A Comparison of HLA Data of the North American Black with African Black and North American Caucasoid Populations

For purposes of genetic comparison, the available HLA data on United States and African Black, together with United States Caucasoid populations, are summarized. Antigen frequencies and pairwise linkage disequilibria are presented for the HLA-A, -B and -C loci in Black populations typed for the 1975 Histocompatibility Testing Workshop. The Black population samples comprise 356 North American Blacks and 411 African Blacks of whom 222 were Bantu. These are compared with a sample of 503 American Caucasoids. All significant linkage disequilibria between the A and B loci found in North American Blacks were also present in the North American Caucasoids. Between the B and C loci, Bw35 and Cw4 were in strong linkage disequilibrium in all groups. Significantly stron association between the A and C loci (Aw28 with Cw3) were observed only in the African Blacks. There were unique disequilibria both in the American Caucasoids and African Blacks. Although the frequencies of many antigens in U.S. Blacks lie between those in Africans and U.S. Caucasoids, there are exceptions such as Aw33, Bw35, Cw4.     

Investigation of the effect of brain-derived neurotrophic factor (BDNF) polymorphisms on the risk of late-onset Alzheimer's disease (AD) and quantitative measures of AD progression

BDNF is a functional candidate gene for AD, owing to its role in neuronal development and survival. The Val66Met (G196A), along with another C270T polymorphism has been associated with AD, however, the effects seem to be inconsistent across studies. We examined the association of the G196A and C270T polymorphisms with sporadic late-onset AD (LOAD) in a large American White cohort of 995 AD cases and 671 controls and an American Black cohort of 64 AD cases and 45 controls. We also examined the association of these polymorphisms with quantitative measures of AD progression, including age at onset (AAO), disease duration and Mini-Mental State Examination (MMSE) scores. No significant difference in allele, genotype or estimated haplotype frequencies was observed between AD cases and controls within the American White and Black cohorts for the G196A and C270T polymorphisms. However, the frequency of the 196*A allele was significantly lower in American Black subjects compared to Whites. While MMSE scores were significantly lower in C270T/CT carriers compared to C270T/CC subjects only among American Blacks, no such effect was observed among American Whites. The BDNF polymorphisms did not affect AAO or disease duration measures in American Whites or Blacks. Our finding does not support any association between the BDNF/G196A or C270T polymorphism and the risk of sporadic LOAD among American Whites or Blacks. The significant effect of the C270T polymorphism observed on MMSE scores among American Blacks needs to be further explored in a larger cohort.     

Mitochondrial and nuclear variants in a U.S. Black population: origins of a hybrid population

The maternal transmission of mitochondria in higher eukaryotes makes it possible to distinguish between reciprocal matings, since offspring possess the mitochondrial DNA variants received from the mother. This possibility can be extended to hybrid populations, the mitochondrial frequencies reflecting the relative maternal contributions from the parental populations. Nuclear variations reflect the relative genetic contributions of the parental populations, irrespective of parental sex. The U.S. Black population is a hybrid of West African and European populations. The African-European matings that contributed to the present Black population are traditionally considered to have been almost exclusively between African females and European males. We have studied nuclear and mitochondrial variants in a sample of U.S. Blacks, comparing them with published frequencies from African and Caucasian groups. Our results suggest that the mitochondria of present-day American Blacks are derived from Caucasians to an extent similar to nuclear genes. In contrast to traditional beliefs, the contribution from Caucasian females is of the same magnitude as that from Caucasian males.     

Religious Coping Among African Americans, Caribbean Blacks and Non-Hispanic Whites

This study examined demographic predictors of attitudes regarding religious coping (i.e., prayer during stressful times and look to God for support, strength and guidance) within a national sample of African American, Caribbean Blacks and non-Hispanic Whites (National Survey of American Life). The findings demonstrate significant Black-White differences in attitudes regarding religious coping with higher endorsements of religious coping among African Americans and Black Caribbeans (Caribbean Blacks). Comparisons of African Americans and Black Caribbeans revealed both similar and divergent patterns of demographic effects. For both African Americans and Black Caribbeans, women were more likely to utilize religious coping than men and married respondents were more likely than never married respondents to report utilizing prayer when dealing with a stressful situation. Further, for both groups, higher levels of education were associated with lower endorsements of the importance of prayer in dealing with stressful situations. Among African Americans only, Southerners were more likely than respondents who resided in other regions to endorse religious coping. Among Black Caribbeans, those who emigrated from Haiti were more likely than Jamaicans to utilize religious coping when dealing with a stressful episode.     

Modified-Symbol Digit Modalities Test for African Americans, Caribbean Black Americans, and non-Latino Whites: nationally representative normative data from the National Survey of American Life.

Normative neuropsychological data for U.S. racial/ethnic minorities are limited. Extant norms are based on small, regional groups that may not be nationally representative. The objectives of this study were to (1) provide norms for a modified Symbol Digit Modalities Test (M-SDMT) based on a nationally representative sample of African Americans, Caribbean Blacks, and non-Latino Whites (NLW) living in areas with large populations of Blacks; and (2) determine significant correlates of M-SDMT performance. The M-SDMT was administered to a subset of respondents from the National Survey of American Life in standard face-to-face interviews. M-SDMT performance was influenced by race/ethnicity, age, education, and gender. African Americans and NLW groups had similar M-SDMT performances, which differed from Caribbean Blacks. The Black ethnic differences in M-SDMT were not explained by the sociodemographic factors considered in this study. Unlike previous work, this study supports the consideration of Black ethnicity when evaluating Black neuropsychological test performance.     

B Cell Antigens of Black Americans

Fourty-four unrelated North American Blacks and one Black family were tested for B-cell specific antigens with 7th International Workshop antisera. DR specificities were clearly defined in this group, but were generally less frequent than reported for Black Americans in the 7th Workshop report and were most similar in frequency to those reported for African Blacks. Five new B-cell specificities (DuB40-43, 45) were identified. In contradistinction to Caucasians, Black Americans type for HLA-D with homozygous typing cells failed to exhibit strong linkage disequilibrium between D and DR types.     

Factor IX mutations in South Africans and African Americans are compatible with primarily endogenous influences upon recent germline mutations

Similar patterns of germline mutations in the factor IX gene (F9) have been observed in certain geographically and racially diverse populations. Germline mutation data have not been available from any region of Africa or from the Black race. Analysis of mutation data for Blacks is of interest, since this race has a high frequency of polymorphism compared to other races. This high frequency has been interpreted as evidence for the "out of Africa" hypothesis for the origin of humans, but it is possible that Blacks have a higher mutation rate due to genetic differences or environmental exposures. We report 26 independent mutations that were detected in patients of mixed races with hemophilia B from South Africa. The pattern of mutation in patients from this African country was similar to that of U.S. Caucasians. In addition, 22 independent mutation were detected in African American patients. The patterns of independent germline mutation in 22 African Americans (and in a combination 34 North American and African Blacks) is similar to that of U.S. Caucasians. Neither genetic differences between the Black and Caucasian races nor environmental and cultural differences between South Africa and the U.S. alter the germline pattern of mutation observed in F9. Hum Mutat 16:372, 2000.     

HLA-DRB1 and -DQB1 alleles in the Brazilian population of the northeastern region of the state of São Paulo

The HLA-DRB1 and -DQB1 alleles in 161 healthy unrelated individuals, including Caucasians, Blacks and Mulattos (mixed Caucasian and Black), from the Northeastern region of the state of S?o Paulo, Brazil were analysed. The 36 different DRB1 alleles detected included not only common Caucasian alleles, but also DRB1*0411, 0807 and 1402, typical of Amerindians, and DRB1*0302, 1503, and 0804, typical of African American Blacks.     

Genetic impact of functional single nucleotide polymorphisms in the 3'-UTR region of the chemoattractant receptor expressed on Th2 cells (CRTH2) gene on asthma and atopy in a Japanese population

BACKGROUND: The human chemoattractant receptor expressed on Th2 cells (CRTH2), the receptor for prostaglandin D2, induces cell migration in eosinophils, basophils, and Th2 cells. The gene encoding CRTH2 is located on chromosome 11q13. Several groups, including ours, have reported significant associations between this region and various traits associated with allergic diseases such as asthma and atopy. Two single nucleotide polymorphisms in the 3'-UTR of the CRTH2 gene (1544G-->C and 1651G-->A) are associated with the mRNA stability of the gene; they have also been associated with asthma in both African American and Chinese populations. METHODS: Because CRTH2 is a biologically important candidate gene on chromosome 11q13, we conducted a case-control analysis using 787 Japanese subjects (384 asthmatics and 403 controls) to evaluate the genetic impact of the CRTH2 gene on asthma and asthma-related traits. Four polymorphisms [1544G-->C (rs11571288), 1651G-->A (rs545659), 11336T-->C (rs2074422), and 12375G-->T (rs561285)] were studied. RESULTS: The allele, genotype, or haplotype frequencies for 2 functional polymorphisms in our Japanese population were significantly different from those in the Chinese or African American populations. No association was found between any polymorphisms or haplotypes in the CRTH2 gene and asthma, atopy, or total serum IgE levels in a Japanese population. CONCLUSIONS: Our data failed to support previous associations of functional polymorphisms at the 3'-UTR of the CRTH2 gene implicated in asthma. We did show a significant difference in the allele and genotype frequencies as well as different haplotype frequencies among African American, Chinese, and Japanese populations, suggesting that the genetic impacts of these functional polymorphisms on asthma and asthma-related phenotypes may vary in different populations.     

Y chromosome microsatellite variation in three populations of Jerba Island (Tunisia)

Six Y-chromosome linked microsatellites were typed in a sample of 135 unrelated males representing three different ethnic groups: Arabs, Berbers and Blacks of Jerba Island (Tunisia). Analysis of variation at the six Y chromosome STRs showed significant differences in allele distributions between the Black group and the two other Islander groups. The Black group revealed the highest level of genetic diversity as compared to Arabs and Berbers, while the latter group was the most homogenous. Allele frequencies obtained for the three islander groups analysed were compared to data available for some European, Mediterranean and African populations. Principal-coordinate analyses showed genetic differentiation between the three geographically closed groups of Jerba. The absence of the YAP insertion marker and the position of Arabs and Jerban Blacks near the European cluster would suggest their relative 'admixture' with European populations.     

Acculturation and Cigarette Smoking Among African Americans: Replication and Implications for Prevention and Cessation Programs

We report a replication of a 1996 study on the role of acculturation in smoking among African American adults. Results with the current sample were nearly identical to the prior ones: smokers tended to be traditional and nonsmokers acculturated, with nearly 70% of Black smokers in both studies being highly traditional in their cultural orientation. Given that coming from a highly traditional Black family was a strong predictor of smoking in both studies, we suggest that new smoking prevention and cessation programs might be culturally tailored for Blacks by focusing on smoking as a familywide issue.     

Differences in HIV-related hospitalization trends between Haitian-born blacks and US-born blacks

OBJECTIVES: To examine the HIV care needs and hospital admission patterns of HIV-positive Haitian-born blacks (Haitians) and compare them with those of US-born blacks (Blacks). METHODS: We abstracted the medical records of 635 Blacks and Haitians consecutively admitted to the adult HIV Service at Jackson Memorial Hospital during 2004 for information on demographics, use of antiretroviral therapy, CD4 cell counts, primary and secondary diagnoses at admission, and substance use. The probability of being prescribed highly active antiretroviral therapy (HAART) was examined by country of origin. RESULTS: There was no statistically significant difference between the groups in likelihood to be prescribed HAART. In controlled analyses, however, Haitians were 76% more likely than Blacks to have a CD4 count <51 cells/mm3 and tended to be more recently diagnosed with HIV Moreover, tuberculosis was the most prevalent opportunistic infection for Haitians compared with candidiasis for Blacks. CONCLUSIONS: Findings suggest that barriers to medical care may exist for Haitians at an early stage of the access continuum and that prevention efforts among the Haitian HIV-positive population should be directed at promoting the need for timely use of health services.     

Identification of P gene mutations in individuals with oculocutaneous albinism in sub-Saharan Africa

Oculocutaneous albinism (OCA) is an inherited disorder resulting in hypopigmentation of the skin, hair, and eyes. OCA type 2 (tyrosinase-positive) is the most common recessively inherited disorder among southern African Blacks. OCA2 is also seen in southern African Caucasoids, but is less frequent. The gene responsible for this type of albinism, P, is the human homolog of the mouse pink-eyed dilution gene. Mutations at this locus are also responsible for the milder hypopigmentation phenotype seen in individuals with brown oculocutaneous albinism (BOCA). A common African P mutation was identified in Black OCA2 individuals, and has since been shown to occur in Black individuals with brown OCA as well. This mutation is a 2.7 kb interstitial deletion. In this study, we undertook to screen the coding region of the P gene for mutations in the non-2.7 kb deletion alleles of OCA2 patients who did not carry the deletion allele in either one or both of their P genes. We identified four mutations (A334V, 614delA, 683insG [corrected], 727insG) in a group of 39 unrelated Black OCA2 patients with a total of 52 non-2.7 kb deletion OCA2 genes. When taking all OCA2 cases into consideration, including those homozygous for the 2.7 kb deletion mutation, these account for a further 1.7% of OCA2 mutations in southern African Blacks, increasing the overall mutation detection rate to 78.7%. Three mutations (E678K, L688F, I370T) were identified in a group of 15 Black patients with an initially unclassified type of OCA and another three mutations (IVS 14-2 (a-->g), V350M, P743L) were identified in nine Caucasoid OCA patients. Relatively few mutations, all with low frequency, were identified in the non-2.7 kb deletion OCA genes. We propose that other mutations may lie either within intronic sequence or within the promoter region of the gene.     

HLA profile of the Mexican Mestizo population

The HLA—A, B and C profile of 665 Mexican Mestizos was studied by microcytotoxicity testing for 30 HLA specificities. Antigen, gene and haplotype frequencies were calculated, and results were compared to those of the three other series of HLA profiles in Mexican Mestizos available in the literature: one from Mexico-City, one from Los Angeles, California, USA, and a recent one from San Antonio, Texas, USA. Comparing the antigen frequencies of our series with those of the other study from Mexico-City, significant differences were only found in three antigens of the HLA-B locus. On the other hand, comparison of either series from Mexico-city with the Los Angeles or the San Antonio studies yielded discrepancies in several specificities of both HLA-A and B loci, most notably the consistent absence of A25 in Mexican Mestizos living in Mexico-City. The presence of this specificity in the Mexican Mestizo Population living in these two American cities could have resulted from input of Caucasian and Black genes over several generations. Differences in haplotype frequency were observed comparing the two series from Mexico-City and the series from San Antonio. Comparison of haplotype frequency with the Los Angeles series was not possible.     

The AGT gene in Africa: a distinctive minor allele haplotype,a polymorphism (V326I), and a novel PH1 mutation (A112D) in Black Africans

We describe a novel missense mutation (A112D) and polymorphism (V326I) in the human AGT gene in two black African patients with primary hyperoxaluria type 1, an autosomal recessive disease resulting from a deficiency of the liver peroxisomal enzyme alanine:glyoxylate aminotransferase (AGT; EC 2.6.1.44). V326I was found in DNA from normal control Blacks with an allele frequency of 3%. Expression studies confirmed that A112D reduced AGT enzyme activity by 95% while V326I had no effect. Both A112D and V326I were homozygous in both patients and lie on a variant of the minor allele of the AGT gene. This variant haplotype, Mi(A), includes an intron 1 duplication and intron 4 VNTR (38 repeat) but lacks the P11L and I340M normally associated with the minor allele in Caucasians. Among the South African Blacks tested, the Mi(A) haplotype had an allele frequency of 12% compared to 3 % for the Caucasian-type minor allele haplotype.     

Genetics of the Lp(a)/apo(a) system in an autochthonous Black African population from the Gabon

Plasma lipoprotein(a) (Lp(a)) is a quantitative trait associated with atherothrombotic disease in European and Asian populations. Lp(a) concentrations vary widely within and between populations, with Africans exhibiting on average two- to threefold higher Lp(a) levels and a different distribution compared to Europeans. The apo(a) gene locus on chromosome 6q26-27 (LPA, MIM 152200) has been identified as the major quantitative trait locus (QTL) for Lp(a) concentrations in Europeans and populations of African descent (North American and South African Blacks) but data on autochthonous Black Africans are lacking.Here, we have analysed Lp(a) plasma concentrations, apo(a) isoforms in plasma and four polymorphisms in the LPA gene in 31 African families with 54 children from Gabon. Weighted midparent-offspring regression estimated a heritability h2=0.76. The correlation of Lp(a) levels associated with LPA alleles identical by descent (IBD) resulted in a heritability estimate of 0.801. Our data demonstrate that Lp(a) concentrations are highly heritable in a Central African population without admixture and high Lp(a) (median 43 mg/dl). LPA is the major QTL, explaining most or all of the heritability of Lp(a) in this population.     

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

The β‐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. Am. J. Hum. Biol. 2010. © 2009 Wiley‐Liss, Inc.     

The relation between total finger ridge-count and variability of counts from finger to finger: genetic implications of racial variation

The measure of ridge-count diversity, S/square root 10, was computed for a sample of American Whites, American Blacks and African Blacks, and the regression of S/square root 10 on total ridge-count was determined for each group. The shapes of the regression lines differed considerably. The American White curve was very similar to that obtained by Holt in an English sample, while the two Negro curves generally showed lower lower S/square root 10 values for ridge-counts over 80. The American Negro curve was found to behave like a mixture of the White and African Negro curve to a degree approximating to the fraction of White genes in their gene pool. Holt's parent-child data are used to construct a simple test of the hypothesis that that S/square root 10 reflects zygosity in total ridge-count genotypes. The preliminary results support this hypothesis.