PubMed · 14076790
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K M CAHILL. 1963-10-01. SMALLPOX.. https://pubmed.ncbi.nlm.nih.gov/14076790/
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An important proportion of the human genome is organized in regions of high linkage disequilibrium (LD) and low haplotype diversity, referred to as haplotype blocks. Here, we perform a genome-wide screen of haplotype-like blocks presenting just two main haplotypes at a frequency higher than 1%, based on single-nucleotide polymorphism (SNP) frequencies from two populations: African-Americans and Caucasians, using data from the Celera SNP database. These haplotype-like blocks of reduced diversity are more abundant and of longer size in Caucasians, in agreement with population history. Several of the discovered blocks are good candidates for targets of natural selection, such as those blocks containing a cluster of bitter taste receptors or the apolipoprotein L1. In addition, several genes putatively involved in susceptibility to common diseases are included in these haplotype-like blocks of reduced diversity. This fact may present important implications in association studies, leading to a reduction of genotyping efforts.
We tested six single nucleotide polymorphisms (SNPs) in the alpha4 subunit gene (CHRNA4) and four SNPs in the beta2 subunit gene (CHRNB2) of nicotinic acetylcholine receptors (nAChRs) for association with nicotine dependence (ND), which was assessed by smoking quantity (SQ), the heaviness of smoking index (HSI) and the Fagerstrom test for ND (FTND) in 2037 subjects from 602 nuclear families of either European-American (EA) or African-American (AA) ancestry. Analysis of the six SNPs within CHRNA4 demonstrated that in the EA sample SNPs rs2273504 and rs1044396 are significantly associated with the adjusted SQ and FTND score, respectively. In the AA samples, SNPs rs3787137 and rs2236196 are each significantly associated with at least two adjusted ND measures. Association of rs2236196 with the adjusted HSI and FTND scores in the AA samples remained significant after correction for multiple testing. Furthermore, analysis revealed gender- and ethnic-specific associations for several SNPs with ND measures in both ethnic samples; however, only the association of SNP rs2236196 with the three adjusted ND measures remained significant after correcting for multiple testing in the AA female samples. Haplotype analysis of rs2273505-rs2273504-rs2236196 showed significant association after Bonferroni correction of a C-G-G haplotype (53.4%) with three adjusted ND measures in samples from the AA females. A similar analysis for the four SNPs within CHRNB2 did not reveal significant association with the three ND measures. In summary, our findings provide convincing evidence for the involvement of the nAChR alpha4 subunit, but not of the nAChR beta2 subunit, in nicotine addiction.
The average results of some laboratory measurements, including the hemoglobin, mean corpuscular volume (MCV), serum transferrin saturation (TS), serum ferritin, and white blood cell count of African-Americans differ from those of whites. Anonymized samples and laboratory data from 1491 African-American and 31 005 white subjects, approximately equally divided between men and women, were analyzed. The hematocrit, hemoglobin, MCV, TS, and white blood cell counts of African-Americans were lower than those of whites; serum ferritin levels were higher. When iron-deficient patients were eliminated from consideration the differences in hematocrit, hemoglobin, and MCV among women were slightly less. The -3.7-kilobase alpha-thalassemia deletion accounted for about one third of the difference in the hemoglobin levels of African-Americans and whites and neither sickle trait nor elevated creatinine levels had an effect. Among all subjects, 19.8% of African-American women would have been classified as "anemic" compared with 5.3% of whites. Among men, the figures were 17.7% and 7.6%. Without iron-deficient or thalassemic subjects, the difference had narrowed to 6.1% and 2.77% and to 4.29% and 3.6%, respectively. Physicians need to take into account that the same reference standards for hemoglobin, hematocrit, MCV, and TS and the white blood cell count do not apply to all ethnic groups.