1996 — 2009 |
Warden, Craig H |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Rapid Isolation of Diet-Responsive Obesity Genes @ University of California Davis
Diet-induced obesity (DIO) is associated with increased incidences of atherosclerosis, diabetes, and hypertension. While identification of genes underlying any complex disease is difficult in humans, these problems will be increased for DIO, where it will be hard to distinguish genes that cause spontaneous obesity from those that cause DIO. In contrast, the tools available for analysis of complex disease in mice, combined with the relative ease of controlling diets, suggest that identification and isolation of genes causing DIO will be possible with mouse models. The long range goal of this project is to isolate and identify genes causing DIO. This proposal is distinguished by its use of existing congenic mouse strains to enable rapid detection and isolation of DIO genes. Congenic mouse strains are derived from inbred mouse strains by a regimen of crossing and selection They are identical to a background strain except for a small chromosomal region derived from a donor strain. The use of existing congenic strains as a rapid approach to positional cloning is generic and the impact on the search for novel genes contributing to other complex diseases could be great. The first objective is to examine the segregation of genes underling DIO in F2 crosses of congenic and background strains. We have identified five strains of congenic mice that exhibit significantly different body lipid percent or adiposity index (sum of fat pad weights divided by carcass weight) than their background strains when both are placed on a high-fat, high-sucrose diet. Each of these strains will be tested for suitability as a resource for positional cloning by examining 100 F2 mice derived from crosses of the congenic and background strains. Identification of two segregating groups, corresponding to congenic and background strain genotypes, will be made by examination of individual phenotypes or combinations of phenotypes. The second objective is to initiate positional cloning of genes underlying diet-induced obesity. The one cross that includes a novel obesity gene and that exhibits the most distinct segregation of obesity traits into two groups will be expanded to include 1000 F2 mice. These mice will be typed for all available PCR markers near the locus. When we identify markers within 1 cM of the gene underlying DIO, then we will isolate linked genomic clones (YAC, BAC, P1 or PAC clones). A contig will be constructed that includes the DIO gene.
|
1 |
1998 — 2002 |
Warden, Craig H |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Genes Causing Spontaneous Obesity @ University of California Davis
The long-term goal of this research is to investigate the mechanisms of spontaneous obesity in mice. Previous work has identified 4 chromosomal regions (mouse chr. 6,7,12,and 15) or loci (QTLs) that contribute to obesity in spontaneously obese BSB mice. BSB mice were produced by a backcross of (Mus spretus x C57BL/6J) F1 x B6. Preliminary data on an available congenic mouse strains confirm that the locus on chr. 7 affects adiposity. The objective of this present proposal is to identify the genes underlying these obesity loci. Congenic mouse strains carrying the spretus chromosomal regions as donor DNA on the B6 background will be created. As co-incident QTLs for obesity, plasma cholesterol and hepatic lipase (HL) activity on mouse chr. 7 were found, the already constructed B6 HL knockout will used to test the hypothesis that alterations of HL activity determine these cholesterol and/obesity loci. BSB backcrosses with the HL KO B6 mouse will yield animals both homozygous and heterozygous for the HL knock-out. QTLs at chromosome 7; will be compared and contrasted in these two groups. The mouse chr. 6,7, and 1 loci include within their 90 percent confidence intervals, respectively, the obese, tubby, and uncoupling protein 2-genes. Molecular and biochemical studies of these candidate genes will be performed to test whether differences are likely to explain the observed effect on the trait. If there are differences in the coding portion of the spretus and B6 leptin, then the biological consequence of the differences will be tested. The chromosome 6 locus was linked to just one of the four fat pads measured in BSB mice. Leptin mRNA levels in the four fat pads will be determined to examine their correlations with plasma leptin and fat pad sizes. They have already found that spretus and B6 UCP2 differ for 2 amino acids, so uncoupling activity of UCP2 from these strains will be examined.
|
1 |
2006 — 2010 |
Warden, Craig H |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Positional Cloning of Obesity Genes From Congenic Mice @ University of California At Davis
Positional cloning - the identification of obesity genes by co-incidence of mapped obesity traits andgenes to a specific chromosomal region, provides a powerful method to discover novel obesity genes and to make novel insights into the mechanisms causing obesity. Mice have been used for the first identification of more human obesity genes than any other model. The goal of this proposal is to use positional cloning methods to identify obesity genes in mouse congenic strains. Congenic mouse strains are identical to a background strain except for a chromosomal region from a donor strain. Phenotype differences between congenic and background are due to alleles of the donor strain with functional effects different from the background strain. The two laboratories contributing to this proposal have identified several mouse congenic strains with statistically significant phenotypes for obesity on mouse chromosome 2 in a region homologous to human chromosome 20, where several obesity quantitative trait loci have been mapped. Our general hypothesis is that one or more genes or transcripts in the congenic donor regions influences obesity. Our specific working hypothesis is that genes/transcripts underlying obesity can be identified for most congenics. We propose seven Specific Aims. We will: determine diet, sex and age effects on obesity in the founding congenics (Aim 1), identify minimal chromosomal loci containing obesity genes by breeding congenics with ever smaller donor regions that retain obesity phenotypes (Aim 2), find differentially expressed donor region genes with whole genome microarrays using RNAfrom eight obesity tissues (Aim 3), sequence selected donor region genes (Aim 4), determine cis or trans control of mRNA levels for differentially expressed genes (Aim 5), produce transgenic mice overexpressing ten candidate genes prioritized by the results of Aims3-5 (Aim 6) and identify microRNAs or other transcribed non-coding genes that may influence obesity (Aim 7). The long term outcome is that we will identify at least one novel and strong and plausible obesity gene.
|
1 |