XRCC1 R194W and R399Q Polymorphisms and Colorectal Cancer Risk in a Northeastern Mexican Population.

Colorectal cancer (CRC) is one of the most common cancers worldwide. Its etiopathogenesis is complex, mainly influenced by genetic instability caused by the accumulation of mutations. The XRCC1 gene, which is involved in DNA repair, has been associated with CRC through the R194W (C194T) and R399Q (G399A) polymorphisms, but the results are inconsistent. Here, we analyzed the association of these polymorphisms with sporadic CRC in a northeastern Mexican population, including 155 male CRC patients and 155 male controls. Genotyping was performed using the RFLP method. An association with CRC was found for the 399A allele (G vs A; OR = 1.48 (1.03-2.13), P=0.034) and for the 399AA genotype in a codominant model (AA vs GG; OR = 3.11 (1.06-9.10), P=0.031). In contrast, there were no significant differences between CRC patients and controls for the C194T polymorphism (C vs T; OR = 0.82 (0.52-1.31), P=0.41). These results are consistent with many similar studies, but further research is needed to verify whether the XRCC1 R194W and R399Q polymorphisms play a role in CRC etiology. The functional significance of these polymorphisms is unclear, but some studies suggest that they influence DNA repair capacity and, thus, cancer risk.

Draft Genome Sequences of 13 Vibrio cholerae Strains from the Rio Grande Delta.

Vibrio cholerae is the etiologic agent of cholera, an acute and often fatal diarrheal disease that affects millions globally. We report the draft genome sequences of 13 non-O1/O139 V. cholerae strains isolated from the Rio Grande Delta in Texas. These genomes will aid future analyses of environmental serovars.

Association of the MTHFR 677C>T Polymorphism with Obesity and Biochemical Variables in a Young Population of Mexico.

BACKGROUND: Methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms have been associated with overweight people and obesity. The goal of this study was to investigate the relationship of the MTHFR 677C>T polymorphism with obesity and biochemical variables in young individuals of Mexico. METHODS: A total of 316 young individuals were included in the study, 172 with normal weight (NW) and 144 with over weight/obesity. Body mass index (BMI) was classified as NW, overweight, and obesity. Also, waist circumference was measured. Moreover, glucose, total cholesterol, and triglycerides were determined. Genotyping for MTHFR 677C>T polymorphism was performed by the PCR-RFLP method. RESULTS: There was no difference in the distribution of the MTHFR 677C>T polymorphism between individuals with NW and overweight/obesity; neither when they were divided by overweight vs NW, nor when we contrasted obese vs NW. However, an analysis stratified by gender showed a significant protector effect of the TT genotype against obesity in males and elevated waist circumference in females. Also, overweight/obese individuals with TT genotype had less risk of high cholesterol or triglycerides than overweight/obese subjects with the other genotypes. CONCLUSIONS: These results suggest that the MTHFR 677T polymorphism might not be a risk factor for being overweight/obesity. Rather, on the basis of our results, this variant could be a protector effect. However, further large-scale population-based studies are still necessary to clarify the role of the MTHFR 677C>T polymorphism in overweight, obesity, and lipid profile level.

Association of the SLC6A4 gene 5HTTLPR polymorphism and ADHD with epilepsy, gestational diabetes, and parental substance abuse in Mexican mestizo children / Asociación del polimorfismo 5HTTLPR del gen SLC6A4 y TDAH con epilepsia, diabetes gestacional y adicción de los padres en niños mestizos mexicanos

Abstract Introduction Attention deficit hyperactivity disorder (ADHD) is one of the most common neuropsychiatric conditions in childhood and a multifactorial condition attributable to genetic and/or environmental influence. Allelic variants in the serotonin transporter gene (SLC6A4) have been associated to lower transcriptional efficiency, changes in serotonin concentration in several brain regions, and ADHD development. Objective To identify the association between the SLC6A4 alleles and ADHD diagnosis and risk factor phenotypes in children from a Mexican mestizo population. Method In this study, 134 unrelated children were included and evaluated for ADHD, genotypification for the 5HTTLPR polymorphism, and identification of multiple phenotypes from their clinical records and family background for association analysis. Results The following distribution of genotypes was observed: 23% SS, 49% SL, and 28% LL. From the phenotypes evaluated in the present study, gestational diabetes mellitus (p = .045), history of epilepsy (p = .047), and parental substance abuse (p = .033) showed an association with ADHD development in regression analysis along with the S variant. Discussion and conclusion Results suggest that interaction of the S allele and some of the phenotypes analyzed may play a relevant role in the development of ADHD in the studied population.

Resumen Introducción El trastorno por déficit de atención e hiperactividad (TDAH) es uno de los padecimientos neuropsiquiátricos más comunes en la infancia. Como su naturaleza es multifactorial, es atribuible a influencias genéticas y/o ambientales. Las variantes alélicas del gen transportador de serotonina (SLC6A4) se han asociado previamente con cambios en los niveles de serotonina en algunas regiones cerebrales, así como con el desarrollo de TDAH. Objetivo Identificar la posible asociación entre los alelos del gen SLC6A4 y el diagnóstico de TDAH, así como factores de riesgo en niños mestizos mexicanos. Método En el presente estudio se incluyeron 134 niños, los cuales fueron evaluados para TDAH, genotipificación del polimorfismo 5HTTLPR e identificación de múltiples fenotipos en su historia clínica y antecedentes familiares para su análisis de asociación estadística. Resultados Se mostró la siguiente distribución de genotipos: 23% SS, 49% SL y 28% LL. En un modelo de regresión, los fenotipos de diabetes mellitus gestacional (p = .045), historia de epilepsia (p = .047) y el abuso de sustancias de los padres (p = .033) mostraron asociación con la variante S y el desarrollo de TDAH. Discusión y conclusión El presente estudio sugiere que el alelo S en conjunto con algunos fenotipos puede cumplir un papel importante en el desarrollo de TDAH en nuestra población.

Genetic Epidemiology of Type 2 Diabetes in Mexican Mestizos.

There are currently about 415 million people with diabetes worldwide, a figure likely to increase to 642 million by 2040. In 2015, Mexico was the second Latin American country and sixth in the world in prevalence of this disorder with nearly 11.5 million of patients. Type 2 diabetes (T2D) is the main kind of diabetes and its etiology is complex with environmental and genetic factors involved. Indeed, polymorphisms in several genes have been associated with this disease worldwide. To estimate the genetic epidemiology of T2D in Mexican mestizos a systematic bibliographic search of published articles through PubMed, Scopus, Google Scholar, and Web of Science was conducted. Just case-control studies of candidate genes about T2D in Mexican mestizo inhabitants were included. Nineteen studies that met the inclusion criteria were found. In total, 68 polymorphisms of 41 genes were assessed; 26 of them were associated with T2D risk, which were located in ABCA1, ADRB3, CAPN10, CDC123/CAMK1D, CDKAL1, CDKN2A/2B, CRP, ELMO1, FTO, HHEX, IGF2BP2, IRS1, JAZF1, KCNQ1, LOC387761, LTA, NXPH1, SIRT1, SLC30A8, TCF7L2, and TNF-α genes. Overall, 21 of the 41 analyzed genes were associated with T2D in Mexican mestizos. Such a genetic heterogeneity compares with findings in other ethnic groups.

Polymorphisms of the XRCC1 gene and breast cancer risk in the Mexican population.

The purpose of this case-control study was to evaluate the association of XRCC1 Arg194Trp and Arg399Gln polymorphisms with susceptibility to breast cancer (BC) in a Mexican population. We analysed DNA samples from 345 BC patients and 352 control subjects by polymerase chain reaction-restriction fragment length polymorphism. The frequency of the 399Gln allele was 23% in controls and 29% in patients [OR 1.38 (1.08-1.76); p = 0.01]; genotypes in controls were 60, 36, and 4% for Arg/Arg, Arg/Gln, and Gln/Gln, respectively, while in patients they were 53, 36, and 11% [OR 2.71 (1.44-5.10); p = 0.0015 for the Gln/Gln genotype]. Regarding the Arg194Trp polymorphism, the frequency of Trp allele was 15% in controls and 16% in patients [OR 1.09 (0.82-1.46); p = 0.54]; the genotype frequencies in controls were 74, 23, and 3% for Arg/Arg, Arg/Trp and Trp/Trp, respectively, while in patients these were 73, 23, and 4% [OR 1.41 (0.64-3.14); p = 0.39 for the Trp/Trp genotype]. Allele frequencies were consistent with Hardy-Weinberg equilibrium (p = 0.20 for Arg194Trp and p = 0.54 for Arg399Gln). Our results indicate that the 399Gln polymorphism is associated with an increased risk of BC. Additionally, we found that some covariates increase the risk of BC in Mexican women; namely, antecedent of abortions [OR 3.69 (2.17-6.27); p < 0.001], not breastfeeding [OR 2.46 (1.45-4.18); p = 0.001], family history of BC [OR 15.9 (5.09-50.23); p < 0.001], other type of family cancer [OR 31.5 (12.5-79.3); p < 0.001], alcoholism [OR 17.7 (5.2-60.42); p < 0.001], type 2 diabetes mellitus [OR 2.28 (1.26-4.10); p = 0.007], and contraceptive use [OR 2.28 (1.26-4.10); p < 0.001].

[Enviromental factors related to depressive disorders]. / Factores ambientales relacionados a trastornos depresivos.

BACKGROUND: As a result of their high prevalence, mayor depressive disorder single episode (MDDSE); major depressive disorder recurrent episodes (MDDREC); and dysthymia are considered an important public health problem. The objective of this paper was to identify and correlate environmental factors in patients with MDDSE, MDDREC and dysthymia. METHODS: 121 patients from the Instituto Mexicano del Seguro Social's Subzone General Hospital of San Andres Tuxtla, at Veracruz, were questioned by history with the risk variables. RESULTS: 16 of them were diagnosed with MDDREC, 72 with MDD and 33 with dysthymia; in all of those cases, females prevailed. Depressive disorders were observed more frequently in people over 40 years, married, with medium or low educational level, with dysfunctional family environment, victims of family violence and who were the middle siblings. The main comorbidities that arose were gastrointestinal disorders, obesity and hypertension. RESULTS: 16 of them were diagnosed with MDDREC, 72 with MDD and 33 with dysthymia; in all of those cases, females prevailed. Depressive disorders were observed more frequently in people over 40 years, married, with medium or low educational level, with dysfunctional family environment, victims of family violence and who were the middle siblings. The main comorbidities that arose were gastrointestinal disorders, obesity and hypertension. CONCLUSIONS: The main risk factors identified for developing depressive disorders were: being female, over 40 years old and being married. The differences obtained in this study, if it is compared with others, are probably due to sample size, selection criteria and ethnic origin.

Introducción: debido a su alta prevalencia, la depresión mayor, episodio único (DMEU); la depresión mayor recurrente (DMR); y la distimia son consideradas un problema importante de salud pública. El objetivo de este estudio fue identificar y relacionar los factores ambientales en pacientes con DMEU, DMR y distimia. Métodos: 121 pacientes procedentes del Hospital General de Subzona del Instituto Mexicano del Seguro Social (IMSS) de San Andrés Tuxtla, Veracruz, fueron cuestionados mediante una historia clínica con las variables de riesgo. Resultados: 16 pacientes presentaron DMEU, 72 DMR y 33 distimia. En todos prevaleció el sexo femenino. Los trastornos depresivos se observaron con más frecuencia en personas de más de 40 años, casadas, con un nivel de estudios medio o bajo, provenientes de una familia disfuncional, víctimas de violencia familiar, además de ser hijos intermedios. Las comorbilidades que se presentaron fueron trastornos gastrointestinales, obesidad e hipertensión arterial. Conclusión: los principales factores de riesgo que se identificaron para desarrollar trastornos depresivos fueron: ser mujer, tener más de 40 años de edad y estar casada. Las diferencias obtenidas en este estudio respecto a otros probablemente se deban al tamaño de la muestra, los criterios de selección y el origen de la etnia.

Amyloid ß peptides modify the expression of antioxidant repair enzymes and a potassium channel in the septohippocampal system.

Alzheimer's disease (AD) is a progressive, neurodegenerative brain disorder characterized by extracellular accumulations of amyloid ß (Aß) peptides, intracellular accumulation of abnormal proteins, and early loss of basal forebrain neurons. Recent studies have indicated that the conformation of Aß is crucial for neuronal toxicity, with intermediate misfolded forms such as oligomers being more toxic than the final fibrillar forms. Our previous work shows that Aß blocks the potassium (K(+)) currents IM and IA in septal neurons, increasing firing rates, diminishing rhythmicity and firing coherence. Evidence also suggests that oxidative stress (OS) plays a role in AD pathogenesis. Thus we wished to determine the effect of oligomeric and fibrillar forms of Aß1₋42 on septohippocampal damage, oxidative damage, and dysfunction in AD. Oligomeric and fibrillar forms of Aß1₋42 were injected into the CA1 region of the hippocampus in live rats. The rats were sacrificed 24 hours and 1 month after Aß or sham injection to additionally evaluate the temporal effects. The expression levels of the K(+) voltage-gated channel, KQT-like subfamily, member 2 (KCNQ2) and the OS-related genes superoxide dismutase 1, 8-oxoguanine DNA glycosylase, and monamine oxidase A, were analyzed in the hippocampus, medial, and lateral septum. Our results show that both forms of Aß exhibit time-dependent differential modulation of OS and K(+) channel genes in the analyzed regions. Importantly, we demonstrate that Aß injected into the hippocampus triggered changes in gene expression in anatomical regions distant from the injection site. Thus the Aß effect was transmitted to anatomically separate sites, because of the functional coupling of the brain structures.

Constitutive type VI secretion system expression gives Vibrio cholerae intra- and interspecific competitive advantages.

The type VI secretion system (T6SS) mediates protein translocation across the cell membrane of Gram-negative bacteria, including Vibrio cholerae - the causative agent of cholera. All V. cholerae strains examined to date harbor gene clusters encoding a T6SS. Structural similarity and sequence homology between components of the T6SS and the T4 bacteriophage cell-puncturing device suggest that the T6SS functions as a contractile molecular syringe to inject effector molecules into prokaryotic and eukaryotic target cells. Regulation of the T6SS is critical. A subset of V. cholerae strains, including the clinical O37 serogroup strain V52, express T6SS constitutively. In contrast, pandemic strains impose tight control that can be genetically disrupted: mutations in the quorum sensing gene luxO and the newly described regulator gene tsrA lead to constitutive T6SS expression in the El Tor strain C6706. In this report, we examined environmental V. cholerae isolates from the Rio Grande with regard to T6SS regulation. Rough V. cholerae lacking O-antigen carried a nonsense mutation in the gene encoding the global T6SS regulator VasH and did not display virulent behavior towards Escherichia coli and other environmental bacteria. In contrast, smooth V. cholerae strains engaged constitutively in type VI-mediated secretion and displayed virulence towards prokaryotes (E. coli and other environmental bacteria) and a eukaryote (the social amoeba Dictyostelium discoideum). Furthermore, smooth V. cholerae strains were able to outcompete each other in a T6SS-dependent manner. The work presented here suggests that constitutive T6SS expression provides V. cholerae with an advantage in intraspecific and interspecific competition.

Association of a serotonin transporter gene (SLC6A4) 5-HTTLPR polymorphism with body mass index categories but not type 2 diabetes mellitus in Mexicans.

The serotonergic system has been hypothesized to contribute to the biological susceptibility to type 2 diabetes mellitus (T2DM) and body-mass index (BMI) categories. We investigate a possible association of 5-HTTLPR polymorphism (L and S alleles) in the promoter region of the serotonin transporter gene (SLC6A4) with the development of T2DM and/or higher BMI by analyzing a sample of 138 individuals diagnosed with T2DM and 172 unrelated controls from the Mexican general population. In the total sample genotypes were distributed according to Hardy-Weinberg equilibrium, and S allele frequency was 0.58. There was no statistical association between 5-HTTLPR polymorphism and the development of T2DM in this Mexican population sample (p = 0.12). Nevertheless, logistic regression analysis of the L allele and increased BMI disclosed an association, after adjusting for age, sex and T2DM (p = 0.02, OR 1.74, 95% CI: 1.079-2.808).

MTHFR C677T, MTHFR A1298C, and OPG A163G polymorphisms in Mexican patients with rheumatoid arthritis and osteoporosis.

MTHFR polymorphisms C677T and A1298C are associated with reduced MTHFR enzyme activity and hyperhomocysteinemia, which has been associated with osteoporosis. The A163G polymorphism in osteoprotegerin (OPG) has been studied in osteoporosis with controversial results. The objective of the present study was to investigate the association(s) among MTHFR C677T, MTHFR A1298C, and OPG A163G polymorphisms in Mexican patients with rheumatoid arthritis and osteoporosis. The femoral neck and lumbar spine bone mineral densities (BMDs) were measured in 71 RA patients, and genotyping for the three polymorphisms was performed via restriction fragment length polymorphism analysis. Patients with osteoporosis/osteopenia exhibited statistically significant differences in the genotype frequencies of MTHFR C677T as well as an association with femoral neck BMD; TT homozygotes had lower BMDs than patients with the CT genotype, and both of these groups had lower BMDs than patients with the CC genotype. The associations of the MTHFR C677T polymorphism with osteoporosis/osteopenia and femoral neck BMD suggest that these polymorphisms confer a risk of developing osteoporosis in patients with rheumatoid arthritis, a risk that may be reduced with folate and B complex supplementation.

Association study of candidate gene polymorphisms and obesity in a young Mexican-American population from South Texas.

BACKGROUND AND AIMS: Obesity is increasingly a health problem and a risk factor for diabetes in young Mexican-American populations. Genetic association studies in older, mostly non-Hispanic populations have reported that polymorphisms in the candidate genes HSD11B1, CRP, ADIPOQ, PPARG, ANKK1, ABCC8 and SERPINF1 are associated with obesity or diabetes. We analyzed the polymorphisms rs846910, rs1205, rs1501299, rs1801282, rs1800497, rs757110 and rs1136287 in these candidate genes, for association with obesity and metabolic traits in a young Mexican-American population from south Texas. METHODS: Genotyping of the seven common SNPs were performed by allelic discrimination assays in 448 unrelated Mexican Americans (median age = 16 years) from south Texas. χ(2) tests and regression analyses using additive models were used for genetic association analyses adjusting for covariates; p values were corrected for multiple testing by permutation analyses. RESULTS: rs1800497 (ANKK1) shows association with waist circumference (p = 0.009) and retains the association (p = 0.03) after permutation testing. Analysis of metabolic quantitative traits shows that rs846910 (HSD11B1) was associated with HOMA-IR (p = 0.04) and triglycerides (p = 0.03), and rs1205 (CRP) with HOMA-IR (p = 0.03) and fasting glucose levels (p = 0.007). However, the quantitative traits associations are not maintained after permutation analysis. None of the other SNPs in this study showed associations with obesity or metabolic traits in this young Mexican-American population. CONCLUSIONS: We report a potential association between rs1800497 (linked to changes in brain dopamine receptor levels) and central obesity in a young Mexican-American population.

[Non-syndromic cleft lip/cleft palate and C677T methylene-tetrahydrofolate reductase variant in Mexican children]. / Variante C677T del gen metileno-tetrahidrofolato reductasa en niños mexicanos con labio/paladar hendido no sindrómico.

BACKGROUND: Non-syndromic cleft lip with or without cleft palate (NSCLP) is a common malformation. The aetiology is multifactorial. An incidence of 1.1-1.39 per 1000 new births had been reported in Mexico. The folic acid intake in preconceptional stage has been reported to prevent malformations such as neural tube defects (NTD) and NSCLP. The C677T variant of the methylene-tetrahydrofolate reductase (MTHFR) gene is responsible of a thermolabile form, related to decrease of folate and increase homocysteine. This variant has been associated with CLP, in different populations, but results are still controversial. Our objective was to determine the allelic (AF) and genotypic frequency (GF) of the MTHFR-C677T variant in Mexican children with NSCLP. METHODS: Transverse comparative study in 67 Mexican children with NSCLP and a control group with 70 unrelated Mexican individuals without NSCLP. RESULTS: The AF in NSCLP was 39 %. There was no statistical difference between AF in the two groups (39 versus 41). CONCLUSIONS: In this population, genotype C677T was not a major risk factor for this malformation, however, sample size, other genes implicated and genes-environment interactions must be considered.

[Mutations in the arginine vasopressin neurophysin-II gene in familial neurohypophyseal diabetes insipidus patients]. / Mutaciones en el gen de arginina vasopresina neurofisina II en pacientes con diabetes insípida neurohipofisiaria familiar.

Neurogenic diabetes insipidus (NDI) is a rare condition characterized by polyuria and polydipsia caused by deficient arginine vasopressin hormone production. More than a 50 mutations have been identified for familial autosomic dominant neurogenic diabetes insipidus (FadNDI). These mutations can cause citotoxicity and lead to the degeneration of magnocellular neurons of the hipofisis by aberrant protein accumulation. The NDI diagnosis is based on the water deprivation test, quantification of AVP hormone and Magnetic Resonance Image (MRI), and in families with history of FadNDI has been suggested the molecular analysis of mutation in the arginine vasopressin neurophisin II gene before the signs and symptoms development, with the purpose of offering a suitable diagnosis, clinical follow up and treatment. The treatment with a synthetic analogue of AVP hormone allows the remission of the signs and symptoms in NDI patients and the advances in gene therapy in animal models has been promising, as much for NDI as for other diseases in which the mutant protein production has been involved.

MDR1 C3435T polymorphism in Mexican children with acute lymphoblastic leukemia and in healthy individuals.

To determine the influence of the MDR1 C3435T polymorphism on the development of childhood acute lymphoblastic leukemia (ALL), we studied 107 children with ALL and 111 healthy subjects. All subjects were genotyped for the C3435T polymorphism using the polymerase chain reaction-restriction fragment length polymorphism method. The genotype frequencies in the patients were 17% homozygous CC, 61% heterozygous CT, and 22% homozygous TT; in healthy individuals the genotype frequencies were 14% CC, 53% CT, and 33% TT. In patients with ALL the allele frequencies were 0.47 for the C allele and 0.53 for the T allele; in the healthy group these allele frequencies were 0.40 and 0.60 for the C and T alleles, respectively. No significant differences in allele frequency (p > 0.176) and genotype frequency (p > 0.255) were detected between the two groups. These findings suggest that the CT or TT genotype does not increase the risk for childhood ALL in Mexican patients. On the other hand, significant differences in allele frequencies were detected in the comparison of Mexican healthy subjects with other populations. Whether these differences are fortuitous or related to diverse genetic backgrounds remains to be elucidated.

A de novo interstitial 6q deletion in a boy with a split hand malformation.

We report on a de novo interstitial deletion of (6)(q15q22.2) in a 5-year-old boy with developmental delay, microcephaly, facial dysmorphism, cryptorchidism, congenital heart defect, and split-hand malformation. Previous reports and this patient suggest that 6q21 may contain a gene or genes related either directly or indirectly to limb development.