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This section provides information about a circadian-period mutant, the tau-mutant hamster.
The Critter
Tau-mutant hamsters are golden hamsters (Mesocricetus auratus) bearing the tau mutation. The tau mutation was identified in Professor Michael Menaker's laboratory (which was located at the University of Oregon at the time) in 1988. The first publication on this mutation was:
Ralph, M. R. and Menaker, M. (1989). A mutation of the circadian system in golden hamsters. Science 241: 1125-1127. PubMed

Large picture of hamster
In external appearance, the tau- mutant hamster is identical to a regular golden hamster.

Also like regular golden hamsters, tau mutants give birth to a dozen pups per litter and have a life span of approximately two years.
The tau mutation was the first single-gene mutation that specifically affects the circadian system to be identified in a mammalian species. The mutant allele drastically reduces the period of circadian rhythms. Homozygous animals have a period of approximately 20 h, as compared to a period of 24 h in wild type hamsters (heterozygotes have a period of 22 h). The difference between phenotypes is clearly seen in the following actograms (activity pattern of a wild type shown on the left and of a homozygous mutant on the right):

Originally restricted to Dr. Menaker's laboratory, tau mutant hamsters are now bred in several labs in the United States, Canada, Europe, and elsewhere.

Dr. Refinetti has been involved in research with tau-mutant hamsters since 1990.

Several single-gene mutations with effects on the circadian system had previously been found in invertebrates such as the fruit fly (Drosophila melanogaster) and bread mold (Neurospora crassa). Soon after the discovery of the tau mutation in the hamster, Dr. Joe Takahashi, at Northwestern University, produced the clock mutation in mice.

Years later, a group of researchers, including Menaker and Takahashi, identified tau as an allele of the gene casein kinase I epsilon in the golden hamster. PubMed

Prof. Andrew Loudon, at the University of Manchester, later induced the tau mutation in mice. PubMed

Our Research
Dr. Refinetti's first contact with tau-mutant hamsters was in the Menaker lab at the University of Virginia in 1990. Because the tau mutation had only been shown to affect the period of the activity rhythm, it was important to know whether it affected also the body temperature rhythm. His studies revealed that the mutation did affect the temperature rhythm, and it did so in a very elegant manner: by proportionally shortening the rhythm without affecting its shape or its mean level. This reinforced the assumption that the effect of the gene was general to the circadian pacemaker rather than restricted to a particular effector mechanism. Many other studies followed, particularly on the effects of circadian period on energy expenditure.

The lab's colony of mutants was terminated in 2014 when Dr. Refinetti moved from South Carolina to Idaho.
The following is a list of publications by Dr. Refinetti that involved tau-mutant hamsters:

REFINETTI, R. (2014). Relationship between circadian period and body size in the tau-mutant golden hamster. Canadian Journal of Physiology and Pharmacology 92: 27-33.

REFINETTI, R. (2007). Absence of circadian and photoperiodic conservation of energy expenditure in three rodent species. Journal of Comparative Physiology B 177: 309-318. PDF

REFINETTI, R. (1998). Influence of early environment on the circadian period of the tau- mutant hamster. Behavior Genetics 28: 153-158. PDF

REFINETTI, R. and MENAKER, M. (1997). Is energy expenditure in the hamster primarily under homeostatic or circadian control? Journal of Physiology 501: 449-453. PDF

REFINETTI, R. (1996). Ultradian rhythms of body temperature and locomotor activity in wild- type and tau-mutant hamsters. Animal Biology 5: 111-115.

MENAKER, M. and REFINETTI, R. (1993). The tau mutation in golden hamsters. In Young, M. (Ed.) Molecular Genetics of Biological Rhythms. New York: Marcel Dekker, pp. 255-270.

REFINETTI, R. and MENAKER, M. (1993). Independence of heart rate and circadian period in the golden hamster. American Journal of Physiology 264: R235-R238. PubMed

REFINETTI, R. and MENAKER, M. (1992). Evidence for separate control of estrous and circadian periodicity in the golden hamster. Behavioral and Neural Biology 58: 27-36. PubMed

REFINETTI, R. and MENAKER, M. (1992). The circadian rhythm of body temperature of normal and tau-mutant golden hamsters. Journal of Thermal Biology 17: 129-133. PDF
Reprints (PDF files) of selected articles are available through the links above. To avoid violation of publisher's copyrights, you must request a reprint before you gain access to it. To do so, please click on the request button.

For information about other animal species used in the lab, check the Animal Species section of this web site. You may also want to visit the Circadian Rhythms section.

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