Life Sciences Division 1997-98 Progress Report

Life Sciences Division
1997-98
Progress Report

Overview
Mission
Structure

Systems Biology

Technology Applications

Mouse Genetics Research Facility

ORNL established a Mammalian Genetics program soon after World War II specifically to assess the biological effects of ionizing radiations in mammals. Experiments were carried out to determine both rates of induction of germline mutations and differential sensitivities of germ cell stages to induced damage in mice. In more recent experiments, mutagenesis has also been carried out using a wide variety of chemicals, in particular with N-ethyl-N-nitrosourea (ENU), a mouse supermutagen discovered here at ORNL. A new animal facility, now in design stage, will house the ORNL mice in a specific pathogen-free, rather than the current conventional, colony. This colony currently houses about 70,000 live mice that represent about 400 mutant strains; a variety of other strains are being or have been cryopreserved. Most of these mutations, many of them radiation-induced deletions, encompass the seven visible genetic loci that were targets for the risk assessment studies. These loci are agouti (a, mouse chromosome 2), brown (b, now tyrosinase-related protein 1, mouse chromosome 4), albino (c, now tyrosinase, mouse chromosome 7), pink-eyed dilution (p, mouse chromosome 7), dilute (d, now myosin Va, mouse chromosome 9), short-ear (se, now bone-morphogenetic protein 5, mouse chromosome 9), and piebald spotting (s, now endothelin receptor B, mouse chromosome 14). We also keep many various inbred and hybrid parental stocks used for experimentation, many other strains that carry coat-color markers for mapping and allelism-testing, and dominant mutations and chromosomal translocations scattered throughout the genome. Ongoing mutagenesis projects involve transgenic technology, including gene knockouts, creation of specifically-targeted deletions, and ectopic or overexpression of transgenes; expertise with these technologies allows us to preselect our gene or chromosomal region chosen for mutation. A database that details available strains and phenotypes is accessible though the Life Sciences Division WWW homepage. Many of the deletion complexes that surround these seven marker loci have been characterized both molecularly and by genetic complementation to determine visible and lethal phenotypes that neighbor the marker locus. In addition, three of the deletion complexes (p, c, and b) have undergone additional mutagenesis studies, using chemicals that induce point mutations, to create other mutant phenotypes within the deleted regions. Any phenotype can be quickly submapped by crosses to mouse stocks that carry other, overlapping deletions that may or may not complement the mutation. We are testing all these mutants for subtle phenotypes that would not traditionally have been recognized, even by our very experienced technicians who consistently recognize mutations that alter general health, size and morphology, and normal motor behavior. For example, both existing and newly generated mutants are being evaluated for behavioral and biochemical aberrations; we are screening all potential mutants for levels of activity, anxiety, and reaction to novelty, for behavioral despair, for neuromuscular coordination, for learning and memory, and for acoustic startle response. Mice that show abnormalities during any of these tests are analyzed in more detail. We are developing technology to increase the sophistication, efficiency, and throughput for these behavioral assessments. We are also measuring various bioactive molecules or byproducts in blood and urine to monitor mutations induced in biochemical pathways. We welcome other investigators to come to Oak Ridge to screen potential mutants for their phenotype of interest, or to identify phenotypic changes in their mouse of interest. The MGRF is a Department of Energy User Facility.

Director: Dabney K. Johnson, 865-574-0953, e-mail: k29@ornl.gov