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.

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