| 研究実績の概要 |
Mice mainly rely on a very sensitive olfactory system to detect predators. Thus, we developed a novel predator odor-based “innate fear” assay that is suitable for high throughput mouse screening. In this 20 minute assay, TMT (2,3,5-trimethyl-3-thiazoline), a component of fox feces, induces robust (innate fear) freezing response in mice. Using “Freezeframe” software to quantify freezing as a readout of fear, wild-type mice freeze 0-20% without odor and 60-95% time in response to TMT. This robust assay has a tight relative standard deviation (RSD) of ~10%, making it feasible to screen for “fearless” mutants with <47% freezing rate [i.e. >3 SD below normal mean of 77%].
To date, we screened 1,596 F1 (c57 B6J/B6N) ENU mutant males and identified ten phenodeviants that showed significantly diminished freezing rate. We established two dominant mutant pedigrees: whereas one showed the “fearless” phenotype, the other mutant called “Popcorn” exhibited an unusual phenotype of jumping up to ~2,500 times/20 minutes when exposed to the predator odor. By single polynucleotide polymorphism (SNP) linkage analysis, we mapped the Popcorn mutation to a 70Mb critical interval on Chromosome 1 (p<10^-15). Exome sequencing of wild-type and mutant mice revealed a candidate causal mutation in a novel gene. We propose that Popcorn is a putative “fearful” mutant, which may be genetically predisposed to fear/anxiety disorders in a manner similar to the “onco(gene) mice” that develop cancer with age.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
We worked very diligently and have excellent help from outstanding collaborators:
1) We collaborate with Drs. Ko and Reiko Kobayakawa, whom are pioneers in the innate fear research, to establish the predator odor-induced innate fear assay.
2) We used the ENU mutant mice generated by Dr. Masashi Yanagisawa for his sleep screen. His extensive experience in forward genetics help expedite our screen.
3) We collaborated with Dr. Shigeharu Wakana, who has many years of experience in genetic mapping, to map the Popcorn mutation.
4) We performed exome sequencing in the Next Generation Sequencing (NGS) core at UT Southwestern Medical Center, USA to identify the Popcorn mutation.
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