fruitless (gene)
The fruitless gene (fru) is a Drosophila melanogaster gene that encodes several variants of a putative transcription factor protein. Normal fruitless function is required for proper development of several anatomical structures necessary for courtship, including motor neurons which innervate muscles needed for fly sexual behaviors.[1] The gene does not have an obvious mammallian homolog, but appears to function in sex determination in species as distant as the mosquito Anopheles gambiae.[2] fruitless serves as an example of how a gene or groups of genes may regulate the development and/or function of neurons involved in innate behavior. Research on fruitless has received attention in the popular press, since it provokes discussion on genetics of human sexual orientation,[3][4] and behaviors such as gender-specific aggression.[5]
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[edit] Function
Male flies with mutations in the fruitless gene display altered sexual behavior. Fruitfly courtship, which involves a complex male-initiated ritual, may be disrupted in a number of ways by mutated fru alleles; fru is necessary for every step in the ritual. Some alleles prevent courting entirely, while others disrupt individual components. Notably, some loss-of-function alleles change or remove sexual preference.[1]
Although many genes are known to be involved in male courtship behavior, the fruitless gene has been considered noteworthy because it exhibits sex-specific alternative splicing. When females produce the male-spliced gene product, they behave as males. Males that do not produce the male-specific product do not court females and are infertile.[1]
fruitless has at least four promoters, each encoding proteins containing both a BTB (Broad complex/tramtrack/bric-a-brac) domain and a zinc finger motif. Alternative splicing occurs at both the 5' and 3' ends, and there are several variants (other than the male- and female-specific splicing patterns).[1] The fruitless gene locus also controls the expression of hundreds of other genes,[6] any subset of which may actually regulate behavior.
[edit] Name
Early work refers to the gene as fruity, an apparent pun on both the common name of D. melanogaster, the fruit fly, as well as a slang word for homosexual. As social attitudes towards homosexuality changed, fruity came to be regarded as offensive, or at best, not politically correct. Thus, the gene was re-dubbed fruitless, alluding to the lack of offspring produced by flies with the mutation.[7] However, despite the original name and a continuing history of misleading inferences by the popular media, fruitless mutants primarily show defects in male-female courtship, though certain mutants cause male-male or female-female courtship.
[edit] References
- ^ a b c d Demir E and Dickson BJ (2005). "fruitless splicing specifies male courtship behavior in Drosophila." Cell 121: 785-794.
- ^ Gailey, D.A. et al., 2005 Functional conservation of the fruitless male sex-determination gene across 250 myr of insect evolution Mol. Biol. Evol. 23(3): 633-643.
- ^ The Atlantic Homosexuality and Biology, The Genetic Quest June 1997, Chandler Burr
- ^ The New York Times Mating Game of Fruit Fly Is Traced to a Single Gene December 13, 1996, Nicholas Wade
- ^ The Guardian Flies reveal gene that makes girls fight like boys November 20, 2006, Ian Sample
- ^ Goldman and Arbeitman (2007) Genomic and functional studies of Drosophila sex hierarchy regulated gene expression in adult head and nervous system tissues PloS Genetics 3(11):e216
- ^ Gailey DA and Hall JC (1989). "Behavior and cytogenetics of fruitless in Drosophila melanogaster: different courtship defects caused by separate, closely linked lesions." Genetics 121: 773-785.
