Fruitless (gene)

{{Short description|Fruit fly gene}} {{lowercase}} {{Infobox nonhuman protein | Name = fruitless | image = | width = | caption = | Organism = Drosophila melanogaster | TaxID = 7227 | Symbol = fru | AltSymbols = | IUPHAR_id = | EntrezGene = 42226 | PDB = | RefSeqmRNA = NM_169821.1 | RefSeqProtein = NP_732349.1 | UniProt = Q8IN81 | ECnumber = | Chromosome = 3R | EntrezChromosome = NT_033777.2 | GenLoc_start = 14222965 | GenLoc_end = 14390656 }} 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.<ref name="Demir_Dickson_2005"/> The gene does not have an obvious mammalian homolog, but appears to function in sex determination in species as distant as the mosquito ''Anopheles gambiae''.<ref name="pmid16319090">{{cite journal | vauthors = Gailey DA, Billeter JC, Liu JH, Bauzon F, Allendorfer JB, Goodwin SF | title = Functional conservation of the fruitless male sex-determination gene across 250 Myr of insect evolution | journal = Molecular Biology and Evolution | volume = 23 | issue = 3 | pages = 633–43 | date = March 2006 | pmid = 16319090 | doi = 10.1093/molbev/msj070 | doi-access = free }}</ref>

''fruitless'' serves as an example of how a gene or a group 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 [[Biology and sexual orientation|genetics of human sexual orientation]],<ref>{{cite web | work = The Atlantic | url = https://www.theatlantic.com/doc/199706/homosexuality-biology/4 | title = Homosexuality and Biology, The Genetic Quest | date = June 1997 | first = Chandler | last = Burr | name-list-style = vanc }}</ref><ref>{{cite web | work = The New York Times | url = https://query.nytimes.com/gst/fullpage.html?res=9B02E1D9173EF930A25751C1A960958260 | title = Mating Game of Fruit Fly Is Traced to a Single Gene | date = December 13, 1996 | first = Nicholas | last = Wade | name-list-style = vanc }}</ref> and behaviors such as gender-specific [[aggression]].<ref>{{cite web | work = The Guardian | url = https://www.theguardian.com/uk_news/story/0,,1952198,00.html | title = Flies reveal gene that makes girls fight like boys | date = November 20, 2006 | first = Ian | last = Sample }}</ref>

== 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 many 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 mutation|loss-of-function]] alleles change or remove [[sexual orientation|sexual preference]].<ref name="Demir_Dickson_2005">{{cite journal | vauthors = Demir E, Dickson BJ | title = fruitless splicing specifies male courtship behavior in Drosophila | journal = Cell | volume = 121 | issue = 5 | pages = 785–94 | date = June 2005 | pmid = 15935764 | doi = 10.1016/j.cell.2005.04.027 | s2cid = 14663286 | doi-access = free }}</ref>

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.<ref name="Demir_Dickson_2005"/> In the brain, a subset (ca. 2,000) of neurons express ''fruitless''<ref>{{cite journal | vauthors = Cachero S, Ostrovsky AD, Yu JY, Dickson BJ, Jefferis GS | title = Sexual dimorphism in the fly brain | journal = Current Biology | volume = 20 | issue = 18 | pages = 1589–601 | date = September 2010 | pmid = 20832311 | doi = 10.1016/j.cub.2010.07.045 | pmc = 2957842 | bibcode = 2010CBio...20.1589C }}</ref> and ''fruitless'' expression is sufficient to instruct sexually dimorphic connectivity.<ref>{{cite journal | vauthors = Kohl J, Ostrovsky AD, Frechter S, Jefferis GS | title = A bidirectional circuit switch reroutes pheromone signals in male and female brains | journal = Cell | volume = 155 | issue = 7 | pages = 1610–23 | date = December 2013 | pmid = 24360281 | doi = 10.1016/j.cell.2013.11.025 | pmc = 3898676 }}</ref><ref>{{cite journal | vauthors = Ruta V, Datta SR, Vasconcelos ML, Freeland J, Looger LL, Axel R | title = A dimorphic pheromone circuit in Drosophila from sensory input to descending output | journal = Nature | volume = 468 | issue = 7324 | pages = 686–90 | date = December 2010 | pmid = 21124455 | doi = 10.1038/nature09554 | bibcode = 2010Natur.468..686R | s2cid = 4412743 }}</ref>

''fruitless'' has at least four [[Promoter (biology)|promoters]], each encoding proteins containing both a BTB (Broad complex/tramtrack/bric-a-brac) domain and a [[zinc finger]] [[Structural motif|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).<ref name="Demir_Dickson_2005"/> The fruitless gene locus also controls the expression of hundreds of other genes,<ref name="pmid18039034">{{cite journal | vauthors = Goldman TD, Arbeitman MN | title = Genomic and functional studies of Drosophila sex hierarchy regulated gene expression in adult head and nervous system tissues | journal = PLOS Genetics | volume = 3 | issue = 11 | pages = e216 | date = November 2007 | pmid = 18039034 | pmc = 2082469 | doi = 10.1371/journal.pgen.0030216 | doi-access = free }}</ref> 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.<ref name="pmid2542123">{{cite journal | vauthors = Gailey DA, Hall JC | title = Behavior and cytogenetics of fruitless in Drosophila melanogaster: different courtship defects caused by separate, closely linked lesions | journal = Genetics | volume = 121 | issue = 4 | pages = 773–85 | date = April 1989 | doi = 10.1093/genetics/121.4.773 | pmid = 2542123 | pmc = 1203660 }}</ref> 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.<ref>{{cite web | title = GeneBrief - fruitless | work = InteractiveFly | publisher = Society for Developmental Biology | url = http://www.sdbonline.org/sites/fly/dbzhnsky/frutles1.htm }}</ref>

== References == {{reflist|32em}}

== External links == *[https://www.ncbi.nlm.nih.gov/gene?linkname=protein_gene&from_uid=24647980 Entrez Gene summary for ''fruitless''] *[http://www.sdbonline.org/fly/dbzhnsky/frutles1.htm Article on ''fruitless'' in The Interactive Fly]

{{DEFAULTSORT:Fruitless (Gene)}} [[Category:Drosophila melanogaster genes|fruitless]] [[Category:Molecular neuroscience]] [[Category:Mating]] [[Category:Sexual orientation and science]] [[Category:Mutated genes]] [[Category:Behavioural genetics]]