Alexander Bachmanov - US grants

Little is known about the genetics of oral chemosensory responses to salts and acids, which often have a complex flavor and multiple mechanism of transduction. Chemosensory qualities representing different salts and acids include saltiness, sourness, bitterness, 'umami' and irritation. Therefore, sensitivity to each of these qualities may affect behavioral responses to salts and acids. In this study, we propose to compare acceptance of several salts [sodium, potassium and ammonium chloride, monosodium glutamate (MSG), inosine 5'-monophosphate (IMP)], acids (hydrochloric, citric and L-glutamic) and irritants (capsaicin and menthol) in thirty inbred mouse strains using 48-h-two-bottle preference tests. Two aspects will be analyzed; strain variation in the responses to individual compounds, and interrelationships among the strain responses to different compounds. Based on the strain variation, hypotheses of single- or multi-gene inheritance for individual compounds will be tested, which will provide a background for subsequent chromosomal mapping and eventually positional cloning of these genes. Co-variation and relatedness between responses to different salts and acids and responses to reference stimuli representing salty, sour, irritant (assessed in this project), bitter and sweet (known from literature) qualities will be assessed. Based on these relationships, patterns of the chemosensory qualities for each compound will be identified. The following questions will be examined: a) the role of genetic differences in bitter and salty taste sensitivity in ingestive responses to salts with a complex flavor (KCl, CaCl2, NH4Cl); b) the existence of a common factor that affects responses to MSG, IMP and glutamic acid, which could be attributed to 'umami' taste sensation; c) the role of genetic differences in salty, sour and sweet taste sensitivity in ingestive responses to 'umami' testing compounds (MSG, IMP, glutamic acid); d) the role of genetic differences in sensitivity to chemosensory irritation in ingestive responses to salts and acids at higher concentrations that evoke irritation. This study will further understanding of chemosensory perception of salts and acids, and will set the stage for future studies directed to identifying genes involved in the responses to salts and acids.

DESCRIPTION (provided by applicant): Excess consumption of ethanol (alcohol) imposes serious problems for human health and has major negative economic impact. A predisposition towards alcohol overconsumption has a genetic component, and the discovery of the genes involved may lead to better control of alcohol consumption. Animal models can provide an efficient tool for discovering such genes. The long-term goal of our studies is to positionally clone genes affecting voluntary ethanol consumption by mice. Our laboratory has recently shown that a quantitative trait locus (QTL) associated with the sweet taste receptor gene, Tas1r3, influences alcohol consumption, suggesting that the taste of alcohol may be an important factor in regulation of intake. A preliminary genome scan indicates several other loci that influence intake of both ethanol and sweeteners. The aim of the current project is high-resolution genetic mapping of these loci. In Specific Aim 1, we will conduct QTL mapping using F2 hybrid and backcross generations originating from two mouse strains with high [C57BL/6ByJ (B6)] and low [129P3/J (129)] ethanol consumption. Dense genotyping and linkage analyses will detect loci responsible for the difference between the B6 and 129 mice in ethanol preference. In Specific Aim 2, these loci will be isolated using genotype-based selection of congenic strains originating from the B6 and 129 strains. In these congenic strains, the size and location of the donor chromosomal fragments will be defined, QTL positions will be determined with high resolution, and possible epistatic interactions among QTLs will be assessed. Detailed characterization of the behavioral responses to ethanol and their relationships with responses to sweeteners will help to elucidate possible mechanisms underlying QTL effects. In Specific Aim 3, based on QTL positions and possible mechanisms of action, and using the sequences of mouse and human genomes, candidate genes will be analyzed in genomic regions encompassing the QTLs. Through these three aims, we intend to isolate loci involved in ethanol preference, identify candidate genes for these loci in mice, and specify their human orthologs.

[unreadable] DESCRIPTION (provided by applicant): The ability to detect, and the innate liking for, sweet-tasting compounds presumably arose in animals to insure an adequate intake of calories and other nutrients. However, excess consumption of some sweet substances by humans has been implicated in a number of health disorders. The mechanisms by which sweeteners are detected and their intake regulated remain unclear although much progress has recently been made. In this project, primarily employing the inbred mouse as a model system, we use behavioral, physiological and molecular biological techniques to further our understanding of factors regulating sweetener perception and ingestion. Recently, we fine-mapped one genetic locus, Sac, to a small region of mouse distal chromosome 4 where we and other investigators have now identified a gene that codes for a sweet receptor. Yet a number of lines of evidence indicate that other genes that may specify additional receptors, transductive elements or central nervous system structures must be involved in determining sweet taste perception, preference and intake. During the project period, we will use a number of tools, some of them newly available, to locate and eventually identify novel genes important in regulating perception and intake of sweeteners. The results of this work will further understanding of sweetness perception, the sense of taste, and sensory biology.

[unreadable] DESCRIPTION (provided by applicant): Excess consumption of ethanol (alcohol) imposes serious problems for human health and has major negative economic impact worldwide, and in the US and Russia especially. A predisposition towards alcohol overconsumption has a genetic component, and the discovery of the genes involved may lead to better control of alcohol consumption. Animal models can provide an efficient tool for discovering such genes. The long-term goal of the parent project is to positionally clone genes affecting voluntary ethanol consumption in C57BL/6ByJ (B6) and 129P3/J (129) mice. This involves developing congenic mouse strains to isolate genetic loci affecting ethanol consumption, and characterizing their behavioral responses to ethanol. The goals of the FIRCA proposal are to optimize experimental procedures and to conduct a comprehensive analysis of chemosensory perception of ethanol in the two parental strains, B6 and 129. To achieve this, we will characterize several aspects of chemosensory responsiveness to ethanol: hedonics, sensitivity, and taste quality perception. We will also examine the contribution of the gustatory, olfactory and trigeminal sensory inputs to the chemosensory responses elicited by ethanol. The most informative tests will then be used to study congenic and consomic mice created in the parent project. These experiments will test the hypothesis that differences between B6 and 129 mice in voluntary ethanol consumption depend in part on differential chemosensory perception of ethanol. The proposed studies will also elucidate the chemosensory modalities responsible for this differential perception. This will help us to elucidate mechanisms underlying the effects of the genetic loci, which will be useful for identification of corresponding candidate genes. Gene identification in mice will be followed by examination of the role of their human orthologs in future studies. This project will set the stage for a long-term collaboration between scientists at the Monell Center and the Pavlov Institute, and will help to build research capabilities at the Pavlov Institute. This research will be done primarily in Russia at the Pavlov Institute of Physiology of the Russian Academy of Sciences in collaboration with Dr. Zolotarev as an extension of the NIH grant # R01 AA011028 of Dr. Bachmanov. Relevance to public health: The goal of this project is to discover genes affecting alcohol consumption, which will lead to better understanding and control of alcohol abuse. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): The sense of taste is the primary sensory system that determines whether a food or beverage will be ingested or rejected. Taste also influences food processing by the digestive system. Consequently, understanding the mechanisms underlying this sense is central to our ability to control intake of nutrients and to modulate the excesses of consumption that may underlie diseases such as obesity, hypertension and the metabolic syndrome. Our approach to advancing understanding of taste perception has been to use mouse models to identify genes involved in perception. We first identify natural variation in behavioral responses to taste stimuli in inbred mouse strains and then use this information to locate and identify the genes responsible for this variation. This approach, sometimes called positional cloning, is capable of detecting genes involved in all stages of taste perception, from reception in taste bud cells to brain functions responsible for behavioral responses to taste stimuli. In our previous studies, which were the first successful use of positional cloning to identify a functional gene involved in mammalian behavior, we identified and characterized a locus that codes for a sweet taste receptor. In the current comprehensive proposal, we describe studies designed to continue to identify genes involved in behavioral responses to sweet compounds. We also propose to expand our scope to include sour taste-related genes. This positional cloning approach will be complemented with behavioral analyses of physiological mechanisms underlying effects of individual genes. These studies, when completed, may provide important new avenues for interventions designed to modify excess food consumption. PUBLIC HEALTH RELEVANCE The sense of taste is the primary sensory system that determines whether a food or beverage will be ingested or rejected. Consequently, understanding the mechanisms underlying this sense is central to our ability to control intake of nutrients and to modulate the excesses of consumption that may underlie diseases such as obesity, hypertension and the metabolic syndrome. We study the taste mechanisms using mouse as a model organism. Our approach, sometimes called positional cloning, is based on chromosomal mapping of genes responsible for variation in taste responsiveness. Previously, we used this approach to identify a locus that codes for a sweet taste receptor. In the current comprehensive proposal, we describe studies designed to continue to identify genes involved in sweet taste. We also propose to expand our scope to include sour taste- related genes. These studies, when completed, may provide important new avenues for interventions designed to modify excess food consumption.

Many Monell scientists conduct studies with animals and need to characterize their chemosensory phenotypes. They will benefit from the Phenotyping Core in the following ways. 1) This Core will provide a centralized resource of equipment and supplies that will receive dedicated support and regular maintenance. The Core will also centralize labor-intensive tasks, such as making equipment for preference tests. Studies will be designed and/or conducted by Core personnel with specialized expertise in phenotyping techniques. This will be more efficient than replicating these techniques and personnel in individual laboratories. Regular use and service will ensure that equipment is always operational and available for experimentation. 2) The Core will provide access to equipment and facilities (e.g., LabMaster, surgical facility) that are not practical to maintain in individual laboratories. The Core will offer a range of services and experimental designs that are not available in individual laboratories. 3) Scientists with no experience in animal phenotyping will receive training and will have access to equipment and expertise of the Core. This will facilitate their research and help them to collect preliminary data for grant applications. 4) This Research Core will be an integral component of the Core Center. Interactions between the Phenotyping Core and other Research Cores will facilitate collaborative and interdisciplinary studies that are often not feasible for individual laboratories. For example, the Phenotyping and Histology Cores will be used to characterize genetically engineered mice generated from constructs produced using the Molecular Biology Core. In forward genetics studies, the same animals will be examined using the Phenotyping and Genotyping Cores, and the data obtained will be used for chromosomal mapping studies. We estimate that 9 of the 13 R01 grants in our Research Base will use services provided by this Core at moderate to extensive levels. We also expect that 11 current faculty research groups at Monell will use the services provided by this Core. As a result, the Phenotyping Core will improve the efficiency and quality of animal model studies at the Center, accelerate existing NIDCD-funded projects, and advance translation of the results into benefits for public health.

DESCRIPTION (provided by applicant): Taste is the primary sensory system that determines whether a food or beverage will be ingested or rejected. Taste also influences the digestion and metabolism of food. Consequently, understanding the mechanisms underlying this sense is central to our ability to control intake of nutrients and modulate the excesses of consumption that contribute to diseases such as obesity, hypertension and the metabolic syndrome. These diseases pose serious problems for human health and have major negative economic impact worldwide, including in the United States and Russia. The long-term goal of the parent project is to positionally clone genes involved in taste and ingestive behavior. This involves developing genetically defined mouse models for genetic mapping and mechanistic studies. This FIRCA proposal will expand these studies to examine the role of sweet taste genes in postingestive endocrine responses to sweeteners. The proposed studies will aid in gene identification in mice, which will reveal the function of their human orthologs and their role in taste-related human behavior. This project will support collaboration between scientists at the Monell Center and the Pavlov Institute and will help to build research capabilities at the Pavlov Institute. The propose research will be done primarily in Russia at the Pavlov Institute of Physiology of the Russian Academy of Sciences in collaboration with Dr. Zolotarev as an extension of NIH grant R01DC000882 (09/19/2008 - 08/31/2013). PHS 398/2590 (Rev. 09/04, Reissued 4/2006) Page Continuation Format Page