Genetic differentiation and origin of the Jordanian population: an analysis of Alu insertion polymorphisms

AIM

Although much of Jordan is covered by desert, its north-western region forms part of the Fertile Crescent region that had given a rich past to Jordanians. This past, scarcely described by historians, is not yet clarified by sufficient genetic data. Thus in this paper we aim to determine the genetic differentiation of the Jordanian population and to discuss its origin.

METHODS

A total of 150 unrelated healthy Jordanians were investigated for ten Alu insertion polymorphisms. Genetic relationships among populations were estimated by a principal component (PC) plot based on the analyses of the R-matrix software.

RESULTS

Statistical analysis showed that the Jordanian population is not significantly different from the United Arab Emirates population or the North Africans. This observation, well represented in PC plot, suggests a common origin of these populations belonging respectively to ancient Mesopotamia, Arabia, and North Africa.

CONCLUSION

Our results are compatible with ancient peoples' movements from Arabia to ancient Mesopotamia and North Africa as proposed by historians and supported by previous genetic results. The original genetic profile of the Jordanian population, very likely Arabian Semitic, has not been subject to significant change despite the succession of several civilizations.

Research of the origin of a particular Tunisian group using a physical marker and Alu insertion polymorphisms

The aim of this study was to show how, in some particular circumstances, a physical marker can be used along with molecular markers in the research of an ancient people movement. A set of five Alu insertions was analysed in 42 subjects from a particular Tunisian group (El Hamma) that has, unlike most of the Tunisian population, a very dark skin, similar to that of sub-Saharans, and in 114 Tunisian subjects (Gabes sample) from the same governorate, but outside the group. Our results showed that the El Hamma group is genetically midway between sub-Saharan populations and North Africans, whereas the Gabes sample is clustered among North Africans. In addition, The A25 Alu insertion, considered characteristic to sub-Saharan Africans, was present in the El Hamma group at a relatively high frequency. This frequency was similar to that found in sub-Saharans from Nigeria, but significantly different from those found in the Gabes sample and in other North African populations. Our molecular results, consistent with the skin color status, suggest a sub-Saharan origin of this particular Tunisian group.

A gradient of NOS1 overproduction alleles in European and Mediterranean populations

AIM

A (CA)n repeat located in the 3' UTR region of exon 29 of the NOS1 gene (encoding for neuronal nitric oxide synthase) has been shown to affect the size of mRNA. NOS1 mRNA is highly diverse, contributing to changes in transcript generation, degradation, processing, or subcellular targeting. In the present work, we analyzed allele frequencies of this (CA)n repeat in nine populations of the Mediterranean area and Middle Europe. We aimed at testing the presence of a north-south positive gradient of frequencies of ≤17 allele repeats, compatible with the hypothesis of positive selection suggested in two of our previous works, related to the past prevalence of malaria infection in Europe.

RESULTS

Results show significant negative correlations of latitude with frequencies of alleles S and genotypes S/S and S/L (p < 0.01).

CONCLUSIONS

In conclusion, the north-south gradient of S alleles found in the present work would confirm our previous observation about the NOS1 gene, reinforcing the hypothesis of a selective action of malaria infection. This hypothesis is strengthened by the role of nitric oxide in the immunity system.

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.

Autosomal and X chromosome Alu insertions in Bolivian Aymaras and Quechuas: two languages and one genetic pool

Thirty-two polymorphic Alu insertions (18 autosomal and 14 from the X chromosome) were studied in 192 individuals from two Amerindian populations of the Bolivian Altiplano (Aymara and Quechua speakers: the two main Andean linguistic groups), to provide relevant information about their genetic relationships and demographic processes. The main objective was to determine from genetic data whether the expansion of the Quechua language into Bolivia could be associated with demographic (Inca migration of Quechua-speakers from Peru into Bolivia) or cultural (language imposition by the Inca Empire) processes. Allele frequencies were used to assess the genetic relationships between these two linguistic groups. Our results indicated that the two Bolivian samples showed a high genetic similarity for both sets of markers and were clearly differentiated from the two Peruvian Quechua samples available in the literature. Additionally, our data were compared with the available literature to determine the genetic and linguistic structure, and East-West differentiation in South America. The close genetic relationship between the two Bolivian samples and their differentiation from the Quechua-speakers from Peru suggests that the Quechua language expansion in Bolivia took place without any important demographic contribution. Moreover, no clear geographical or linguistic structure was found for the Alu variation among South Amerindians.

The Mediterranean Sea as a barrier to gene flow: evidence from variation in and around the F7 and F12 genomic regions

Background

The Mediterranean has a long history of interactions among different peoples. In this study, we investigate the genetic relationships among thirteen population samples from the broader Mediterranean region together with three other groups from the Ivory Coast and Bolivia with a particular focus on the genetic structure between North Africa and South Europe. Analyses were carried out on a diverse set of neutral and functional polymorphisms located in and around the coagulation factor VII and XII genomic regions (F7 and F12).

Results

Principal component analysis revealed a significant clustering of the Mediterranean samples into North African and South European groups consistent with the results from the hierarchical AMOVA, which showed a low but significant differentiation between groups from the two shores. For the same range of geographic distances, populations from each side of the Mediterranean were found to differ genetically more than populations within the same side. To further investigate this differentiation, we carried out haplotype analyses, which provided partial evidence that sub-Saharan gene flow was higher towards North Africa than South Europe.

Conclusions

As there is no consensus between the two genomic regions regarding gene flow through the Sahara, it is hard to reach a solid conclusion about its role in the differentiation between the two Mediterranean shores and more data are necessary to reach a definite conclusion. However our data suggest that the Mediterranean Sea was at least partially a barrier to gene flow between the two shores.

Polymorphism FXII 46C>T and cardiovascular risk: additional data from Spanish and Tunisian patients

BACKGROUND

Previous studies showed an association between Coagulation Factor XII 46C>T polymorphism and variation in FXII plasma levels, as 46C>T seems to affect the translation efficiency. Case-control studies in Spanish samples indicated that genotype T/T is an independent risk factor for venous thrombosis, ischemic stroke and acute coronary artery disease. In this study, we tried to reaffirm the importance of 46C>T in two samples from Spain and Tunisia.

FINDINGS

A Transmission Disequilibrium Test (TDT) based on 101 family trios from Barcelona with one offspring affected by ischemic heart disease and a classical case-control study based on 76 patients with IHD and 118 healthy individuals from North and Centre-South Tunisia were conducted. Subjects were genotyped for 46C>T and data were analyzed accordingly, revealing no association in any of the two samples (TDT: P = 0.16, relative risk 1.17; case-control study: P = 0.59, odds ratio 1.36).

CONCLUSION

The results suggest that 46C>T is not a risk factor for ischemic heart disease in any of the two analyzed samples and therefore the polymorphism seems not to be a universal risk factor for cardiovascular diseases.

Alu polymorphisms in Jerba Island population (Tunisia): Comparative study in Arab and Berber groups

Jerba Island represents an interesting area because four distinct ethnic groups have been cohabiting there until now: Arabs, Berbers, dark-skinned people of sub-Saharan origin and Jews. Religious and cultural differences seem to have constituted an obstacle to their intermixing. Our aim is to provide further information on the genetic structure of the Arab and Berber groups for whom previous data based on haploid markers confirmed their reproductive isolation. Five polymorphic Alu markers (HS 4.69, Sb 19.3, TPA-25, ACE and APO-A1) were analysed in a sample of 43 Arabs and 48 Berbers of Jerba. The genetic relationships among these groups and several populations from North Africa, sub-Saharan Africa and Europe were analysed using genetic distances based on allele frequencies. The results showed a homogeneous distribution of Alu insertions in the two geographically close groups, reflecting ancient relationships between them. This study also revealed that Arabs from Jerba present close genetic distances to other North African populations, whilst Berbers of Jerba occupy an intermediate position among Mediterranean populations.

Apolipoprotein gene polymorphisms and plasma levels in healthy Tunisians and patients with coronary artery disease

Aim

To analyze apolipoprotein gene polymorphisms in the Tunisian population and to check the relation of these polymorphisms and homocysteine, lipid and apolipoprotein levels to the coronary artery disease (CAD).

Methods

In healthy blood donors and in patients with CAD complicated by myocardial infarction (MI) four apolipoprotein gene polymorphisms [APO (a) PNR, APO E, APO CI and APO CII] were determined and plasma levels of total homocysteine, total cholesterol (TC), triglycerides (TG), HDL-cholesterol (HLD-C) and apolipoproteins (apo A-I, Apo B, Apo E) were measured.

Results

Analysis of the four apolipoprotein gene polymorphisms shows a relative genetic homogeneity between Tunisian population and those on the other side of Mediterranean basin. Compared to controls, CAD patients have significantly higher main concentrations of TC, TG, LDL-C, apo B and homocysteine, and significantly lower ones of HDL-C, apo A-I and apo E. The four apolipoprotein gene polymorphisms have not showed any significant differences between patients and controls. However, the APO E4 allele appears to be associated to the severity of CAD and to high levels of atherogenic parameters and low level of apo E, which has very likely an anti-atherogenic role.

Conclusion

Although APO (a) PNR, APO CI and APO CII genes are analyzed in only few populations, they show a frequency distribution, which is not at variance with that of APO E gene and other widely studied genetic markers. In the Tunisian population the APO E 4 appears to be only indirectly involved in the severity of CAD. In the routine practice, in addition of classic parameters, it will be useful to measure the concentration of apo E and that of Homocysteine and if possible to determine the APO E gene polymorphism.

Frequencies of promoter pentanucleotide (TTTTA)n of CYP11A gene in European and North African populations

The present work attempts to determine the distribution of CYP11A (TTTTA)n genotype and allele frequencies in 10 European and North African populations. This polymorphism has been associated with hyperandrogenism by several association studies. To our knowledge, this is the first study investigating the ethnic variation of this polymorphism. DNA was extracted from 868 whole-blood samples with the standard phenol-chloroform technique, and PCR reactions were carried out using fluorescent primers as described previously. PCR products were analyzed by an ABI 3,730 DNA Analyzer. A total of six alleles were identified, ranging from 220 bp (4 repeats [4R]) to 250 bp (10R). The most frequent allelic fragment size in all populations was 4R, with frequencies ranging from 47.9% (Sicily) to 62.8% (Tuscany and Germany). Allelic frequencies showed high heterogeneity between analyzed populations. We detected a significant gradient for alleles 4R and 8R. In this study, we report the allele frequency distribution of CYP11A (TTTTA)n showing a north-south geographic gradient. This result could be useful for epidemiological studies about hyperandrogenism.

How many populations set foot through the Patagonian door? Genetic composition of the current population of Bahía Blanca (Argentina) based on data from 19 Alu polymorphisms

The city of Bahía Blanca occupies a strategic place in Argentina south of the Pampean region in the north-east corner of the Patagonia. Since 1828, this city has been the historical and political border between Amerindian lands in the south, and the lands of European colonists. Nowadays, Bahía Blanca is an urban population mainly composed by descendents of immigrants from Spain and other European countries with apparently low admixture with Amerindians. In view of the unexpectedly high Amerindian admixture levels (about 46.7%) suggested by mtDNA data, and protein markers (19.5%), we analyzed a set of 19 Alu polymorphisms (18 autosomal, 1 of Chromosome Y) in a well-documented genealogical sample from Bahía Blanca. The genotyped sample was made up of 119 unrelated healthy individuals whose birth place and grandparent origins were fully documented. According to available genealogical records, the total sample has been subdivided into two groups: Bahía Blanca Original (64 individuals with all 4 gandparents born in Argentina) and Bahía Blanca Mix (55 individuals with one to three grandparents born out of Argentina). Allele frequencies and gene diversity values in Bahía Blanca fit well into the European ranges. Population relationships have been tested for 8 Alu markers, whose variation has been described in several Amerindian and European samples. Reynolds genetic distances underline the significant genetic similarity of Bahía Blanca to Europeans (mean distance 0.044) and their differentiation from Amerindians (0.146). Interestingly enough, when the general sample is divided, Bahía Blanca Original appears slightly closer to Amerindians (0.127) in contrast to Bahía Blanca Mix (0.161). Furthermore, the genetic relationships depicted through a principal components analysis emphasize the relative similarity of Bahía Blanca Original to Amerindians. A thorough knowledge of the sample origins has allowed us to make a subtle distinction of the genetic composition of Bahía Blanca.

Y-chromosome-Specific STR haplotype data on the Rapanui population (Easter Island)

Located in the south Pacific Ocean, Rapanui is one of the most isolated inhabited islands in the world. Cultural and biological data suggest that the initial Rapanui population originated from central Polynesia, although the presence of foreign or exotic genes in the contemporary population, as a result of admixture with Europeans and/or South Americans during the last two centuries, also has to be considered. To estimate the genetic affinities of the Rapanui population with neighboring populations, we analyzed seven microsatellite polymorphisms of the Y chromosome that recently have been indicated as useful in the study of local population structure and recent demographic history. Phylogenetic analysis of Rapanui Y-chromosome haplotypes identified two clusters. The largest cluster contained 60% of all haplotypes and is characterized, in particular, by the presence of the DYS19*16, DYS390*20, and DYS393*14 alleles, a combination found frequently in Western Samoa. The second cluster is characterized by the presence of the DYS19*14, DYS390*24, and DYS393*13 alleles, and these have a relatively high frequency in European and European-derived populations but are either infrequent or absent in native Pacific populations. In addition to the two clusters, one male is of haplogroup Q*, which is indicative of native American ancestry. The genetic structure of the current male population of Rapanui is most likely a product of some genetic contribution from European and South American invaders who mated with the indigenous Polynesian women. However, analysis of Rapanui's relationships with other Pacific and Asian populations indicates that, as in Western Samoa and Samoa, the population has experienced extreme drift and founder events.

Tracing Past Human Male Movements in Northern/Eastern Africa and Western Eurasia: New Clues from Y-Chromosomal Haplogroups E-M78 and J-M12

Detailed population data were obtained on the distribution of novel biallelic markers that finely dissect the human Y-chromosome haplogroup E-M78. Among 6,501 Y chromosomes sampled in 81 human populations worldwide, we found 517 E-M78 chromosomes and assigned them to 10 subhaplogroups. Eleven microsatellite loci were used to further evaluate subhaplogroup internal diversification. The geographic and quantitative analyses of haplogroup and microsatellite diversity is strongly suggestive of a northeastern African origin of E-M78, with a corridor for bidirectional migrations between northeastern and eastern Africa (at least 2 episodes between 23.9-17.3 ky and 18.0-5.9 ky ago), trans-Mediterranean migrations directly from northern Africa to Europe (mainly in the last 13.0 ky), and flow from northeastern Africa to western Asia between 20.0 and 6.8 ky ago. A single clade within E-M78 (E-V13) highlights a range expansion in the Bronze Age of southeastern Europe, which is also detected by haplogroup J-M12. Phylogeography pattern of molecular radiation and coalescence estimates for both haplogroups are similar and reveal that the genetic landscape of this region is, to a large extent, the consequence of a recent population growth in situ rather than the result of a mere flow of western Asian migrants in the early Neolithic. Our results not only provide a refinement of previous evolutionary hypotheses but also well-defined time frames for past human movements both in northern/eastern Africa and western Eurasia.

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 (approximately 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.

Population genetic data on four STR loci, PAI (CA)n, GpIIIa (CT)n, PLAT (TG)14 (CA)12, and NOS2A (CCTTT)n, in Mediterranean populations

In the present study, we have analyzed four highly polymorphic regions (STRs) chosen from four candidate genes involved in: (1) Platelet aggregation: alpha subunit of the platelet GpIIb/GpIIIa integrin complex (GpIIIa (CT)n; 17q21.31), (2) Coagulation fibrinolysis: Plasminogen Activator Tissue (PLAT5 (TG)14(TA)12; 8p12-q11.2) and Plasminogen Activator Inhibitor-1 (PAI-1 (CA)n; 7q21.3-q22), (3) Oxidative metabolism: the inducible nitric oxide (NO) synthase (iNOS) gene (NOS2A (CCTTT)n; 17cen-q11.2). Allele frequencies for these four STR loci were investigated in several Mediterranean populations. The population data deviate from the Hardy-Weinberg equilibrium in all populations for GpIIIa (CT)n polymorphism.

Genetic change in the polynesian population of Easter Island: evidence from Alu insertion polymorphisms

The origin of Pacific islanders is still an open issue in human population genetics. To address this topic we analyzed a set of 18 Alu insertion polymorphisms in a total of 176 chromosomes from native Easter Island inhabitants (Rapanui). Available genealogical records allowed us to subdivide the total island sample into two groups, representative of the native population living in the island around 1900, and another formed by individuals with some ancestors of non-Rapanui origin. Significant genetic differentiation was found between these groups, allowing us to make some biodemographic and historical inferences about the origin and evolution of this geographically isolated island population. Our data are consistent with equivalent and recent contributions from Amerindian and European migrants to the 1900s Rapanui population, with an accelerated increase in the European gene flow during the 20(th) century, especially since the 1960s. Comparative analysis of our results with other available Alu variation data on neighbouring populations supports the "Voyaging Corridor" model of Polynesian human settlement, which indicates that pre-Polynesians are mainly derived from Southeast Asian and Wallacean populations rather than from Taiwan or the Philippines. This study underlines the importance of sampling and taking into account historical information in genetic studies to unravel the recent evolution of human populations.

Human CHIT1 gene distribution: new data from Mediterranean and European populations

A 24 bp duplication in the CHIT1 gene (H allele) is associated with a deficiency in the activity of chitotriosidase, an enzyme with the capability to hydrolyse chitin. A recent study in European and two sub-Saharan populations suggested a relationship between the presence of the mutation, improved environmental conditions, and the disappearance of parasitic diseases, including Plasmodium falciparum malaria. This result was not supported by the high frequency of the 24 bp duplication in a sample from Taiwan, an area with high malaria endemicity until 40 years ago. In this study, we analysed the frequency variability of the H allele in Mediterranean populations and its internal variability in Sardinia (Italy) with respect to malaria, which had been endemic on the island until its eradication during 1946-1950. The pattern of H frequency distributions is not consistent with the hypothesis of selective pressures acting on CHIT1 gene. The Moran's index coefficient and correlogram seem to indicate, indeed, that allele distribution was determined by random factors. The pattern of frequency distribution suggests a possible Asiatic origin of the H allele, but it could be possible also that the mutant allele had diffused out of Africa, and was subsequently lost from African populations.