Polymorphic admixture typing in human ethnic populations.

A panel of 257 RFLP loci was selected on the basis of high heterozygosity in Caucasian DNA surveys and equivalent spacing throughout the human genome. Probes from each locus were used in a Southern blot survey of allele frequency distribution for four human ethnic groups: Caucasian, African American, Asian (Chinese), and American Indian (Cheyenne). Nearly all RFLP loci were polymorphic in each group, albeit with a broad range of differing allele frequencies (delta). The distribution of frequency differences (delta values) was used for three purposes: (1) to provide estimates for genetic distance (differentiation) among these ethnic groups, (2) to revisit with a large data set the proportion of human genetic variation attributable to differentiation within ethnic groups, and (3) to identify loci with high delta values between recently admixed populations of use in mapping by admixture linkage disequilibrium (MALD). Although most markers display significant allele frequency differences between ethnic groups, the overall genetic distances between ethnic groups were small (.066-.098), and < 10% of the measured overall molecular genetic diversity in these human samples can be attributed to "racial" differentiation. The median delta values for pairwise comparisons between groups fell between .15 and .20, permitting identification of highly informative RFLP loci for MALD disease association studies.

Isolation and characterization of a specific receptor for biologically active phorbol and ingenol esters.

A high-affinity, specific receptor for biologically active phorbol and ingenol esters has been purified to electrophoretic homogeneity from murine brains using ammonium sulfate fractionation, and DEAE-cellulose, Sephadex G-200, Affi-Gel Blue, and phenyl-Sepharose chromatographies. The receptor is a single-chain hydrophobic protein with a molecular weight (Mr) of 81,500, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The receptor has a sedimentation coefficient of 5.2 S and Stokes radius of 30.3 A. It has an isoelectric point (pI) of 5.5. The receptor is heat and acid labile. The receptor absolutely depends upon phosphatidylserine or phosphatidylinositol (optimum concentration approximately 4-8 micrograms/ml) for its activity. A variety of divalent cations stimulates the binding activity of the receptor. A molecule of receptor binds 1-2 molecules of phorbol-12, 13-dibutyrate (PDBu) with a Kd value of 4.2 nM. Those phorbol and ingenol esters which stimulate cell growth in culture and have tumor-promoting activity in vivo inhibit the binding of labeled PDBu to its homogeneous receptor, while the biologically inactive derivatives fail to do so. The homogeneous receptor protein contains a protein kinase activity.