T-->C (Leu 10 Pro), 74G-->C (Arg 25 Pro) and 788C-->T (Thr 263Ile), and compared their frequencies between the two groups of subjects. To confirm results of the RFLP study and to identify new SNPs in the RSA women, we then sequenced their DNA samples for seven exons and adjacent intronic regions of TGFB1. Consequently, 10 SNPs were detected; one (-14G-->A) was located in the upstream region of exon 1, three in exons (two in exon 1 and one in exon 5) and six in intronic regions. Two (IVS5+18G-->C and IVS6+910G-->A) of the 10 SNPs were novel. Statistical analysis on the frequency of six most frequent SNPs, including the three cSNPs, as well as on the frequencies of genotypes and 13 haplotypes regarding the 6 SNPs, revealed no significant difference between RSA and control women. Therefore, this study concludes that there is no association between exonic and adjacent intronic polymorphisms of TGFB1 and RSA.

Coding region polymorphisms in the indoleamine 2,3-dioxygenase (INDO) gene and recurrent spontaneous abortion.

Indoleamine 2,3-dioxygenase (INDO) catalyzes degradation of the indole ring of indoleamines and locally depletes tryptophan. INDO expression suppresses T cell proliferation and activation. Genetic variation in the INDO gene may contribute to the variable INDO enzyme expression, activity and severity of some diseases. Recurrent spontaneous abortion (RSA) is a common pregnancy complication and the exact causes of RSA are not yet known. We performed an association study between INDO single nucleotide polymorphisms (SNPs) and RSA. To identify INDO SNPs we sequenced DNA samples for ten exons and adjacent intronic regions from 111 RSA patients. Consequently 10 SNPs were detected; four in exons (one in exon 4, two in exon 9 and one in exon 10) and six in intronic regions (one in intron 3, three in intron 6, one in intron 8 and one in intron 9). Three (IVS3+562 del C, IVS8+116 T→G and IVS9+2431 G→A) of these ten SNPs have been registered at the NCBI SNP database. Statistical analysis of allele, genotype and haplotype frequency distribution in the three most frequent SNPs (IVS3+562 del C, IVS6+61 G→A and IVS9+2431 G→A) showed no significant differences between the 111 RSA and 105 matched control women. CGA and CGG were the most frequent haplotypes in both the RSA and control groups. We conclude that there is no association between INDO polymorphisms and susceptibility of Iranian women to RSA.