Gerald E. McClearn, PhD - US grants

epizootiology; prognosis;

The proposed research will extend our ongoing project investigating alcohol-related processes in mice using an adaptation of the recombinant inbred (RI) strain method. RI analysis, which has previously been used to identify and map major-gene effects, has been adapted for analysis of quantitative traits and quantitative trait loci (QTL). The integrative and cumulative nature of this approach holds great promise for advancing our understanding of alcohol-related processes. Our current grant characterizes the most widely-used RI mouse series, BXD RI, on an extensive battery of alcohol-related traits and applies RI QTL analysis to these data. Multivariate RI QTL analysis has also been developed to analyze QTL sources of genetic correlations among these alcohol-related processes, as well as to BXD data reported by other investigators. The proposed research has three goals. The first goal is to confirm, extend, and generalize our RI QTL results using a series of increasingly informative procedures: F1 crosses among the RI strains will be used to attempt replication of our RI results with increased power, and to investigate dominance; F2 crosses will provide a further replication test of the RI and F1 results and extend them to genetically-segregating individuals; heterogeneous stock (HS) will test the generalization of BXD RI results to outbred mice more representative than the F2 of the mouse genome. The HS research will also set the stage for the use of QTL markers in chromosomal regions syntenic to the human genome as candidate genes in QTL analyses of human alcohol use and abuse. The second goal is to extend our ongoing characterization of alcohol-related behaviors to neuropharmacological mechanisms which have been shown either to modulate or respond to ethanol actions. Specifically, the BXD series will be characterized in relation to ethanol effects on neurotensin, corticotropin-releasing hormone and tyrosine hydroxylase. The third goal is to initiate the first selection studies based upon genotype rather than phenotype in the generation of single and multiple QTL animal models of alcohol-related processes in otherwise genetically segregating (HS) animals.

Individual differences both in rate and pattern of aging are generally acknowledged to be great. Understanding the origins of this variability is of fundamental importance for basic scientific understanding of aging processes. This basic knowledge may also lay the groundwork for eventual application in the prediction of differential decline in functional capacity and utilization of health and care services, and in informing the search for rational therapeutic and preventive interventions. Recent research has just begun to explore the genetic and environmental bases of individual differences in aging by the study of monozygotic (identical) and dizygotic (fraternal) twins. However, these studies are principally concerned with the "young-old." Practically nothing is yet known in this regard concerning the "old-old," those individuals 80 years of age and older, who comprise the most rapidly growing segment of the population, with the highest incidence of decline in health and competence, and with the greatest need for medical care. This proposal is for support of a study of octogenarian and nonagenarian Swedish twins on measures of physical health and functioning, cognitive functioning, interpersonal relationships, life satisfaction, personality, and mental health. Analyses will estimate the relative contributions of environmental and genetic factors to the variability in these measures. All cooperating Swedish twins of the appropriate ages, estimated to number about 375 pairs, will be studied. Interpretation of the study will be enriched by the availability of data from the twin study of the "young-old" and from singleton studies of Swedish single-born octogenarians.

This program project is concerned with individual differences in behavioral and neurochemical response to cocaine. It is designed to characterize the influence of genetics on the individual cocaine-related processes measured, and on the correlations among them. It will furthermore identify the chromosome regions wherein are located effective genetic loci accounting for as little as 15 per cent of the phenotypic variance. This information will be used to breed selectively to generate lines of animals differing with respect to two of the most influential of these loci and both in combination, with the rest of their genotypes being randomly distributed. These lines will constitute powerful models for investigating the mechanisms underlying the genetic influence.

Individual differences both in rate and pattern of aging are large, pervasive and ubiquitous. Individuals are distributed between the extremes of those who remain intact throughout life and those who experience early decline in vitality and functional capacity. Understanding the origins of this multifaceted variability is of fundamental importance both for basic- science understanding of aging and age-related processes and for the development of rational health- and disease-related applications. Quantitative genetics offers an explicit analytical model for the identification of relative contributions of two broad domains of influence on living systems --genetics and environment. The study of monozygotic and dizygotic twins is one of the strongest available methods for decomposing the manifest variance in complex traits into genetic and environmental components. This proposal seeks support for a longitudinal extension of our current grant (AGO8861), "Origins of Variance in the Old-Old: Octogenarian Twins" (OCTO-Twin). The aim of OCTO-Twin is to explore the genetic and environmental bases of variability in age-related variables in the oldest- old. The proposed inclusion of two additional measurement occasions at two-year intervals will provide unique information on the relative contributions of genetic and environmental influences to change and continuity in advanced ages. The longitudinal data will also identify significant numbers of individuals giving evidence of cognitive impairment, which will shed light on the critical question of whether late-onset diagnosable dementias are distinct, categorical conditions or whether they represent the low end of a continuous distribution of cognitive function.

cognition; behavioral genetics; child (0-11); genetic markers; intelligence; alleles; genotype; genetic mapping; human genetic material tag; restriction fragment length polymorphism; human subject; polymerase chain reaction; clone cells; psychometrics;

Individual differences both in rate and pattern of aging are large, pervasive and ubiquitous. Individuals are distributed between the extremes of those who remain intact throughout life and those who experience early decline in vitality and functional capacity. Understanding the origins of this multifaceted variability is of fundamental importance both for basic- science understanding of aging and age-related processes and for the development of rational health- and disease-related applications. Quantitative genetics offers an explicit analytical model for the identification of relative contributions of two broad domains of influence on living systems --genetics and environment. The study of monozygotic and dizygotic twins is one of the strongest available methods for decomposing the manifest variance in complex traits into genetic and environmental components. This proposal seeks support for a longitudinal extension of our current grant (AGO8861), "Origins of Variance in the Old-Old: Octogenarian Twins" (OCTO-Twin). The aim of OCTO-Twin is to explore the genetic and environmental bases of variability in age-related variables in the oldest- old. The proposed inclusion of two additional measurement occasions at two-year intervals will provide unique information on the relative contributions of genetic and environmental influences to change and continuity in advanced ages. The longitudinal data will also identify significant numbers of individuals giving evidence of cognitive impairment, which will shed light on the critical question of whether late-onset diagnosable dementias are distinct, categorical conditions or whether they represent the low end of a continuous distribution of cognitive function.

The focus of this project is on the analysis of quantitative trait loci (QTLs) associated with length of life, or longevity, as a phenotype of aging. Although previous findings suggest that the upper range of heritability of longevity is about 0.30, the findings from these studies may be confounded by viral pathogens and so indicate genetic predisposition to disease rather than longevity. In this study, a pathogen-free barrier environment will be provided for 480 animals (10 males and 10 females, each of 22 RI stains and 2 progenitor strains) throughout their lives. In order to follow future post-mortem examination, animals will be examined at regular intervals throughout the day to retrieve individuals within a short time of expiration in order to prevent or minimize autolysis. QTL analysis based on the RI strain means will relate longevity to the genotypic strain distribution patterns. An advantage of the fixed genotype of the RIs is that it will allow relationships to be adduced between the biomarker phenotypes measured in other RI samples to that of longevity, providing correlation between the marker variables and length of life.

The Animal Model Core will maintain breeding stock of C57/BL/6 and DBA/2 mice, of 22 BXD recombinant inbred (RI) strains derived initially from these strains, and of an F2 generation derived from the same strains. Mice will be produced from these stocks in sufficient number to meet the statistical requirements for cross-sectional biomarker assessment beginning at approximately 150, 450, or 750 days of age. An additional F2 group will be produced that will be maintained until natural death. All animals will be born, reared, and maintained in a specific-pathogen- free barrier facility. This Core will also serve as the common resource for the genotyping will also serve as the common resource for the genotyping of all of the subject animals for which genotyping is required, in order to provide the relevant data enabling the detection of quantitative trail loci (QTLs). The pathological analysis of all cross-sectional animals will also be the responsibility of this Core.

DESCRIPTION (provided by applicant): The strong negative influence of the aging-related loss of muscle mass, strength and quality, i.e., sarcopenia, on impaired motor function in old age has become increasingly evident. Further, sarcopenia, which varies considerably between individuals, is a major determinant of healthy aging. The loss of muscle function associated with sarcopenia promotes a) inactivity, b) falls, and c) loss of confidence, which in turn can lead to physical dependency and associated medical and socio-economic problems. However, to date, the muscle wasting associated with aging has not been correlated with relevant genetic markers. The long-term goal of this project is to identify the genes influencing the aging-related loss of muscle mass and altered qualitative properties of skeletal muscle. Morphological and biochemical techniques will be used to assess aging- and gender-specific changes in skeletal muscle quantity and quality in a panel of recombinant strains, their progenitor strains, and the derived F2. Genetic analyses will subsequently be performed in order to locate chromosomal regions containing the quantitative trait loci (QTLs) which effect skeletal muscle quantity and quality. In future studies, results from QTL analysis with specific changes in muscle quantity and the quality of the molecular motor protein myosin, will permit both the sequencing of genes and the identification of specific products of those genes involved in the specific aging-related quantitative and qualitative changes in skeletal muscle, i.e., sarcopenia.