Publications

U.S. populations are genetically admixed, but surprisingly little empirical data exists documenting the impact of such heterogeneity on type I and type II error in genetic-association studies of unrelated individuals. By applying several complementary analytical techniques, we characterize genetic background heterogeneity among 810 self-identified African American subjects sampled as part of a multisite cohort study of cardiovascular disease in older adults. On the basis of the typing of 24 ancestry-informative biallelic single-nucleotide-polymorphism markers, there was evidence of substantial population substructure and admixture. We used an allele-sharing-based clustering algorithm to infer evidence for four genetically distinct subpopulations. Using multivariable regression models, we demonstrate the complex interplay of genetic and socioeconomic factors on quantitative phenotypes related to cardiovascular disease and aging. Blood glucose level correlated with individual African ancestry, whereas body mass index was associated more strongly with genetic similarity. Blood pressure, HDL cholesterol level, C-reactive protein level, and carotid wall thickness were not associated with genetic background. Blood pressure and HDL cholesterol level varied by geographic site, whereas C-reactive protein level differed by occupation. Both ancestry and genetic similarity predicted the number and quality of years lived during follow-up, but socioeconomic factors largely accounted for these associations. When the 24 genetic markers were tested individually, there were an excess number of marker-trait associations, most of which were attenuated by adjustment for genetic ancestry. We conclude that the genetic demography underlying older individuals who self identify as African American is complex, and that controlling for both genetic admixture and socioeconomic characteristics will be required in assessing genetic associations with chronic-disease-related traits in African Americans. Complementary methods that identify discrete subgroups on the basis of genetic similarity may help to further characterize the complex biodemographic structure of human populations.

Renal tubular epithelial cells in all nephron segments express a distinct member of the metalloprotease-disintegrin family, ADAM9 (a disintegrin and metalloprotease 9), in a punctate basolateral distribution co-localized to the beta1 integrin chain [Mahimkar, Baricos, Visaya, Pollock and Lovett (2000) J. Am. Soc. Nephrol. 11, 595-603]. Discrete segments of the nephron express several defined beta1 integrins, suggesting that ADAM9 interacts with multiple renal integrins and thereby regulates epithelial cell-matrix interactions. Intact ADAM9 and a series of deletion constructs sequentially lacking the metalloprotease domain and the disintegrin domain were assembled as chimaeras with a C-terminal GFP (green fluorescent protein) tag. Stable expression of the ADAM9/GFP protein on the surface of HEK-293 cells (human embryonic kidney 293 cells) significantly decreased adhesion to types I and IV collagen, vitronectin and laminin, but had little effect on adhesion to fibronectin. Expression of the disintegrin/cysteine-rich/GFP construct yielded a similar, but more marked pattern of decreased adhesion. Expression of the cysteine-rich/GFP construct had no effect on adhesion, indicating that the disintegrin domain was responsible for the competitive inhibition of cell-matrix binding. To define the specific renal tubular beta1 integrins interacting with the ADAM9 disintegrin domain, a recombinant GST (glutathione S-transferase)-disintegrin protein was used as a substrate in adhesion assays in the presence or absence of specific integrin-blocking antibodies. Inclusion of antibodies to alpha1, alpha3, alpha6, alphav and beta1 blocked adhesion of HEK-293 cells to GST-disintegrin protein. Immobilized GST-disintegrin domain perfused with renal cortical lysates specifically recovered the alpha3, alpha6, alphav and beta1 integrin chains by Western analysis. It is concluded that ADAM9 is a polyvalent ligand, through its disintegrin domain, for multiple renal integrins of the beta1 class.

We here report the molecular cloning of a novel family of killer-cell lectin-like (KLR) receptors in the rat and the mouse, termed KLRI. In both species, there are two members, KLRI1 and KLRI2. While the extracellular lectin-like domains of KLRI1 and KLRI2 are similar [74% (rat) and 83% (mouse) amino acid identity], they differ intracellularly. KLRI1 has two immunoreceptor tyrosine-based inhibition motifs (ITIMs) in the cytoplasmic domain, suggesting an inhibitory function. KLRI2 has no ITIM, but a positively charged lysine residue in the transmembrane region, suggesting association with activating adapter molecules. Klri1 and Klri2 are localized within the natural killer (NK) cell gene complex on rat chromosome 4 and mouse chromosome 6. By RT-PCR and Northern blot analysis KLRI1 and KLRI2 were selectively expressed by NK cells in both rat and mouse. Epitope-tagged expression constructs of rat KLRI1 and rat KLRI2 induced surface expression of a nondisulphide-linked protein of M(r) 36,000/39,000 and M(r) 34,000, respectively.