Esther Esteban

APO E Polymorphism in Spanish and Moroccan populations

Apolipoprotein E (apoE) gene polymorphism was analyzed by polymerase chain reaction in one Moroccan and six Spanish populations, a total of 660 individuals. No significant differences were observed between samples, and the mean relative frequencies (with 95% confidence intervals) found were 0.104 (0.069–0.139) for the e4 allele, 0.855 (0.813–0.897) for e3 and 0.041 (0.015–0.067) for e2. Frequencies of the e4 allele were low in comparison to Northern European populations, but similar to those reported for other South‐European populations. The presence of a rare mutation, E2 Christchurch, in one Basque individual was confirmed by sequence analysis.

Mixed origin of the current Tunisian population from the analysis of Alu and Alu /STR compound systems

During successive historical periods, Tunisia has been a crossroads of multiple civilizations and their corresponding key population movements. The aim of this study was to provide genetic information relating to the mixed origin of the Tunisian population, and to analyze its genetic relationship with other North African and Mediterranean populations. A set of 16 Alu and 3 Alu/STR compound systems has been analyzed in 268 autochthonous Tunisians from the north-center and the south of the country. Our two sampled populations showed no significant differentiation from one another in any of the three Alu/STR compound systems, whereas the analysis of the 16 Alu markers revealed a significant genetic differentiation between them. A sub-Saharan component shown by the three Alu/STR combinations is more noticeable in our north-center sample than in that of the south. The presence of two Alu/STR combinations specific to North African ancestral populations also suggests that the ancient Berber component is relatively more substantial in the north and center regions than in the south. Our Tunisian samples cluster together with other Berber samples from Morocco and Algeria, underpinning the genetic similarity among North Africans regardless of their current linguistic status (Berber or Arabic).

Androgen receptor CAG and GGC polymorphisms in Mediterraneans: repeat dynamics and population relationships

AbstractMicrosatellite variation (CAG and GGC repeats) of the androgen receptor (AR) gene shows remarkable differences among African and non-African populations. In vitro studies have demonstrated an inverse relationship between the length of both microsatellites and AR activity. This fact may explain the observed association of the AR gene with prostate cancer and the strong ethnic differences in the incidence of this cancer. CAG and GGC genetic variation has been tested in a large set of populations from the Ivory Coast as well as 12 Mediterranean samples whose variation is described for the first time. The pattern of frequencies observed in the Ivory Coast agrees with data previously reported for other Sub-Saharan populations. Concerning the Mediterranean variation, Sardinian samples are characterised by low genetic diversities, and Egyptian Siwa Berbers by a particular pattern of GGC frequencies. High and Middle Atlas Moroccan Berbers are the most closely related to the Sub-Saharan variation. For both the CAG and GGC repeats, the Ivory Coast and some Moroccan samples exhibit high frequencies of low size alleles (CAG under 18 repeats, and GGC under 15 repeats) that have been associated with prostate cancer.

Population relationships in the Mediterranean revealed by autosomal genetic data (Alu and Alu/STR compound systems).

The variation of 18 Alu polymorphisms and 3 linked STRs was determined in 1,831 individuals from 15 Mediterranean populations to analyze the relationships between human groups in this geographical region and provide a complementary perspective to information from studies based on uniparental markers. Patterns of population diversity revealed by the two kinds of markers examined were different from one another, likely in relation to their different mutation rates. Therefore, while the Alu biallelic variation underlies general heterogeneity throughout the whole Mediterranean region, the combined use of Alu and STR points to a considerable genetic differentiation between the two Mediterranean shores, presumably strengthened by a considerable sub-Saharan African genetic contribution in North Africa (around 13% calculated from Alu markers). Gene flow analysis confirms the permeability of the Sahara to human passage along with the existence of trans-Mediterranean interchanges. Two specific Alu/STR combinations-CD4 110(-) and DM 107(-)-detected in all North African samples, the Iberian Peninsula, Greece, Turkey, and some Mediterranean islands suggest an ancient genetic background of current Mediterranean peoples.

Classical polymorphisms in Berbers from Moyen Atlas (Morocco): genetics, geography, and historical evidence in the Mediterranean peoples.

Background : Mediterranean population relationships have recently been reviewed through the analysis of classical and DNA markers. The differentiation between Berbers and Arabic-speakers to the south, and the genetic impact of the seven centuries of Muslim domination in the Iberian Peninsula have been among the most interesting questions posed in these studies. Aim : The present study seeks to assess the degree of genetic affinity between the two main population groups of Morocco: Berbers and Arabic-speakers. Data from the Berber study population were also compared with published information on 20 circum-Mediterranean groups. Subjects and methods : A Berber sample of 140 indviduals from Moyen Atlas (Morocco) has been characterized using 15 classical markers (ABO, Duffy, MNSs, Rh, ACPl, AKl, ESD, GLOI, 6-PGD, PGMl, GC, HP, PI, PLG and TF). Results : Allele frequencies in the Berbers fit well into the general southern Mediterranean ranges, albeit with some peculiarities, such as the high FY*A, ACPl*C, and PI*S values. The general pattern of relationships among Mediterranean peoples tested by genetic variance analysis was compatible with a north-south geographical differentiation. Spatial auto-correlation analysis in the different geographical regions of the Mediterranean reveals that the highest degree of association between allele frequencies and geographical distances corresponds to the western (41% of significant correlograms) and northern Mediterranean populations (33%). When only southern Mediterranean groups were considered, the degree of geographical structure considerably decreases (11% of significant correlograms). Conclusions : The different loci studied revealed close similarity between the Berbers and other north African groups, mainly with Moroccan Arabic-speakers, which is in accord with the hypothesis that the current Moroccan population has a strong Berber background. Differences in the spatial pattern of allele frequencies also are compatible with specific population histories in distinct Mediterranean areas, rather than general population movements across the whole region.

New insights into the genetic history of Tunisians: data from Alu insertion and apolipoprotein E gene polymorphisms.

Background: Among polymorphisms of non-transcribed DNA sequences and functional genes, those of Alu insertions and that of the APOE gene have been widely used to clarify the degree of genetic relationships between human populations. Aim: APOE gene and eight Alu insertion polymorphisms were investigated in Tunisians and compared with data from neighbour populations in order to gain new insights into the genetic position of Tunisia in the Mediterranean region. Subjects and methods: A total of 121 individuals from the North and Centre-South regions were sampled. Results: No significant genetic differences were found between Tunisians and North Africans when samples representative of wide areas were considered. APOE gene variation seemed slightly less powerful than the Alu polymorphisms in detecting North–South Mediterranean differences. Conclusion: North African populations show a substantial degree of genetic homogeneity, which may reflect the similarity of their origins, mainly when samples from large geographical areas are compared. The relative genetic homogeneity of the whole Mediterranean region probably reflects a common origin and/or remarkable levels of gene flow. However, this gene flow has not yet erased the differentiation between the two Mediterranean shores, as revealed by Alu insertion polymorphisms.

Genetic relationships between southeastern Spain and Morocco: New data on ABO, RH, MNSs, and DUFFY polymorphisms

The genetic polymorphism of four blood group systems (ABO, RH, MNSs, and DUFFY) was analyzed in two well‐defined population samples coming from south‐central Morocco and southeastern Spain. Both a controversial ancient common substrate and the long period of coexistence between North Africa and southern Spain during the eight centuries of the Islamic invasion of the Iberian Peninsula suggest a particular genetic relationship between northwestern Africa and southern Spain. Allele distributions in each sample are in general agreement with that expected according to the geographical and historical characteristics in the Mediterranean region. However, the differences between the Moroccan sample and other north African groups illustrate considerable genetic variability in this geographical region. In comparison with other samples from different regions of the Iberian Peninsula, the markers examined fail to demonstrate any particular affinity between the southern Spanish sample of La Alpujarra and Moroccan populations. Am. J. Hum. Biol. 11:745–752, 1999.

Genetic study of the population of Tenerife (Canary Islands, Spain): Protein markers and review of classical polymorphisms

Data on six protein polymorphisms (19 alleles) from the human population of Tenerife are presented and discussed along with other classical markers in relation to the origin of the Canarians. Genetic influences from three population groups were considered: the Iberians, and the Berbers and non-Berbers (Arabs) from north Africa. The systems examined show the Tenerife population lies within the limits of variation described for various Iberian groups, with a slight tendency towards the characteristics of north African populations. When blood groups, red cell enzymes and serum protein data were considered, the similarity of the Canary population to Iberians seems strengthened (70% estimated contribution of Iberian peninsula genes to the present-day Canarian pool), while some relation with north African groups is shown. Genetic distances between Canarians and Arabs and Canarians and Berbers are lower than those between the two north African groups, indicating a relative and comparable contribution of each to the present-day gene pool of the Canarian population. The Arab contribution could be attributable to the slaves who were introduced to these islands after the conquest in the 15th century, while the Berber contribution could be the remnants of the extinct aboriginal peoples of the islands (Guanches) or a more recent immigration due to slavery. Genetic data do not allow us to distinguish between these two possibilities.

The X chromosome Alu insertions as a tool for human population genetics: data from European and African human groups.

Alu elements are the most abundant mobile elements in the human genome (∼1 100 000 copies). Polymorphic Alu elements have been proved to be useful in studies of human origins and relationships owing to two important advantages: identity by descent and absence of the Alu element known to be the ancestral state. Alu variation in the X chromosome has been described previously in human populations but, as far as we know, these elements have not been used in population relationship studies. Here, we describe the allele frequencies of 13 ‘young’ Alu elements of the X chromosome (Ya5DP62, Ya5DP57, Yb8DP49, Ya5a2DP1, Yb8DP2, Ya5DP3, Ya5NBC37, Yd3JX437, Ya5DP77, Ya5NBC491, Yb8NBC578, Ya5DP4 and Ya5DP13) in six human populations from sub-Saharan Africa (the Ivory Coast), North Africa (Moroccan High Atlas, Siwa oasis in Egypt, Tunisia), Greece (Crete Island) and Spain (Basque Country). Eight out of 13 Alu elements have shown remarkably high gene diversity values in all groups (average heterozygosities: 0.342 in the Ivory Coast, 0.250 in North Africa, 0.209 in Europe). Genetic relationships agree with a geographical pattern of differentiation among populations, with some peculiar features observed in North Africans. Crete Island and the Basque Country show the lowest genetic distance (0.0163) meanwhile Tunisia, in spite of its geographical location, lies far from the other two North African samples. The results of our work demonstrate that X chromosome Alu elements comprise a reliable set of genetic markers useful to describe human population relationships for fine-scale geographical studies.

STR genetic diversity in a Mediterranean population from the south of the Iberian Peninsula

Abstract Sixteen Y-chromosomal short tandem repeats (STRs) (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS385, DYS437, DYS438, DYS439, DYS448, DYS456, DYS458, DYS635 and GATA H4.1) were typed in DNA samples from 52 unrelated men and 15 autosomal STRs (CSF1PO, D2S1338, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D19S433, D21S11, FGA, TH01, TPOX, vWA) were also studied for a group of 90 individuals (men and women) from the same population (Andalusians from La Alpujarra, South of Spain). The Alpujarrenian population represents an example of an isolated population with remarkable geographical, cultural and historical characteristics. High haplotype diversities were observed for the studied polymorphisms, 0.98 and 1 for YSTRs and autosomal STRs, respectively. Population comparisons for the autosomal STR allele distributions revealed remarkable levels of global homogeneity among samples geographically related.