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. The gene does not have an obvious mamallian homolog, but appears to function in sex determination in species as distant as the mosquito Anopheles gambiae [ Gailey, D.A. et al., 2005 [http://mbe.oxfordjournals.org/cgi/content/full/23/3/633 Functional conservation of the fruitless male sex-determination gene across 250 myr of insect evolution] "Mol. Biol. Evol. 23(3)": 633-643.] . "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, [The Atlantic [http://www.theatlantic.com/doc/199706/homosexuality-biology/4 Homosexuality and Biology, The Genetic Quest] June 1997, Chandler Burr] [The New York Times [http://query.nytimes.com/gst/fullpage.html?res=9B02E1D9173EF930A25751C1A960958260 Mating Game of Fruit Fly Is Traced to a Single Gene] December 13, 1996, Nicholas Wade] and behaviors such as gender-specific aggression. [The Guardian [http://www.guardian.co.uk/uk_news/story/0,,1952198,00.html Flies reveal gene that makes girls fight like boys] November 20, 2006, Ian Sample]

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.Demir E and Dickson BJ (2005). "fruitless" splicing specifies male courtship behavior in "Drosophila"." "Cell 121": 785-794.]

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.

"fruitless" has at least four promoters, each encoding proteins with a beta-turn-beta domain containing 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). The fruitless gene locus also controls the expression of hundreds of other genes [Goldman and Arbeitman (2007) [http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.0030216 Genomic and functional studies of Drosophila sex hierarchy regulated gene expression in adult head and nervous system tissues] PloS Genetics 3(11):e216] , any subset of which may actually regulate behavior.

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.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.] However, it should be noted that -- 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.

References

External links

* [http://www.ncbi.nlm.nih.gov/sites/entrez?db=protein&cmd=Link&LinkName=protein_gene&from_uid=24647980 Entrez Gene summary for "fruitless"]
* [http://www.365gay.com/newscon05/06/060305fruitFly.htm Article on "fruitless" on 365Gay.com]