Neural tube defects and epigenetics: role of histone post-translational histone modifications

Neural tube defects (NTDs) are the most common congenital anomalies of the CNS. It is widely appreciated that both genetic and environmental factors contribute to their etiology. The inability to ascribe clear genetic patterns of inheritance to various NTD phenotypes suggests it is possible that epigenetic mechanisms are involved in the etiology of NTDs. In this context, the contribution of DNA methylation as an underlying contributing factor to the etiology of NTDs has been extensively reviewed. Here, an updated accounting of the evidence linking post-translational histone modifications to these birth defects, relying heavily upon studies in humans, and the possible molecular implications inferred from reports based on cellular and animal models, are presented.

PEMT variants are associated with nonsyndromic cleft lip with or without cleft palate in Chile

Aim: To assess the association between PEMT variants and nonsyndromic cleft lip with or without cleft palate in Chile and the effects of these variants on global DNA methylation. Subjects & methods: The authors obtained genotypes for nine variants from 247 cases and 453 controls for genotype-phenotype associations. The effect of significant polymorphisms on global DNA methylation (percentage of long interspersed element-1 methylation) was evaluated in a subsample of 95 controls. Results: After multiple comparison corrections, variants rs7649 and rs4646409 were associated with nonsyndromic cleft lip with or without cleft palate. Carriers of risk alleles presented lower DNA methylation levels than noncarriers. Conclusion: According to functional analysis for risk variants from previous reports, the authors infer that a decrease of methyl group availability is occurring in affected subjects.

Vitamin B12 Transport Genes and Nonsyndromic Cleft Lip With or Without Cleft Palate in Chile

The aims of this study were to assess the association between polymorphisms within genes involved in vitamin B12 transport and nonsyndromic cleft lip with or without cleft palate (NSCL/P) and global DNA methylation in Chile. From 247 cases and 453 controls, we obtained variant genotypes for CBLIF, CUBN, AMN, ABCC1, CD320, and TCN2 from a single nucleotide polymorphisms array. Global DNA methylation in 95 controls was obtained through LINE-1 methylation. After multiple comparison corrections, only rs780807 in CUBN remains associated with NSCL/P at dominant model (OR 0.564, p-value = 0.0006, q-value = 0.0450). Carriers of protective allele showed lower levels of DNA methylation than non-carriers (p = 0.0259). Further studies are necessary in order to explain relations with the phenotype and DNA methylation due to the absence of functional evidence for rs780807 in CUBN.

Environmental factors in non-syndromic orofacial clefts: A review based on meta-analyses results

Non-syndromic orofacial clefts (NSOFCs) are prevalent birth defects with a complex etiology where several interacting genetic and environmental factors have been observed. This narrative review describes maternal exposures that have been significantly associated with protective effects or risk factors. The statistically significant information reported here was found in meta-analysis studies, taking advantage of their precision in defining intervention effects and their management of heterogeneity between studies. In addition, I propose a hypothesis explaining the biological basis for the results of the meta-analyses. This review aims to improve the evidence available in parent counseling, to prevent the occurrence of orofacial clefts by suggesting lifestyle changes.

Maternal genotypes of folate/one-carbon metabolism gene variants and nonsyndromic cleft lip with or without cleft palate risk in Chile

The aim of this study was to evaluate, in a case-control design, the association between maternal genotypes for variants in 23 genes involved in folate/one-carbon metabolism and nonsyndromic cleft lip with or without cleft palate (NSCL/P) in a Chilean population. After applying several filters to an Illumina array, we extracted 175 single nucleotide polymorphisms (SNPs) from 150 mothers of NSCL/P cases and 150 control women. Association was evaluated using computed odds ratio (OR) with a 95% confidence interval (95% CI) in additive, recessive, and dominant models. After multiple comparison correction, only SNP rs4451422 (A>C), located 237 bp downstream of the gene encoding the human folylpolyglutamate synthetase (FPGS), maintained a significant association with NSCL/P in the offspring (OR 3.03; 95% CI 1.69-5.26). The variant rs4451422 is associated with a decrease in FPGS expression according to database annotation. Our results lead to a new hypothesis that a lower activity of FPGS enzyme reduces intracellular folate levels and increases the risk of an offspring having NSCL/P.

The Chilean socio-ethno-genomic cline

Studies of the current Chilean population performed using classical genetic markers have established that the Chilean population originated primarily from the admixture of European people, particularly Spaniards, and Amerindians. A socioeconomic-ethno-genetic cline was established soon after the conquest. Spaniards born in Spain or Chile occupied the highest Socioeconomic Strata, while Amerindians belonged to the lowest. The intermediate strata consisted of people with different degrees of ethnic admixture; the larger the European admixture, the higher the Socioeconomic Level. The present study of molecular genomic markers sought to calculate the percentage of Amerindian admixture and revealed a finer distribution of this cline, as well as differences between two Amerindian groups: Aymara and Mapuche. The use of two socioeconomic classifications - Class and Socioeconomic Level - reveals important differences. Furthermore, Self-reported Ethnicity (self-assignment to an ethnic group) and Self-reported Ancestry (self-recognition of Amerindian ancestors) show variations and differing relationships between socioeconomic classifications and genomic Amerindian Admixture. These data constitute a valuable input for the formulation of public healthcare policy and show that the notions of Ethnicity, Socioeconomic Strata and Class should always be a consideration in policy development.

Nonsyndromic orofacial clefts in Chile: LINE-1 methylation and MTHFR variants

Aim: To evaluate the risk of nonsyndromic orofacial clefts (NSOFCs) associated with LINE-1 methylation, as a marker of global DNA methylation, and the effect of MTHFR functional variants on this variable. Patients & methods: LINE-1 methylation was evaluated by bisulfite modification coupled to DNA pyrosequencing in 95 NSOFC cases and 95 controls. In these subjects, MTHFR genotypes for variants c.C677T (rs1801133) and c.A1298C (rs1801131) were obtained. Results: Middle levels (second tertile) of LINE-1 methylation increase the risk of NSOFCs. In addition, LINE-1 methylation depends on c.A1298C genotypes in controls but not in cases. Conclusion: A nonlinear association between global DNA methylation and NSOFCs was detected in this Chilean population, which appears to be influenced by MTHFR functional variants.

Association analysis in a Latin American population revealed ethnic differences in rheumatoid arthritis-associated SNPs in Caucasian and Asian populations

Large genome-wide association studies (GWAS) have increased our knowledge of the genetic risk factors of rheumatoid arthritis (RA). However, little is known about genetic susceptibility in populations with a large admixture of Amerindian ancestry. The aim of the present study was to test the generalizability of previously reported RA loci in a Latin American (LA) population with admixed ancestry. We selected 128 single nucleotide polymorphisms (SNPs) in linkage equilibrium, with high association to RA in multiple populations of non-Amerindian origin. Genotyping of 118 SNPs was performed in 313 RA patients/487 healthy control subjects by mid-density arrays of polymerase chain reaction (PCR). Some of the identified associations were validated in an additional cohort (250 cases/290 controls). One marker, the SNP rs2451258, located upstream of T Cell Activation RhoGTPase Activating Protein (TAGAP) gene, showed significant association with RA (p = 5 × 10-3), whereas 18 markers exhibited suggestive associations (p < 0.05). Haplotype testing showed association of some groups of adjacent SNPs around the signal transducer and activator of transcription 4 (STAT4) gene (p = 9.82 × 10-3 to 2.04 × 10-3) with RA. Our major finding was little replication of previously reported genetic associations with RA. These results suggest that performing GWAS and admixture mapping in LA populations has the potential to reveal novel loci associated with RA. This in turn might help to gain insight into the 'pathogenomics' of this disease and to explore trans-population differences for RA in general.

Development of a small panel of SNPs to infer ancestry in Chileans that distinguishes Aymara and Mapuche components

Background

Current South American populations trace their origins mainly to three continental ancestries, i.e. European, Amerindian and African. Individual variation in relative proportions of each of these ancestries may be confounded with socio-economic factors due to population stratification. Therefore, ancestry is a potential confounder variable that should be considered in epidemiologic studies and in public health plans. However, there are few studies that have assessed the ancestry of the current admixed Chilean population. This is partly due to the high cost of genome-scale technologies commonly used to estimate ancestry. In this study we have designed a small panel of SNPs to accurately assess ancestry in the largest sampling to date of the Chilean mestizo population (n = 3349) from eight cities. Our panel is also able to distinguish between the two main Amerindian components of Chileans: Aymara from the north and Mapuche from the south.

Results

A panel of 150 ancestry-informative markers (AIMs) of SNP type was selected to maximize ancestry informativeness and genome coverage. Of these, 147 were successfully genotyped by KASPar assays in 2843 samples, with an average missing rate of 0.012, and a 0.95 concordance with microarray data. The ancestries estimated with the panel of AIMs had relative high correlations (0.88 for European, 0.91 for Amerindian, 0.70 for Aymara, and 0.68 for Mapuche components) with those obtained with AXIOM LAT1 array. The country’s average ancestry was 0.53 ± 0.14 European, 0.04 ± 0.04 African, and 0.42 ± 0.14 Amerindian, disaggregated into 0.18 ± 0.15 Aymara and 0.25 ± 0.13 Mapuche. However, Mapuche ancestry was highest in the south (40.03%) and Aymara in the north (35.61%) as expected from the historical location of these ethnic groups. We make our results available through an online app and demonstrate how it can be used to adjust for ancestry when testing association between incidence of a disease and nongenetic risk factors.

Conclusions

We have conducted the most extensive sampling, across many different cities, of current Chilean population. Ancestry varied significantly by latitude and human development. The panel of AIMs is available to the community for estimating ancestry at low cost in Chileans and other populations with similar ancestry.

A SHMT1 variant decreases the risk of nonsyndromic cleft lip with or without cleft palate in Chile

OBJECTIVE

To assess the association between polymorphic variants from SHMT1 and MTHFS genes, involved in the cytoplasmic futile folate cycle, and the risk of nonsyndromic cleft lip with or without cleft palate (NSCL/P) in the Chilean population.

SUBJECTS AND METHODS

In a sample of 139 Chilean NSCL/P cases and 278 controls, we obtained the genotypes for nine variants of SHMT1 and MTHFS and the association between them and the phenotype was evaluated using odds ratios (OR) in additive (allele), dominant, and recessive models.

RESULTS

After correction for multiple comparisons, only the variant rs1979277 (G > A; p.Leu474Phe) from SHMT1 showed a significant and protective effect for additive (OR 0.60; 95% CI 0.42-0.86; p = .0054, q = 0.0488) and dominant models (OR 0.48; 95% CI 0.29-0.75; p = .0009; q = 0.0081). Our bioinformatic prediction plus functional evidence from previous reports demonstrate that the A allele for this missense variant decreases the enzymatic activity.

CONCLUSIONS

Owing to the rs1979277 A allele, which reduces the cytoplasmic SHMT activity and has a higher frequency in controls than in NSCL/P cases, we hypothesized that a low enzyme activity may increase the cytoplasmic concentration of folates and, therefore, explain the protective role against OFCs.

Premature Vascular Aging in Guinea Pigs Affected by Fetal Growth Restriction

Cardiovascular risk associated with fetal growth restriction (FGR) could result from an early impaired vascular function. However, whether this effect results in premature vascular aging has not been addressed. We studied the ex vivo reactivity of carotid and femoral arteries in fetal (near term), adults (eight months-old) and aged (16 months-old) guinea pigs in normal (control) and FGR offspring. Additionally, an epigenetic marker of vascular aging (i.e., LINE-1 DNA methylation) was evaluated in human umbilical artery endothelial cells (HUAEC) from control and FGR subjects. Control guinea pig arteries showed an increased contractile response (KCl-induced) and a progressive impairment of NO-mediated relaxing responses as animals get older. FGR was associated with an initial preserved carotid artery reactivity as well as a later significant impairment in NO-mediated responses. Femoral arteries from FGR fetuses showed an increased contractility but a decreased relaxing response compared with control fetuses, and both responses were impaired in FGR-adults. Finally, FGR-HUAEC showed decreased LINE-1 DNA methylation compared with control-HUAEC. These data suggest that the aging of vascular function occurs by changes in NO-mediated responses, with limited alterations in contractile capacity. Further, these effects are accelerated and imposed at early stages of development in subjects exposed to a suboptimal intrauterine environment.

Platelet Serotonin Levels Are Associated with Plasma Soluble Leptin Receptor Concentrations in Normoglycemic Women

Most peripheral serotonin (5-hydroxytryptamine (5HT)) is synthetized in the gut with platelets being its main circulating reservoir. 5HT is acting as a hormone in key organs to regulate glucose and lipid metabolism. However, the relation between platelet 5HT levels and traits related to glucose homeostasis and lipid metabolism in humans remains poorly explored. The objectives of this study were (a) to assess the association between platelet 5HT levels and plasma concentration of nonesterified fatty acids (NEFAs) and some adipokines including leptin and its soluble leptin receptor (sOb-R), (b) to assess the association between platelet 5HT levels and anthropometric traits and indexes of insulin secretion/sensitivity derived from oral glucose tolerance test (OGTT), and (c) to evaluate changes in platelet 5HT levels in response to OGTT. In a cross-sectional study, 59 normoglycemic women underwent a standard 2-hour OGTT. Plasma leptin, sOb-R, total and high molecular weight adiponectin, TNFα, and MCP1 were determined by immunoassays. Platelet 5HT levels and NEFAs were measured before and after OGTT. The free leptin index was calculated from leptin and sOb-R measurements. Insulin sensitivity indexes derived from OGTT (HOMA-S and Matsuda ISICOMP) and plasma NEFAs (Adipose-IR, Revised QUICKI) were also calculated. Our data show that among metabolic traits, platelet 5HT levels were associated with plasma sOb-R (r = 0.39, p = 0.003, corrected p = 0.018). Platelet 5HT levels were reduced in response to OGTT (779 ± 237 vs.731 ± 217 ng/10⁹ platelets, p = 0.005). In conclusion, platelet 5HT levels are positively associated with plasma sOb-R concentrations and reduced in response to glucose intake possibly indicating a role of peripheral 5HT in leptin-mediated appetite regulation.

Gene-gene interaction for nonsyndromic cleft lip with or without cleft palate in Chilean case-parent trios

OBJECTIVE

Nonsyndromic cleft lip with or without cleft palate (NSCL/P) is a birth defect for which several genes susceptibility genes been proposed. Consequently, it has been suggested that many of these genes belong to common inter-related pathways during craniofacial development gene-gene interaction. We evaluated the presence of gene-gene interaction for single nucleotide polymorphisms within interferon regulatory factor 6 (IRF6), muscle segment homeobox 1 (MSX1), bone morphogenetic protein 4 (BMP4) and transforming growth factor 3 (TGFB3) genes in NSCL/P risk in Chilean case-parent trios.

DESIGN

From previous studies, we retrieved genotypes for 13 polymorphic variants within these four genes in 152 case-parent trios. Using the trio package (R) we evaluate the gene-gen interaction in genetic markers pairs applying a 1°-of-freedom test (1df) and a confirmatory 4°-of-freedom (4df) test for epistasis followed by both a permutation test and a Benjamini-Hochberg test for multiple comparisons adjustment.

RESULTS

We found evidence of gene-gene interaction for rs6446693 (MSX1) and rs2268625 (TGFB3) (4df p = 0.024; permutation p = 0.015, Benjamini-Hochberg p = 0.001).

CONCLUSIONS

A significant gene-gene interaction was detected for rs6446693 (MSX1) and rs2268625 (TGFB3). This finding is concordant with research in animal models showing that MSX1 and TGFB3 are expressed in common molecular pathways acting in an epistatic manner during maxillofacial development.

No Evidence for Linkage and Association between 4q Microsatellite Markers and Nonsyndromic Cleft Lip and Palate in Chilean Case-Parents Trios

Objective

Nonsyndromic cleft lip/palate (NSCLP) has the characteristics of a complex genetic trait. Linkage and association studies have suggested that one or more clefting loci may be located on chromosome 4q. The goal of this study was to evaluate the possible linkage and association due to linkage disequilibrium between five microsatellite markers located on 4q28 to 4q33 and NSCLP, using the case-parent trio design.

Subjects and Methods

A total of 56 Chilean families (32 simplex and 24 multiplex) were recruited. Microsatellite markers were analyzed using polymerase chain reaction with fluorescent-labeled forward primers, followed by electrophoresis on a laser-fluorescent sequencer. Case-parents trios were ascertained to assess linkage and linkage disequilibrium through a multistage procedure. Transmission disequilibrium tests for multiple alleles were carried out to assess the statistical significance of 4q28 to 4q33 microsatellite markers.

Results

Only weak evidence for linkage was obtained for the FGA marker (asymptotic uncorrected p value = .08 and empirical p value = .05). Only the FGA and UCP1 markers were selected for association analysis in trios, with unrelated cases achieving a nearly significant result for the UCP1 marker (asymptotic uncorrected p value = .07 and empirical p value = .19).

Conclusion

Though the FGA and UCP1 markers showed nearly significant p values for linkage and association, respectively, the results of the present study provided insufficient evidence of the existence of a major susceptibility locus in the 4q region that was analyzed in the present study.

Association between 10 Microsatellite Markers and Nonsyndromic Cleft Lip Palate in the Chilean Population

Objective

The objective of this case-control study was to evaluate the possible association between nonsyndromic cleft lip/palate (NSCLP) and 10 genetic markers in four chromosomal regions in the admixed Spanish-Amerindian Chilean population.

Setting

Study participants included 56 patients with NSCLP identified and interviewed for positive family history during the course of clinical examinations at different rehabilitation centers in the cities of Santiago and Talca, Chile. A control group of 59 normal individuals without known familial antecedents of clefting was obtained from blood bank donors of the University Hospital, University of Chile. Cases and controls belonged to low- to low-middle socioeconomic strata.

Results

Ten markers from chromosome 4p, 4q, 6p, 17q, and 19q were assessed (MSX1, D4S175, D4S192, F13A1, EDN1, D6S89, D6S105, D6S109, D17S579, BCL3). Four of them showed significant deviations from Hardy-Weinberg expectations in controls, according to the exact test (D4S192, BCL3, F13A1, and D6S89). The case-control comparison by means of the CLUMP program showed significant differences only in BCL3, and D6S109 almost reached statistical significance.

Conclusions

Most of the genetic regions with positive results in Caucasian populations may not be involved in NSCLP in Chile, regardless of the positive evidence for the candidate region on chromosome 19. Similar findings have been reported recently in the Chinese population.

Haplotype-based gene-gene interaction of bone morphogenetic protein 4 and interferon regulatory factor 6 in the etiology of non-syndromic cleft lip with or without cleft palate in a Chilean population

Non-syndromic cleft lip with or without cleft palate (NSCL/P) is the most common craniofacial birth defect in humans, the etiology of which can be dependent on the interactions of multiple genes. We previously reported haplotype associations for polymorphic variants of interferon regulatory factor 6 (IRF6), msh homeobox 1 (MSX1), bone morphogenetic protein 4 (BMP4), and transforming growth factor beta 3 (TGFB3) in Chile. Here, we analyzed the haplotype-based gene-gene interaction for markers of these genes and NSCL/P risk in the Chilean population. We genotyped 15 single nucleoptide polymorphisms (SNPs) in 152 Chilean patients and 164 controls. Linkage disequilibrium (LD) blocks were determined using the Haploview software, and phase reconstruction was performed by the Phase program. Haplotype-based interactions were evaluated using the multifactor dimensionality reduction (MDR) method. We detected two LD blocks composed of two SNPs from BMP4 (Block 1) and three SNPs from IRF6 (Block 2). Although MDR showed no statistical significance for the global interaction model involving these blocks, we found four combinations conferring a statistically significantly increased NSCL/P risk (Block 1-Block 2): T-T/T-G C-G-T/G-A-T; T-T/T-G C-G-C/C-G-C; T-T/T-G G-A-T/G-A-T; and T-T/C-G G-A-T/G-A-T. These findings may reflect the presence of a genomic region containing potential causal variants interacting in the etiology of NSCL/P and may contribute to disentangling the complex etiology of this birth defect.

Linkage Disequilibrium between MSX1 and Non-syndromic Cleft Lip/Palate in the Chilean Population

Non-syndromic cleft lip/palate (NSCLP) is a complex genetic trait. Linkage and association studies have suggested that a clefting locus could be located on chromosome 4p. Sixty Chilean families were recruited for this study; from these, we used unrelated trios to evaluate the possible linkage disequilibrium between MSX1 and NSCLP. An intragenic marker, MSX1-CA, and an extragenic marker, D4S432 at a distance of 0.8 cM from MSX1, were analyzed by means of polymerase chain-reaction with fluorescent-labeled forward primers, followed by electrophoresis on a laser-fluorescent sequencer. We carried out a transmission/disequilibrium test (TDT) for multiple alleles to evaluate the presence of linkage disequilibrium. Results showed a preferential transmission of the 169-bp allele of MSX1 (p = 0.03). Although there was no preferential transmission for the D4S432 marker, the overall extended TDT (ETDT) showed a significant result (p = 0.01). The authors’ findings support the hypothesis of the contribution of MSX1 in the etiology of NSCLP in the Chilean population.

Inhibition of the 3-hydroxy-3-methyl-glutaryl-CoA reductase induces orofacial defects in zebrafish

BACKGROUND

Orofacial clefts (OFCs) are common birth defects, which include a range of disorders with a complex etiology affecting formation of craniofacial structures. Some forms of syndromic OFCs are produced by defects in the cholesterol pathway. The principal enzyme of the cholesterol pathway is the 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR). Our aim is to study whether defects of HMGCR function would produce orofacial malformation similar to those found in disorders of cholesterol synthesis.

METHODS

We used zebrafish hmgcrb mutants and HMGCR inhibition assay using atorvastatin during early and late stages of orofacial morphogenesis in zebrafish. To describe craniofacial phenotypes, we stained cartilage and bone and performed in situ hybridization using known craniofacial markers. Also, we visualized neural crest cell migration in a transgenic fish.

RESULTS

Our results showed that mutants displayed loss of cartilage and diminished orofacial outgrowth, and in some cases palatal cleft. Late treatments with statin show a similar phenotype. Affected-siblings displayed a moderate phenotype, whereas early-treated embryos had a minor cleft. We found reduced expression of the downstream component of Sonic Hedgehog-signaling gli1 in ventral brain, oral ectoderm, and pharyngeal endoderm in mutants and in late atorvastatin-treated embryos.

CONCLUSION

Our results suggest that HMGCR loss-of-function primarily affects postmigratory cranial neural crest cells through abnormal Sonic Hedgehog signaling, probably induced by reduction in metabolites of the cholesterol pathway. Malformation severity correlates with the grade of HMGCR inhibition, developmental stage of its disruption, and probably with availability of maternal lipids. Together, our results might help to understand the spectrum of orofacial phenotypes found in cholesterol synthesis disorders. Birth Defects Research (Part A) 106:814-830, 2016. © 2016 Wiley Periodicals, Inc.

Fluoxetine impairs insulin secretion without modifying extracellular serotonin levels in MIN6 β-cells

INTRODUCTION

Pancreatic β-cells synthetize and store Serotonin (5-Hydroxytriptamine, 5HT) which is co-released with insulin. It has been proposed that extracellular 5HT binds to specific cell surface receptors and modulate insulin secretion. On the other hand, Selective Serotonin Reuptake Inhibitor (SSRI) fluoxetine seems to reduce Glucose-Stimulated Insulin Secretion (GSIS). However, it is unknown whether this effect results from changes in extracellular 5HT concentration owed to the blockade of 5HT transporter (SERT) or from non-5HT dependent actions. The aims of this work were: 1) to quantify extracellular 5HT levels and GSIS in β-cell lines, 2) to determine whether extracellular 5HT levels and GSIS are changed by fluoxetine or 5-Hydroxytryptophan (5HTP, the immediate 5HT biosynthetic precursor), and 3) to quantify the expression of Slc6a4 gene (encoding SERT) in β-cell lines in relation to other genes involved in 5HT system.

MATERIAL AND METHODS

β-cell lines MIN6 and RINm5f were subjected to GSIS protocols, after treatment with fluoxetine, 5HTP or 5HT. Insulin and 5HT were quantified by ELISA and HPLC, respectively. Relative mRNA expression was quantified by RT-qPCR.

RESULTS

MIN6 β-cells secretes 5HT in response to glucose, showing a sharp increase in 5HT release when cells were preloaded with 5HTP. Treatment with 5HT or fluoxetine reduces GSIS. Fluoxetine fails to further increases 5HTP-induced elevation of secreted 5HT. MIN6 β-cells express both isoforms of Tryptophan Hydroxylase (Tph1 and Tph2), and have high expression levels of L-Dopa decarboxylase (Ddc), both enzymes involved in 5HT biosynthetic pathway, but do not express the 5HT transporters Slc6a4 or Slc6a3 (the Dopamine-5HT transporter) genes.

CONCLUSION

The inhibitory effect of fluoxetine on β-cell glucose stimulated insulin secretion is not mediated by blockage of 5HT transporter through SERT.

Novel splice-affecting variants in CYP27A1 gene in two Chilean patients with Cerebrotendinous Xanthomatosis

Cerebrotendinous Xanthomatosis (CTX), a rare lipid storage disorder, is caused by recessive loss-of-function mutations of the 27-sterol hydroxylase (CYP27A1), producing an alteration of the synthesis of bile acids, with an accumulation of cholestanol. Clinical characteristics include juvenile cataracts, diarrhea, tendon xanthomas, cognitive impairment and other neurological manifestations. Early diagnosis is critical, because treatment with chenodeoxycholic acid may prevent neurological damage. We studied the CYP27A1 gene in two Chilean CTX patients by sequencing its nine exons, exon-intron boundaries, and cDNA from peripheral blood mononuclear cells. Patient 1 is a compound heterozygote for the novel substitution c.256-1G > T that causes exon 2 skipping, leading to a premature stop codon in exon 3, and for the previously-known pathogenic mutation c.1183C > T (p.Arg395Cys). Patient 2 is homozygous for the novel mutation c.1185-1G > A that causes exon 7 skipping and the generation of a premature stop codon in exon 8, leading to the loss of the crucial adrenoxin binding domain of CYP27A1.

Association between TGFB3 and nonsyndromic cleft lip with or without cleft palate in a Chilean population

OBJECTIVE

To assess the possible association between TGFB3 allele variants and nonsyndromic cleft lip with or without cleft palate in a Chilean population.

DESIGN

In our study we used a case-parents trios design. The sample consisted of 150 unrelated trios ascertained through probands affected with nonsyndromic cleft lip with or without cleft palate. Three TGFB3 polymorphisms were analyzed (rs2268626, rs2268625, and rs3917201). An allele/haplotype transmission disequilibrium test was used to evaluate the possible genotype-phenotype association.

RESULTS

An overtransmission from parents to affected progeny was observed for the A allele of rs3917201 (p = .03) and for the rs2268625-rs3917201 A-A haplotype (p = .022). A defect of transmission of rs2268625-rs3917201 G-G haplotype (p = .022) was observed also.

CONCLUSIONS

Allelic and haplotypic associations implicate a possible role of TGFB3 in nonsyndromic cleft lip with or without cleft palate in the Chilean population. Additional studies are needed in order to elucidate the possible mechanisms that can explain the role of TGFB3 genetic variants in the condition.

Novel splice-affecting variants in CYP27A1 gene in two Chilean patients with Cerebrotendinous Xanthomatosis

Cerebrotendinous Xanthomatosis (CTX), a rare lipid storage disorder, is caused by recessive loss-of-function mutations of the 27-sterol hydroxylase (CYP27A1), producing an alteration of the synthesis of bile acids, with an accumulation of cholestanol. Clinical characteristics include juvenile cataracts, diarrhea, tendon xanthomas, cognitive impairment and other neurological manifestations. Early diagnosis is critical, because treatment with chenodeoxycholic acid may prevent neurological damage. We studied the CYP27A1 gene in two Chilean CTX patients by sequencing its nine exons, exon-intron boundaries, and cDNA from peripheral blood mononuclear cells. Patient 1 is a compound heterozygote for the novel substitution c.256-1G > T that causes exon 2 skipping, leading to a premature stop codon in exon 3, and for the previously-known pathogenic mutation c.1183C > T (p.Arg395Cys). Patient 2 is homozygous for the novel mutation c.1185-1G > A that causes exon 7 skipping and the generation of a premature stop codon in exon 8, leading to the loss of the crucial adrenoxin binding domain of CYP27A1.

Genetic risk score for nonsyndromic cleft lip with or without cleft palate for a Chilean population

It has been widely accepted that nonsyndromic cleft lip with or without cleft palate (NSCLP) depends on the altered function of several genes during craniofacial development. The construction of genetic risk score (GRS) have allowed to estimate the combined effect of risk alleles from genes interacting in different molecular pathways in order to improve an estimation of the individual's susceptibility to a complex disease. The aim of our study was to construct a GRS considering markers showing previous allele/haplotype association with NSCLP in Chile. Considering 10 risk markers from IRF6, MSX1, BMP4 and TGFB3 genes, we estimate a GRS for each of 152 NSCLP cases and 164 controls. GRS showed no significant results when comparing cases and controls for these markers. These results could be explained by a possible indirect relationship of these genes between them in NSCLP which GRS is not capable of detecting and/or the modest number of risk alleles considered herein.

Daam1a mediates asymmetric habenular morphogenesis by regulating dendritic and axonal outgrowth

Although progress has been made in resolving the genetic pathways that specify neuronal asymmetries in the brain, little is known about genes that mediate the development of structural asymmetries between neurons on left and right. In this study, we identify daam1a as an asymmetric component of the signalling pathways leading to asymmetric morphogenesis of the habenulae in zebrafish. Daam1a is a member of the Formin family of actin-binding proteins and the extent of Daam1a expression in habenular neuron dendrites mirrors the asymmetric growth of habenular neuropil between left and right. Local loss and gain of Daam1a function affects neither cell number nor subtype organisation but leads to a decrease or increase of neuropil, respectively. Daam1a therefore plays a key role in the asymmetric growth of habenular neuropil downstream of the pathways that specify asymmetric cellular domains in the habenulae. In addition, Daam1a mediates the development of habenular efferent connectivity as local loss and gain of Daam1a function impairs or enhances, respectively, the growth of habenular neuron terminals in the interpeduncular nucleus. Abrogation of Daam1a disrupts the growth of both dendritic and axonal processes and results in disorganised filamentous actin and α-tubulin. Our results indicate that Daam1a plays a key role in asymmetric habenular morphogenesis mediating the growth of dendritic and axonal processes in dorsal habenular neurons.

Family-based association study between SLC2A1, HK1, and LEPR polymorphisms with myelomeningocele in Chile

Obese/diabetic mothers present a higher risk to develop offspring with myelomeningocele (MM), evidence supporting the role of energy homeostasis-related genes in neural tube defects. Using polymerase chain reaction-restriction fragment length polymorphism, we have genotyped SLC2A1, HK1, and LEPR single-nucleotide polymorphisms in 105 Chilean patients with MM and their parents in order to evaluate allele-phenotype associations by means of allele/haplotype transmission test (TDT) and parent-of-origin effects. We detected an undertransmission for the SLC2A1 haplotype T-A (rs710218-rs2229682; P = .040), which was not significant when only lower MM (90% of the cases) was analyzed. In addition, the leptin receptor rs1137100 G allele showed a significant increase in the risk of MM for maternal-derived alleles in the whole sample (2.43-fold; P = .038) and in lower MM (3.20-fold; P = .014). Our results support the role of genes involved in energy homeostasis in the risk of developing MM, thus sustaining the hypothesis of diverse pathways and genetic mechanisms acting in the expression of such birth defect.

Prevalence of metabolic syndrome in obese Chilean children and association with gene variants of the leptin-melanocortin system

Metabolic syndrome (MS) related to adult type 2 diabetes mellitus and cardiovascular disease is prevalent among obese children/adolescents. Genetic variants of the leptin-melanocortin system have been associated with components of MS. The aim of our study is to estimate the prevalence of MS (according to Cook's criteria) in a Chilean cross-sectional sample of 259 obese children (47.1% girls, aged 6-12 years), and to assess the association between common genetic variants of leptin-melanocortin pathway genes (LEP, LEPR, POMC, MC3R and MC4R) with components of the MS using logistic regression. We observed an overall MS prevalence of 26.3% (32.2% in girls and 21.1% in boys) in obese Chilean children. No associations were detected between genetic variants of leptin-melanocortin genes and MS components. MS prevalence among our obese children sample is similar to those previously described in Chile, demonstrating the increased risk of diseases in adulthood that obese children carry.

Risk variants in BMP4 promoters for nonsyndromic cleft lip/palate in a Chilean population

Background

Bone morphogenetic protein 4 gene (BMP4) plays a key role during maxillofacial development, since orofacial clefts are observed in animals when this gene is conditionally inactivated. We recently reported the existence of association between nonsyndromic cleft lip/palate (NSCLP) and BMP4 polymorphisms by detecting transmission deviations for haplotypes that include a region containing a BMP4 promoter in case-parent trios. The aim of the present study was to search for possible causal mutations within BMP4 promoters (BMP4.1 and BMP4.2).

Methods

We analyzed the sequence of BMP4.1 and BMP4.2 in 167 Chilean NSCLP cases and 336 controls.

Results

We detected three novel variants in BMP4.1 (c.-5514G > A, c.-5365C > T and c.-5049C > T) which could be considered as cleft risk factors due to their absence in controls. Additionally, rs2855530 G allele (BMP4.2) carriers showed an increased risk for NSCLP restricted to males (OR = 1.52; 95% C.I. = 1.07-2.15; p = 0.019). For this same SNP the dominant genotype model showed a higher frequency of G/G+G/C and a lower frequency of C/C in cases than controls in the total sample (p = 0.03) and in the male sample (p = 0.003). Bioinformatic prediction analysis showed that all the risk variants detected in this study could create new transcription factor binding motifs.

Conclusions

The sex-dependent association between rs2855530 and NSCLP could indirectly be related to the differential gene expression observed between sexes in animal models. We concluded that risk variants detected herein could potentially alter BMP4 promoter activity in NSCLP. Further functional and developmental studies are necessary to support this hypothesis.

Association between bone morphogenetic protein 4 gene polymorphisms with nonsyndromic cleft lip with or without cleft palate in a chilean population

Nonsyndromic cleft lip with or without cleft palate (NSCLP) is one of the most common birth defects in humans with both genetic and environmental components involved in its expression. Experimental evidences have postulated that bone morphogenetic protein 4 gene (Bmp4) is involved in the etiology of cleft lip with or without cleft palate (CL/P) in mice. In our study we analyzed the association between BMP4 and NSCLP in a sample of 150 unrelated trios ascertained through affected probands. Three BMP4 polymorphisms were analyzed, two intronic (rs762642 and rs2855532) and rs1957860, located 5.7 kb upstream from BMP4. Transmission/disequilibrium tests were performed at the allele and haplotype levels. Our results did not detect preferential transmission for individual single-nucleotide polymorphisms. Significant transmission distortion was observed for haplotypes rs1957860-rs762642 (p = 0.018), especially for C-T (p = 0.015) and T-T (p = 0.018) which include the genomic region where the promoter and an enhancer of BMP4 are located. Thus, despite the positive association detected between these haplotypes and NSCLP they probably do not have a functional effect on BMP4 expression or protein activity but possibly reflect NSCLP susceptibility changes which are in linkage disequilibrium with these polymorphisms. The findings of our study support a role for BMP4 in NSCLP in the admixed Chilean population.

HER2+ Tumors with Lack Steroid Receptors Showed a Shorter DFS but Similar OS Compared to HER2+ Tumors That Also Express ER and/or PR

Background: HER2 expression is widely measured on tumor tissue from breast cancer patients since it gives prognostic and predictive information. Data suggest that breast cancer growth is regulated by the coordinated action of the estrogen receptor (ER) and receptor tyrosine kinase signaling pathways. The aim of this retrospective analysis was to evaluate the additional prognostic value of the ER/PR status for the subset of patients with HER2-positive tumors.Methods: From 2000-2002, 203 breast tumors were tested for HER2 and steroid receptors levels. HER2-positivity was defined as ≥2 copies of the HER2 gene by FISH or 3+ by IHC. A cut-off point of 10 % was used as positivity for ER and/or progesterone receptor (PR) levels.Results: Among the 203 patients, 103 had HER2+/ER-/PR- tumors and 100 had HER2+/ER+ and/or PR+ tumors. Patients' characteristics were comparable between the two groups as far as age, menopausal status, pTNM (stage I-II-III) status and type of initial therapy. All patients had surgery followed by standard chemotherapy and radiotherapy and hormonal therapy if the tumor was ER+ or PR+. No patients received adjuvant treatment with trastuzumab. The median follow-up for the entire cohort was 73 months (range 12-110). Comparisons of disease-free survival (DFS), overall survival (OS) as well as site of first recurrence were made between the two groups. The 5-year DFS was statistically different between the two groups: 69.9% for HER2+/ER-/PR- patients and 81.0% for the HER2+/ER+ and/or PR+ (p=0.037). The 5-year OS was not different between the two groups with 82.5% for HER2+/ER-/PR- patients and 86.0% for the HER2/ER+ and/or PR+ (p=0.402).Conclusions: Patients with HER2+/ER-/PR- breast cancers treated with surgery and standard adjuvant chemotherapy exhibit a statistically worse DFS compared to patients with HER2+/ER+ and/or PR+ tumors. However, overall survival was similar in both groups; additional factors should be evaluated to explain this finding.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6052.

[Possible association due to linkage disequilibrium of TGFA, RARA and BCL3 with nonsyndromic cleft lip with or without cleft palate in the Chilean population]

BACKGROUND

Nonsyndromic cleft lip/palate (NSCLP) is a congenital malformation with the characteristics of a complex genetic trait. Based on experimental evidences as well as on association and linkage studies candidate genes TGFA, RARA and BCL3 have been postulated as being involved in the genetic etiology of this pathology.

AIM

To test the possible association due to linkage disequilibrium between microsatellite markers located at less than 1cM from the three candidate genes and nonsyndromic cleft lip/palate using the case-parents trio design.

PATIENTS AND METHODS

The sample consisted of 58 case-parents trios. Two microsatellite markers, flanking each one of the candidate genes were analyzed by means of the polymerase chain reaction (PCR) with fluorescent labeled microsatellite markers. Electrophoresis of the PCR products was performed on a laser-fluorescent automatic DNA sequencer. Nonparametric ETDT was used to analyze the genotype data.

RESULTS

Significant linkage disequilibrium was detected between D2S443 (TGFA) and NSCLP. Significance was almost reached between D17S800 (RARA) and NSCLP. Alleles 239bp (D2S443) and 172bp (D17S800) showed significant preferential transmission from heterozygous parents to affected offspring. In the case of BCL3 both markers showed no significant results.

CONCLUSIONS

The results of the present study do not show clear evidence that TGFA or RARA could be involved in the genetic etiology of NSCLP. Even though the importance of retinoic acid in the development of the embryo is well documented the results obtained for RARA are difficult to analyze. In relation to the possible role of BCL3 in NSCLP, recent information postulates that other genes located in the same chromosome region could be involved in NSCLP.

[Evaluation of the association between microsatellite markers located on 6p22-25 and no syndromic cleft lip palate using the case-parents trio design in Chilean population ]

BACKGROUND

Genetic studies indicate that nonsyndromic cleft lip/palate (NSCLP) has the characteristics of a complex genetic trait. Reports from different authors have suggested several candidate genes mapping in different chromosome regions. Association studies have suggested that a clefting locus is located on chromosome 6p. On these grounds we have investigated the possible association between five microsatellite markers located on 6p22-25 and NSCLP.

AIM

To test the hypothesis on the possible association of a clefting locus with microsatellite markers located in 6p22-25.

PATIENTS AND METHODS

The sample consisted of 54 unrelated case-parent trios that comprise 54 NSCLP probands and 108 parents. Five microsatellite markers spanning the region 6p22-25 were analyzed for each individual by means of polymerase chain reaction with fluorescent labeled microsatellite markers. Electrophoresis of the PCR products was performed on a laser-fluorescent DNA sequencer. Nonparametric ETDT and MCETDT programs, were used to analyze the genotype data.

RESULTS

The family based association study showed that for the genotype wise analysis, only D6S259 presented a significant p-value (0.03). Nevertheless no individual allele of this marker showed an evident preferential transmission from heterozygous parents to affected offspring.

CONCLUSIONS

The results of the present study do not show a clear evidence that a candidate gene for NSCLP may be located within or near the analyzed chromosome region in our sample. Nevertheless, it must be emphasized that the genotype wise analysis shows a significant p-value for D6S259 marker.

[Association between cleft lip/palate phenotype and non syndrome microsatellite markers located in 6p, 17q and 19q]

BACKGROUND

In the search of the major genes responsible for the genetic etiology of Nonsyndromic Cleft Lip and Palate (NSCLP), an association study between this malformation and four molecular markers, F13A1 and EDN1 (6p), D17S579 (17q) and BCL3 (19q), was done.

AIM

To determine, in a Chilean population, the presence of NSCLP susceptibility regions, as proposed for Caucasian populations in the 6p, 17q and 19q chromosomal regions.

MATERIAL AND METHODS

A sample of unrelated NSCLP patients, that belonged to Simplex (Sx) and Multiplex (Mx) families, was analyzed. Blood donors were used as a control group (Co). The DNA of the four markers was amplified by means of PCR, their products analyzed by PAGE denaturants and visualized by silver staining. Statistical analysis was performed using chi 2 log ratio.

RESULTS

Allele frequency distribution of D17S579 was significantly different in all patients with NSCLP and their subgroups, when compared to control subjects. Significant differences in EDN1 frequency were observed between the total groups of NSCLP patients and those pertaining to the Mx subgroup, when compared to controls. Differences in F13A1 distribution were only observed between NSCLP-Mx patients and controls. There was a slight difference in BCL3 distribution, between the total sample of NSCLP patients and controls.

CONCLUSIONS

Our results support the hypothesis of the existence of cleft susceptibility regions in 6p and 17q. The small significance of BCL3, suggests that ethnicity can influence the interactions between involved genes.

[Case and control study of atypical manifestations in gastroesophageal reflux disease]

OBJECTIVE

To study the prevalence of atypical symptoms of gastroesophageal reflux disease (GERD) in patients with esophagitis compared to controls.

METHODS

We studied consecutive patients who underwent upper endoscopy between January and August of 1997. They were classified in two groups: a) Cases, patients with endoscopic diagnosis of reflux esophagitis, and b) Controls, patients without esophagitis nor typical symptoms of GERD. They answered a questionnaire to evaluate the presence of typical and atypical symptoms of GERD.

RESULTS

There were 50 cases and 50 controls. There were no intergroups differences related to gender (p = 0.2), age (p = 0.4), smoking history (p = 0.7) or history of allergic diseases (p = 0.6). The atypical symptoms of GERD were more frequent in cases (66%) than controls (42%) (OR = 2.7%, 95% CI = 1.2-6, p = 0.02). The atypical manifestations more frequent in the cases were hoarseness (OR = 9.3, CI 1.1-77), thoracic pain (4.9, 1.7-14) and globus (2.8, 0.9-9). The presence of atypical symptoms was not associated to the degree of esophagitis (p = 0.7), intensity of typical symptoms (p = 0.2), gender (0.4) or age of patients (p = 0.2).

CONCLUSION

Patients with reflux esophagitis have a higher risk to develop extraesophageal disorders of the pharynx, larynx and lungs.

[Gastropathy caused by nonsteroidal anti-inflammatory agents]

Nonsteroidal anti-inflammatory drugs (NSAID) are widely used in current clinical practice. Several gastric lesions occur as a side effect. This review paper describes the spectrum of gastric lesions, its pathogenesis, prevalence and incidence as well as clinical data, common risk factors, treatment and the prophylaxis of NSAID gastric toxicity.

[Acute infectious cholangitis]

AIM

To know the results in the treatment of acute infectious cholangitis (IAC) and to identify risk factors related to morbidity and mortality.

MATERIAL AND METHODS

We reviewed the records of patients with AIC in a 7 year period. Clinical presentation, diagnostic methods and treatment were analyzed.

RESULTS

There were 85 cases (61% females and 39% males). Abdominal pain, fever and jaundice were the symptoms most frequently observed. Choledocholithiasis was present in 75% of the cases, malignant obstruction in 12% and other causes in 13%. All patients received antibiotics and 74% underwent any form of biliary drainage. There were complications in 32% of the cases and 14% died. Malignant obstruction was related to high risk of death (OR 11.1).

CONCLUSION

The IAC is a potentially life-threatening disease and is most ominous in cases of malignant occlusion of biliary tree.

[Open cholecystectomy in cirrhotic patients. Experience at the Salvador Zubirán National Institute of Nutrition]

BACKGROUND

AIMS

To inform the morbidity and mortality observed in cirrhotic patients who underwent open cholecystectomy.

METHODS

We reviewed the clinical records of 31 cirrhotics that underwent open cholecystectomy and they were compared with a control group of the same age and sex.

RESULTS

Despite administration of plasma or vitamin K or both, bleeding and transfusions during surgery were observed more frequently in cirrhotics. The morbidity was 13% in the controls and 42% in the cases. Renal failure, cardiac failure and upper gastrointestinal bleeding were present only in the cirrhotics. Mortality was 16% in this group (one Child A patient and four Child B-C patients). The variable related with major morbimortality was Child B or C classification.

CONCLUSIONS

Open cholecystectomy was associated with high morbimortality. The valoration and preparation before surgery must be careful, and the indication from this procedure needs to be made with caution.