Genetics of sweet taste preferences*
Alexander A. Bachmanov1, Danielle R. Reed1, Xia
Li1, and Gary K. Beauchamp1,2,**
1Monell Chemical Senses Center, 3500 Market Street,
Philadelphia, PA 19104, USA; 2Department of Psychology and School of
Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104,
USA
Abstract: Inbred mouse strains display marked differences
in avidity for sweet solutions due in part to genetic differences among
strains. Using several techniques, we have located a number of regions
throughout the genome that influence sweetener acceptance. One prominent
locus regulating differences in sweetener preferences among mouse strains
is the saccharin preference (Sac) locus on distal chromosome
4. Afferent responses of gustatory nerves to sweeteners also vary as
a function of allelic differences in the Sac locus, suggesting that
this gene may encode a sweet taste receptor. Using a positional cloning
approach, we identified a gene (Tas1r3) encoding the third member
of the T1R family of putative taste receptors, T1R3. Introgression by
serial back-crossing of a chromosomal fragment containing the Tas1r3
allele from the high sweetener-preferring strain onto the genetic background
of the low sweetener-preferring strain rescued its low sweetener-preference
phenotype. Tas1r3 has two common haplotypes, one found in mouse
strains with elevated sweetener preference and the other in strains
relatively indifferent to sweeteners. This study, in conjunction with
complimentary recent studies from other laboratories, provides compelling
evidence that Tas1r3 is equivalent to the Sac locus and that
the T1R3 receptor (when co-expressed with taste receptor T1R2) responds
to sweeteners. However, other sweetness receptors may remain to be identified.
* A special topic issue on the science
of sweeteners.
** Corresponding author.
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