Use of chromosomally mapped and identified mouse brain proteins for behavioral genetic analysis of alcoholism

Out of the bottleneck: the Diversity Outcross and Collaborative Cross mouse populations in behavioral genetics research

The historical origins of classical laboratory mouse strains have led to a relatively limited range of genetic and phenotypic variation, particularly for the study of behavior. Many recent efforts have resulted in improved diversity and precision of mouse genetic resources for behavioral research, including the Collaborative Cross and Diversity Outcross population. These two populations, derived from an eight way cross of common and wild-derived strains, have high precision and allelic diversity. Behavioral variation in the population is expanded, both qualitatively and quantitatively. Variation that had once been canalized among the various inbred lines has been made amenable to genetic dissection. The genetic attributes of these complementary populations, along with advances in genetic and genomic technologies, makes a systems genetic analyses of behavior more readily tractable, enabling discovery of a greater range of neurobiological phenomena underlying behavioral variation.

Alcoholism and the 'new genetics'

Molecular biology is transforming our view of psychiatry. For the first time methods are becoming available to detect directly the genetic abnormalities leading to psychiatric illness. This article examines the ways in which the new marker technology might bridge the gap between classical genetic knowledge of alcoholism and the precise identification and localization of specific genes implicated in its aetiology.

Voluntary consumption of ethanol in WSP, WSC and WSR selectively bred mouse lines

The genetic correlation between voluntary consumption of ethanol solutions and severity of withdrawal seizures after chronic ethanol exposure was assessed using the selectively bred Withdrawal Seizure Prone (WSP) and Resistant (WSR) mouse lines. WSP mice have at least ten-fold more severe withdrawal than WSR mice after equal chronic ethanol exposure, and withdrawal in a nonselected control line (WSC) is intermediate to withdrawal in the WSP and WSR lines. In the first experiment, mice from the WSP, WSC and WSR lines were offered a choice between 2.2, 4.6 and 10.0% ethanol solutions and water in three consecutive eight-day sessions. WSR mice consumed more ethanol than WSP mice, and WSC mice were intermediate. In a second experiment, WSP and WSR mice were offered ethanol solutions in concentrations that were adjusted up or down every two days depending upon the amount of ethanol consumed. WSP and WSR mice displayed very different patterns of drinking, with WSP mice drinking more ethanol in early stages of the experiment, and WSR mice drinking more ethanol later. Results of these experiments suggest that some genes influencing severity of withdrawal from ethanol also influence voluntary ethanol drinking.

Molecular markers for linkage of genetic loci contributing to alcoholism

Specific locus and random locus linkage approaches to identify markers for genes whose allelic variants predispose to alcoholism or for genes controlling relevant physiological and behavioral phenotypes are discussed. Sib-pair analysis is superior for the direct analysis of complex genetic traits such as alcoholism, but classic family analysis will be useful for transmission and linkage analysis for marker traits whose genetics is less complex. In mice, a large number of inbred strains, recombinant inbred and congenic strains, and specifically selected outbred strains are available. In the human, an intriguing linkage result has emerged between a brain protein variant and alcoholism accompanied by suicide. In the mouse, preliminary linkages have been established to loci controlling ethanol preference and also activation after ethanol. Large panels of random DNA and protein genetic probes and of probes for specific loci will in the future increase the probability of establishing linkage in both species.

Mapping of a putative genetic locus determining ethanol intake in the mouse

In the mouse, there is evidence that a single genetic locus is a major determinant of differences in ethanol intake between some preferring and non-preferring inbred strains. In this report, we present evidence from two independent experiments indicating that this locus maps to chromosome 1 and that its expressed product is the abundant protein LTW-4 (a 28 kDa, pI 5.6 protein expressed in brain, liver and kidney). The genetic association was found using a panel of 14 polypeptides of mouse brain which were visualized by two-dimensional electrophoresis and which exhibit genetic variation in isoelectric point. Fifteen BXD recombinant inbred strains and the two parental strains were typed for these loci and also tested for ethanol acceptance. Strains exhibiting the basic allele showed significantly higher ethanol acceptance. When 19 distantly related inbred mouse strains were tested for ethanol acceptance and typed for LTW-4, it was again found that strains exhibiting the basic allele showed significantly higher ethanol acceptance.

Protein polymorphisms detected by two-dimensional electrophoresis: an analysis of overall informativeness of a panel of linkage markers

Forty-two independent polymorphic loci are detectable by two-dimensional electrophoresis (2DE) of four peripherally accessible human tissues. Fifteen have been chromosomally mapped and, taken together, these constitute a useful panel of markers for genetic linkage studies in humans. An analysis of the overall informativeness for linkage of this panel of markers is presented, taking into account the effect of varying the number of families or matings studies. Use of 2DE polymorphic markers for linkage of genetically determined behaviour traits in humans and mice is reviewed.