CFTR gene analysis in Latin American CF patients: heterogeneous origin and distribution of mutations across the continent.

BACKGROUND: Cystic Fibrosis (CF) is the most prevalent Mendelian disorder in European populations. Despite the fact that many Latin American countries have a predominant population of European-descent, CF has remained an unknown entity until recently. Argentina and Brazil have detected the first patients around three decades ago, but in most countries this disease has remained poorly documented. Recently, other countries started publishing their results. METHODS: We present a compilation and statistical analysis of the data obtained in 10 countries (Argentina, Brazil, Chile, Colombia, Costa Rica, Cuba, Ecuador, Mexico, Uruguay and Venezuela), with a total of 4354 unrelated CF chromosomes studied. RESULTS: The results show a wide distribution of 89 different mutations, with a maximum coverage of 62.8% of CF chromosomes/alleles in the patient's sample. Most of these mutations are frequent in Spain, Italy, and Portugal, consistent with the origin of the European settlers. A few African mutations are also present in those countries which were part of the slave trade. New mutations were also found, possibly originating in America. CONCLUSION: The profile of mutations in the CFTR gene, which reflects the heterogeneity of its inhabitants, shows the complexity of the molecular diagnosis of CF mutations in most of the Latin American countries.

PCR-heterodúplex por agrupamiento: implementación de un método de identificación de portadores de la mutación más común causal de fibrosis quística en Colombia / PCR-heteroduplex by grouping: rapid screening carrier method for cystic fibrosis F508del mutation in Colombia

Introducción: La fibrosis quística (FQ) es una enfermedad autosómica recesiva frecuente, con una incidencia de 1 en 2,500 recién nacidos. La causan más de 1,300 mutaciones distintas en el gen regulador de la conductancia transmembranal de la fibrosis quística (CFTR). Sin embargo, la mutación F508del es la más común en la mayoría de las poblaciones. Objetivos: Desarrollo de una técnica rápida, de bajo costo y confiable que permita filtrar con rapidez a los portadores o afectados por esta mutación que mediante el asesoramiento genético, contribuya a disminuir la aparición de nuevos casos y a un diagnóstico temprano de los enfermos y así lograr un descenso en la morbilidad y la mortalidad asociadas con la fibrosis quística en Colombia. Metodología: En el presente estudio se aplicó la técnica PCR-heterodúplex por agrupamientos, gracias al análisis de 400 muestras de sangre en papel filtro obtenidas de individuos asintomáticos para la FQ. Resultados: En las pruebas de validación de la técnica PCR-heterodúplex por agrupamiento se obtuvo una eficiencia, reproducibilidad y especificidad de 100% y una sensibilidad de 92%. Conclusiones: Se demostró la sensibilidad y reproducibilidad de la técnica PCR Directa-heterodúplex por agrupamientos de hasta 10 muestras, que se pueden emplear en programas para filtrar heterocigotos y afectados de F508del.

Background: Cystic fibrosis (CF) is the most frequent autosomal recessive disorder in the Caucasian population with an incidence of 1 in 2,500 newborns. More than 1,300 mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that causes CF have been described. However, mutation F508del is the most common mutation in different populations around the world. Objective: To develop a fast, reliable and low-cost technique to screen carriers and affected individuals for the F508del mutation. This kind of analysis will have an impact on genetic counselling to decrease the incidence of new cases, in the early diagnosis and instauration of appropriate treatment to decrease morbidity and mortality associated to CF in Colombia. Methods: The reliability of the PCR-heteroduplex by grouping technique by analysis of 400 blood spot samples from asymptomatic CF patients was defined. Results: Using PCR-heteroduplex by grouping technique 100% efficiency, reproducibility and specificity and 92%sensitivity were found.Conclusions: The sensitivity and reproducibility of the PCR-heteroduplex by grouping technique up to pooling of 10 samples were demonstrated. This kind of analysis could be used in heterozygotes and affected screening programs.

CFTR mutations in patients from Colombia: implications for local and regional molecular diagnosis programs.

Cystic Fibrosis is a worldwide distributed hereditary disease. The incidence of the main (p.F508del) and other frequent mutations has been determined in a great number of countries and ethnic groups, but its incidence in most Latin American countries has remained unknown until recently. It is now beginning to be recognized as a frequent cause of infant mortality, and some countries report the incidence of their mutations. Colombia started several years ago a concerted program of molecular study of patients which were clinically diagnosed as probable cystic fibrosis. We screened the whole CFTR (ABCC7) coding sequence in 92 patients from 6 different geographic regions, using conventional PAGE analyses and DGGE followed by sequencing. Additionally, we established the frequency of the p.F508del mutation in 130 unrelated healthy controls. The results of this pilot study in Colombian patients from various ethnic admixture show six main mutations: p.F508del (41.8%), c.1811+1.6kbA>G (6.5%), p.G542X (3.8%), p.S549R (2.2%), p.W1282X (1.1%) and p.R1162X (1.1%). Thirteen other rare mutations, including three novel, were detected, accounting for a total of 63.6% known mutations. There is a great variability between the geographic regions, both in the frequency of the p.F508del mutation and non-p.F508del CF chromosomes. Our results point to a varied origin of the disease genes. These results also show that careful scrutiny of the mutations is needed in each part of Latin America in order to establish priority-screening protocols adapted to each country and region.

Mitochondrial DNA studies show asymmetrical Amerindian admixture in Afro-Colombian and Mestizo populations.

The origin of the African populations that arrived on the Colombian coasts at the time of the Spanish conquest and their subsequent settlement throughout the country and interaction with Amerindian and Spanish populations are features that can be analyzed through the study of mitochondrial DNA (mtDNA) markers. For this purpose, the present study investigates the admixture between these populations by analyzing the markers defining the main (A, B, C, D) and minor (X) founder haplogroups in Native Americans, the principal African haplogroup (L), and additional generic markers present in Caucasian (I, J, K, H, T, U, V, W) and minor African lineages (L3). As part of an interdisciplinary research program (the Expedición Humana, furthered by the Universidad Javeriana and directed by J.E. Bernal V.), 159 Afro-Colombians from five populations in which they are the majority and 91 urban Mestizos were studied. No Amerindian haplogroups (A-D, X) were detected in 81% of the Afro-Colombians. In those samples with Amerindian lineages (average 18.8%, with a range from 10% to 43%), haplogroup B predominated. When analyzed for the presence of African haplotypes, Afro-Colombians showed an overall frequency of 35.8% for haplogroup L mtDNAs, although with broad differences between populations. A few Afro-Colombian samples (1.9%) had mutations that have not been described before, and might therefore be considered as previously unsampled African variants or as new mutations arising in the American continent. Conversely, in Mestizos less than 22% of their mtDNAs belonged to non-Amerindian lineages, of which most were likely to be West Eurasian in origin. Haplogroup L mtDNAs were found in only one Mestizo (1.1%), indicating that, if present, admixture with African women would bring in other, rarer African lineages. On the other hand, in an accompanying paper (Keyeux et al. 2002) we have shown that Amerindians from Colombia have experienced little or no matrilineal admixture with Caucasians or Africans. Taken together, these results are evidence of different patterns of past ethnic admixture among Africans, Amerindians, and Spaniards in the geographic region now encompassing Colombia, which is also reflected in much of the region's cultural diversity.

Possible migration routes into South America deduced from mitochondrial DNA studies in Colombian Amerindian populations.

Mitochondrial DNA haplotype studies have been useful in unraveling the origins of Native Americans. Such studies are based on restriction site and intergenic deletion/insertion polymorphisms, which define four main haplotype groups common to Asian and American populations. Several studies have characterized these lineages in North, Central, and South American Amerindian, as well as Na Dene and Aleutian populations. Siberian, Central Asian, and Southeast Asian populations have also been analyzed, in the hope of fully depicting the route(s) of migration between Asia and America. Colombia, a key route of migration between North and South America, has until now not been studied. To resolve the current lack of information about Colombian Amerindian populations, we have investigated the presence of the founder haplogroups in 25 different ethnic groups from all over the country. The present research is part of an interdisciplinary program, Expedición Humana, fostered by the Universidad Javeriana and Dr. J. E. Bernal V. The results show the presence of the four founder A-D Amerindian lineages, with varied distributions in the different populations, as well as the presence of other haplotypes in frequencies ranging from 3% to 26%. These include some unique or private polymorphisms, and also indicate the probable presence of other Asian and a few non-Amerindian lineages. A spatial structure is apparent for haplogroups A and D, and to a lesser extent for haplogroup C. While haplogroup A and D frequencies in Colombian populations from the northwestern side of the Andes resemble those seen in Central American Amerindians more than those seen in South American populations, their frequencies on the southeastern side more closely resemble the bulk of South American frequencies so far reported, raising the question as to whether they reflect more than one migration route into South America. High frequencies of the B lineage are also characteristic of some populations. Our observations may be explained by historical events during the pre-Columbian dispersion of the first settlers and, later, by disruptions caused by the European colonization.

Declaración universal sobre genoma humano y los derechos humanos / Universal declaration about human genome and human rigths

A partir de la necesidad de despejar los valores comunes de la humanidad que permitan conciliar los progresos científicos y tecnológicos con los derechos y libertades fundamentales de las personas se presentan los cuestionamientos básicos que fueron la base de la Declaración Universal sobre el Genoma Humano y los Derechos Humanos

Estudios moleculares en pacientes colombianos con Fibrosis quística

La fibrosis quística (FQ), la enfermedad autosómica recesiva más frecuente en poblaciones caucásicas, tiene una incidencia promedio de 1/2.500 recién nacidos