Languages, geography and HLA haplotypes in native American and Asian populations

Alzheimer's disease and its related dementias in US Native Americans: A major public health concern

Alzheimer's disease (AD) and Alzheimer's related dementias (ADRD) are growing public health concerns in aged populations of all ethnic and racial groups. AD and ADRD are caused by multiple factors, such as genetic mutations, modifiable and non-modifiable risk factors, and lifestyle. Studies of postmortem brains have revealed multiple cellular changes implicated in AD and ADRD, including the accumulation of amyloid beta and phosphorylated tau, synaptic damage, inflammatory responses, hormonal imbalance, mitochondrial abnormalities, and neuronal loss. These changes occur in both early-onset familial and late-onset sporadic forms. Two-thirds of women and one-third of men are at life time risk for AD. A small proportion of total AD cases are caused by genetic mutations in amyloid precursor protein, presenilin 1, and presenilin 1 genes, and the APOE4 allele is a risk factor. Tremendous research on AD/ADRD, and other comorbidities such as diabetes, obesity, hypertension, and cancer has been done on almost all ethnic groups, however, very little biomedical research done on US Native Americans. AD/ADRD prevalence is high among all ethnic groups. In addition, US Native Americans have poorer access to healthcare and medical services and are less likely to receive a diagnosis once they begin to exhibit symptoms, which presents difficulties in treating Alzheimer's and other dementias. One in five US Native American people who are 45 years of age or older report having memory issues. Further, the impact of caregivers and other healthcare aspects on US Native Americans is not yet. In the current article, we discuss the history of Native Americans of United States (US) and health disparities, occurrence, and prevalence of AD/ADRD, and shedding light on the culturally sensitive caregiving practices in US Native Americans. This article is the first to discuss biomedical research and healthcare disparities in US Native Americans with a focus on AD and ADRD, we also discuss why US Native Americans are reluctant to participate in biomedical research.

Genetic, geographic, and environmental correlates of human temporal bone variation

Temporal bone shape has been shown to reflect molecular phylogenetic relationships among hominoids and offers significant morphological detail for distinguishing taxa. Although it is generally accepted that temporal bone shape, like other aspects of morphology, has an underlying genetic component, the relative influence of genetic and environmental factors is unclear. To determine the impact of genetic differentiation and environmental variation on temporal bone morphology, we used three-dimensional geometric morphometric techniques to evaluate temporal bone variation in 11 modern human populations. Population differences were investigated by discriminant function analysis, and the strength of the relationships between morphology, neutral molecular distance, geographic distribution, and environmental variables were assessed by matrix correlation comparisons. Significant differences were found in temporal bone shape among all populations, and classification rates using cross-validation were relatively high. Comparisons of morphological distances to molecular distances based on short tandem repeats (STRs) revealed a significant correlation between temporal bone shape and neutral molecular distance among Old World populations, but not when Native Americans were included. Further analyses suggested a similar pattern for morphological variation and geographic distribution. No significant correlations were found between temporal bone shape and environmental variables: temperature, annual rainfall, latitude, or altitude. Significant correlations were found between temporal bone size and both temperature and latitude, presumably reflecting Bergmann's rule. Thus, temporal bone morphology appears to partially follow an isolation by distance model of evolution among human populations, although levels of correlation show that a substantial component of variation is unexplained by factors considered here.

Worldwide analysis of multiple microsatellites: Language diversity has a detectable influence on DNA diversity

Previous studies of the correlations between the languages spoken by human populations and the genes carried by the members of those populations have been limited by the small amount of genetic markers available and by approximations in the treatment of linguistic data. In this study we analyzed a large collection of polymorphic microsatellite loci (377), distributed on all autosomes, and used Ruhlen's linguistic classification, to investigate the relative roles of geography and language in shaping the distribution of human DNA diversity at a worldwide scale. For this purpose, we performed three different kinds of analysis: (i) we partitioned genetic variances at three hierarchical levels of population subdivision according to language group by means of a molecular analysis of variance (AMOVA); (ii) we quantified by a series of Mantel's tests the correlation between measures of genetic and linguistic differentiation; and (iii) we tested whether linguistic differences are increased across known zones of increased genetic change between populations. Genetic differences appear to more closely reflect geographic than linguistic differentiation. However, our analyses show that language differences also have a detectable effect on DNA diversity at the genomic level, above and beyond the effects of geographic distance.

POPULATION GENETICS, HISTORY, AND HEALTH PATTERNS IN NATIVE AMERICANS

Over the past two decades, detailed studies of mitochondrial DNA and the Y chromosome have increased our understanding of the history and population genetics of Native American populations. Variation in autosomal DNA has also been investigated, but to a more limited extent. A low level of genetic diversity in Native American populations is a robust finding from all lines of evidence. In contrast to the previous multiple migration scenarios for the Pleistocene peopling of the Americas, it now seems that a single migration satisfactorily explains the genetic data. Native Americans show greater genetic similarity to populations in east central Asia than they do to the current easternmost Siberian populations. Recent studies on the Y chromosome indicate a date of entry (about 17,000 years ago) into the Americas roughly consistent with the archaeological record. Native Americans experienced two episodes of reduced population size: one with the peopling of the Americas and the other with European contact. The former is the more important determinant for the number of gene lineages and founding haplotypes seen in populations. It may also be an important determinant of the genetic variation underlying common complex diseases, and especially diabetes. The tribal structure of contemporary Native American populations is relevant to the distribution of rare Mendelian disorders because most tribes constitute relatively small, semi-independent gene pools. This leads us to expect that the allelic spectrum for Mendelian diseases will be simple within individual tribes but complex for Native Americans as a whole.

Cutaneous diseases in Native Americans

Native Americans have a rich and complex heritage and culture. Although the genetic pool has changed with increasing integration with other Americans with different ancestry, there are important conditions that are unique to Native Americans, the most prominent example being actinic prurigo. The scientific literature dealing with Native American skin conditions is sparse and more studies are needed to understand more fully cutaneous disease in Native Americans.

Classification of cytotoxic T-cell and natural killer cell lymphomas

Mature or peripheral T-cell lymphomas are uncommon, accounting for only 10% to 15% of all non-Hodgkin's lymphomas. The classification of these neoplasms has been controversial. In contrast to B-cell lymphomas, cytologic features have not been useful in defining disease entities, and cytologic grade has not helped predict the clinical course. Similarly, many entities of T-cell or natural killer (NK) cell derivation do not have a specific immunophenotype. Clinical features are of major importance in defining T-cell and NK cell neoplasms, and in some cases the clinical syndrome, may be more important than the precise cell of origin. The majority of cytotoxic T-cell and NK cell lymphomas arise in extranodal sites. The expression of cytotoxic molecules in these lymphomas may predispose to apoptosis by tumor cells and normal bystander cells. Three major categories of extranodal T/NK cell tumors are recognized in the World Health Organization (WHO) classification: extranodal NK/T, nasal-type; enteropathy-type; and subcutaneous panniculitis-like. Epstein Barr virus (EBV) is closely linked to nasal NK/T-cell lymphoma, but shows geographic and racial variations in other subtypes. Tumors resembling the prototype of nasal NK/T-cell lymphoma occur in a variety of extranodal sites, and are referred to as nasal-type. Hepatosplenic T-cell lymphoma is a more systemic disease derived from functionally immature cytotoxic cells, usually gammadelta T-cell origin. Cytotoxic T-cell lymphomas of mature gammadelta T-cell origin most often arise in mucocutaneous sites, and may resemble the prototypes of extranodal T/NK cell lymphoma: nasal, enteropathy-associated, and panniculitis-like. Cytotoxic T/NK cell lymphomas occur with increased frequency in the setting of immune suppression, especially following organ transplantation. The nodal T-cell lymphoma most often exhibiting a cytotoxic immunophenotype is anaplastic large cell lymphoma (ALCL). Primary cutaneous ALCL frequently but not invariably expresses cytotoxic molecules. While the majority of extranodal neoplasms are derived from innate immune effector cells of NK cell and T-cell origin (gammadelta greater than alphabeta), most nodal cytotoxic T-cell lymphomas probably belong to the adaptive immune system. Studies of these neoplasms may assist in unraveling the diversity of their normal counterparts.

Genetic affinities among Mongol ethnic groups and their relationship to Turks

The central Asian country Mongolia is home to more than 20 tribes and ethnic groups, some of which are related to neighboring Turkic populations. The main Mongolian people, Khalkha, live in central and eastern Mongolia while the Tsaatan minority lives in the north of the country. The Oold minority is from the western Altai mountain region and live in close proximity with Turkic people. We have typed the HLA-A, -B, -Cw, -DRB1 and -DQB1 loci by PCR-SSP in these three Mongolian populations as well as a sample of the German population. To examine their genetic relationships, a sample of the Turkish population already typed at the HLA-A, -B and -DRB1 loci were used. Altogether five populations were analyzed: Khalkha (n = 100), Tsaatan (n = 72), Oold (n = 52), German (n = 260) and (Anatolian) Turkish (n = 498). Nei's unbiased genetic identity (GI) and genetic distance (GD) were estimated from genotypes using PopGene v1.31, and dendrograms were constructed using phylip. The results suggested a close relationship of the Khalkha to the Tsaatan. The Turks and Germans were equally distant to all three Mongolian populations. These results confirmed the lack of strong genetic relationship between the Mongols and the Turks despite the close relationship of their languages (Altaic group) and shared historical neighborhood. This study has provided useful population data for genetic and anthropologic studies bridging eastern and western populations.

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.

Population genetic structure and vocal dialects in an amazon parrot

The relationship between cultural and genetic evolution was examined in the yellow-naped amazon Amazona auropalliata. This species has previously been shown to have regional dialects defined by large shifts in the acoustic structure of its learned contact call. Mitochondrial DNA sequence variation from a 680 base pair segment of the first domain of the control region was assayed in 41 samples collected from two neighbouring dialects in Costa Rica. The relationship of genetic variation to vocal variation was examined using haplotype analysis, genetic distance analysis, a maximum-likelihood estimator of migration rates and phylogenetic reconstructions. All analyses indicated a high degree of gene flow and, thus, individual dispersal across dialect boundaries. Calls sampled from sound libraries suggested that temporally stable contact call dialects occur throughout the range of the yellow-naped amazon, while the presence of similar dialects in the sister species Amazona ochrocephala suggests that the propensity to form dialects is ancestral in this clade. These results indicate that genes and culture are not closely associated in the yellow-naped amazon. Rather, they suggest that regional diversity in vocalizations is maintained by selective pressures that promote social learning and allow individual repertoires to conform to local call types.