International Mammalian Genome Society

The 15th International Mouse Genome Conference (2001)


POSTER 233 - IDENTIFICATION OF NOVEL CIRCADIAN RHYTHM AND ENTRAINMENT MUTATIONS IN MICE USING ENU MUTAGENESIS

Dr Patrick Nolan
MRC Mammalian Genetics Unit
Harwell, Didcot
Oxfordshire
OX11 0RD
UK

Co-Authors: Ooi L, Greenfield A, Bacon Y
Institutions: MRC Mammalian Genetics Unit

The mammalian circadian clock consists of input (entrainment), the endogenous pacemaker and output pathways. Forward genetic screens in flies and mice have identified components of pacemaker function, but events leading to output rhythms and mechanisms by which the endogenous clock is entrained to environmental light:dark cycles remain to be determined. We have adapted the forward genetics approach in an attempt to identify some of these components, using the mutagen N-ethyl-N-nitrosourea (ENU). Male BALB/c mice treated with ENU are mated with C3H females. Progeny are screened for abnormal phenotypes by maintenance in a 24hr light:dark cycle (LD12:12) for 7-10 days followed by 7-10days in constant darkness (DD). Mice are then exposed to a 15min light pulse (150lux) at circadian time 16 (CT16), and maintained in DD for a further 7-10 days. Wheel running-activity parameters are measured using Clocklab data collection and analysis packages. Parameters measured include activity status and duration in LD and DD, circadian period in DD and light induced phase shift in activity onset at CT16. To date, 5% of the F1 progeny screened have abnormal phenotypes. We have confirmed inheritance in 7 lines (1.4% of those screened). For example, one mutant has a multiple phenotype of an absent phase shift, short free-running period (22.5hrs) and anticipation onsets during the rest period. Mutant lines are currently being characterised further.


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