Use of short tandem repeats loci to study the genetic structure of several populations from Zulia State, Venezuela.

Genetic relationships between populations can be studied by comparing genotypic and allelic similarities. This investigation aims to demonstrate that selected autosomal microsatellite markers could be used to study the genetic structures of different populations living in northwest Venezuela, in Zulia State. Seven autosomal systems (CSF1PO, TPOX, TH01, vWA, D7S820, D13S317, and D5S818) were tested by PCR in a multiplex format on 688 different chromosomes from unrelated individuals living in Maracaibo, "Isla de Toas," and "San José de Heras," and from two Amerindian populations from the "Sierra de Perijá," Barí' and Yukpa. Allele frequencies, Hardy-Weinberg equilibria, genetic distances, phylogenetic trees, and ethnic admixtures were estimated. The study shows the existence of a clear genetic difference among these populations in accordance with their historic evolution. The populations of Maracaibo and "Isla de Toas" showed a triracial origin, with a large European contribution, followed by an Amerindian component and a small African component. The indigenous groups, Barí' and Yukpa, showed exclusively an Amerindian component, and "San José de Heras" showed only an African component. These results indicate that microsatellite markers are useful for molecular anthropology in a regional and worldwide context and provide important genetic information about contemporary populations of Venezuela.

Mixed gonadal dysgenesis: a syndrome of broad clinical, cytogenetic and histopathologic spectrum.

Mixed gonadal dysgenesis (MGD) is an abnormality of sexual differentiation (ASD), which encompasses an heterogeneous group of different gonadal and phenotypic abnormalities. This study describes the main clinical features found in 16 patients with MGD, relating the clinical presentation with cytogenetic evaluation and histopathological findings. For purpose of this study, MGD was considered in those patients who fulfilled the following diagnostic criteria: 1) müllerian and/or wolfflan derivatives; 2) any of the following gonadal characteristics: a) bilateral intrabdominal or scrotal immature testicular tissue; b) intrabdominal or scrotal immature testicular tissue with contralateral streak gonad. Patients were selected from an ASD study which was carried out in Medical Genetic Unit of University of Zulia (UGM-LUZ), Maracaibo, Venezuela, from 1980 to 1997. The following information was extracted from the medical history at UGM-LUZ: age, gender which patient was reared, clinical presentation, cytogenetic evaluation, laparoscopic findings and gonadal biopsy. Sixteen patients fulfilled the diagnostic criteria and ranged in age from 1.2 to 39.4 years with an average of 12.65 years. Only 5 patients were reared as males. Twelve patients consulted for genital ambiguity. Chromosomal evaluation was as following: 8 patients with 45,X/46,XY mosaicism: 5 had a 46,XY normal male karyotype and the remaining patients: 46,XX; 46,XX/46,XY and 45,X/46,Xi(Xq) karyotypes, respectively. All patients showed müllerian derivatives and occasionally wolffian derivatives. Gonadal tumors were present in 2 patients. Molecular studies of genes that govern gonadal development are necessary for a better understanding of the wide heterogeneity present in MGD.

[Analysis of Bcl I polymorphism of factor VIII gene in the molecular diagnosis of female hemophilia A carriers in families from northwestern Venezuela]. / Análisis del polimorfismo Bcl I del gen del factor VIII en el diagnóstico molecular de portadoras de Hemofilia A en familias del noroccidente de Venezuela.

PURPOSE: To identify carrier females in segregant families of haemophilia A from Zulia state-Venezuela. PATIENTS AND METHODS: The polymorphisms' analysis linked to the gene, independently of the mutation nature is the most suitable method to identify carriers, because it permits to track the mutated gene. This study is comprised of 139 ADN samples distributed in 20 families affected by haemophilia A. The diagnosis of carrier was made by polymerase chain reaction (PCR), a fragment of 142 pb corresponding to intron 18 of the factor VIII gene, which shows a restriction polymorphism for the Bcl I enzyme. RESULTS: The frequency of the Bcl I alleles in the 43 unrelated individuals was 0.35 and 0.65 for the 142 pb and 99 + 43 pb, respectively. In the 35 women that required diagnosis, we were able to establish the carrier status for 11, and 4 were excluded to be. CONCLUSIONS: The Bcl I polymorphism at the FVIII gene was useful in the 43% (15/35) of the women that required diagnosis. It's possible to identify carriers for haemophilia A in most of the families from Zulia state-Venezuela employing several polymorphisms at the Factor VIII gene.

[Prenatal diagnosis. I: Prenatal diagnosis program at the Medical Genetics Unit of the Universidad de Zulia, Maracaibo, Venezuela]. / Diagnóstico prenatal. I: Programa de diagnóstico prenatal de la Unidad de Genética Médica de La Universidad del Zulia, Maracaibo, Venezuela.

The Prenatal Diagnosis Program of the Medical Genetic Unit of University of Zulia has the following objectives: Identification of Genetic Risk Factors (GRF) in those couples who attend to the Prenatal Genetic Clinic, application of different prenatal diagnostic procedures (PDP), and providing adequate genetic counseling. The goal of this paper is to show preliminary results obtained between January 1993 and December 1996. Three hundred and twenty one pregnant women were analyzed by determining the GRF and taking into account the genetic clinical history. The GRF analyzed were: Advanced maternal age (AMA), congenital malformation history (CMH), previous child with chromosomic anomalies (PCCA), defects of neural tube history (DNTH), congenital heart disease history (CHDH), any parent carrier of chromosomic anomaly (PCA), habitual abortion (HA), abnormal fetal echography (AFE), altered maternal serum levels of alpha-feto-protein (AMSAFP) and OTHERS: exposure to teratogenic agents, history of Mendelian diseases, maternal systemic diseases and anxiety in the mother or in her partner. The PDP was designed according to the GRF, which included fetal echography (FE), fetal echocardiography (FEc), amniocentesis (AMN), chordocentesis (CCT) and AMSAFP. Results showed that 58.4% of the expectant mothers asked for counseling during the 2nd trimester, 70% of the total showed only one GRF, and AMA was the most frequent GRF found (40.3%), followed by PCCA, AFE, CHDH, HA, DNTH, PCA, and OTHERS in that order. The specific PDP applied to the identified GRF allowed a health evaluation of the fetus. The GRF identification gave the opportunity of establishing a Prenatal Diagnostic Program producing a response to the couple's needs and showed the utility of an integral and multidisciplinary management directed to any expecting mother in order to identify any high GRF.

[Prenatal molecular diagnosis of cystic fibrosis. Report of 3 cases]. / Diagnóstico molecular prenatal de fibrosis quística. Reporte de tres casos.

Cystic Fibrosis (CF) is a severe and relatively common autosomic recessive disease caused by a variety of mutations in the CFTR gene. The most frequent mutation worldwide, consists of the deletion of the phenylalanine codon at position 508 (delta F508). Here we report the first cases of prenatal diagnosis of CF by DNA analysis in couples at risk in Venezuela. The study focused on the detection of delta F508 alleles analyzing DNA recovered directly from amniocytes or from their cultures, using the polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis. Two of three fetuses resulted homozygotic for the delta F508 allele and the third one turned out to be a delta F508 carrier. This information sustained the genetic counseling of the couples and allowed them to take objective reproductive decisions, a direct consequence of the availability of gene analysis at the DNA level.