Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in folate metabolism. Folate deficiency has been related to several conditions, including neural tube defects (NTDs) and cardiovascular diseases. Hence, MTHFR genetic variants have been studied worldwide, particularly the C677T and A1298C. We genotyped the C677T and A1298C MTHFR polymorphisms in Mexican Amerindians (MAs), from the largest sample included in a genetic study (n = 2026, from 62 ethnic groups), and in a geographically-matched Mexican Mestizo population (MEZ, n = 638). The 677T allele was most frequent in Mexican individuals, particularly in MAs. The frequency of this allele in both MAs and MEZs was clearly enriched in the South region of the country, followed by the Central East and South East regions. In contrast, the frequency of the 1298C risk allele in Mexicans was one of the lowest in the world. Both in MAs and MEZs the variants 677T and 1298C displayed opposite allele frequency gradients from southern to northern Mexico. Our findings suggest that in Mestizos the 677T allele was derived from Amerindians while the 1298C allele was a European contribution. Some subgroups showed an allele frequency distribution that highlighted their genetic diversity. Notably, the distribution of the frequency of the 677T allele was consistent with that of the high incidence of NTDs reported in MEZ.

Background Myelomeningocele (MMC) is the most severe and frequent type of spina bifida. Its etiology remains poorly understood. The Hedgehog (Hh), Wnt, and planar cell polarity (PCP) signaling pathways are essential for normal tube closure, needing a structural‐functional cilium for its adequate function. The present study aimed to investigate the impact of different gene variants (GV) from those pathways on MMC genotype‐subphenotype correlations. Methods The study comprised 500 MMC trios and 500 controls, from 16 Telethon centers of 16 Mexican states. Thirty‐four GVs of 29 genes from cilia, Hh, PCP, and Wnt pathways, were analyzed, by an Illumina on design microarray. The total sample (T‐MMC) was stratified in High‐MMC (H‐MMC) when thoracic and Low‐MMC (L‐MMC) when lumbar‐sacral vertebrae affected. STATA/SE‐12.1 and PLINK software were used for allelic association, TDT, and gene–gene interaction (GGI) analyses, considering p value <.01 as statistically significant differences (SSD). Results Association analysis showed SSD for COBL‐rs10230120, DVL2‐rs2074216, PLCB4‐rs6077510 GVs in T‐MMC and L‐MMC, and VANGL2‐rs120886448 in T‐MMC and H‐MMC, and INVS‐rs7024375 exclusively in L‐MMC. TDT assay showed SSD preferential transmissions of C2CD3‐rs826058 in H‐MMC, and LRP5‐rs3736228, and BBS2‐rs1373 in L‐MMC. Statistically significant GGI was observed in four in T‐MMC, four completely different in L‐MMC, and one in H‐MMC. Interestingly, no one repeated in subphenotypes. Conclusions Our results support an association of GVs in Hh, Wnt, PCP, and cilia pathways, with MMC occurrence location, although further validation is needed. Furthermore, present results show a distinctive panel of gene‐variants in H‐MMC and LMMC subphenotypes, suggesting a feasible genotype–phenotype correlation.

Isolated postaxial polydactyly (I-PAP), as a single defect, is a frequent malformation, characterized by an extra digit placed on the ulnar or fibular side of the limbs. Worldwide prevalence varies from as high as 225/10,000 in Nigerians to so low as 6.08/10,000 in Argentinians. Genetic-ethnic background significantly affects worldwide prevalence and type of I-PAP. Herein we describe the epidemiological characteristics of I-PAP in 697 newborns, 383 males and 314 females identified in 1,178,993 examined live births from a multicenter case-control hospital-based population study, the Mexican program of Registry and Epidemiological Surveillance of Congenital Malformations (RYVEMCE). The main characteristics analyzed included total I-PAP, stratified in Types A and B, defined as complete or incomplete extra-digitformation, respectively, sex prevalence, affected limb, laterality, parity, prematurity, delivery-type, twinning, consanguinity, and parental age. Males (6.35/10,000) are significantly more frequently affected than females (5.45/10,000), hands more than feet, left more than right limbs, and Type B (74.50%) more than A (25.50%). Prematurity and forceps use were significantly more frequent in cases than controls. An evident decreasing time-trend prevalence was present. Similar findings with other studies were males, upper and left limbs more frequently affected. Findings that were not previously reported include prematurity, forceps use, a significant decreasing time trend and an inverse ethnic prevalence for Types A (75%) and B (25%) in the Mayan population in contrast to other worldwide ethnic groups. K E Y W O R D S epidemiologic characteristics, isolated postaxial polydactyly, multicenter study