Developing a Rapid Screen to Detect Olfactory Mutants

P.I.:  Steven L. Youngentob, Ph.D.

Location:

Department of Neuroscience and Physiology
SUNY Upstate Medical University
Institute for Human Performance
505 Irving Ave. Syracuse, NY 13210

Description:  The mouse has become an increasingly important tool in the study of olfaction. At present the mouse is the most developed mammalian system for genetic analysis and a number of exciting insights into the biology of olfactory system function and behavior have come from the specific experimental manipulation of well-characterized genes in this species. The number of uncharacterized genes, however, is still rather large and an alternate strategy that has been proposed is to identify them based upon the phenotypes that they confer. That is, to systematically mutagenize mice and then screen the progeny of these animals for individuals with "interesting" altered characteristics. Unfortunately, the rigorous and time consuming methods usually associated with psychophysical evaluations of the olfactory system are not amenable to the needs of a high-throughput screening environment that would be created by the random mutagenesis approach. Instead, the screening goals require a rapid, yet sensitive and operationally defined method for the initial detection of abnormal phenotypes, which, once identified, could be studied behaviorally, in detail, with psychophysical methods. At present, we are developing a behavioral assay that can be systematically and easily implemented in order to screen large numbers of mutagenized mice in a high-throughput environment. Following successful protocol development and validation, we plan to acquire reference screening data on different standard inbred mouse strains. The purpose of this final phase of the development process will be to provide reference data and operational screening procedures for the future evaluation of mutagenized mice, as well as the possible characterization of existing targeted mouse mutations.

     For the behavioral assay, our approach is directed toward developing a precision screening technique that utilizes the monitoring of stimulus-induced sniffing (i.e., respiratory changes) in response to odors, as a method for the rapid quantification of odorant sensitivity. The foundation for this approach can be found both in our own previous work and the work of others. To accomplish this, we are combining specific elements of the rigorous psychophysical methodologies and techniques that are standard in our laboratory with elements from other simpler techniques that have been used in olfactory behavioral research. Specifically, we are: (1) applying our experience in measuring an animal's sniffing behavior (i.e., respiratory measures) in response to the presentation of different concentrations of an odorant; (2) applying taste potentiated odor aversion conditioning techniques to improve stimulus control over the reflexive or unconditioned sniffing response to the presentation of odorant, and thereby increase the sensitivity of the measure; (3) applying computer-controlled olfactometry to provide precise control over odorant stimulus generation and delivery; and (4) applying our automated tracking paradigm to rapidly acquire a threshold measure of stimulus-induced sniffing in a single testing session.

Contact:  Individuals interested in the development of the above rapid screening technique or more precise psychophysical evaluations of olfactory system function (e.g., odorant quality perception, discrimination and sensitivity) may call or e-mail Steven L. Youngentob, Ph.D. (315-464-7758: youngens@mail.upstate.edu).

Selected References:

1. Alberts, J.R. and May, B. (1980) Development of nasal respiration and sniffing in the rat. Physiol. Behav. 24:957-963.

2. Alberts, J.R. and May, B. (1980) Ontogeny of Olfaction: Development of the rat's sensitivity to urine and amyl acetate. Physiol. Behav. 24:965-970.

3. Pourtier, L., and Sicard, G. (1990) Comparison of the sensitivity of C57BL/6J and AKR/J mice to airborne molecules of isovaleric acid and amyl acetate. Behav. Genet. 20:499-509.

4. Youngentob, S.L., Mozell, M.M., Sheehe, P.R. and Hornung, D.E. (1987) Quantitative analysis of sniffing strategies in rats performing learned odor detection tasks. Physiol. Behav. 41:59-69.

5. Youngentob, S.L., Markert, L.M., Mozell, M.M., and Hornung, D.E. (1990) A method for establishing a five odorant identification confusion matrix in rats. Physiol. Behav. 47:1053-1059.

6. Youngentob, S.L., Schwob, J.E., Sheehe, P.R., and Youngentob, L.M. (1997) Odorant threshold following methyl bromide-induced lesions of the olfactory epithelium. Physiol. Behav. 62:1241-1252.

7. Youngentob, S.L. and Margolis, F.L. (1999) OMP gene deletion causes an elevation in behavioral threshold sensitivity. NeuroReport 10:15-19.