PubMed Health⌕ Search

Biomedical subjects

S Borrego

Publications and source records attributed to S Borrego.

At least 19 recordsLinked to original sources
PubMed2005

Ancestral RET haplotype associated with Hirschsprung's disease shows linkage disequilibrium breakpoint at -1249.

BACKGROUND: Hirschsprung disease (HSCR) is a complex disorder with traditional germline mutations in RET in up to 30% of familial cases and in 3% of sporadic cases in a population-based series. We have previously demonstrated that an ancestral haplotype at the 5' end of RET (haplotype 0) was strongly associated with a large subset of isolated HSCR cases and that a putative low penetrance susceptibility locus was encompassed within this ancestral haplotype, anchored by exon 2 SNP A45A. OBJECTIVE: To determine the 5' extent of the HSCR-associated ancestral haplotype by defining the linkage disequilibrium breakpoint in search for the low penetrance susceptibility locus. METHODS: Systematic screening of the region upstream of the anchoring A45A SNP, comprising RET intron 1, exon 1, and promoter in 117 population-based HSCR cases and 100 controls. Dual luciferase assay to determine differential activities between SNP combinations near a transcription start site. RESULTS: New SNP's were found which formed upstream haplotypes, anchored by A45A, in linkage disequilibrium with HSCR (2 = 76.96, p<0.00000001). Linkage disequilibrium appeared to break at the -1249C/T SNP. Further, the HSCR-associated genotype (00) was found in >60% of HSCR but only 2% of controls. Because only 2 variants, -200A>G and -196C>A, lie within the promoter region and are in proximity to the transcriptional start site (at -195), we modelled these combinations into constructs for luciferase reporter assay. The HSCR-associated SNP combination showed the lowest activity and the control-associated combination, the highest. CONCLUSIONS: Our observations seem to discard the existence of a HSCR-causing mutation as it is conceived in the traditional sense, but strengthen the idea of a specific combination of variants conferring susceptibility to the disease in a low penetrance fashion. The data derived from our functional "in vitro" studies would suggest that the HSCR-associated haplotype 0 may result in a lower level of expression of the RET gene [corrected]

Case-Control Studies↗
PubMed2005

Polymorphisms in the promoter regions of FAS and FASL genes as candidate genetic factors conferring susceptibility to endometriosis.

Although the pathophysiological mechanisms leading to endometriosis remain unknown, several hypothesis have been proposed, including a dysregulation of the normal apoptotic process which takes place in the endometrium. One of the apoptotic pathways playing a crucial role in the programmed cell death within the endometrium is the Fas-FasL system. In this study we have performed a case-control analysis in order to evaluate three polymorphisms located within FAS (-1377G>A and -670A>G) and FASL (-843C>T) genes, as susceptibility factors for endometriosis. We have analysed a series of women with endometriosis compared respectively to a group of women without symptoms of the disease, and to a group of confirmed unaffected women. The genotyping of the three variants was carried out by Fluorescence Resonance Energy Transfer (FRET) technology, and statistical analysis was performed using chi2 test with Yates correction. Our results show that the differences in the distribution of the polymorphic variants were not statistically significant when the group of patients was compared to the other groups. Thus, it seems to indicate that the variants here analysed are not involved in the pathogenesis of the disease in our population. However this does not let us to completely exclude such genes as potential candidates for the disease. A complete genetic analysis of the genes involved in the intricate regulatory system of the apoptosis may lead to the identification of susceptibility factors for the disease and a better understanding of its etiology.

Adult↗
PubMed2004

Analysis of the involvement of CCR5-Delta32 and CCR2-V64I variants in the development of endometriosis.

Several arguments support the proposal that the cytokine network plays a critical role in the aetiology of endometriosis. Among various chemokines, regulated-on-activation, normal-T-cell-expressed and -secreted (RANTES) and monocyte chemotactic protein 1 (MCP-1) concentrations have been shown to be increased in the peritoneal fluid of women with endometriosis. Some studies have demonstrated that, in the context of endometriosis, these chemokines are involved in apoptosis, angiogenesis and/or chemotaxis. Since the chemokines exert their effects by binding to their receptors, it would be plausible that factors affecting such interactions might play a role in the pathogenesis of endometriosis. Thus we postulated that the genes encoding CCR5 and CCR2, which are the receptors for RANTES and MCP-1 respectively, could be good candidate genes for the disease. We have used real-time PCR and FRET technologies to genotype and evaluate the variants CCR5-Delta32 and CCR2-V64I, as susceptibility factors in a cohort of Spanish women with endometriosis. No differences have been found in the frequencies of the two polymorphisms nor in the haplotype/genotype distribution between cases and controls. These data would suggest the lack of association between these polymorphisms and endometriosis in our population, although they do not permit us to discard completely a possible role of other variants within CCR5 and CCR2 genes in this pathology.

Endometriosis↗
PubMed2003

Evaluation of germline sequence variants within the promoter region of RANTES gene in a cohort of women with endometriosis from Spain.

The RANTES (regulated upon activation normal T cells expressed and secreted) chemokine, is known to be expressed in endometriotic lesions in a concentration correlating with the severity of endometriosis. Since it has been widely demonstrated that endometriosis has a genetic basis, we postulated that the gene encoding RANTES could be a good candidate gene for the disease. We have used fluorescence resonance energy transfer (FRET) technology to genotype and evaluate the role of the variants -403G-->A and -28C-->G, located within the promoter region of the gene, as susceptibility factors in a cohort of Spanish women with endometriosis. No differences have been found in the allelic frequencies of both variants nor in the haplotype/ genotype distribution between patients and controls. These data are consistent with the lack of association between these polymorphisms and endometriosis in our population. They do not exclude completely a possible role of other variants within RANTES gene in this pathology.

Adult↗
PubMed2001

[Molecular analysis of the RPE65 gene in 72 Spanish families with autosomal recessive retinitis pigmentosa].

BACKGROUND: Autosomal recessive retinitis pigmentosa (arRP) is the most common form of retinitis pigmentosa (RP). It is characterized by a high degree of allelic and non-allelic genetic heterogeneity. Previously,it has been demonstrated that the RPE65 gene is responsible for 2% recessive or isolated RP cases and 16% Leber's congenite amaurosis cases. Although the concrete function of RPE65 is unknown as yet, it has been found to be involved in vitamin A metabolism and rhodopsin regeneration. PATIENTS AND METHOD: We studied the involvement of the RPE65 gene in 72 arRP Spanish families by means of indirect molecular and mutation analysis. RESULTS: The results obtained using the intragenic microsatellite marker D1S2803 allowed us to exclude RPE65 as the causative gene of the disease in 80.5% of the families studied. Three new variants of the RPE65 gene have been identified: IVS6-43delA, IVS6-42delT and IVS6-33CG. We found that IVS6-33C-->G was a common polymorphism. The other variants, namely IVS6-43delA and IVS6-42delT, were not identified in 150 control chromosomes studied. The segregation analysis of IVS6-42delT variant seemed to exclude it as being involved in the disease. CONCLUSIONS: Our results argue against the involvement of RPE65 gene in the families studied, indicating that the prevalence of RPE65 abnormalities in arRP Spanish families may be lower than that observed in other populations.

Carrier Proteins↗
PubMed2001

Fluorescence resonance energy transfer analysis of CCR-V64I and SDF1-3'a polymorphisms: prevalence in southern Spain hiv type 1+ cohort and noninfected population.

The relationship between host genotype and AIDS, as well as the different genotype frequencies observed in different populations, have become important topics in HIV research. Therefore, the development of methods that provide faster and reliable results may contribute to further development and knowledge of those topics. We present the results of genotyping SDF1-3'A and CCR2-V64I in 440 HIV-1-infected people and 100 noninfected controls from southern Spain, using a novel method based on real-time PCR with LightCycler technology and fluorescence resonance energy transfer. Frequencies obtained were 23.8% for SDF1-3'A and 9.5% for CCR2-V64I for both HIV+ cohort and general population. Both polymorphisms are in accordance with the Hardy-Weinberg equilibrium law and no differences between patients and controls have been observed.

Alleles↗
PubMed2001

Germline sequence variant S836S in the RET proto-oncogene is associated with low level predisposition to sporadic medullary thyroid carcinoma in the Spanish population.

OBJECTIVE: The molecular basis of sporadic medullary thyroid carcinoma (MTC) remains elusive. While germline gain-of-function mutations in the RET proto-oncogene cause hereditary MTC, somatic activating RET mutations and loss of heterozygosity of markers in various chromosomal regions representing deletions of tumour suppressor genes, have been described in a variable number of sporadic MTC. A previous report suggested that the presence of a germline variant at RET codon 836 (S836S) was associated with the development of sporadic MTC and, furthermore, that the presence of S836S was highly correlated with somatic RET M918T mutation in the MTC. Thus, we sought to determine if the S836S variant would be associated with sporadic MTC from a completely different population base, that of Andalucia. DESIGN: This is a case-control study to determine whether the presence of RET germline S836S is correlated with sporadic MTC in Andalucia. PATIENTS: Thirty-two patients with sporadic MTC from the Andalucia region of Spain, serviced by our University Hospital, were ascertained throughout the period 1995-99. Sporadic MTC was defined as a lack of personal or family history suggestive of multiple endocrine neoplasia type 2 (MEN 2) and lack of germline RET mutations which define any MEN 2 subtype. A region and race matched cohort of 250 controls was also obtained. MEASUREMENTS: The frequency of the S836S allele was determined in cases and controls and compared using the standard chi-squared statistic and Fisher's exact test. RESULTS: The polymorphic allele frequency at codon 836 in the control population (18/500 chromosomes, 3.6%) differed significantly from the MTC case cohort, 9.3% of case chromosomes (six of 64 alleles, Fisher's exact test, two-tailed, P = 0.043). CONCLUSIONS: Germline RET S836S variant is associated with a two- to three-fold risk of sporadic MTC in the Spanish population, in accordance with a previous study based on German cases. Our observations suggest that this phenomenon might be universal and not limited to Germany.

Adult↗
PubMed2001

Novel technique for scanning of codon 634 of the RET protooncogene with fluorescence resonance energy transfer and real-time PCR in patients with medullary thyroid carcinoma.

BACKGROUND: The multiple endocrine neoplasia 2 (MEN 2) syndromes [MEN 2A, MEN 2B, and familial medullary thyroid carcinoma (FMTC)] are caused by germline mutations of the RET protooncogene. Because 85% of MEN 2A patients and 30% of FMTC patients have mutations at codon 634, the recommended molecular analyses begin at exon 11, where codon 634 is located. METHODS: We scanned codon 634 of the RET protooncogene with real-time PCR and fluorescence resonance energy transfer (FRET), using a unique pair of internal probes to detect mutations localized at codon 634. We compared results with sequencing results in 66 patients. RESULTS: The method detected all codon 634 mutations available in our laboratory (Cys634Tyr, Cys634Arg, Cys634Phe, Cys634Trp). Comparing this method with the direct sequencing of exon 11 in a cohort of 66 patients with MTC, the system identified all 14 MTC patients carrying germline mutations at codon 634. One apparent false-positive result occurred among 52 patients. CONCLUSIONS: The simultaneous scanning of multiple mutations is possible with the FRET system. The method allows rapid characterization of germline mutations at codon 634 in MTC patients.

Carcinoma, Medullary↗
PubMed2000

Study of the microbial aggregation in Mycobacterium using image analysis and electron microscopy.

Cellular aggregation, which occurs in both prokaryotes and eukaryotes, is controlled by the hydrophobicity as well as the electrokinetic potential of the cell surface and substratum. It is known that the Mycobacterium genus form aggregates, but the influence of sugar on the cellular aggregation has not been reported for this genus. The mutant strain Mycobacterium sp. MB-3683 that transforms sterol to androstenedione (AD), a steroidal precursor used by the pharmaceutical industries, was employed in this study. This strain was cultivated in a synthetic medium on three sugars (glycerol, glucose and fructose) at different concentrations, and at 144 h microbial growth, cellular aggregation, hydrophobicity, lipid content, fatty acid composition, and width of cellular walls were measured. It was observed that at different sugar concentrations, similar growth and pH were obtained. However, in fructose, the aggregation level was significantly high, followed by glycerol and glucose (fructose < glycerol < glucose). These results were confirmed using electron microscopy and the aggregate area quantified by image analysis. Hydrophobicity was the highest in fructose and the lowest in glucose. The total lipids, in contrast to cellular hydrophobicity, were higher in glucose than glycerol. Although, the hydrophilic-lipophilic balance (HLB) of principal fatty acids isolated was similar regardless of sugar used. In glycerol and fructose, the paraffins were observed, which are responsible for the high cellular hydrophobicity detected above. The width of cell wall of the organisms grown on glucose and fructose was similar, but in glycerol the walls were very thin. There is a correspondence between cell wall width and lipid content.

Bacteriological Techniques↗
PubMed2000

RET genotypes comprising specific haplotypes of polymorphic variants predispose to isolated Hirschsprung disease.

BACKGROUND: Hirschsprung disease (HSCR), which may be sporadic or familial, occurs in 1:5000 live births and presents with functional intestinal obstruction secondary to aganglionosis of the hindgut. Germline mutations of the RET proto-oncogene are believed to account for up to 50% of familial cases and up to 30% of isolated cases in most series. However, these series are highly selected for the most obvious and severe cases and large familial aggregations. Population based studies indicate that germline RET mutations account for no more than 3% of isolated HSCR cases. Recently, we and others have noted that specific polymorphic sequence variants, notably A45A (exon 2), are over-represented in isolated HSCR. PURPOSE: In order to determine if it is the variant per se, a combination thereof, or another locus in linkage disequilibrium which predisposes to HSCR, we looked for association of RET haplotype(s) and disease in HSCR cases compared to region matched controls. METHODS: Seven loci across RET were typed and haplotypes formed for HSCR cases, their unaffected parents, and region matched controls. Haplotype and genotype frequencies and distributions were compared among these groups using the transmission disequilibrium test and standard case-control statistic. RESULTS: Twelve unique haplotypes, labelled A-L, were obtained. The distributions of haplotypes between cases and controls (chi(11)(2) =81.4, p<<0.0001) and between cases and non-transmitted parental haplotypes were significantly different (chi(2)(11)=53.1, p<0.0001). Genotypes comprising pairs of haplotypes were formed for cases and controls. There were 38 different genotypes among cases and controls combined. Inspection of the genotypes in these two groups showed that the genotype distribution between cases and controls was distinct (chi(37)(2)=93. 8, p<<0.0001). For example, BB, BC, BD, and CD, all of which contain at least one allele with the polymorphic A45A, are prominently represented among HSCR cases, together accounting for >35% of the case genotypes, yet these four genotypes were not represented among the population matched normal controls. Conversely, AA, AG, DD, GG, and GJ, none of which contains A45A, are commonly represented in the controls, together accounting for 43% of the control genotypes, and yet they are never seen among the HSCR cases. CONCLUSIONS: Our data suggest that genotypes comprising specific pairs of RET haplotypes are associated with predisposition to HSCR either in a simple autosomal recessive manner or in an additive, dose dependent fashion.

Alleles↗