Effect of B9 and B12 vitamin intake on semen parameters and fertility of men with MTHFR polymorphisms

The methylenetetrahydrofolate reductase (MTHFR) gene codes a crucial enzyme which involve in folate metabolism. The effect of MTHFR gene polymorphisms on male fertility status is uncertain and controversial. We evaluated the effect of B vitamin family intake on total homocysteine content and semen parameters of men with MTHFR gene polymorphisms. MTHFR genotypes frequency and serum total homocysteine concentration were measured among 280 men with impaired spermatogenesis (asthenospermia, oligospermia, severe oligospermia and azoospermia) and 85 control participants. B vitamin family dietary intakes were assessed using a semi-quantitative food-frequency questionnaire. In addition, concentrations of vitamins B9 and B12 were evaluated in serum samples of some participants (n = 60). We observed significantly higher frequency of TC or TT genotypes in C677T polymorphism among oligospermic, severe oligospermic and azoospermic men. CC genotype of A1298C polymorphism was significantly higher only in azoospermic men. Also, we observed critical effect of vitamin B9 and B12 intake on decreasing of total homocysteine and improving of semen parameters among the men with T allele of MTHFR C677T polymorphism. Our investigation showed that sufficient consumption of vitamins B9 and B12 influences sperm parameters of men with different MTHFR polymorphisms, especially genotypes with T allele.

Leber hereditary optic neuropathy: do folate pathway gene alterations influence the expression of mitochondrial DNA mutation?

BACKGROUND

Leber hereditary optic neuropathy (LHON) is an inherited form of bilateral optic atrophy leading to the loss of central vision. The primary cause of vision loss is mutation in the mitochondrial DNA (mtDNA), however, unknown secondary genetic and/or epigenetic risk factors are suggested to influence its neuropathology. In this study folate gene polymorphisms were examined as a possible LHON secondary genetic risk factor in Iranian patients.

METHODS

Common polymorphisms in the MTHFR (C677T and A1298C) and MTRR (A66G) genes were tested in 21 LHON patients and 150 normal controls.

RESULTS

Strong associations were observed between the LHON syndrome and C677T (P= 0.00) and A66G (P= 0.00) polymorphisms. However, no significant association was found between A1298C (P =0.69) and the LHON syndrome.

CONCLUSION

This is the first study that shows MTHFR C677T and MTRR A66G polymorphisms play a role in the etiology of the LHON syndrome. This finding may help in the better understanding of mechanisms involved in neural degeneration and vision loss by LHON and hence the better treatment of patients.

Differences between the radiation hybrid and genetic linkage maps of bovine chromosome 5 resolved with a quasi-phylogenetic method of analysis

Two major differences were detected in gene order between the radiation hybrid map and the genetic linkage map of bovine Chromosome (Chr) 5, and these were resolved by analyzing the raw radiation hybrid data by a quasi-phylogenetic method. Seventeen loci were typed on the new cattle whole genome radiation hybrid panel. Most of these loci are framework loci and include AGLA293, BM315, BM6026, BP1, BZRP, CD9, CSSM22, CSSM34, CYP2D@, ETH2, ETH10, ETH152, IGF1, LALBA, SLC2A3, SYT1, and TPI1. BP1 was found to be closer to the centromere than either BM6026 or SYT1 with two standard computer software packages for analyzing radiation hybrid panel data. This is inconsistent with any of the genetic linkage maps as well as their consensus. CYP2D@ was placed between ETH2 and BZRP, and this is also inconsistent with the genetic linkage maps, since CYP2D@ should be the most telomeric of the loci tested in this study. Resolution was reached by analyzing the raw radiation hybrid data for clones that bind some but not all of the loci, and the binding pattern was more consistent with the linkage maps and less consistent with the software-generated radiation hybrid map. The comparative mapping data confirm the relative inversion of gene order of SYT1 compared with humans and mice. A non-polymorphic fragment for CD9 indicates the conservation of gene order for three loci located on human Chr 12p. The genes of bovine Chr 5 conserved on human Chr 12p are located separately from the genes conserved on human Chr 12q. It is recommended that the raw data for radiation hybrid maps be made publicly available so that conflicts in gene order can be evaluated explicity.

Comparative mapping of genes from human chromosome 12 by genetic linkage mapping in cattle

Loci from human chromosome 12 were mapped in cattle to compare the gene order between species. Polymorphisms were detected in cattle in six loci that had been mapped with high precision in humans. Four of these loci, LALBA, SLC2A3, SYT1, and TPI1, mapped to bovine chromosome 5, and one, PLA2G1B, mapped to bovine chromosome 17. The sixth locus, SLC2A3L, due to a fragment produced by the SLC2A3 primers, maps to the telomeric region of BTA18. The differences in gene order between human chromosome 12 and cattle chromosome 5, when these loci are added to others already mapped in cattle, show evidence of significant rearrangement in gene order requiring several evolutionary events. There is also evidence in cattle chromosome 5 of the interspersal of material conserved on human chromosome 22 into the material conserved on human chromosome 12, consistent with ZOOFISH analyses. This analysis indicates that the larger block near the centromere is conserved on the long arm of human chromosome 12 and the smaller block near the telomere is conserved as part of the short arm of human chromosome 12. The level of variation detected in the amplified cattle DNA was approximately 1 variant per 464 nucleotides of haploid DNA using single-strand conformation polymorphism analysis. This corresponds to a per individual level of 1 variant per 1, 961 nucleotides of haploid DNA. This confirms lower genetic variability in cattle compared to humans but indicates the potential for millions of single nucleotide polymorphisms in cattle.

Report of the first workshop on the genetic map of bovine chromosome 1

A report of the first workshop on the genetic map of bovine chromosome 1 (BTA1) is presented. Five laboratories contributed 31,962 informative meioses from 70 loci. Thirty-two loci which had been typed by at least two laboratories were used to construct a framework genetic map with a likelihood ratio support of at least 1000:1 for locus order. The resulting sex-averaged framework map contained 26 loci and spanned 163.6 CM. The lengths of the female and male maps were 159.5 CM and 165.3 CM, respectively, and there was evidence for an expansion in the telomeric one-third of the male map. Of the four cases where order for closely linked loci differed among the maps produced for each of the contributing laboratories, a consensus order was obtained for three in the framework map. The average genetic distance between framework loci on the sex-averaged map was 6.3 CM.