Beta-globin gene cluster haplotypes in two North American indigenous populations

Estimating the age of Hb G-Coushatta [β22(B4)Glu→Ala] mutation by haplotypes of β-globin gene cluster in Denizli, Turkey

BACKGROUND

Hb G-Coushatta variant was reported from various populations' parts of the world such as Thai, Korea, Algeria, Thailand, China, Japan and Turkey. In our study, we aimed to discuss the possible historical relationships of the Hb G-Coushatta mutation with the possible migration routes of the world. For this purpose, associated haplotypes were determined using polymorphic loci in the beta globin gene cluster of hemoglobin G-Coushatta and normal populations in Denizli, Turkey.

METHODS

We performed statistical analysis such as haplotype analysis, Hardy-Weinberg equilibrium, measurement of genetic diversity and population differentiation parameters, analysis of molecular variance using F-statistics, historical-demographic analyses, mismatch distribution analysis of both populations and applied the test statistics in Arlequin ver. 3.5 software program.

RESULTS

The diversity of haplotypes has been shown to indicate different genetic origins for two populations. However, AMOVA results, molecular diversity parameters and population demographic expansion times showed that the Hb G-Coushatta mutation develops on the normal population gene pool. Our estimated τ values showed the average time since the demographic expansion for normal and Hb G-Coushatta populations ranged from approximately 42,000 to 38,000 ybp, respectively.

CONCLUSION

Our data suggest that Hb G-Coushatta population originate in normal population in Denizli, Turkey. These results support the hypothesis that the multiple origin of Hb G-Coushatta and indicate that mutation may have been triggered the formation of new variants on beta globin haplotypes.

β-globin gene cluster haplotypes in ethnic minority populations of southwest China

The genetic diversity and relationships among ethnic minority populations of southwest China were investigated using seven polymorphic restriction enzyme sites in the β-globin gene cluster. The haplotypes of 1392 chromosomes from ten ethnic populations living in southwest China were determined. Linkage equilibrium and recombination hotspot were found between the 5′ sites and 3′ sites of the β-globin gene cluster. 5′ haplotypes 2 (+−−−), 6 (−++−+), 9 (−++++) and 3′ haplotype FW3 (−+) were the predominant haplotypes. Notably, haplotype 9 frequency was significantly high in the southwest populations, indicating their difference with other Chinese. The interpopulation differentiation of southwest Chinese minority populations is less than those in populations of northern China and other continents. Phylogenetic analysis shows that populations sharing same ethnic origin or language clustered to each other, indicating current β-globin cluster diversity in the Chinese populations reflects their ethnic origin and linguistic affiliations to a great extent. This study characterizes β-globin gene cluster haplotypes in southwest Chinese minorities for the first time, and reveals the genetic variability and affinity of these populations using β-globin cluster haplotype frequencies. The results suggest that ethnic origin plays an important role in shaping variations of the β-globin gene cluster in the southwestern ethnic populations of China.

Beta-globin gene cluster haplotypes in Afro-Uruguayans from two geographical regions (South and North)

The beta-globin gene cluster haplotypes were identified in 52 and 40 chromosomes from two Afro-Uruguayan populations located in the South and North of the country, respectively. In both regions, the 5' haplotype 2 (+ - - - -), characteristic of non-African populations, was the most frequent, reflecting a strong process of admixture in Afro-Uruguayans (0.355 and 0.262, respectively). The haplotypes 3 (- - - - +) and 4 (- + - - +), characteristics of African sub-Saharan populations, present inverse frequencies in North and South: whereas in the South haplotype 3 is the second most frequent (0.232), and haplotype 4 presents a low frequency (0.019), in the North haplotype 4 is the third most frequent (0.140), and haplotype 3 only reaches an intermediate frequency (0.088). The pairwise F(ST) and the exact test of differentiation show genetic heterogeneity between both regions. Nei's genetic distance show that South and North present affinities with Bantu groups, although the North present the smallest genetic distance with the Mandenka, a Senegalese population. With respect to 3' haplotypes, haplotype I was the most frequent in both populations, followed by haplotype II, characteristic of sub-Saharan Africans. The high frequencies of haplotype III-Asian could indicate admixture with Native American populations. The differences observed between both Uruguayan regions could be explained by microevolutionary events as genetic drift, founder effects, differential admixture, and/or distinct origin of the African slaves introduced in those regions.

The β-globin gene cluster distribution revisited—Patterns in Native American populations

New frequencies for the beta-globin gene cluster haplotypes are presented for the Aché (N = 82 individuals), Guarani (N = 76), and Kaingang (N = 54), three Native South American populations that live in an area between parallels 20 degrees S and 30 degrees S not covered by previous studies at this locus. The haplotype frequencies obtained for the three populations are within the interval observed for 28 other Native American populations. The Aché show much less haplotypes (five) than the other two populations (9-10), the haplotype prevalences being more similar to those of the Guarani than to the Kaingang. The Native American total heterozygosity was about half (0.41) that obtained for the African populations (0.71), but was not much different from those obtained for other continents. A geographical pattern was disclosed in South America by mapping the frequencies of the most common haplotype (haplotype 2), and by means of spatial correlation analysis. The analysis of molecular variance (AMOVA) and pairwise F(ST) data suggest three distinct sectors for the genetic landscape of Native South America: the Andes, the Center/Southeast region, and the Amazon.

Alu insertion polymorphisms in Native Americans and related Asian populations

BACKGROUND

Alu insertions provide useful markers for the study of inter-population affinities and historical processes, but data on these systems are not numerous in Native Americans and related populations.

AIM

The study aimed to answer the following questions: (a) do the population relationships found agree with ethnic, historical and geographical data? and (b) what can heterozygote levels and associated results inform us about the events that led to the colonization of the New World?

SUBJECTS AND METHODS

Twelve Alu insertion polymorphisms were studied in 330 individuals belonging to South American Native, Siberian and Mongolian populations. These data were integrated with those from 526 persons, to ascertain the relationships between Asian, Northern Arctic and Amerindian populations.

RESULTS

A decreasing trend concerning heterozygosities and amount of gene flow was observed in the three sets, in the order indicated above. Most results indicated the validity of these subdivisions. However, no clear structure could be observed within South American Natives, indicating the importance of dispersive (genetic drift, founder effects) factors in their differentiation.

CONCLUSIONS

The answers to the questions are: (a) yes; and (b) an initial moderate bottleneck, intensified by more recent historical events (isolation and inbreeding), can explain the current Amerindian pattern of diversity.

β-globin cluster haplotypes in normal individuals and β039-thalassemia carriers from Sardinia, Italy

Seven polymorphic sites in the beta-globin cluster in association with specific thalassemia mutations were analyzed in a sample from Sardinia, Italy. In order to verify previous works carried out on normal samples (beta(A)/beta(A)) and family studies on beta-thalassemia homozygotes individuals, the haplotype frequencies in both normal individuals (beta(A)/beta(A)) and beta(0)39-thalassemia carriers (beta(A)/beta0) were studied. In our work chromosomes carrying beta(0)39 mutation are characterized by a prevalence of haplotype II (- + + - + + +) (52%) relative to haplotype I (+- - - - + +) (29%), in contrast, among chromosomes with beta(A) the frequency of haplotype I is much greater than that of haplotype II. These data confirm what was found by other authors. Nevertheless, our results disagree with those of previous studies of Sardinians, both in frequencies values and in the numbers of haplotypes identified. Population analysis performed with samples carrying the beta-thalassemic mutation highlighted the peculiarity of Sardinians with respect to other Mediterranean populations. The Corsican population is most similar to the Sardinian population, confirming previous analyses performed with both classical markers and mitochondrial and genomic DNA.

Molecular variability in Amerindians: widespread but uneven information

A review was made in relation to the molecular variability present in North, Central, and South American Indian populations. It involved results from ancient DNA, mitochondrial DNA in extant populations, HLA and other autosomal markers, X and Y chromosome variation, as well as data from parasitic viruses which could show coevolutionary changes. The questions considered were their origin, ways in which the early colonization of the continent took place, types and levels of the variability which developed, peculiarities of the Amerindian evolutionary processes, and eventual genetic heterogeneity which evolved in different geographical areas. Although much information is already available, it is highly heterogeneous in relation to populations and types of genetic systems investigated. Unfortunately, the present trend of favoring essentially applied research suggest that the situation will not basically improve in the future.