Association of tyrosine hydroxylase 01 (TH01) microsatellite and insulin gene (INS) variable number of tandem repeat (VNTR) with type 2 diabetes and fasting insulin secretion in Mexican population

PURPOSE

A variable number of tandem repeats (VNTR) in the insulin gene (INS) control region may be involved in type 2 diabetes (T2D). The TH01 microsatellite is near INS and may regulate it. We investigated whether the TH01 microsatellite and INS VNTR, assessed via the surrogate marker single nucleotide polymorphism rs689, are associated with T2D and serum insulin levels in a Mexican population.

METHODS

We analyzed a main case-control study (n = 1986) that used univariate and multivariate logistic regression models to calculate the risk conferred by TH01 and rs689 loci for T2D development; rs689 results were replicated in other case-control (n = 1188) and cross-sectional (n = 1914) studies.

RESULTS

TH01 alleles 6, 8, 9, and 9.3 and allele A of rs689 were independently associated with T2D, with differences between sex and age at diagnosis. TH01 alleles with ≥ 8 repeats conferred an increased risk for T2D in males compared with ≤ 7 repeats (odds ratio, ≥ 1.46; 95% confidence interval, 1.1-1.95). In females, larger alleles conferred a 1.5-fold higher risk for T2D when diagnosed ≥ 46 years but conferred protection when diagnosed ≤ 45 years. Similarly, rs689 allele A was associated with T2D in these groups. In males, larger TH01 alleles and the rs689 A allele were associated with a significant decrease in median fasting plasma insulin concentration with age in T2D cases; the reverse occurred in controls.

CONCLUSION

Larger TH01 alleles and rs689 A allele may potentiate insulin synthesis in males without T2D, a process disabled in those with T2D.

The role of single nucleotide variant rs3819817 of the Histidine Ammonia-Lyase gene and 25-Hydroxyvitamin D on bone mineral density, adiposity markers, and skin pigmentation, in Mexican population

PURPOSE

Vitamin D (VD) deficiency and osteoporosis have become a global public health problem. A variant in the Histidine Ammonia-Lyase (HAL) gene has been associated with VD levels and bone mineral density (BMD). However, whether this variant has an influence on VD levels and BMD in Mexican adults remain unclear.

METHODS

This cross-sectional analysis included 1,905 adults participating in the Health Worker Cohort Study and 164 indigenous postmenopausal women from the Metabolic Analysis in an Indigenous Sample (MAIS) cohort. The rs3819817 variant was genotyped by TaqMan probe assay. Total 25 hydroxyvitamin D levels were measured by DiaSorin Liaison. BMD at the different sites was assessed through dual-energy X-ray absorptiometry. Linear and logistic regression models were performed to evaluate the associations of interest.

RESULTS

The prevalence of VD deficiency was 41%, showing differences between sexes. Obesity and skin pigmentation were associated with lower levels of VD in males and females. rs3819817-T allele was associated with low levels of 25-hydroxyvitamin D, VD deficiency, and hip and femoral neck BMD values (g/cm²). We found two interactions with VD levels, one between adiposity and rs3819817-T allele (P = 0.017) and another between skin pigmentation and rs3819817-T allele (P = 0.019). In indigenous postmenopausal women, we observed higher VD levels in the southern region compared to the northern region (P < 0.001); however, we did not observe differences by genotype.

CONCLUSION

Our findings confirm that the genetic variant rs3819817 has an essential function in VD levels and BMD and suggests a role in skin pigmentation in the Mexican population.

Pigmentary mosaicism as a recurrent clinical manifestation in three new patients with mosaic trisomy 12 diagnosed postnatally: cases report and literature review

Background

To date, only twenty-one cases diagnosed postnatally with mosaic trisomy 12 have been reported. The most frequent phenotypic manifestations are developmental delay, dysmorphic facial features, congenital heart defects, digital alterations, and pigmentary disorders. In the present report, detailed clinical and genetic profiles of three unrelated new patients with mosaic trisomy 12 are described and compared with previously reported cases.

Case presentation

In the present report, we include the clinical, cytogenetic, and molecular description of three Mexican patients diagnosed postnatally with mosaic trisomy 12. At phenotypic level, the three patients present with developmental delay, dysmorphic facial features, congenital heart defects and skin pigmentary anomalies. Particularly, patient 1 showed unique eye alterations as bilateral distichiasis, triple rows of upper lashes, and digital abnormalities. In patient 2 redundant skin, severe hearing loss, and hypotonia were observed, and patient 3 presented with hypertelorism and telecanthus. Hyperpigmentation with disseminated pigmentary anomalies is a common trait in all of them. The cytogenetic study was carried out under the strict criteria of analysis, screening 50–100 metaphases from three different tissues, showing trisomy 12 mosaicism in at least one of the three different tissues analyzed. With SNParray, the presence of low-level mosaic copy number variants not previously detected by cytogenetics, and uniparental disomy of chromosome 12, was excluded. STR markers allowed to confirm the absence of uniparental disomy as well as to know the parental origin of supernumerary chromosome 12.

Conclusions

The detailed clinical, cytogenetic, and molecular description of these three new patients, contributes with relevant information to delineate more accurately a group of patients that show a heterogeneous phenotype, although sharing the same chromosomal alteration. The possibility of detecting mosaic trisomy 12 is directly associated with the sensitivity of the methodology applied to reveal the low-level chromosomal mosaicism, as well as with the possibility to perform the analysis in a suitable tissue.

Association between vitamin D deficiency and common variants of Vitamin D binding protein gene among Mexican Mestizo and indigenous postmenopausal women

PURPOSE

Vitamin D deficiency (VDD) and polymorphisms in the group-specific component (GC) gene are known to be associated in different populations. However, the effects of such genetic variants may vary across different populations. Thus, the objective of this study was to estimate the association between Vitamin D-Binding Protein (VDBP) haplotypes and VDD in mestizo postmenopausal women and Mexican Amerindian ethnic groups.

METHODS

This was a cross-sectional study of 726 postmenopausal Mexican women from the Health Workers Cohort Study (HWCS) and 166 postmenopausal women from the Metabolic Analysis in an Indigenous Sample (MAIS) cohort in Mexico. GC polymorphisms (rs7045 and rs4588) were analyzed by TaqMan probes. Serum 25-hydroxyvitamin D [25(OH)D] levels were measured by Chemiluminescent Microparticle Immuno Assay.

RESULTS

The prevalence of VDD serum 25(OH)D < 20 ng/mL was 43.7% in mestizo women and 44.6% in indigenous women. In HWCS, the single nucleotide polymorphisms (SNPs) rs7041 and rs4588 were associated with VDD. In addition, women from the HWCS, carrying the haplotypes GC2/2 and GC1f/2 had higher odds of VDD (OR = 2.83, 95% CI 1.14, 7.02; and OR = 2.30, 95% CI 1.40, 3.78, respectively) compared to women with haplotype 1f/1 s. These associations were not statistically significant in the MAIS cohort.

CONCLUSIONS

Our results show genetic association of the analyzed SNPs and related haplotypes, on the GC gene, with VDD in mestizo Mexican postmenopausal women. Moreover, a high prevalence of VDD with high genetic variability within the country was observed. Our results support the need for national policies for preventing VDD.

Curcumin induces p53-independent inactivation of Nrf2 during oxidative stress-induced apoptosis

The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) is a master regulator of a battery of antioxidant and detoxificant genes with cytoprotective function. Since Nrf2 inactivation is necessary for the complete execution of apoptosis in the presence of extensive cellular damage caused by oxidative stress, constant activation of Nrf2 may protect tumoral cells from apoptosis. The tumor suppressor gene p53 has been suggested to participate in apoptosis-related repression of Nrf2. Thus, we studied the inactivation of Nrf2 during oxidant-induced apoptosis in a p53 dysfunctional cellular model. Using curcumin dose-response assay and time-response assay in an immortalized lymphoblastoid cell line (control line 45), we observed a time-dependent increase in apoptotic markers such as deoxyribonucleic acid (DNA) fragmentation, phosphatidylserine exposure, and caspase-3, caspase-9 and poly (ADP-ribose) polymerases (PARP) cleavage. Interestingly, at early times of exposure to a proapoptotic dose of curcumin (15 μM), we observed nuclear accumulation of Nrf2 and the expression of Nrf2 target genes, whereas at late exposure times we found a reduction of total and nuclear protein levels of Nrf2 as well as downregulation of Nrf2 target genes in the absence of p53 activation. These data suggest that apoptosis-related inactivation of Nrf2 could occur in a p53 dysfunctional background, opening the possible occurrence of p53-independent mechanism to explain Nrf2 inactivation during apoptosis.

Origin of the myotonic dystrophy type 1 mutation in Mexican population and influence of Amerindian ancestry on CTG repeat allelic distribution

Myotonic dystrophy type 1 is caused by expansion of a CTG trinucleotide repeat situated in the DMPK gene. Worldwide genetic studies suggest a single or limited number of mutational events cause the disease. However, distribution of CTG alleles and disease incidence varies among ethnicities. Due to the great ethnic diversity of the Mexican population, the present study was aimed at analyzing the impact of different lineages in shaping the CTG-repeat allelic distribution in the contemporary Mexican-Mestizo population as well as to shed light on the DM1 ancestral origin. Distribution of CTG-repeat alleles was similar among Mestizo and Amerindian subpopulations with (CTG)_11-13 being the most frequent alleles in both groups, which implies that Mexican-Mestizo allelic distribution has been modeled by Amerindian ancestry. We diagnosed a relatively high number of cases, consistent with the high frequency of large-normal alleles found in Mexican subpopulations. Haplotype analysis using various polymorphic-markers in proximity to DMPK gene indicates that a single founder mutation originates myotonic dystrophy type 1 in Mexico; however, Y-STR haplogroups data and the presence of pre-mutated and large normal alleles in Amerindians support the hypothesis that both European and Amerindian ancestral chromosomes might have introduced the disease to the Mexican population, which was further disseminated through mestizaje.

ERBIN deficiency links STAT3 and TGF-β pathway defects with atopy in humans

Lyons et al. show that STAT3 negatively regulates TGF-β signaling via ERBIN and that cell-intrinsic deregulation of TGF-β pathway activation promotes the IL-4/IL-4Rα/GATA3 axis to support atopic phenotypes in humans.

Nonimmunological connective tissue phenotypes in humans are common among some congenital and acquired allergic diseases. Several of these congenital disorders have been associated with either increased TGF-β activity or impaired STAT3 activation, suggesting that these pathways might intersect and that their disruption may contribute to atopy. In this study, we show that STAT3 negatively regulates TGF-β signaling via ERBB2-interacting protein (ERBIN), a SMAD anchor for receptor activation and SMAD2/3 binding protein. Individuals with dominant-negative STAT3 mutations (STAT3^mut) or a loss-of-function mutation in ERBB2IP (ERBB2IP^mut) have evidence of deregulated TGF-β signaling with increased regulatory T cells and total FOXP3 expression. These naturally occurring mutations, recapitulated in vitro, impair STAT3–ERBIN–SMAD2/3 complex formation and fail to constrain nuclear pSMAD2/3 in response to TGF-β. In turn, cell-intrinsic deregulation of TGF-β signaling is associated with increased functional IL-4Rα expression on naive lymphocytes and can induce expression and activation of the IL-4/IL-4Rα/GATA3 axis in vitro. These findings link increased TGF-β pathway activation in ERBB2IP^mut and STAT3^mut patient lymphocytes with increased T helper type 2 cytokine expression and elevated IgE.

La relación de <i>Helicobacter pylori</i> con la displasia y el cáncer gástrico en Costa Rica

Se comparó la incidencia de labaéteria Hdicobacter pylori en un lugar pe baja incidencia de cáncer gástrico, Poás ( 15. 13%) y otro de incidencia muy alta, Puriscal (83. 53%) Se eligió a 185 adultos de cada cantón, similares en edad y sexo y se practicó un estudio serológico para buscar anticuerpos IgG para H. pylori, y una gastroscopía para tomar dos biopsias por caso. Los resultados no apoyan la existencia de una fuerte relación entre H. pylori y cáncer gástrico

SPINK5 and ADRB2 haplotypes are risk factors for asthma in Mexican pediatric patients

BACKGROUND

Asthma is one of the most common respiratory diseases worldwide, and the complexity of its etiology has been widely documented. Chromosome 5q31-33 is one of the main loci implicated in asthma and asthma-related traits. IL13, CD14 and ADRB2, which are located in this risk locus, are among the genes most strongly associated with asthma susceptibility.

OBJECTIVES

This study evaluated whether single-nucleotide polymorphisms or haplotypes at 5q31-33 conferred risk for asthma in Mexican-Mestizo pediatric patients.

METHODS

We performed a case-controlled study including 851 individuals, 421 of them affected with childhood-onset asthma and 430 ethnically matched unaffected subjects. We used the TaqMan Allelic Discrimination Assay to genotype 20 single-nucleotide polymorphisms within IL5, RAD50, IL13, IL4, CD14, SPINK5, HTR4, ADRB2 and IL12B.

RESULTS

Although no association was detected for any risk allele, three SPINK5 haplotypes (GGCT: p = 6 × 10(-6); AATC: p = 0.0001; AGTT: p = 0.0001) and five ADRB2 haplotypes (AGGACC: p = 0.0014; AGGAAG: p = 0.0002; TGAGAG: p = 0.0001; AGGAAC: p = 0.0002; AAGGAG: p = 0.003) were associated with asthma. Notably, the AGTT SPINK5 haplotype exhibited a male gender-dependent association (p = 7.6 × 10(-5)).

CONCLUSION

Our results suggest that SPINK5 and ADRB2 haplotypes might play a role in the susceptibility to childhood-onset asthma.

Nuclear factor erythroid 2-related factor gene variants and susceptibility of arsenic-related skin lesions

Inorganic arsenic (iAs) is an important pollutant associated with various chronic-degenerative diseases. The cytoprotective protein nuclear factor erythroid 2-related factor (NRF2) has been proposed as an important responsive mechanism against iAs exposure. The aim of this study was to determine whether the risk of skin lesions in people exposed to iAs-contaminated water could be modified by the presence of single nucleotide polymorphisms in the NRF2 coding gene. We studied 117 individuals with long-term iAs exposure and 120 nonexposed individuals. Total As was determined in water, meanwhile iAs and its metabolites were measured in urine. The iAs-induced skin lesion status was evaluated by expert dermatologists. We sequenced the promoter region of NRF2 in a sample of 120 healthy donors. We found four polymorphisms previously reported and one novel polymorphism in the 5′ regulatory region of the NRF2. In this study, we did not find allelic and genotype association of NRF2 polymorphisms with iAs-related skin lesion. However, the analysis of haplotypes composed by –653GA, and –617CA NRF2 single nucleotide polymorphisms showed a significant association with protection against skin lesions in the low-As exposure group. This is the first report studying the association between NRF2 polymorphisms and susceptibility of As-related skin lesions. Increasing the sample size will allow us to confirm this data.

Juvenile rheumatoid arthritis and asthma, but not childhood-onset systemic lupus erythematosus are associated with FCRL3 polymorphisms in Mexicans

A regulatory single nucleotide polymorphism located in the 5' region (-169T/C) of the Fc receptor-like 3 (FCRL3_3) gene has been associated with both susceptibility and protection in immune diseases. This case-control study aimed to evaluate the association between FCRL3 polymorphisms and juvenile rheumatoid arthritis (JRA), asthma, and childhood-onset systemic lupus erythematosus (SLE) in a Mexican population. We performed PCR-based genotyping to identify four FCRL3 single nucleotide polymorphisms (FCRL3_3 to FCRL3_6) in patients with JRA (n=202), asthma (n=239), or childhood-onset SLE (n=377), and healthy controls (n=400). The case-control analysis showed a male-gender dependent association between the FCRL3_3C, FCRL3_5C, and FCRL3_6A alleles and either JRA (OR=0.57, p=0.003; OR=0.55, p=0.002; OR=0.53, p=0.0007, respectively) or asthma (OR=0.72, p=0.04; OR=0.74, p=0.05; OR=0.70, p=0.02, respectively). As expected, minor alleles of these SNPs with the CGCA haplotype were also significantly associated with JRA (OR=0.35, p=0.00005) and asthma (OR=0.61, p=0.007). We found no association between FCRL3 SNPs or haplotypes and childhood-onset SLE. These results supported the notion that FCRL3 is involved in the etiology of several immune diseases. Our results also suggested that SNPs located in the FCRL3 gene were protective against JRA and asthma in male Mexican patients.

MiR-146a polymorphism is associated with asthma but not with systemic lupus erythematosus and juvenile rheumatoid arthritis in Mexican patients

Extensive research has shown that aberrant expression of microRNAs (miRNAs) plays an important role in innate and adaptive immune responses. The rs2910164 polymorphism has been identified as a functional variant, which affects the transcription and expression level of miR-146a and, thereby, contributes to the pathogenesis of several inflammatory and autoimmune diseases. To investigate whether the rs2910164 G/C polymorphism was associated with asthma, systemic lupus erythematosus (SLE) or juvenile rheumatoid arthritis (JRA), we performed an association study in a pediatric Mexican cohort. We included 979 pediatric patients (asthma: 402, SLE: 367 and JRA: 210) and 531 control subjects without inflammatory or immune diseases. Genotyping was performed using the 5' exonuclease technique. The genotype distribution of the rs2910164 polymorphism was in Hardy-Weinberg equilibrium in each group. No significant differences were detected in the distribution of this polymorphism between cases and controls (P = 0.108, 0.609 and 0.553 for subjects with asthma, JRA and SLE, respectively). However, stratification by gender showed a statistically significant difference between asthmatic and control females, where the C allele was significantly associated with protection to asthma (odds ratio = 0.694, 95% confidence interval 0.519-0.929, P = 0.0138). Our results provide evidence that rs2910164 may play a role in the susceptibility to childhood-onset asthma, but not SLE or JRA in Mexicans. Further association studies may contribute to determining the role of miR-146a single-nucleotide polymorphisms in immune-mediated diseases.

The NRF2 gene variant, -653G/A, is associated with nephritis in childhood-onset systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease associated with oxidative stress and characterized by chronic inflammation. Kidney malfunction, an aggressive characteristic of this disease, is not present in all affected individuals. The Nrf2-Keap1 pathway is important in protecting against oxidative stress and inflammation. Mouse models and genome-wide scans have suggested NRF2 (Nuclear factor (erythroid-derived 2)-like 2) as a candidate gene for susceptibility to SLE. We therefore investigated whether NRF2 polymorphisms are associated with childhood-onset SLE in a Mexican Mestizo population. Two single nucleotide polymorphisms (SNPs) were genotyped by TaqMan((R)) assays in 362 patients with childhood-onset SLE and 379 controls. We found no significant association between susceptibility to SLE and NRF2 polymorphisms. However, after population stratification by gender, the heterozygous genotype of the -653G/A SNP was significantly associated with nephritis in females only [OR = 1.81, CI (1.04-3.12), p = 0.032]. This association was stronger in females affected with severe nephritis [classes IV-VI; OR = 2.16, CI (1.12-4.15), p = 0.019]. Our results suggest that NRF2 is not associated with susceptibility to childhood-onset SLE, but it could confer a risk for developing kidney malfunction in SLE-affected individuals.

STAT4 associates with systemic lupus erythematosus through two independent effects that correlate with gene expression and act additively with IRF5 to increase risk

OBJECTIVES

To confirm and define the genetic association of STAT4 and systemic lupus erythematosus (SLE), investigate the possibility of correlations with differential splicing and/or expression levels, and genetic interaction with IRF5.

METHODS

30 tag SNPs were genotyped in an independent set of Spanish cases and controls. SNPs surviving correction for multiple tests were genotyped in five new sets of cases and controls for replication. STAT4 cDNA was analysed by 5'-RACE PCR and sequencing. Expression levels were measured by quantitative PCR.

RESULTS

In the fine mapping, four SNPs were significant after correction for multiple testing, with rs3821236 and rs3024866 as the strongest signals, followed by the previously associated rs7574865, and by rs1467199. Association was replicated in all cohorts. After conditional regression analyses, two major independent signals, represented by SNPs rs3821236 and rs7574865, remained significant across the sets. These SNPs belong to separate haplotype blocks. High levels of STAT4 expression correlated with SNPs rs3821236, rs3024866 (both in the same haplotype block) and rs7574865 but not with other SNPs. Transcription of alternative tissue-specific exons 1, indicating the presence of tissue-specific promoters of potential importance in the expression of STAT4, was also detected. No interaction with associated SNPs of IRF5 was observed using regression analysis.

CONCLUSIONS

These data confirm STAT4 as a susceptibility gene for SLE and suggest the presence of at least two functional variants affecting levels of STAT4. The results also indicate that the genes STAT4 and IRF5 act additively to increase the risk for SLE.

BCR-ABL, ETV6-RUNX1 and E2A-PBX1: prevalence of the most common acute lymphoblastic leukemia fusion genes in Mexican patients

This study was conducted to determine the frequency of the most common fusion genes in Mexican pediatric patients with acute lymphoblastic leukemia (ALL). Molecular analysis using RT-PCR was carried out in 53-blood samples: 52 patients with de novo ALL and one with relapsed ALL. The ETV6-RUNX1 fusion was found in 7 cases (13.5%), BCR-ABL fusion was detected in 2 cases (3.8%), and 6 patients (11.5%) expressed the chimeric gene E2A-PBX1. The prevalence of E2A-PBX1 is one of the highest that has been described thus far in childhood ALL. Furthermore, we detected both the BCR-ABL, and E2A-PBX1 fusion in the relapsed patient. With regards to the immunophenotype, ETV6-RUNX1 was expressed in both pre-B and T-cell cases, while the presence of E2A-PBX1 and BCR-ABL was associated with the pre-B ALL phenotype. The prevalence of E2A-PBX1 in Mexican pediatric cases supports the existence of ethnic differences in the frequency of molecular markers of ALL.

Spectrum of RB1 gene mutations and loss of heterozygosity in Mexican patients with retinoblastoma: identification of six novel mutations

RB1 mutation detection has greatly improved the clinical management of retinoblastoma and provides critical information to predict the risk of inheriting the disease. We screened for RB1 gene sequence alterations in both peripheral blood and tumor specimens from a total of 48 Mexican retinoblastoma patients using an SSCP-based screening approach followed by sequencing. Overall, 21 (43.8%) cases were bilateral and 27 (56.2%) were unilateral. Interestingly, 51.8% of unilateral patients developed the tumor before age 1 year and 10 of which (71.4%) were diagnosed before the age of 6 months. Thirteen different oncogenic mutations were detected in 14/48 (29.2%) patients, 9 of which were germline (64.3%). Six of these mutations are novel (IVS3-1G>T, 125X, 389X, 610X, 750X and -149G>T). The most frequent types of mutation were frameshift and nonsense (30.8% each). Moreover, 5 intronic variants were identified, two of which are novel (g.41908 C/A and g.161976del6T). Loss of heterozygosity of the RB1 gene as assessed by intron1/BamHI and intron17/XbaI intragenic markers was 50.0% (18 of 36 informative cases), being higher in tumors with known mutations (76.9% vs 34.8%). This low mutation detection rate and the earlier age at diagnosis in unilateral retinoblastoma cases suggest that other RB1 inactivating mechanisms could be present in the retinoblastoma development. In this study, mutation analysis was not helpful to distinguish sporadic and hereditary retinoblastoma, so, other approaches are needed to improve the molecular diagnosis of retinoblastoma and supports further investigations of Mexican retinoblastoma patients.

Association analysis of the PTPN22 gene in childhood-onset systemic lupus erythematosus in Mexican population

Several studies have identified a functional single nucleotide polymorphism 1858C/T in the PTPN22 gene to be associated with several autoimmune diseases. Association studies of this polymorphism with familial and sporadic systemic lupus erythematosus (SLE) have shown some discrepancies. To our knowledge, this is the first study that includes only pediatric-onset SLE patients. We performed a case-control association study in 250 unrelated Mexican patients with childhood-onset SLE consisting of 228 cases with sporadic SLE and 22 cases with familial SLE and 355 healthy controls. We observed a statistically significant difference in the frequency of the PTPN22 1858T allele between SLE patients (3.4%) and healthy controls (1.1%) (P=0.0062, odds ratio (OR) 3.09 (95% confidence interval 1.32-7.21)). The association was also observed when only sporadic cases were analyzed (OR=3.19). Our results support the association of the PTPN22 1858T allele with sporadic childhood-onset SLE in Mexican population.

[Treatment of strabismus associated with psychomotor impairment using botulinum toxin]

PURPOSE

Strabismus is associated with 80% of people with psychomotor retardation. Surgical treatment is difficult owing to brain instability. The aim of this study is to determine the efficacy of a direct application of botulinum toxin in cases strabismus related to psychomotor retardation.

METHODS

This is a retrospective, longitudinal, observational study of treatment of strabismus associated to brain damage (under the Laws of Health of Mexico) using a direct application technique of botulinum toxin, considering age, type of strabismus, number of toxin applications, response and cause of brain damage.

RESULTS

We analyzed 30 patients, age: 3.5 years old (S.D.: 2), follow-up 12.7 (S.D.: 2.3 months). Eighty percent of the patients had moderate psychomotor retardation and 20% had a severe retardation. The response was good in 44% and moderate in 24%, there were no cases without response. The patients were treated with 1.7 (S.D.:1) injections of toxin. Age and type of strabismus was not related to success of treatment (X2: 9.4; 7.8 to null hypothesis). First application of toxin determines the response to treatment (Fisher test: <0.05). Moderate retardation was related to better response. Bad results were related to unstable brain disease.

CONCLUSIONS

The difficulty and prognosis of surgical treatment of strabismus in patients with brain damage and psychomotor retardation, causes us to consider the use of botulinum toxin as the first choice for this cases.

XV-2c/KM-19 haplotype analysis of cystic fibrosis mutations in Mexican patients

We analyzed 97 unrelated Mexican cystic fibrosis (CF) patients and their first-degree relatives to study the association of XV2C/TaqI/KM19/PstI haplotypes with CF mutations in this population. Haplotype phases could be established in 148 CF and 110 normal chromosomes, and haplotype distributions of normal and CF chromosomes differed significantly (P < 0.001). DeltaF508 and G542X mutations accounted for 56% of CF chromosomes and were found to be associated with haplotype B in 97.2% and 72.7% of chromosomes, respectively. The haplotype distribution of CF chromosomes carrying other rare and unknown mutations was similar to that of normal chromosomes (P > 0.05), haplotypes A and C being the most frequent. This is in accordance with the extensive heterogeneity and the spectrum of mutations reported in Mexican CF patients. We also report the haplotype distribution of all informative chromosomes bearing rare mutations; some were found to be associated with previously reported haplotypes, whereas others were found on different haplotypes. Recombination or recurrence of mutations may explain these different associations, although other intragenic markers must be used to better understand the origin and dispersion of CF mutations in our country. XK haplotype analysis allowed carrier detection among sibs in 24.3% of families, showing that this method may be useful for carrier detection in populations with high allelic heterogeneity.

Carrier detection and prenatal molecular diagnosis in a Duchenne muscular dystrophy family without any affected relative available

In this paper we report a family where the affected DMD patients were not available for study and a molecular strategy was used for female carriers detection and for prenatal diagnosis. Linkage analysis was performed with two markers within the DMD gene, in all family members screened. DMD markers used (pERT87.8/Taq1 and pERT87.15/Xmn1) seemed not to be informative because the propositas mother (II-2) was homozygous for the minor allele at each marker (T2 and X2), however, the proposita and one sister carried only the major allele, which was inherited from the father. These results suggested that a deletion involving both markers could be present, and was inherited from the mother to both daughters. Quantitative multiplex PCR confirmed the deletion in female carriers, involving at least exons 12 to 17. DNA studies of cultured amniotic fluid cells at 14 weeks gestation, by amplification of specific Y-chromosome sequences, followed by multiplex PCR, lead to the diagnosis of a male fetus affected by DMD.

Hemodynamic effects of iodixanol and iohexol during ventriculography in patients with compromised left ventricular function

A crossover study was performed to compare the hemodynamic effects of the iso-osmolar contrast agent iodixanol (Visipaque) 320 mg I/ml to those of the low-osmolar iohexol (Omnipaque) 350 mg I/ml. The main hypothesis was that iodixanol and iohexol would affect left ventricular end-diastolic pressure (LVEDP) to different degrees. In 48 patients with reduced cardiac function (mean ejection fraction 33. 4%), one ventricular injection was performed with each contrast medium. Ventricular, aortic and right atrial pressures and heart rate were measured continuously. Cardiac output (using Fick's principle) and systemic vascular resistance were calculated. LVEDP increased with both agents, but significantly less after iodixanol than after iohexol (P < 0.01), also in subgroups of patients in whom baseline LVEDP was severely increased and in whom 3-vessel disease was present. Immediate changes in variables reflecting vasodilatation were similar with both agents. In conclusion, both contrast agents influenced hemodynamics during ventriculography, but iodixanol had significantly less influence on LVEDP than did iohexol.

Alport syndrome and diffuse leiomyomatosis. Clinical aspects, pathology, molecular biology and extracellular matrix studies. A synthesis

The Alport syndrome-diffuse leiomyomatosis association can be defined as a hereditary disease of type IV collagen combining features of Alport syndrome (hematuric nephropathy, deafness and ocular abnormalities: anterior lenticonus, maculopathy) and leiomyomatosis involving oesophagus (diffuse type), tracheobronchial tree, and genitals (only in women). This entity is transmitted as an X-linked dominant trait. Mutations of both the COL4A5 and COL4A6 genes, located head to head in Xq22 encoding the alpha 5 and alpha 6(IV) chains are responsible for the abnormalities. Molecular studies have shown deletions of the 5' end of both COL4A5 and COL4A6 including the intergenic region. The breakpoint in COL4A6 is always located within intron 2. Immunohistochemistry has shown significant alterations of basement membranes in the kidney and esophageal leiomyomas. Leiomyomas lack alpha 5 and alpha 6(IV) chains, fibronectin and laminin beta 1 chains in the muscle basement membranes where they are normally expressed. The tumors also show myocyte anomalies: irregular expression of the alpha 5 integrin subunits, and disorganization of actin and desmin filaments. It is hypothesized that a third as yet unknown gene, situated within the large intron 2 in a critical 90 kb region, is responsible for the smooth muscle proliferation. Abnormalities of the basement membranes could destabilize interactions between muscular cells and the extracellular matrix.

Spectrum of CFTR mutations in Mexican cystic fibrosis patients: identification of five novel mutations (W1098C, 846delT, P750L, 4160insGGGG and 297-1G-->A)

We have analyzed 97 CF unrelated Mexican families for mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Our initial screening for 12 selected CFTR mutations led to mutation detection in 56.66% of the tested chromosomes. In patients with at least one unknown mutation after preliminary screening, an extensive analysis of the CFTR gene by single stranded conformation polymorphism (SSCP) or by multiplex heteroduplex (mHET) analysis was performed. A total of 34 different mutations representing 74.58% of the CF chromosomes were identified, including five novel CFTR mutations: W1098C, P750L, 846delT, 4160insGGGG and 297-1G-->A. The level of detection of the CF mutations in Mexico is still lower than that observed in other populations with a relatively low frequency of the deltaF508 mutation, mainly from southern Europe. The CFTR gene analysis described here clearly demonstrated the high heterogeneity of our CF population, which could be explained by the complex ethnic composition of the Mexican population, in particular by the strong impact of the genetic pool from southern European countries.

Ataxia-pancytopenia syndrome

We report on a Mexican girl who developed cerebellar ataxia at age 3 years and pancytopenia at age 13 years. Cerebral computed tomography scan and magnetic resonance imaging showed evidence of severe cerebellar atrophy. Telangiectasias were not present; immunoglobulins and alpha-fetoprotein levels were normal. Cytogenetic studies showed no evidence of spontaneous chromosome aberrations, a normal rate of diepoxybutane (DEB) and mitomycin C (MMC)-induced chromosome aberrations, but an increased response to bleomycin. The phenotype support the diagnosis of ataxia-pancytopenia syndrome, although monosomy of chromosome 7 was not found in bone marrow. The cytogenetic studies suggest that this may be a chromosomal instability disorder.

Molecular diagnosis of the fragile X and FRAXE syndromes in patients with mental retardation of unknown cause in Mexico

The fragile X syndrome (Fra-X) is the most common cause of inherited mental retardation with X-linked semi-dominant inheritance. The prevalence of Fra-X in the Mexican population is unknown. The aim of this population screening study was to determine if Fra-X or FRAXE mutations are the cause of a number of cases of mental retardation in a sample of Mexican children with mental retardation of unknown cause (MRUC) and to stress the importance of performing molecular analysis of the FMR-1 gene in all patients with MRUC. We report here the direct analysis of CGG and GCC repeats within the FMR-1 and FMR-2 genes, respectively, in 62 unrelated patients with MRUC. Two male index cases had the CGG expansion, although they did not express the Xq27.3 fragile site cytogenetically. Fra-X diagnosis was highly suspected on a clinical basis in one of the patients, but not in the other. Both mothers were found to be premutation carriers. The molecular studies of FMR-1 showed that the proportion of MRUC patients with Fra-X is 3.2%. This frequency was not significantly different to that reported in most populations. As reported in other series, no patients with FRAXE were found in our sample. Our findings confirm that the molecular analysis of the FMR-1 gene is necessary in MRUC patients to achieve unequivocal diagnosis of fragile X syndrome, carrier premutation detection and for accurate genetic counseling.

High frequency of de novo deletions in Mexican Duchenne and Becker muscular dystrophy patients. Implications for genetic counseling

Duchenne muscular dystrophy (DMD) is the most common lethal hereditary neuromuscular disease. As there is no effective treatment, accurate carrier detection is essential for genetic counseling and prevention. Although linkage analysis has been widely used for this purpose, being an indirect analysis it has several limitations. Using linkage analysis for carrier detection, we found serious limitations, mainly because 82.9% of all proposita were isolated cases. We used quantitative polymerase chain reaction for direct carrier detection in families with exon deletions and found a higher than expected frequency of de novo deletions (62.2%). Furthermore, only 20.7% of the mothers of isolated deletion DMD/Becker muscular dystrophy (BMD) patients were found to be carriers. This result suggests that the Mexican population has a high frequency of de novo DMD mutations.

[The relation of Helicobacter pylori with dysplasia and stomach neoplasms in Costa Rica]

Occurrence of the bacterium Helicobacter pylori was compared for two Costa Rican sites with contrasting levels of gastric cancer incidence, Poás (incidence 15.13%) and Puriscal (83.53%). A sample of 185 adults of similar age and sex proportions was studied in each site, using both H. pylori antiserum tests and gastroscopy to collect two biopsies per case. No clear association between H. pylori and gastric cancer was found.

Cytogenetic Monitoring of Farmers exposed to pesticides in Colombia

We have monitored 30 pesticide-exposed workers and 30 matched controls for expression of chromosome aberrations (CA) and sister chromatid exchanges (SCE) in their lymphocytes. Peripheral blood cultures were set up within 3 hr after the collection of samples, and four cultures were set up from each donor. For CA analysis, 100 complete metaphase cells from each donor were evaluated. For the SCE assay, 50 complete metaphase cells from each donor were analyzed. The CA and SCE data were analyzed for differences between the two groups using the chi 2 and the Student's t-test, respectively. From the CA analysis it was obvious that the overwhelming majority of aberrations were chromatid breaks and isochromatid breaks; therefore, only these data are presented and used for statistical analysis. Isochromatid breaks were counted as two breaks each and chromatid breaks as one in calculating the total chromatid break frequencies. Statistical evaluation of the data indicates that there is no significant difference (p > 0.05; chi 2 test) between the exposed and the nonexposed groups based on chromatid breaks per 100 cells (1.2 +/- 0.3 and 1.5 +/- 0.2, respectively) and total chromatid breaks per 100 cells (1.7 +/- 0.3 and 2.1 +/- 0.2, respectively). No significantly difference between the two groups (p > 0.05, Student's t-test) was observed with SCE frequencies (5.0 +/- 1.1 and 4.8 +/- 0.9, respectively). Linear regression analysis indicates that the data were not influenced by age, cigarette smoking, or alcohol consumption. It is assuring that the exposure conditions among these Indian farmers have not caused detectable increases of chromosome damage using standard assays; this suggests the lack of serious long-term health problems. However, periodic monitoring of such exposed populations should be conducted using the same or other more sensitive assays. In addition, other populations with exposure to different types of pesticides in Colombia should also be investigated.

G542X mutation in Mexican cystic fibrosis patients

We analyzed the frequency of the G542X mutation in a sample of 76 Mexican cystic fibrosis patients and the genotype-phenotype correlation. The mutation was screened using PCR-mediated site-directed mutagenesis, and was present on 7.2% of the CF chromosomes. This frequency is significantly higher than the worldwide frequency according to the Cystic Fibrosis Genetic Analysis Consortium (3.4%, p < 0.01), and similar to that reported in Spain (8%), which is in accordance with the ethnic origin of the Mexican population. All patients carrying G542X on at least one allele had mild to moderate pulmonary disease. In patients with hepatobiliary involvement, the frequency of G542X chromosomes was higher than the frequency of the mutation in all the Mexican CF chromosomes.

Mild cystic fibrosis disease in three Mexican delta-F508/G551S compound heterozygous siblings

We describe three delta-F508/G551S compound heterozygous siblings with a mild CF phenotype, characterized by mild chronic pulmonary disease, pancreatic sufficiency and increased sweat chloride levels. PCR-mediated site-directed mutagenesis detected the delta-F508 mutation on one allele, and the G551S mutation was detected by SSCP and sequence analysis of exon 11. Two previously described sisters who were homozygous for the G551S mutation had a very mild phenotype with normal sweat chloride concentrations. In our patients the mild phenotype resulted from the combined effect of the mild G551S allele with the severe delta-F508 allele.

Identification of the I507 deletion by site-directed mutagenesis

We describe a compound heterozygous delta-F508/delta-I507 cystic fibrosis patient. Molecular analysis by polymerase chain reaction (PCR)-mediated site-directed mutagenesis showed the 219 bp fragment observed in delta-F508 homozygotes. The father showed a delta-F508 heterozygous pattern while the mother and sister showed a normal pattern. There were four possibilities to explain these results: a) the patient was a delta-F508/delta-I507 compound heterozygote, because the delta-I507 allele fails to amplify when analyzed with delta-F508 primers due to a double mismatch between the primers and template; b) uniparental isodisomy; c) nonmaternity; and d) sample processing mix-up. We then tested for the delta-I507 mutation using specific primers with a single base mismatch, and we found that the patient was in fact a compound heterozygote who inherited the delta-F508 mutation from the father and the delta-I507 from the mother. We underscore the need to detect this rare deletion in patients showing a delta-F508 homozygous pattern when one parent, particularly the father, is a noncarrier.

Alport-leiomyomatosis syndrome: an update

Alport-leiomyomatosis syndrome is a polygenic syndrome with a dominant X-linked inheritance pattern resulting from a large deletion in the 5' end of the COL4A5 gene coding for the type IV collagen alpha 5 chains. Hypothetically, the deletion extends beyond the 5' end and probably includes a second contiguous gene responsible for leiomyomatosis (the DL gene) and even a third one coding for congenital cataract (the CCT gene).

[Alport's syndrome: new findings]

The Alport's syndrome is a disease characterized by a symptomatic triad: nephropathy, hypoacusia and ocular alterations. This syndrome is genetically heterogeneous and results from numerous mutations in COL4A5 gene, whose locus resides on the long arm of the X chromosome (Xq22). This gene codifies for IV collagen alpha 5 chain, which is a fundamental constituent of the glomerular, lens and Corti's organ basal membranes. Present knowledge on molecular genetics and the characterization of the different mutations that affect the Alport's gene will lead to classification of this syndrome in subtypes, according to those mutations, and to its phenotypic expressions; in addition, some syndromes, phenotypically similar, will probably have to be distinguished from Alport's disease, in a future, if a genetic alteration is found in genes other than COL4A5.

[A molecular study of the delta-F508 mutation and genetic analysis of a sample of cystic fibrosis patients]

The delta-F508 mutation was investigated in 39 index cases with cystic fibrosis (CF) using PCR-mediated site-directed mutagenesis. Eight patients were delta-F508 homozygous, 16 were delta-F508/unknown mutation compound heterozygous and 15 had unknown mutations in both alleles. Thus, delta-F508 was present in 41% of CF chromosomes and this frequency is lower than the observed among Northern European and North American Caucasians (70%), Southern Europe populations (50%) and Northern Mexico (59.1%). Age at present, age of onset of clinical data and age at diagnosis were lower in the group of delta-F508 homozygous, although the difference was not statistically significant. In this same group growth deficiency was more frequent than in the others. Among 84 brothers, 25 (28.9%) were affected. Pedigrees analysis showed that among 782 cousins, two were affected and in two families, other relatives born to non consanguineous parents had CF. These data suggest that, probably, the disease and heterozygous frequencies do not differ from the reported in Caucasians (1/2500 and 1/25 respectively). The low frequency of delta-F508 mutation could be due to the small size of the sample but it can also be explained by the heterogeneous genetic composition of the population living in Mexico or because a number of delta-F508 homozygous patients die at early ages without being diagnosed.

Frequency of delta F508 in a Mexican sample of cystic fibrosis patients

This paper reports the frequency of the delta F508 mutation in a cohort of 50 Mexican patients with cystic fibrosis (CF). The mutation was detected by PCR mediated site directed mutagenesis. delta F508 was found in 39% of CF chromosomes, a frequency lower than that reported in Argentina and Spain. The high rate of CF cases who die undiagnosed, the ethnic origin of Mexican populations, and the limited number of cases studied could account for the low frequency of the delta F508 mutation found in this preliminary report.

Detection of the cystic fibrosis delta-F508 mutation at autopsy by site-directed mutagenesis

In Caucasian populations cystic fibrosis (CF) is the most common autosomal recessive disorder. CF was previously considered rare in Mexico; however, the reported frequency is about 1% in autopsies. This discrepancy appears to be due to the inability to diagnose the illness during life. It is now known that in developing countries a great number of affected children die without the benefit of CF diagnosis and appropriate treatment. In this study we have used the PCR-mediated site-directed mutagenesis technique for the detection of the delta-F508 mutation in a 6-month-old Mexican boy who died without definitive diagnosis. The tissue available from the child was a formaldehyde fixed paraffin-embedded liver. We identified the delta-F508 mutation in homozygous form in the propositus and in a heterozygous form in his parents. This represents the first report of CF molecular diagnosis in Mexico.