Interethnic differences in UGT1A4 genetic polymorphisms between Mexican Mestizo and Spanish populations.

UDP-glucuronosyltransferase 1A4 (UGT1A4) is a phase II drug-metabolizing enzyme that catalyzes the glucuronidation of many clinically-important drugs. Interethnic differences in the genetic polymorphism of UGT1A4 have been reported; however, there is no information in Mexican Mestizos (MMs) and Spaniards (SPs). Furthermore, MM is an admixed population with 26 % of Caucasian genes mainly from Spain. Therefore, this study aimed to investigate the potential differences between 318 SPs and 248 MMs healthy individuals regarding UGT1A4*1b, UGT1A4*2 and UGT1A4*3 alleles and to compare the observed frequencies with those previously reported in different populations. The allelic frequencies of the three UGT1A4 polymorphisms showed interethnic differences between MMs and SPs (p < 0.05). The analyzed SNPs variants in this genetic region were not in linkage disequilibrium (LD) for the MM population, suggesting that these mutations have arisen independently in the same genetic background. In contrast, UGT1A4*2 and UGT1A4*3 were in LD in the SP population. Comparison of present data with other in different ethnic groups revealed that the frequencies of UGT1A4*2 and UGT1A4*3 in SP were similar to other Caucasians and higher than in Asians, whereas in MMs were lower than in Caucasians and higher than in Asians only for UGT1A4*2. Present results could be helpful to improve the use of UGT1A4 drug substrates in order to adjust them to the ethnic background of a given population, specifically for Hispanics.

Pharmacogenetics of the antiepileptic drugs phenytoin and lamotrigine.

Patients treated with antiepileptic drugs can exhibit large interindividual variability in clinical efficacy or adverse effects. This could be partially due to genetic variants in genes coding for proteins that function as drug metabolizing enzymes, drug transporters or drug targets. The purpose of this article is to provide an overview of the current knowledge on the pharmacogenetics of two commonly prescribed antiepileptic drugs with similar mechanisms of action; phenytoin (PHT) and lamotrigine (LTG). These two drugs have been selected in order to model the pharmacogenetics of Phase I and Phase II metabolism for PHT and LTG, respectively. In light of the present evidence, patients treated with PHT could benefit from CYP2C9 and CYP2C19 genotyping/phenotyping. For those under treatment with LTG, UGT1A4 and UGT2B7 genotyping might be of clinical use and could contribute to the interindividual variability in LTG concentration to dose ratio in epileptic patients.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) in two Mexican brothers harboring a novel mutation in the ECGF1 gene.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare autosomal recessive disease caused by mutations in the thymidine phosphorylase gene located on chromosome 22q13.32-ter, causing defective functioning of the enzyme. At present 87 sporadic or familial cases have been reported and 52 different mutations identified. We present herein the clinical, neuromuscular and molecular findings of two affected brothers from an indigenous Mexican family living in a very small village not far from Mexico City, both brothers being homozygous for a novel mutation (Leu133Pro) in exon 3 of the ECGF1 gene.

Microsatellite analysis in Turner syndrome: parental origin of X chromosomes and possible mechanism of formation of abnormal chromosomes.

Turner syndrome is a chromosomal disorder in which all or part of one X chromosome is missing. The meiotic or mitotic origin of most cases remains unknown due to the difficulty in detecting hidden mosaicism and to the lack of meiotic segregation studies. We analyzed 15 Turner patients, 10 with a 45,X whereas the rest had a second cell line with abnormal X-chromosomes: a pseudodicentric, an isochromosome, one large and one small ring, and the last with a long arm deletion. Our aims were: to detect X cryptic mosaicism in patients with a 45,X constitution; to determine the parental origin of the abnormality; to infer the zygotic origin of the karyotype and to suggest the timing and mechanism of the error(s) leading to the formation of abnormal X chromosomes from maternal origin. Molecular investigation did not revealed heterozygosity for any microsatellite, excluding X mosaicism in the 45,X cases. Parental origin of the single X chromosome was maternal in 90% of these patients. Three of the structurally abnormal Xs were maternally derived whereas the other two were paternal. These results allowed us to corroborate breakpoints in these abnormal X chromosomes and suggest that the pseudodicentric chromosome originated from post-zygotic sister chromatid exchange, whereas the Xq deleted chromosome probably arose after a recombination event during maternal meiosis.

Low frequency of common LRRK2 mutations in Mexican patients with Parkinson's disease.

Mutations in leucine-rich repeat kinase 2 gene (LRRK2) account for as much as 5-6% of familial Parkinson's disease (PD) and 1-2% of sporadic PD. These mutations represent the most frequent cause of autosomal dominant PD, particularly in certain ethnic groups. In this first report concerning LRRK2 mutations in Mexican-mestizos, we screened 319 consecutive PD patients (186 males; 133 females; mean age at onset: 52.4 years) for LRRK2 mutations in exons 31 and 41 and for the mutation in exon 35, which produces the Y1699C substitution. Three (0.94%) patients, two with sporadic PD and one with familial PD (disease mean age at onset, 53.3 years), were heterozygous for LRRK2 mutations. Of these three, two patients had one of two different mutations in exon 31 (R1441G and R1441H, respectively); the other patient carried the G2019S mutation in exon 41. The Y1699C mutation was absent from this PD sample. Four additional subjects, unaffected relatives of one PD patient with a mutation in LRRK2, were subsequently genetically tested. None of the three LRRK2 mutations identified was present in 200 neurologically healthy Mexican control individuals. These findings have important implications for molecular testing of LRRK2 mutations in Mexican PD patients.

A novel PtdIns3P and PtdIns(3,5)P2 phosphatase with an inactivating variant in centronuclear myopathy.

In eukaryotic cells, phosphoinositides are lipid second messengers important for many cellular processes and have been found dysregulated in several human diseases. X-linked myotubular (centronuclear) myopathy is a severe congenital myopathy caused by mutations in a phosphatidylinositol 3-phosphate (PtdIns3P) phosphatase called myotubularin, and mutations in dominant centronuclear myopathy (CNM) cases were identified in the dynamin 2 gene. The genes mutated in autosomal recessive cases of CNMs have not been found. We have identified a novel phosphoinositide phosphatase (hJUMPY) conserved through evolution, which dephosphorylates the same substrates as myotubularin, PtdIns3P and PtdIns(3,5)P(2), in vitro and ex vivo. We found, in sporadic cases of CNMs, two missense variants that affect the enzymatic function. One of these appeared de novo in a patient also carrying a de novo mutation in the dynamin 2 gene. The other missense (R336Q) found in another patient changes the catalytic arginine residue of the core phosphatase signature present in protein tyrosine/dual-specificity phosphatases and in phosphoinositide phosphatases and drastically reduces the enzymatic activity both in vitro and in transfected cells. The inheritance of the phenotype with regard to this variant is still unclear and could be either recessive with an undetected second allele or digenic. We propose that impairment of hJUMPY function is implicated in some cases of autosomal CNM and that hJUMPY cooperates with myotubularin to regulate the level of phosphoinositides in skeletal muscle.