An Integrated Software System for EEG/EMG-Based Forward Genetic Screen of Sleep/Wake Abnormalities in ENU-Mutagenized Mice

The executive neural circuitry and chemistry for sleep/wake switching mechanisms have been increasingly revealed in recent years. However, the very fundamental mechanism of sleep regulation remains a mystery, for example, with the question of what is the neural substrate for “sleepiness” still unanswered. My project tackles this challenging but highly interesting question through forward genetics in mice. We have initiated a dominant screen of ENU-mutagenized mice, in which a comprehensive set of sleep parameters is measured via EEG/EMG-based somnography analysis in basal light/dark periods as well as in the recovery period following forced sleep deprivation. A major obstacle for such large-scale genetic studies of sleep/wakefulness in mice has been the low throughput of EEG/EMG-based sleep analysis. In order to break this bottleneck, I have developed an automated sleep-scoring program, which adapts itself to the EEG/EMG variability between and within individual mice through a simple pattern-matching algorithm. This new software, combined with highly streamlined surgical procedures as well as a custom database software for administering large-scale experimental logistics, have enabled us to sustain a throughput of up to 112 mice fully sleep-scored per week. Importantly, quantitative parameters of sleep behavior provide relative standard deviations as small as 5-10% in isogenic cohorts of mice, enabling a robust screen. We have so far screened ~7,000 ENU-mutagenized mice, and established >10 heritable phenodeviant pedigrees, including one exhibiting markedly increased NREM sleep amounts, and one with reduced episode durations and amounts of REM sleep. The causal mutations for these two pedigrees have been positionally cloned through the whole-exome sequencing in combination with a classical linkage analysis.