Origin of Mayans according to HLA genes and the uniqueness of Amerindians

Ancient genomes reveal insights into ritual life at Chichén Itzá

The ancient city of Chichén Itzá in Yucatán, Mexico, was one of the largest and most influential Maya settlements during the Late and Terminal Classic periods (AD 600-1000) and it remains one of the most intensively studied archaeological sites in Mesoamerica1-4. However, many questions about the social and cultural use of its ceremonial spaces, as well as its population's genetic ties to other Mesoamerican groups, remain unanswered2. Here we present genome-wide data obtained from 64 subadult individuals dating to around AD 500-900 that were found in a subterranean mass burial near the Sacred Cenote (sinkhole) in the ceremonial centre of Chichén Itzá. Genetic analyses showed that all analysed individuals were male and several individuals were closely related, including two pairs of monozygotic twins. Twins feature prominently in Mayan and broader Mesoamerican mythology, where they embody qualities of duality among deities and heroes5, but until now they had not been identified in ancient Mayan mortuary contexts. Genetic comparison to present-day people in the region shows genetic continuity with the ancient inhabitants of Chichén Itzá, except at certain genetic loci related to human immunity, including the human leukocyte antigen complex, suggesting signals of adaptation due to infectious diseases introduced to the region during the colonial period.

HLA study in Mexico Nahua/Aztec Amerindians: Close relatedness to the ancient Central America ethnic groups

Nahua population (also named Aztec or Mexica) was studied for HLA class II genes in a Mexican rural city (Santo Domingo Ocotitlan, Morelos State) belonging to the nowadays Náhuatl speaking areas in Mexico. The most frequent HLA class II alleles were typical Amerindian (HLA-DRB1*04:07, DQB1*03:01 DRB1*04:03 or DRB1*04:04) and also were some calculated extended haplotypes (HLA-DRB1*04:07-DQB1*03:02,DRB1*08:02-DQB1*04:02, or DRB1*10:01-DQB1*05:01 among others). When using HLA-DRB1 Neís genetic distances, our isolated Nahua population was found to be close to other Central America Amerindians like the ancient-established Mayans or Mixe. This may suggest that Nahuas origin was also from Central America. It contrasts to legend that assumes they came from the North, and they built the Aztec Empire after submitting Central America neighbouring ethnic groups before 1519 CE when Spaniards led by Hernán Cortés arrived to Mexico.

Human leukocyte antigen Class II alleles associated with acral lentiginous melanoma in Mexican Mestizo patients: A case-control study

Background Melanoma is an aggressive cutaneous cancer. Acral lentiginous melanoma is a melanoma subtype arising on palms, soles, and nail-units. The incidence, prevalence and prognosis differ among populations. The link between expression of major histocompatibility complex Class II alleles and melanoma progression is known. However, available studies report variable results regarding the association of melanoma with specific HLA Class II loci. Aims The aim of the study was to determine HLA Class II allele frequencies in acral lentiginous melanoma patients and healthy Mexican Mestizo individuals. Methods Eighteen patients with acral lentiginous melanoma and 99 healthy controls were recruited. HLA Class II typing was performed based on the sequence-specific oligonucleotide method. Results Three alleles were associated with increased susceptibility to develop acral lentiginous melanoma, namely: HLA-DRB1*13:01; pC = 0.02, odds ratio = 6.1, IC95% = 1.4-25.5, HLA-DQA1*01:03; pC = 0.001, odds ratio = 9.3, IC95% = 2.7-31.3 and HLA-DQB1*02:02; pC = 0.01, odds ratio = 3.7, IC95% = 1.4-10.3. Limitations The small sample size was a major limitation, although it included all acral lentiginous melanoma patients seen at the dermatology department of Dr. Manuel Gea González General Hospital during the study period. Conclusion HLA-DRB1*13:01, HLA-DQB1*02:02 and HLA-DQA*01:03 alleles are associated with increased susceptibility to develop acral lentiginous melanoma in Mexican Mestizo patients.

HLA molecular study of patients in a public kidney transplant program in Guatemala

Guatemala is a country located in Central America, and while it is one of the most populated countries in the region, the genetic diversity of the population has been poorly analyzed. Currently, there are no analyses of the distribution of human leukocyte antigen (HLA) system alleles in mixed ancestry (i.e., ladino) populations in Guatemala. The HLA system exhibits the most extensive polymorphism in the human genome and has been extensively analyzed in a large number of studies related to disease association, transplantation, and population genetics (with particular importance in the understanding of diversity in the human population). Here, we present HLA typing data from 127 samples of unrelated individuals from the kidney transplant program of the San Juan de Dios General Hospital (Guatemala City) using a PCR-SSOP-based (PCR-sequence specific oligonucleotide probes) typing method. We found 16 haplotypes that accounted for 39.76 % of the total haplotype diversity, of which thirteen have been reported previously in Native American populations and three have been reported in European populations. The analyses showed no deviations from Hardy-Weinberg equilibrium, and admixture estimates calculated with k = 3 ancestral components showed that Native American was the most represented component, followed by the European component. The African component was less prominent in the Guatemala mixed ancestry sample in comparison to samples from other countries in Central America. The HLA-based admixture results for Central America showed a continuum in the distribution of Native American, European and African ancestries throughout the region, which is consistent with the complex demographic history of the region.

Fear, violence, inequality, and stunting in Guatemala

BACKGROUND

Stunting is defined by the public health community as a length- or height-for-age <-2 SD of a growth standard or reference and is claimed to be caused by poor nutrition, repeated infection, and inadequate psychosocial stimulation.

MATERIAL AND METHODS

Stunting is common at all income levels in middle- and low-income countries. At the higher income levels, stunting is unlikely to be caused by nutrient deficiency or infectious disease.

RESULTS

In Guatemala, 17% of <5-year-olds in the highest family income quintile are stunted. Guatemala has a history of violence from armed conflict, current-day social and economic inequalities, government corruption, and threat of kidnapping for the wealthiest families.

DISCUSSION AND CONCLUSION

The high level of persistent violence creates an ecology of fear, an extreme range of inequalities in Social-Economic-Political-Emotional resources, and biosocial stress that inhibits skeletal growth and causes stunting for people of all income levels.

HLA-G in Mayas from Yucatan: An evolutionary approach

HLA-G allele frequencies were studied in Yucatán (Mexico) Maya Amerindians by a direct exon DNA sequencing technique. It is described that Mayas are probably one of the first populations together with Olmecs that populated Meso America and that important HLA genetic differences between Mexican and Guatemalan Mayas support that Maya languages were imposed to several neighbouring Amerindian groups. HLA-G*01:01:02, HLA-G*01:01:01 and HLA-G*01:04:01 are the most frequent alleles in this population. It is remarkable that HLA-G*01:05N allele was not found in the population in accordance with similar results found in another Amerindians. Also, protein allele HLA-G*01:04 frequency is found not to differ to those found in another far or close living Amerindians in contrast to other World populations. It seems that while high HLA-G*01:05N frequency is found in Iran and Middle East populations, probably where this allele appeared within an ancestral HLA-A*19 group of alleles haplotype and it is maintained by unknown evolutionary forces, Amerindians do not have a high frequency because a founder effect or because required natural evolutionary forces do not exist in America. Finally, we believe useful to study HLA-G evolution for its physiopathology understanding in addition to the many papers on statistics on HLA-G and in vitro models that are yearly published.

The immunogenetic diversity of the HLA system in Mexico correlates with underlying population genetic structure

We studied HLA class I (HLA-A, -B) and class II (HLA-DRB1, -DQB1) allele groups and alleles by PCR-SSP based typing in a total of 15,318 mixed ancestry Mexicans from all the states of the country divided into 78 sample sets, providing information regarding allelic and haplotypic frequencies and their linkage disequilibrium, as well as admixture estimates and genetic substructure. We identified the presence of 4268 unique HLA extended haplotypes across Mexico and find that the ten most frequent (HF > 1%) HLA haplotypes with significant linkage disequilibrium (Δ'≥0.1) in Mexico (accounting for 20% of the haplotypic diversity of the country) are of primarily Native American ancestry (A*02~B*39~DRB1*04~DQB1*03:02, A*02~B*35~DRB1*08~DQB1*04, A*68~B*39~DRB1*04~DQB1*03:02, A*02~B*35~DRB1*04~DQB1*03:02, A*24~B*39~DRB1*14~DQB1*03:01, A*24~B*35~DRB1*04~DQB1*03:02, A*24~B*39~DRB1*04~DQB1*03:02, A*02~B*40:02~DRB1*04~DQB1*03:02, A*68~B*35~DRB1*04~DQB1*03:02, A*02~B*15:01~DRB1*04~DQB1*03:02). Admixture estimates obtained by a maximum likelihood method using HLA-A/-B/-DRB1 as genetic estimators revealed that the main genetic components in Mexico as a whole are Native American (ranging from 37.8% in the northern part of the country to 81.5% in the southeastern region) and European (ranging from 11.5% in the southeast to 62.6% in northern Mexico). African admixture ranged from 0.0 to 12.7% not following any specific pattern. We were able to detect three major immunogenetic clusters correlating with genetic diversity and differential admixture within Mexico: North, Central and Southeast, which is in accordance with previous reports using genome-wide data. Our findings provide insights into the population immunogenetic substructure of the whole country and add to the knowledge of mixed ancestry Latin American population genetics, important for disease association studies, detection of demographic signatures on population variation and improved allocation of public health resources.

Association between NDO-LID and PGL-1 for leprosy and class I and II human leukocyte antigen alleles in an indigenous community in Southwest Amazon

The frequencies of the Human leukocyte antigen (HLA) alleles in the Puyanawa indigenous reserve population and their association with the NDO-LID and ELISA PGL-1 rapid serological test was assessed. This was a cross-sectional study with an epidemiological clinical design conducted in two indigenous communities in the state of Acre, Brazil. Blood was collected in a tube with EDTA to identify HLA alleles and perform serological tests. DNA was obtained using the salting out procedure. The LabType™ technique (One-Lambda-USA) was used for HLA class I (loci A*, B* and C*) and II (loci DRB1*, DQA1* and DQB1*) typing. Allele frequency was obtained by direct count, and the chi-square test was used to assess the association with the NDO-LID and PGL-1 tests. The most frequent alleles in the two communities were: HLA-A*02:01, HLA-B*40:02, HLA-DRB1*16:02, HLA-DQA1*05:05 and HLA-DQB1*03:01. The allele HLA-C*04:01 was the most common in the Barão community, and the allele HLA-C*07:01 in Ipiranga. Among individuals who presented seropositivity to the NDO-LID test, the association with alleles HLA-A*02 (43.18% vs 24.8%, p = 0.03, OR = 2.35) and HLA-B*53 (6.83% vs 0.0%, p = 0.03, OR = 8.95) was observed in the Barão community. HLA-B*15 was associated with non-seroconversion to the NDO-LID test in Ipiranga. In both communities, HLA-B*40 and HLA-C*03 were associated with positive serological response to ELISA PGL-1. The HLA class I and II alleles most frequently found in this study have already been described among Terena indigenous groups, and HLA class I contributes to seroconversion to NDO-LID and PGL-1 tests in inhabitants of the Barão and Ipiranga communities.

HLA genes in Amerindians from Mexico San Vicente Tancuayalab Teenek/Huastecos

Huastecos or Teenek Amerindians are presently living at North East Mexico (San Luis Potosi State). They have probably one of the most ancient culture of Mexico and Central America together with Mayas and Olmec groups with which also show close relationships. Proximity to Atlantic Ocean/Mexican Gulf originated that Spaniards had very early contact with them at about 1519 CE or before. In the present paper we have aimed to study HLA gene profile which may be useful for HLA and disease epidemiology and transplant programs in Teeneks. HLA-DRB1*04:07, -DRB1*14:06 and -DRB1*04:11 have been found in high frequency like in other Amerindian groups. High frequency typical Amerindians HLA extended haplotypes have been found, such as A*02-B*35-DRB1*04:07-DQB1*03:02; A*68-B*39-DRB1*04:07-DQB1*03:02 and A*02-B*39-DRB1*04:07-DQB1*03:02; also new haplotypes have been described, like A*02-B*52-DRB1*04:11-DQB1*03:02, A*68-B*35-DRB1*14:02-DQB1*03:01 and A*68-B*40-DRB1*16:02-DQB1*03:01. Genetic proximity is observed not only to linguistically close Mayans, but also to Mazatecans, Mixtecans and Zapotecans, who speak an altogether different languages; it shows once more that genes and languages do not correlate. This population was greatly diminished after European contact between 1500 and 1600 years CE; in fact, North and South America First Inhabitants population was brought from 80 down to 8 million people because of diseases (i.e.: measles, smallpox or influenza), slavery and war.

Diversity of HLA Class I and Class II blocks and conserved extended haplotypes in Lacandon Mayans

Here we studied HLA blocks and haplotypes in a group of 218 Lacandon Maya Native American using a high-resolution next generation sequencing (NGS) method. We assessed the genetic diversity of HLA class I and class II in this population, and determined the most probable ancestry of Lacandon Maya HLA class I and class II haplotypes. Importantly, this Native American group showed a high degree of both HLA homozygosity and linkage disequilibrium across the HLA region and also lower class II HLA allelic diversity than most previously reported populations (including other Native American groups). Distinctive alleles present in the Lacandon population include HLA-A*24:14 and HLA-B*40:08. Furthermore, in Lacandons we observed a high frequency of haplotypes containing the allele HLA-DRB1*04:11, a relatively frequent allele in comparison with other neighboring indigenous groups. The specific demographic history of the Lacandon population including inbreeding, as well as pathogen selection, may have elevated the frequencies of a small number of HLA class II alleles and DNA blocks. To assess the possible role of different selective pressures in determining Native American HLA diversity, we evaluated the relationship between genetic diversity at HLA-A, HLA-B and HLA-DRB1 and pathogen richness for a global dataset and for Native American populations alone. In keeping with previous studies of such relationships we included distance from Africa as a covariate. After correction for multiple comparisons we did not find any significant relationship between pathogen diversity and HLA genetic diversity (as measured by polymorphism information content) in either our global dataset or the Native American subset of the dataset. We found the expected negative relationship between genetic diversity and distance from Africa in the global dataset, but no relationship between HLA genetic diversity and distance from Africa when Native American populations were considered alone.

The influence of maternal height on offspring's birth weight in Merida, Mexico

OBJECTIVES

To analyze the influence of maternal height (MH) on offspring's birth weight (BW) in infants born from January 2016 to May 2017, in Merida, Mexico.

METHODS

A total of 3462 singletons born at term in a public hospital were analyzed. Data extracted from hospital records were MH; number of previous births; and infant's sex, BW, and gestational length. MH was divided into 4 categories at quartile points: Q1:129-147, Q2:148-151, Q3:152-155, and Q4:156-180 cm. BW data were transformed to z-score values using the WHO Child Growth Standard. The association between MH and infants' BW was analyzed through a multiple regression model in which gestational length, infant's sex, maternal age, ethnicity, and number of previous birth were included as covariates.

RESULTS

Mean values of MH and infants' BW were 151.43 cm (SD = 6.32) and 3172 g (SD = 401) (corresponding to -0.29 SD in BW z-score), respectively. The regression model showed that the shortest quartile of MH was associated with -0.43 (95% CI -0.35 -0.51) SD in infants' BW compared with the highest quartile. The second and third shortest quartiles of MH were associated with -0.24 (95% CI -0.16 -0.32) and -0.17 (95% CI -0.09 -0.25) SD of infants BW, respectively.

CONCLUSIONS

MH remains an important factor for infant BW even in the presence of other determinants. The influence of MH on infants' BW in this population is similar to that found in other populations in low-, middle-, and high-income countries.

HLA-G in Amerindians: Epidemiology and Worldwide Population Comparison

Background:

HLA-G molecules are immunosuppressive and avoid fetal rejection by giving negative signals to maternal immune system from fetal trophoblast cell surface. HLA-G genes have been associated to different pathologies: Spontaneous abortions, autoimmunity, tumor progression, transplant rejection and infection. In addition, different World populations show remarkable different HLA-G allele frequencies in the allele that does not produce a full HLA-G molecule (HLA-G*05N); this allele is almost absent in studied Amerindians.

Objectives:

The aim is to study HLA-A.-B,-DRB1 and –G alleles and extended haplotypes in Amerindians for the first time. This may be useful to asses HLA-G epidemiology, association to disease and Preventive Medicine in Amerindians.

Methods:

HLA-A,-B and -DRB1 have been typed by using standard automatic protocols. HLA-G alleles have been detected by direct HLA-G exon 2, exon 3 and exon 4 DNA sequencing. Computer calculations have been done by specific standard methods.

Results:

HLA-A,-B,-DRB1 and –G extended haplotypes have been calculated in Amerindians for the first time. Also, their HLA-G frequencies have been compared with worldwide populations.

Conclusion:

Low frequencies of null HLA-G*01:05N allele are found in Amerindians. The extended haplotypes with this allele bear other typical Amerindian HLA-DRB1 alleles and its origin is discussed. HLA-G allele frequency profile is closer to that of Europeans than to that of Far East Asians. Our findings are useful to Preventive Medicine and Epidemiology associated to Fertility and HLA-G associated pathology and transplantation.

Ancestry of Amerindians and its Impact in Anthropology, Transplantation, HLA Pharmacogenomics and Epidemiology by HLA Study in Wiwa Colombian Population

Background:

HLA autosomic genes are unique because they conform the most polymorphic human system. Importance of this system is recognized in Medicine for Transplantation, Epidemiology (HLA and disease linkage), Pharmacogenomics (HLA linked to drug side effects) and for defining the origin of populations in both male and female lineages.

Objectives:

Studying HLA profile of a isolated Amerindian group from North Colombia (Wiwa) in order to draw conclusions about its Preventive Medicine, the genetic relationship with Worldwide populations and America peopling, since this last issue is hotly debated.

Methodology:

A total of 14,660 HLA chromosomes were included. Peripheral blood was obtained from volunteer blood donors belonging to Wiwa (also named Arsario) ethnic group. HLA-A, -B, -C, -DRB1 and -DQB1 genes were analyzed by standard methods. Wiwa Amerindians relationships with others were calculated by using Arlequin, Dispan and Vista software computer packages.

Results:

Extended HLA, -A, -B, -C, -DRB1 and -DQB1 haplotypes have been studied for the first time in this population. Classical Amerindian haplotypes have been found and also new Wiwa (Arsario) Amerindian haplotypes. New haplotypes are A*68:01 - B*15:01 - C*03:03 - DRB1*14:02 - DQB1*03:02, A*11:01 - B*07:02 - C*07:02 - DRB1*15:03 - DQB1*06:02 and A*68:01 - B*15:01 - C*03:04 - DRB1*14:02 - DQB1*03:01.

Conclusion:

They have been reached after exhaustive comparisons of Wiwa with other Amerindians and Worldwide populations by using genetic distances, Neighbor Joining trees, correspondence analysis and specific group of alleles which are common and frequent in both Amerindians and Pacific Islanders. They are: 1) The Americas First Inhabitants have been probably come through Bering Strait and also through Pacific (from Austronesia and Asia) and Atlantic (from Europe) routes. A bidirectional gene flow is not discarded. 2) Genetic HLA Amerindian profile is separated from that of other Worldwide populations. 3) Amerindians geographical proximity groups’ relatedness is not concordant with HLA genetic relatedness, neither with language. This may be explained by a substantial population decrease that occurred after Europeans invaded America in 1492 and carried new pathogens and epidemics. 4) Our results are also useful for Wiwa and other Amerindians future preventive medicine (HLA linked diseases), HLA pharmacogenomics and transplantation regional programs.

Epstein-Barr Virus in Nasopharyngeal Carcinoma of Guatemalan and Brazilian Patients

BACKGROUND

Nasopharyngeal carcinoma (NPC) is highly associated with Epstein-Barr virus (EBV), particularly the undifferentiated nonkeratinizing subtype. Prevalence of EBV in NPC in countries such as Guatemala and Brazil has not been studied.

METHODS

We analyzed 19 cases of NPC, 11 from Guatemala and 8 from Brazil, for the presence of EBV by in situ hybridization and immunohistochemistry. Additionally, 19 hyperplastic adenoids from children were analyzed for EBV by in situ hybridization, 12 from Guatemala and 7 from Brazil.

RESULTS

All the NPC cases from Guatemala and 5 from Brazil were of the undifferentiated nonkeratinizing type. EBV-negative cases comprised 2 keratinizing NPC and 1 differentiated nonkeratinizing NPC. All undifferentiated nonkeratinizing NPC from both samples showed intense positivity for EBER, while LMP-1 only focally and scarcely expressed. EBER was positive in 75% and 43% of the adenoids from Guatemala and Brazil, respectively.

CONCLUSIONS

All undifferentiated nonkeratinizing NPC irrespective of origin from Guatemala or Brazil were highly associated with EBV.

Pharmacogenetic research activity in Central America and the Caribbean: a systematic review

AIM

The present review was aimed at analyzing the pharmacogenetic scientific activity in Central America and the Caribbean.

MATERIALS & METHODS

A literature search for pharmacogenetic studies in each country of the region was conducted on three databases using a list of the most relevant pharmacogenetic biomarkers including 'phenotyping probe drugs' for major drug metabolizing enzymes. The review included 132 papers involving 47 biomarkers and 35,079 subjects (11,129 healthy volunteers and 23,950 patients).

RESULTS

The country with the most intensive pharmacogenetic research was Costa Rica. The most studied medical therapeutic area was oncology, and the most investigated biomarkers were CYP2D6 and HLA-A/B. Conclusion: Research activity on pharmacogenetics in Central American and the Caribbean populations is limited or absent. Therefore, strategies to promote effective collaborations, and foster interregional initiatives and research efforts among countries from the region could help for the rational clinical implementation of pharmacogenetics and personalized medicine.

Pharmacogenetics in Central American healthy volunteers: interethnic variability

Ethnicity is one of the major factors involved in interindividual variability to drug response. This study aims to describe the frequency of the most relevant pharmacogenetic biomarkers and metabolic phenotypes in Central American healthy volunteers and to determine its interethnic variability. Twenty-six original research articles on allelic, genotypes or metabolic phenotype frequencies were analyzed, in which a total number of 7611 Central American healthy volunteers were included (6118 were analyzed for genotype and 1799 for metabolic phenotype). No reports were available for population from Belize and Honduras. The CYP2D6*4 and *5 frequencies in Amerindian populations from Costa Rica have shown to be among the highest frequencies so far reported in the world. Furthermore, NAT2*5 and *6 presented higher frequencies in admixed populations than in Amerindians, but, inversely, the NAT2*7 was more frequent in Amerindians compared to an admixed population. Likewise, different patterns of distribution have been shown in HLA-A*02, *03 and HLA-B*07 among Native populations from Latin America. Reports on Central American populations were also found for the CYP2C19, LDLR, CYP2E1, MDR1, G6PD, TP53, CYP1A2, CYP3A4 and CYP3A5 biomarkers, but no data were available for the other 91 pharmacogenetic biomarkers revised in Central American populations. Differences in the frequency of some pharmacogenetic biomarkers and metabolic phenotypes were found, showing interethnic variability within Central American and with other Latin American populations.

HLA class II alleles in the Otomi population of the Mezquital Valley: a genetic approach to the history of interethnic migrations in the Mexican Central Plateau

From a historical and genetic point of view, the Otomi of the Mezquital Valley are a frontier people that have played an important role in the population dynamics of the Mexican Central Plateau. Due to the antiquity of their presence in the area, the Otomi may be bearers of ancient genetic variability, shared mainly today with other groups belonging to the Otomanguean linguistic family and with the Nahua. In this study we analyzed the HLA class II allele frequencies reported in Mexican indigenous populations, in order to provide an intraregional-level historical perspective of the genetic relationships between the Otomi of the Mezquital Valley and indigenous populations from other regions of Mexico. We examined genetic variation in HLA-DRB1 and -DQB1 loci in 66 nonrelated individuals belonging to seven indigenous communities from the Ixmiquilpan municipality in the Mezquital Valley, in the State of Hidalgo, Mexico. The variability of the HLA-DRB1 gene among the Otomi of the Mezquital Valley was mainly concentrated in five alleles: -DRB1*08:02 (31.06%), -DRB1*04:07 (25.77%), -DRB1*14:06 (7.55%), -DRB1*14:02 (6.06%), and -DRB1*16:02 (4.55%); these alleles have been previously described in other indigenous populations. The most frequent alleles at the HLA-DQB1 locus were -DQB1*03:02 (34.09%), -DQB1*04:02 (31.03%), and -DQB1*03:01 (19.7%). Furthermore, the HLA-DQB1*02:02 allele was found in the Otomi group with a frequency of 2.27%; this allele has not been reported in Mexican indigenous populations. In conclusion, the genetic constitution of the Otomi population is intermediate to the northern groups and the genetic variability shared by the peoples of the central regions of Mexico. Furthermore, HLA-DRB1 and -DQB1 allelic variability among the Otomi provides insight into the historical processes implied in the biological admixture with European, Asian, and African populations as well as in the admixture with the population of Mexico City associated with long-standing migratory processes.

Genomic insights on the ethno-history of the Maya and the 'Ladinos' from Guatemala

Background

Guatemala is a multiethnic and multilingual country located in Central America. The main population groups separate ‘Ladinos’ (mixed Native American-African-Spanish), and Native indigenous people of Maya descent. Among the present-day Guatemalan Maya, there are more than 20 different ethnic groups separated by different languages and cultures. Genetic variation of these communities still remains largely unexplored. The principal aim of this study is to explore the genetic variability of the Maya and ‘Ladinos’ from Guatemala by means of uniparental and ancestry informative markers (AIMs).

Results

Analyses of uniparental genetic markers indicate that Maya have a dominant Native American ancestry (mitochondrial DNA [mtDNA]: 100%; Y-chromosome: 94%). ‘Ladino’, however, show a clear gender-bias as indicated by the large European ancestry observed in the Y-chromosome (75%) compared to the mtDNA (0%). Autosomal polymorphisms (AIMs) also mirror this marked gender-bias: (i) Native American ancestry: 92% for the Maya vs. 55% for the ‘Ladino’, and (ii) European ancestry: 8% for the Maya vs. 41% for the ‘Ladino’. In addition, the impact of the Trans-Atlantic slave trade on the present-day Guatemalan population is very low (and only occurs in the ‘Ladino’; mtDNA: 9%; AIMs: 4%), in part mirroring the fact that Guatemala has a predominant orientation to the Pacific Ocean instead of a Caribbean one. Sequencing of entire Guatemalan mitogenomes has led to improved Native American phylogeny via the addition of new haplogroups that are mainly observed in Mesoamerica and/or the North of South America.

Conclusions

The data reveal the existence of a fluid gene flow in the Mesoamerican area and a predominant unidirectional flow towards South America, most likely occurring during the Pre-Classic (1800 BC-200 AD) and the Classic (200–1000 AD) Eras of the Mesoamerican chronology, coinciding with development of the most distinctive and advanced Mesoamerican civilization, the Maya. Phylogenetic features of mtDNA data also suggest a demographic scenario that is compatible with moderate local endogamy and isolation in the Maya combined with episodes of gene exchange between ethnic groups, suggesting an ethno-genesis in the Guatemalan Maya that is recent and supported on a cultural rather than a biological basis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1339-1) contains supplementary material, which is available to authorized users.

HLA class I and class II conserved extended haplotypes and their fragments or blocks in Mexicans: implications for the study of genetic diversity in admixed populations

Major histocompatibility complex (MHC) genes are highly polymorphic and informative in disease association, transplantation, and population genetics studies with particular importance in the understanding of human population diversity and evolution. The aim of this study was to describe the HLA diversity in Mexican admixed individuals. We studied the polymorphism of MHC class I (HLA-A, -B, -C), and class II (HLA-DRB1, -DQB1) genes using high-resolution sequence based typing (SBT) method and we structured the blocks and conserved extended haplotypes (CEHs) in 234 non-related admixed Mexican individuals (468 haplotypes) by a maximum likelihood method. We found that HLA blocks and CEHs are primarily from Amerindian and Caucasian origin, with smaller participation of African and recent Asian ancestry, demonstrating a great diversity of HLA blocks and CEHs in Mexicans from the central area of Mexico. We also analyzed the degree of admixture in this group using short tandem repeats (STRs) and HLA-B that correlated with the frequency of most probable ancestral HLA-C/−B and -DRB1/−DQB1 blocks and CEHs. Our results contribute to the analysis of the diversity and ancestral contribution of HLA class I and HLA class II alleles and haplotypes of Mexican admixed individuals from Mexico City. This work will help as a reference to improve future studies in Mexicans regarding allotransplantation, immune responses and disease associations.

HLA genetic profile of Mapuche (Araucanian) Amerindians from Chile

Amerindian Mapuche (Araucanians) are now living in Chile and Argentina at both sides of Andean Mountains. They are anthropologically and genetically different from southernmost South America Patagonian Amerindians. Most of the HLA alleles found in our Mapuche sample are frequent or very frequent in North and South America Amerindians: (1) Class I: A*02:01, A*03:01, A*68:01, B*39:09, B*51:01, (2) Class II: DRB1*03:01, DRB1*04:03, DRB1*07:01, DRB1*08:02, DRB1*14:02, DRB1*16:02. One of the nine most frequent extended haplotypes seems to be from European origin, suggesting the existence of a degree of admixture with Europeans in our Mapuche sample. It has been calculated of about 11 % admixture. Three of the extended haplotypes are also found in other Amerindians and five of them are newly found in Mapuche Amerindians: A*68:01-B*39:09-DRB1*08:02-DQB1*04:02; A*68:01-B*51:01-DRB1*04:03-DQB1*03:02; A*29:01-B*08:01-DRB1*03:01-DQB1*02:01; A*02:01-B*15:01-DRB1*04:03-DQB1*03:02; A*33:01-B*14:02-DRB1*07:01-DQB1*03:03. The medical importance of calculating HLA profile is discussed on the diagnostic (HLA and disease) and therapeutical bases of HLA pharmacogenomics and on the construction of a virtual transplantation HLA list profile. Also, anthropological conclusions are drawn.

Frequency of thiopurine S-methyltransferase mutant alleles in indigenous and admixed Guatemalan patients with acute lymphoblastic leukemia

Thiopurine S-methyltransferase (TPMT) polymorphisms affect the enzyme's activity and are predictive for the efficacy and toxicity of thiopurine treatment of acute lymphoblastic leukemia (ALL), autoimmune diseases and organ transplants. Because inter-ethnic differences in the distribution of these polymorphisms have been documented, we sequenced the TMPT gene in 95 Guatemalans, yet identified no new alleles. We also determined the frequency of the TPMT 2, 3A, 3B and 3C alleles in 270 admixed and 177 indigenous pediatric patients with ALL and healthy subjects from Guatemala using TaqMan assays and DNA sequencing. Among the 447 subjects genotyped, 10.0 % of the ALL cases and 13.6 % of the healthy controls were heterozygous for one of the four TPMT variants screened. The genotype frequencies in ALL and control populations were 0.7 and 1.7 % for TPMT 1/ 2, 7.4 and 10 % for TPMT 1/3A, 0.3 and 0 % for TPMT 1/B, and 1.5 and 1.1 % for TPMT 1/C, respectively (p = 0.30). No statistically significant differences between admixed and indigenous ALL (p = 0.67) or controls (p = 0.41) groups were detected; however, 17 % of the admixed healthy group bore one TPMT mutant allele, and they have one of the highest reported frequencies of TPMT mutant allele carriers. Because of the clinical implications of these variants for therapeutic response, TPMT allele testing should be considered in all Guatemalan patients to reduce adverse side-effects from thiopurine drug treatments.

HLA-G(∗)01:05N null allele in Mayans (Guatemala) and Uros (Titikaka Lake, Peru): evolution and population genetics

HLA-G molecules seem to have a protective effect for the semi-allogeneic fetus by mother immunosuppression. Also, pregnancy pathologies have been associated to HLA-G(∗)01:05N "null allele". In addition, other general regulatory immune functions have been associated to HLA-G in infections, tumors and autoimmunity. Thus, it is striking that HLA(∗)01:05N allele is maintained in a substantial frequency in certain human populations. In the present work, we have analysed HLA-G allele frequencies in Amerindian Mayans from Guatemala and in Uros from Titikaka Lake "totora" (reed) floating islands (Peru). No HLA-G(∗)01:05N has been found in both of these Amerindian populations. Further studies in Worldwide populations show that the highest HLA-G(∗)01:05 allele frequencies are found in Middle East; these findings have a bearing in future clinical/epidemiological studies in Amerindians. This would suggest that either this area was close to the "null" allele origin (as predicted by us) and/or some evolutive pressures are maintaining these high frequencies in Middle East. However, the fact that Cercopithecinae primate family (primates postulated as distant human ancestors) has also a MHC-G "null" allele in all individuals suggests that this allele may confer some advantage either at maternal/fetal interface or at other immune HLA-G function level (tumors, infections, autoimmunity). Human HLA-G(∗)01:05N may produce HLA-G isoforms, like Cercopithecinae monkeys may, which may suffice for function.

Human leukocyte antigen profiles of latin american populations: differential admixture and its potential impact on hematopoietic stem cell transplantation

The outcome of hematopoietic stem cell transplantation (HSCT) is shaped by both clinical and genetic factors that determine its success. Genetic factors including human leukocyte antigen (HLA) and non-HLA genetic variants are believed to influence the risk of potentially fatal complications after the transplant. Moreover, ethnicity has been proposed as a factor modifying the risk of graft-versus-host disease. The populations of Latin America are a complex array of different admixture processes with varying degrees of ancestral population proportions that came in different migration waves. This complexity makes the study of genetic risks in this region complicated unless the extent of this variation is thoroughly characterized. In this study we compared the HLA-A and HLA-B allele group profiles for 31 Latin American populations and 61 ancestral populations from Iberia, Italy, Sub-Saharan Africa, and America. Results from population genetics comparisons show a wide variation in the HLA profiles from the Latin American populations that correlate with different admixture proportions. Populations in Latin America seem to be organized in at least three groups with (1) strong Amerindian admixture, (2) strong Caucasian component, and (3) a Caucasian-African gradient. These results imply that genetic risk assessment for HSCT in Latin America has to be adapted for different population subgroups rather than as a pan-Hispanic/Latino analysis.

The Origin of Amerindians and the Peopling of the Americas According to HLA Genes: Admixture with Asian and Pacific People

The classical three-waves theory of American peopling through Beringia was based on a mixed anthropological and linguistic methodology. The use of mtDNA, Y chromosome and other DNA markers offers different results according to the different markers and methodologies chosen by different authors. At present, the peopling of Americas remains uncertain, regarding: time of population, number of peopling waves and place of peopling entrance among other related issues. In the present review, we have gathered most available HLA data already obtained about First Native American populations, which raise some doubts about the classical three waves of American peopling hypothesis. In summary, our conclusions are: 1) North West Canadian Athabaskans have had gene flow with: a) close neighboring populations, b) Amerindians, c) Pacific Islanders including East Australians and d) Siberians; 2) Beringia was probably not the only entrance of people to America: Pacific Ocean boat trips may have contributed to the HLA genetic American profile (or the opposite could also be true); 3) Amerindians entrance to America may have been different to that of Athabaskans and Eskimos and Amerindians may have been in their lands long before Athabaskans and Eskimos because they present and altogether different set of HLA-DRB1 allele frequencies; 4) Amerindians show very few “particular alleles”, almost all are shared with other Amerindians, Athabaskans and Pacific Islanders, including East Australians and Siberians; 5) Our results do not support the three waves model of American peopling, but another model where the people entrance is not only Beringia, but also Pacific Coast. Reverse migration (America to Asia) is not discarded and different movements of people in either direction in different times are supported by the Athabaskan population admixture with Asian-Pacific population and with Amerindians, 6) HLA variability is more common than allele veriability in Amerindians. Finally, it is shown that gene genealogy analises should be completed with allele frequency analyses in population relatednes and migrations studies.

HLA Genes in Mayos Population from Northeast Mexico

HLA class I and class II alleles have been studied in 60 unrelated people belonging to Mayos ethnic group, which lives in the Mexican Pacific Sinaloa State. Mayos HLA profile was compared to other Amerindians and worldwide populations’ profile. A total of 14,896 chromosomes were used for comparisons. Genetic distances between populations, Neigbour-Joining dendrograms and correspondence analyses were performed to determine the genetic relationship among population. The new specific Mayo HLA haplotypes found are: HLA-A*02-B*35-DRB1*1406-DQB1*0301; HLA-A*02-B*48-DRB1*0404-DQB1*0302; HLA-A*24-B*51-DRB1*0407-DQB1*0302 and HLA-A*02-B*08-DRB1*0407-DQB1*0302. However, the typical Meso American HLADRB1*0407 represents a 40% of all DRB1 alleles. While common HLA characteristics are found in Amerindian distant ethnic groups, still new group specific HLA haplotypes are being found, suggesting that a common founder effect (i.e. high DRB1*0407) is noticed. Moreover, new HLA haplotypes are almost certainly appearing along time probably due to specific pathogen (?) selection for diversity. Mayo language is close to the Tarahumara one (another geographically close group); notwithstanding both groups are not genetically close according to our results, showing again the different evolution of genes and languages, which do not correlate. Finally, Sinaloa is one of the Mexican States in which more European genes are found. However, the results presented in this paper, where no European HLA genes are seen in Mayos, should have a bearing in establishing transplant programs and in HLA and disease studies.

Las Alpujarras region (South East Spain) HLA genes study: evidence of a probable success of 17th century repopulation from North Spain

Conquest of Granada Muslim Kingdom (1492 AD) finished with Muslim occupation; they were mostly North African Berbers who had reached Iberia by 711 AD. A politics of Iberian Christianization followed after this date: Jewish were expelled in 1492 and Moriscos (Spaniards practicing Muslim religion or speaking Arab) were expelled from all Spanish territory on 1609 AD. Las Alpujarras is a southern Spain mountainous secluded region, which underwent a repopulation from North Spain and a specific Muslim (Moriscos)-Christian war took place according to historical records. Both Las Alpujarras repopulation by northern Iberians and Moriscos expulsion success have been debated and are regarded as non-clarified episodes. In this study, we have addressed the question whether the repopulation succeeded by determining HLA genes of present day Las Alpujarras inhabitants and compared with those of other Mediterranean populations HLA frequencies and genealogies. HLA frequencies show ambiguous results because of extant HLA similar gene frequencies there exist in North Africa and Spain. This is reflected by the finding of North and South western Mediterraneans close relatedness of HLA dendrograms and correspondence analyses. However, the genealogical study of extended HLA haplotypes particularly Alpujarran high frequency of HLA-A29-B44-DRB1*0701-DQA1*02-DQB1*02 (not found in Algerians but frequent in North and Central Spain) and Alpujarran low frequency extended haplotype HLA-A3-B7-DRB1*1501-DQA1*0102-DQB1*0602 (frequent in North Europe) reveals that a significant HLA gene flow from North Spain is observed in present day Alpujarrans: both haplotypes are characteristic of North Spain and North Europe, respectively. This may indicate that enforced Alpujarran repopulation from North Spain may have been a success, which was started by Spanish King Philip II in 1571 AD.

Role of major histocompatibility complex and ethnicity in acute renal graft rejection

BACKGROUND

The major histocompatibility complex (MHC) plays a main role in antigen presentation. Class I, II, and III genes form defined "blocks" of conserved DNA sequences (conserved extended haplotypes) that are useful to follow the ancestry of a population. Each variant encodes a specific peptide that determines a particular individual's immune response. In addition, differential expression of HLA antigens in certain physiological and pathological conditions may participate in the pathogenesis of allograft rejection versus tolerance.

OBJECTIVES

The aim of this study was to determine whether the specific HLA ancestry was associated with acute renal graft rejection among the Mexican mestizo population.

MATERIALS AND METHODS

We studied 544 Mexican mestizo renal donors and their respective recipients for their serologically determined HLA and based on antigens haplotype assignments. The acute rejection group was compared with the nonrejection group among donors and recipients, correspondingly.

RESULTS

Frequent Mexican alleles were observed in this study. Moreover, HLA-B*61/-DR*04, HLA-A*35/-DR*06 (Amerindian ancestry), HLA-A*68/-DR*01, HLA-A*28/-B*65/-DR*01 (African ancestry), and HLA-A*33/-B*65 (Caucasian ancestry) in donors were associated with acute renal graft rejection episodes.

CONCLUSION

Knowing the ancestry of a donor's HLA molecules may help to individualize immunosuppressive therapy for posttransplant surveillance, because they may be more membrane-exposed in parenchymal cells, making them more susceptible of being recognized by the recipient's immune system.

HLA genes in Uros from Titikaka Lake, Peru: origin and relationship with other Amerindians and worldwide populations

Uros population from the Titikaka Lake live in about 42 floating reed ('totora') islands in front of Puno City (Peru) at a 4000 m high altiplano. They present both an mtDNA and a human leucocyte antigen (HLA) profile different from the surrounding populations: mtDNA A2 haplogroup is common to Uros and Amazon forest lowland Amerindians. HLA genetic distances between populations have been calculated and neighbour-joining dendrograms and correspondence analyses were carried out. Approximately 15 006 HLA chromosomes from worldwide populations have been used for comparisons. Only eight HLA-A alleles have been found, three of them accounting for most of the frequencies. The same phenomenon is seen for HLA-B, HLA-DRB1 and HLA-DQB1 alleles: a few alleles (3, 4 and 3, respectively) are present in most individuals. The presence of HLA-B*4801 and HLA-DRB1*0901 alleles in a relatively high frequency (although not the most frequent alleles found) is a characteristic shared with Asians and some populations from the Andean altiplano. Three specific Uros haplotypes have been found among the most frequent ones: HLA-A*680102-B*3505-DRB1*0403-DQB1*0302; HLA-A*2402-B*1504-DRB1*1402-DQB1*0301; and HLA-A*2402-B*4801-DRB1*0403-DQB1*0302. The present study suggests that Uros may have been one of the first populations from the shores of the Titikaka Lake coming from the Amazonian forest, which might have given rise to other later differentiated ethnic group (i.e. Aymaras). Uros HLA profile is also useful to study genetic epidemiology of diseases linked to HLA and to construct a future transplant waiting list by adding up regional lists in order to get a bigger pool for transplanting with better HLA matching.

Origin of Bolivian Quechua Amerindians: their relationship with other American Indians and Asians according to HLA genes

The Incas were Quechua-speaking people who settled down near Cuzco (Peru). They had an empire ranging from Ecuador to Chile, when Spanish conquerors seized their kingdom around 1532 AD. Nowadays, Quechua-speaking people inhabits Colombia, Ecuador, Bolivia, Peru and Argentina; however, Quechua language was imposed by both Incas and Spaniards to many non-Quechua speaking communities. We have taken a sample of Quechuan Bolivian blood donors from La Paz (Titicaca Lake region) where Inca-Quechuas themselves believed that came from. This group was compared with 6892 individuals from 68 different world populations regarding HLA/DNA allele frequencies distribution. Genetic distances, dendrograms and correspondence analyses were carried out in order to establish relationships among populations. The main conclusions are: (1) DRB1 and -DQB1 haplotypes shared with Asians are found in Quechuas and are not observed in other (Mesoamerican) Amerindians. (2) Aymara-speaking people from the same Titicaca Lake (La Paz) area shows close genetic distances with Quechuas in one dimension results (genetic distances); however, their HLA gene frequency distribution differs according to Neighbor-Joining (NJ) trees and correspondence analysis (multidimensional and more reliable analyses). Also, the common high frequency Asian and Athabascan HLA-DRB1*0901 allele is found in Quechuas in a significant frequency. Quechuas are clearly included within the Amerindian group.

HLA class I and class II haplotypes in admixed families from several regions of Mexico

We studied HLA class I and class II alleles in 191 Mexican families (381 non-related individuals) to directly obtain the HLA-A/B/DRB1/DQB1 haplotypes and their linkage disequilibrium (LD). The most frequent HLA haplotypes observed were: A*02-B*39-DRB1*04-DQB1*0302, A*02-B*35-DRB1*04-DQB1*0302, A*68-B*39-DRB1*04-DQB1*0302, A*02-B*35-DRB1*08-DQB1*04, A*33-B*1402-DRB1*01-DQB1*05, and A*24-B*35-DRB1*04-DQB1*0302. The four most common haplotypes found by our study involve those previously reported in Amerindian populations. LD analysis of HLA-A-B and HLA-B-DRB1 loci showed significant associations between A29(19)-B44(12), A33(19)-B65(14), A1-B8, A26(19)-B44(12), A24(9)-B61(40), B65(14)-DR1, B8-DR17(3), B44(12)-DR7, B7-DR15(2), and B39(16)-DR4. Also, all DRB1-DQB1 associations showed significant LD values. Admixture estimations using a trihybrid model showed that Mexicans from the State of Sinaloa (Northern Mexico) have a greater proportion of European genetic component compared with Mexicans from the Central area of Mexico, who have a greater percentage of Amerindian genes. Our results are important for future comparative genetic studies of different Mexican ethnic groups with special relevance to disease association and transplantation studies.

HLA genes of Aleutian Islanders living between Alaska (USA) and Kamchatka (Russia) suggest a possible southern Siberia origin

Aleuts HLA profile has been compared with that of neighboring and worldwide populations. Thirteen thousand one hundred and sixty-four chromosomes have been used for this study. Computer programs have obtained HLA allele frequencies, genetic distances between populations, NJ relatedness dendrograms, correspondence analysis and most frequent HLA extended haplotypes. Aleuts have inhabited Aleutian Islands since about 9000 years BP according to fossil and genetic (mtDNA) records. They are genetically different to Eskimo, Amerindian and Na-Dene speakers according to their HLA profile; this correlates with cultural and anthropological Aleut distinctiveness. No typical Amerindian HLA alleles have been found in a significant frequency. Their HLA relatedness to Saami (or Lapps, northern Scandinavians), Finns and Pomors (North-West Russia) indicates an ancient possible origin from the Baikal Lake Area (southern Siberia) around the present day Buryat peopling area; other origins are not discarded. Aleuts characteristic HLA profile may influence future transplantation programs in the region and be useful to study diseases linked to HLA epidemiology.

Human genetic variation studies and HLA class II loci

Human leucocyte antigen (HLA) loci widely known for their role in generation of immune responses by encoding cell-surface heterodimers are often considered to be effective for the purpose of reconstructing human phylogenies due to high degree of polymorphism and less recombination. In the present study, we have made an attempt to study HLA class II loci (DRB1, DQA1 and DQB1) in inferring phylogenetic relationship based on both phylogenetic and haplotype approach. In the phylogenetic approach, the compiled database of 19 populations got segregated and finely resolved in three basal clusters with very high bootstrap values corresponding to four geo-ethnic groups of Africans, Orientals, Americans and Caucasians. Maximum- likelihood phylogram has placed North Indian Hindus alongside other Caucasian populations. Haplotype analysis revealed high range of haplotype diversity with nearly 144 observed haplotypes. The haplotype distribution suggested that numbers of Caucasian-specific haplotypes are frequently found among north Indian Hindus. Our results indicate that if the property of less recombination is explored to assign extended haplotypes, followed by strong interpretation based on more logistic statistical model, then there is a high possibility that HLA class II loci can infer exact and accurate phylogenetic assessments as revealed by mtDNA and Y-chromosome markers.

Nxwisen, ntzarrin or ntzo'lin? Mapping children's respiratory symptoms among indigenous populations in Guatemala

Estimating the prevalence of asthma is an epidemiologic challenge, particularly in rural areas of lesser-developed countries characterized by low literacy and poor access to health care. To avoid under or over reporting of symptoms, questionnaires must use terminology familiar to participants and that accurately describes the triad of cough, wheeze and breathlessness characteristic of asthma. In preparation for a large longitudinal cohort study entitled Chronic Respiratory Effects of Early Childhood Exposure to Respirable Particulate Matter (CRECER) that will examine the effects of variable early lifetime woodsmoke exposure on the respiratory health of Mam-speaking children residing in communities in the western highlands of Guatemala, we conducted individual interviews (n=18) and five focus groups (n=46) with indigenous women from 17 of these communities to elicit and define local Mam and Spanish terms for common respiratory symptoms used to describe their own and their children's respiratory symptoms. Focus group participants were also shown an International Study of Asthma and Allergies in Childhood (ISAAC) video of wheezing children and adults. We developed a conceptual framework that can be used as an efficient model for future studies investigating health and/or disease terminology in isolated communities, an integral step in the development of standardized questionnaires. Among this Mam-speaking population, wheeze was best described as nxwisen or ntzarrin, "breathing sounds that are heard in the neck but come from the chest." The variation in understanding of terms between women with and without children with a history of wheeze (such that for those without wheezing children some terms were virtually unrecognized), has important implications for large-scale population surveys within countries and comparative surveys such as ISAAC. It is important to use linguistically and culturally appropriate terminology to describe wheeze in prevalence studies of asthmatic symptoms among relatively isolated communities in lesser-developed countries.

HLA genes in Cubans and the detection of Amerindian alleles

Caribbean Islands including Cuba were first inhabited by Meso-American and later by Arawak-speaking Amerindians from nowadays Venezuela. Spanish invaders brought to almost extinction to the Amerindian population after 1492. Black slaves from West Africa were taken into Cuba by Europeans. The degree of admixture among populations is approached. HLA alleles were studied by DNA techniques. Comparison with other worldwide populations (a total of 14.094 chromosomes) included genetic distances, Neighbour-Joining dendrograms, correspondence analyses and calculation of extended haplotypes. While African-European HLA features were clearly found, Amerindian HLA characteristics are less evident, indicating that Amerindian devastation was particularly marked after 1492 AD. However, typical Amerindian alleles have been found in our Cuban sample, i.e. DRB1*0403, DRB1*0404, DRB1*0407, DRB1*0411, DRB1*0802 and DRB1*1602. The presence of Amerindian alleles in Cubans [corrected] may have a bear in the making up of transplantation registries (both for bone marrow and solid organ transplantation) at the regional level and also be important for epidemiological studies of diseases linked to HLA.

High-resolution molecular characterization of the HLA class I and class II in the Tarahumara Amerindian population

We describe for the first time the high-resolution profiling of HLA-A, -B, -C, -DRB1, -DQB1 and -DPB1 in a culturally and geographically distinct Mexican ethnic group, the Tarahumaras. The alleles most frequently found by reference strand-mediated conformational analysis in this population were for class I: HLA-A*240201, *020101/09, *0206, *310102, *680102; HLA-B*4002, *1501, *510201, *3501/02/03, *4005, *4801; HLA-Cw*0304, *0801, *0102, *040101; and for class II: HLA-DRB1*080201, *1402, *040701; HLA-DQB1*0402, *0301, *0302/07; HLA-DPB1*0402, *0401, *020102. In addition, a novel allele, HLA-A*0257, was found. Based on comparison of presently known HLA-DRB1 and -DQB1 allele frequencies in Amerindian groups and worldwide populations, the Tarahumaras are unexpectedly more related to the geographically and linguistically distant Aymara and Terena Amerindian groups than they are to neighbouring tribes.

Association of HLA subtype DRB1*0407 in Colombian patients with actinic prurigo

BACKGROUND

Human leukocyte antigen (HLA) DRB1*0407 had been associated with actinic prurigo in different populations. This class II HLA-DR subtype had not been studied in Colombia.

OBJECTIVE

The objective of this study was to establish whether there was an association of actinic prurigo with HLA DR in a Colombian population.

MATERIALS AND METHODS

Forty patients with a clinical diagnosis of actinic prurigo and 40 healthy subjects, paired by age, sex and birthplace, were studied. HLA typing for HLA DRB1 and DRB1*04, if necessary, was performed by the PCR-SSP method using blood samples.

RESULTS

A high frequency of HLA DRB1*0407 was found in the patients (97.5% vs. 30%; P<0.00001). The allelic frequency of HLA DRB1*0407 was 63.8% in the case group, and 14.5% in the controls (P<0.00001). In the control group, there was a higher frequency of the alleles DRB1*01 (14.5% vs. 1.25%; P=0.0027) and DRB1*13 (23.7% vs. 2.5%; P=0.00013).

LIMITATIONS

The small number of controls does not allow us to drive conclusions about other HLA alleles.

CONCLUSIONS

HLA subtype DRB1*0407, found in actinic prurigo patients in studies conducted in England, Scotland, Ireland and Mexico, was also associated in Colombian patients. This finding, concordant in patients from different ethnic groups, could be helpful in the diagnosis of this disease and probably important in its pathogenesis. DRB1*01 and DRB1*13 alleles were more frequent in controls than in patients; we do not know whether they play any role in the resistance to the disease.

HLA-A and HLA-B allele frequencies in a mestizo population from Guadalajara, Mexico, determined by sequence-based typing

HLA-A and HLA-B genes were typed by DNA sequencing in a mestizo population from Guadalajara, Jalisco, Mexico. Thirty-seven HLA-A and 51 HLA-B alleles were observed in 103 samples. The common typical Amerindian alleles (>5%) and haplotypes (>or=2.0%) found were A*02010101, *24020101, *310102, B*350101, and *4002, and A*310102-B*4002, A*240201-B*350101, and the typical European alleles were A*010101, *29010101, B*1402, B*180101, and A*020101-B*1402, A*020101-B*510101, and A*3002-B*180101. This reflects the blending of the two main parental populations of mestizos: Amerindian and Iberian. Mexicans were found to be relatively closer to the Portuguese than to Spaniards. This proximity may indicate a larger Portuguese influence in Mexicans than previously considered. Present data contribute to the understanding of the genetic structure in Mexico.

Latino populations: a unique opportunity for the study of race, genetics, and social environment in epidemiological research

Latinos are the largest minority population in the United States. Although usually classified as a single ethnic group by researchers, Latinos are heterogeneous from cultural, socioeconomic, and genetic perspectives. From a cultural and social perspective, Latinos represent a wide variety of national origins and ethnic and cultural groups, with a full spectrum of social class. From a genetic perspective, Latinos are descended from indigenous American, European, and African populations. We review the historical events that led to the formation of contemporary Latino populations and use results from recent genetic and clinical studies to illustrate the unique opportunity Latino groups offer for studying the interaction between racial, genetic, and environmental contributions to disease occurrence and drug response.

HLA genes in Mexican Teeneks: HLA genetic relationship with other worldwide populations

The HLA allele frequency distribution of the Mexican Teenek Indians has been studied and compared with those of other First American Natives and worldwide populations (a total of 15694 chromosomes from 73 different populations were analyzed). This study corroborate the restricted HLA polymorphism in the Amerindian populations and demonstrate how the Amerindians show a relatively homogeneity as opposed to other First Native American groups. Finally, the present data support previous ones that state the lack of complete correlation between language and genetics in micro-environmental studies; Teenek Mayan language does not correspond with a close Mayan (Guatemala) relatedness.

Origin of Aymaras from Bolivia and their relationship with other Amerindians according to HLA genes

Aymara Amerindians from the Titicaca Lake Andean highlands are studied for HLA-A, HLA-B, HLA-DRB1 and HLA-DQB1 gene frequencies. Genetic distances, neighbour-joining and correspondence analyses are performed by using other Amerindian and worldwide populations (15384 chromosomes are studied). The HLA genetic profile of Aymaras is different from neighbouring and language-related Quechuas (Incas). Both Quechuas and Aymaras seem to present an HLA-DRB1*0901 high frequency, which is present in a very low frequency or absent in Mesoamericans (Mazatecans, Mayans) and most studied Amerindians. Moreover, it is observed a closer relatedness of Aymaras with Amerindians from the Amazon Basin and Chaco lowlands, compared to Quechuans.

Human leukocyte antigen haplotypes and HFE mutations in Spanish hereditary hemochromatosis and sporadic porphyria cutanea tarda

BACKGROUND AND AIMS

It has been postulated that the HFE C282Y mutation (linked to human leukocyte antigen [HLA]-A3-B7 haplotype) is not only responsible for hereditary hemochromatosis; HLA class I alleles would also contribute to the disease pathogenesis. In addition, H63D mutation linked to HLA-A29-B44 would also be pathogenetic, particularly in the Mediterranean Basin and throughout the world. However, sporadic porphyria cutanea tarda (s-PCT) has also been linked to these HFE mutations. In the present work, we have studied HFE mutations and HLA genes to test these hypotheses.

METHODS

C282Y and H63D mutations together with HLA genetic typing have been performed in Spanish hereditary hemochromatosis (n = 98) and PCT (n = 63) patients. The etiologic fraction (delta) has been used to determine the absolute strongest gene linkage to both diseases.

RESULTS

The Spanish frequent HLA-A29-B44 haplotype is not significantly associated to the H63D mutations in hereditary hemochromatosis patients (although it is found more frequently in patients than in controls). Sporadic porphyria cutanea tarda patients do not show a significant association to H63D mutations, although it is also more frequent than in controls; however, compound H63D/C282Y subjects seem to bear a significant risk to s-PCT. Allelic C282Y (and not H63D) frequencies show a significant association with s-PCT.

CONCLUSIONS

The postulated additional risk of hereditary hemochromatosis given by class I HLA antigens may be secondary to the HFE gene linkage disequilibrium with certain class I alleles or to the existence of other neighboring genetic pathogenetic factors in our Spanish sample.

HLA class I allele distribution of a Hong Kong Chinese population based on high-resolution PCR-SSOP typing

A stem cell registry population from Hong Kong, of Chinese ethnicity, was examined for HLA-A and HLA-B alleles using a two-stage sequence-specific oligonucleotide probe system. Comparison of the HLA-A and HLA-B frequencies with different populations showed a close relationship with a Chinese population from Singapore, although there were several differences in the presence/absence of alleles at the HLA-B locus. Having the data available on these registry donors will influence the search strategy and the ongoing compilation of new donors to the registry. In addition, knowing which alleles do/do not occur in this population will aid in the distinction of ambiguities which result from the use of many of the typing kits available.