A HIGH-THROUGHPUT ASSAY FOR GENETIC STUDIES OF SLEEP

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Arousal states are a fundamental aspect of global nervous system function; yet, measures of sleep and wake are rarely performed in genetically altered mice due to the difficulty of EEG analysis. We propose to develop a high-throughput alternative to EEG recordings in mice that will greatly facilitate the measurement of sleep and wake. Our system utilizes a simple piezoelectric transducer comprising the flexible floor upon which the animal rests. Distension of the floor by respiratory or other movements produces electrical signals. During slow wave sleep, rhythmic breathing results in a consistent, regular pattern of electical signals. REM sleep produces a less consistent signal due to more irregular breathing, while wake produces a dramatically irregular pattern caused by a variety of movements. Therefore, all three vigilance states can be accurately determined. We have already validated this system in young rats. Since no surgery is required and the signal patterns are simpler than those produced by EEG, the technology to perform high-throughput phenotyping of arousal states will be relatively easy. An immediate test and use of our system will be to investigate genes that underlie sleep parameters. Twin studies, adoption studies, and the analysis of inbred strains of mice have demonstrated that variation in sleep related traits are largely determined by genotype. Specifically, we propose to validate our system in common inbred strains of mice by comparing our piezo recordings with traditional EEG recordings. Based on our prior EEG data, we expect to confirm large sleep differences between AKR/J and DBA/2J inbred strains. This will be followed by examination of AKD2F1 hybrids and AKXD recominant inbred lines. QTL analysis of these data should identify candidate loci that underlie the variability of sleep traits in these two strains. With this high throughput system we will also be able to examine large numbers of progeny from appropriate genetic crosses between these or other strains to confirm putative QTLs. This system also makes large scale screening of mutagenized mice far more feasible, and we will begin to examine such mice in the proposed study. In general, the project we propose will provide an important index of nervous system function, and specifically will allow genetic approaches towards understanding sleep and sleep disorders that would not be possible with existing technology.