Biomedical subjects

R P Stokowski

Publications and source records attributed to R P Stokowski.

4 recordsLinked to original sources

PubMed2001

Blocks of limited haplotype diversity revealed by high-resolution scanning of human chromosome 21.

Global patterns of human DNA sequence variation (haplotypes) defined by common single nucleotide polymorphisms (SNPs) have important implications for identifying disease associations and human traits. We have used high-density oligonucleotide arrays, in combination with somatic cell genetics, to identify a large fraction of all common human chromosome 21 SNPs and to directly observe the haplotype structure defined by these SNPs. This structure reveals blocks of limited haplotype diversity in which more than 80% of a global human sample can typically be characterized by only three common haplotypes.

Algorithms↗

PubMed2001

Evolutionarily conserved sequences on human chromosome 21.

Comparison of human sequences with the DNA of other mammals is an excellent means of identifying functional elements in the human genome. Here we describe the utility of high-density oligonucleotide arrays as a rapid approach for comparing human sequences with the DNA of multiple species whose sequences are not presently available. High-density arrays representing approximately 22.5 Mb of nonrepetitive human chromosome 21 sequence were synthesized and then hybridized with mouse and dog DNA to identify sequences conserved between humans and mice (human-mouse elements) and between humans and dogs (human-dog elements). Our data show that sequence comparison of multiple species provides a powerful empiric method for identifying actively conserved elements in the human genome. A large fraction of these evolutionarily conserved elements are present in regions on chromosome 21 that do not encode known genes.

Animals↗

PubMed2000

Functional analysis of the neurofibromatosis type 2 protein by means of disease-causing point mutations.

Despite intense study of the neurofibromatosis type 2 (NF2) tumor-suppressor protein merlin, the biological properties and tumor-suppressor functions of merlin are still largely unknown. In this study, we examined the molecular activities of NF2-causing mutant merlin proteins in transfected mammalian cells, to elucidate the merlin properties that are critical for tumor-suppressor function. Most important, we found that 80% of the merlin mutants studied significantly altered cell adhesion, causing cells to detach from the substratum. This finding implies a function for merlin in regulating cell-matrix attachment, and changes in cell adhesion caused by mutant protein expression may be an initial step in the pathogenesis of NF2. In addition, five different mutations in merlin caused a significant increase in detergent solubility of merlin compared to wild type, indicating a decreased ability to interact with the cytoskeleton. Although not correlated to the cell-adhesion phenotype, four missense mutations decreased the binding of merlin to the ERM-interacting protein EBP-50, implicating this interaction in merlin inhibition of cell growth. Last, we found that some NF2 point mutations in merlin most closely resembled gain-of-function alleles in their cellular phenotype, which suggests that mutant NF2 alleles may not always act in a loss-of-function manner, as had been assumed, but may include a spectrum of allelic types with different phenotypic effects on the function of the protein. In aggregate, these cellular phenotypes provide a useful assay for identifying the functional domains and molecular partners necessary for merlin tumor-suppressor activity.

Alleles↗

PubMed1995

Knockout of the mouse apolipoprotein B gene results in embryonic lethality in homozygotes and protection against diet-induced hypercholesterolemia in heterozygotes.

Apolipoprotein B is synthesized by the intestine and the liver in mammals, where it serves as the main structural component in the formation of chylomicrons and very low density lipoproteins, respectively. Apolipoprotein B is also expressed in mammalian fetal membranes. To examine the consequences of apolipoprotein B deficiency in mice, we used gene targeting in mouse embryonic stem cells to generate mice containing an insertional disruption of the 5' region of the apolipoprotein B gene. Mice that were heterozygous for the disrupted apolipoprotein B allele had an approximately 20% reduction in plasma cholesterol levels, markedly reduced plasma concentrations of the pre-beta and beta-migrating lipoproteins, and an approximately 70% reduction in plasma apolipoprotein B levels. When fed a diet rich in fat and cholesterol, heterozygous mice were protected from diet-induced hypercholesterolemia; these mice, which constitute an animal model for hypobetalipoproteinemia, should be useful for studying the effects of decreased apolipoprotein B expression on atherogenesis. The breeding of heterozygous mice yielded no viable homozygous apolipoprotein B knockout mice. Most homozygous embryos were resorbed by midgestation (before gestational day 11.5); several embryos that survived until later in gestation exhibited exencephalus. The embryonic lethal phenotype was rescued by complementation with a human apolipoprotein B transgene--i.e., human apolipoprotein B transgenic mice that were homozygous for the murine apolipoprotein B knockout mutation were viable. Our findings indicate that apolipoprotein B plays an essential role in mouse embryonic development.

Animals↗