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For admixture mapping studies in Mexican Americans (MAM), we define a genomewide single-nucleotide–polymorphism (SNP) panel that can distinguish between chromosomal segments of Amerindian (AMI) or European (EUR) ancestry. These studies used genotypes for >400,000 SNPs, defined in EUR and both Pima and Mayan AMI, to define a set of ancestry-informative markers (AIMs). The use of two AMI populations was necessary to remove a subset of SNPs that distinguished genotypes of only one AMI subgroup from EUR genotypes. The AIMs set contained 8,144 SNPs separated by a minimum of 50 kb with only three intermarker intervals >1 Mb and had EUR/AMI FST values >0.30 (mean FST=0.48) and Mayan/Pima FST values

Association studies in populations that are genetically heterogeneous can yield large numbers of spurious associations if population subgroups are unequally represented among cases and controls. This problem is particularly acute for studies involving pooled genotyping of very large numbers of single-nucleotide-polymorphism (SNP) markers, because most methods for analysis of association in structured populations require individual genotyping data. In this study, we present several strategies for matching case and control pools to have similar genetic compositions, based on ancestry information inferred from genotype data for approximately 300 SNPs tiled on an oligonucleotide-based genotyping array. We also discuss methods for measuring the impact of population stratification on an association study. Results for an admixed population and a phenotype strongly confounded with ancestry show that these simple matching strategies can effectively mitigate the impact of population stratification.

Coronary heart disease (CHD) accounts for half of the 1 million deaths annually ascribed to cardiovascular disease and for almost all of the 1.5 million acute myocardial infarctions. Within families affected by early and apparently heritable CHD, dyslipidemias have a much higher prevalence than in the general population; 20%-30% of early familial CHD has been ascribed to primary hypoalphalipoproteinemia (low HDL-C). This study assesses the evidence for linkage of low HDL-C to chromosomal region 11q23 in 105 large Utah pedigrees ascertained with closely related clusters of early CHD and expanded on the basis of dyslipidemia. Linkage analysis was performed by use of 22 STRP markers in a 55-cM region of chromosome 11. Two-point analysis based on a general, dominant-phenotype model yielded LODs of 2.9 for full pedigrees and 3.5 for 167 four-generation split pedigrees. To define a localization region, model optimization was performed using the heterogeneity, multipoint LOD score (mpHLOD). This linkage defines a region on 11q23.3 that is approximately 10 cM distal to-and apparently distinct from-the ApoAI/CIII/AIV gene cluster and thus represents a putative novel localization for the low HDL-C phenotype.

The ZNF202 gene resides in a chromosomal region linked genetically to low high density lipoprotein cholesterol in Utah families. Here we show that the ZNF202 gene product is a transcriptional repressor that binds to elements found predominantly in genes that participate in lipid metabolism. Among its targets are structural components of lipoprotein particles (apolipoproteins AIV, CIII, and E), enzymes involved in lipid processing (lipoprotein lipase, lecithin cholesteryl ester transferase), and several genes involved in processes related to energy metabolism and vascular disease. Based on the linkage and apparent transcriptional function of ZNF202, we propose that ZNF202 is a candidate susceptibility gene for human dyslipidemia.

To the Editor: In this issue, four independent research teams present new genetic association data for 13 SNPs previously reported by us to be potentially associated with Parkinson disease (PD [MIM 168600]).1 Two groups2,3 report statistically significant association between one or more of these SNPs and PD, whereas two groups4,5 find no statistically significant association between PD and any of the SNPs investigated. In an accompanying letter,6 Dr. Richard H. Myers provides his qualitative assessment of the implications of these new results. We have performed a Mantel-Haenszel analysis, using 10 of the 13 SNPs not displaying linkage disequilibrium (LD) with each other—combining the data of Li et al.,3 Farrer et al.,4 and Goris et al.5—to provide an overall quantitative assessment of the new results. The odds ratios (ORs) are reported for the SNP alleles that increase the risk of PD1 (table 1). The X-linked SNP rs7878232 was not included in this analysis, since subgroup-level data for males and females were not reported by all groups. The results of Clarimon et al.2 were also not included, given the significant difference in SNP allele frequency observed between the European and Taiwanese control samples. This analysis reveals that none of the 10 SNPs shows statistically significant association with PD (i.e., P

Fertilization of the eggs of the sea urchin Arbacia punctulata is followed by the phosphorylation of ribosomal protein S6. The increase in phosphorylation starts at the same time that protein synthesis begins to increase, and leads to the appearance of mono-, di-, and triphosphorylated S6 derivatives. Essentially all the S6 is phosphorylated by first cleavage. This phosphorylation requires the occurrence of both the normal Ca2+ transient and the consequent Na+H+ exchange. Protein synthesis can be partially activated by an increase in intracellular pH brought about by weak bases, but this neither causes S6 phosphorylation, nor the inactivation of the specific S6 phosphatase present in unfertilized Arbacia eggs.