Background: During a search for obesity candidate genes in a small region of the mouse genome, we noticed that many genes when knocked out influence body weight. To determine whether this was a general feature of gene knockout or a chance occurrence, we surveyed the Jackson Laboratory Mouse Genome Database for knockout mouse strains and their phenotypes. Body weights were not available for all strains so we also obtained body weight information by contacting a random sample of investigators responsible for a knockout strain.

TORDOFF, M.G., L.K. ALARCON AND M.P. LAWLER. Preferences of 14 rat strains for 17 taste compounds. PHYSIOL BEHAV 00(0) 000-000, 2008.--Two-bottle choice tests were used to assess the taste preferences of 8 male and 8 female rats from 3 outbred strains (SD, LE, WI) and 11 inbred strains (BN, BUF, COP, DA, Dahl-S, F344, FHH, LEW, Noble, PVG, SHR). Each rat received a series of 109 48-h tests with a choice between water and a "taste solution". Four to eight concentrations of the following compounds were tested: NaCl, CaCl 2 , NH 4 Cl, KCl, MgCl 2 , saccharin, sucrose, ethanol, HCl, citric acid, quinine hydrochloride (QHCl), caffeine, denatonium, monosodium glutamate (MSG), Polycose, corn oil, and capsaicin. Strain differences (p<0.001) were observed in preferences for at least one concentration of all compounds tested except denatonium (p = 0.0015). There were also strain differences in the following ancillary measures: fungiform papillae number, water intake, food intake, and body weight. There were sex differences in food intake and body weight but no concerted sex differences in any of the other measures, including preferences for any taste solution. This comprehensive source of information can be used to guide the choice of appropriate rat strains and taste solution concentrations for future genetic studies. Keywordssweet; sour; salty; bitter; umami; calcium; oil; trigeminal; strain survey Rats have been used in many experiments to understand the mechanisms underlying the selection of nutrients and taste compounds. The large majority of these studies have been focused on physiological and behavioral controls of ingestion but rarely on genetic ones. The genetic approach has been spearheaded by work in mice, and has led to several recent important advances, such as the identification of sweet, sour, bitter and umami receptors [reviews (4,10,76)]. One reason for this is that genetic and molecular tools are available for the mouse but not well-developed for the rat, although this is changing [e.g., (2,54,55,62,74)]. Another is that there are few appropriate taste phenotype data available for the rat. Genetic analyses in mice generally begin with the discovery of phenotypic differences among inbred strains but most studies aimed at understanding rat taste preferences have used outbred strains. There are a few comparisons of different rat strain preferences for sodium and ethanol (see below) but very limited data involving other taste compounds.The purpose of this study was to provide comprehensive information about the taste preferences of rats that could be used as the basis for subsequent genetic analyses. To this end, we used Address for all correspondence: Michael G. Tordoff, Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA 19104, Phone: (267)-519-4805, Fax: (267)-519-4738, e-mail: tordoff@monell.org. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscri...

Although hundreds if not thousands of quantitative trait loci (QTL) have been described for a wide variety of complex traits, only a very small number of these QTLs have been reduced to quantitative trait genes (QTGs) and quantitative trait nucleotides (QTNs). A strategy, Multiple Cross Mapping (MCM), is described for detecting QTGs and QTNs that is based on leveraging the information contained within the haplotype structure of the mouse genome. As described in the current report, the strategy utilizes the six F(2) intercrosses that can be formed from the C57BL/6J (B6), DBA/2J (D2), BALB/cJ (C), and LP/J (LP) inbred mouse strains. Focusing on the phenotype of basal locomotor activity, it was found that in all three B6 intercrosses, a QTL was detected on distal Chromosome (Chr) 1; no QTL was detected in the other three intercrosses, and thus, it was assumed that at the QTL, the C, D2, and LP strains had functionally identical alleles. These intercross data were used to form a simple algorithm for interrogating microsatellite, single nucleotide polymorphism (SNP), brain gene expression, and sequence databases. The results obtained point to Kcnj9 (which has a markedly lower expression in the B6 strain) as being the likely QTG. Further, it is suggested that the lower expression in the B6 strain results from a polymorphism in the 5'-UTR that disrupts the binding of at least three transcription factors. Overall, the method described should be widely applicable to the analysis of QTLs.

Although improvements are needed in the expression databases, the integration of QTL and gene expression analyses seems to have potential as a high-throughput strategy for moving from QTL to QTG.

Clay consumption can occur during illness but there has been little work to understand why. To investigate whether consuming clay confers an advantage to the sick animal, we compared the recovery from illness of adult male rats with or without access to kaolin. Illness was induced by injection of 6 mg/kg, ip, cisplatin, a toxic chemotherapy agent, and recovery was assessed by changes in daily food intake, water intake, and body weight. Relative to saline-injected controls, cisplatininjected rats reduced food and water intake and lost weight. However, those with access to kaolin ate more food and lost less body weight than did those without access to kaolin. Thus, clay consumption appeared beneficial in that it either protected the rats from illness or enhanced recovery and might prove useful as an adjunct therapy for other animals, including humans, experiencing visceral malaise.