This web page was produced as an assignment for Genetics 677, an undergraduate course at UW-Madison
Genderblind, SLC7A11 and Mating Behavior
Genderblind Function
There has been a recently discovered gene in the Drosophilia melanogaster genome that when mutated, significantly alters mating behavior in the affected male flies. Named genderblind (gb), the corresponding protein product is a amino acid transporter that takes cystine into the cell while releasing glutamate. It is important to note that glutamate is an important neurotransmitter (1). When genderblind is knocked out, extracellular glutamate is halved in comparison to the wild type (3). The most notable difference in genderblind mutants, and the reason for the gene's name, is that affected male flies cannot correctly differentiate between males and females when attempting to copulate (4). This leads the flies to have a "bisexual" orientation in which they will initiate physical contact, sing a species specific song, and lick the genitalia of the members of both sex. It is also interesting to note that this orientation can be switched on and off in the flies via RNAi showing that this gene is active in the mature fly rather than being only utilized in development. This behavior can be seen in the two videos below. Both videos only contain male flies. The video on the left shows wild type behavior (no attempts at mating) and the video on the right shows the mutated genderblind phenotype (all of the flies are attempting to copulate with one another).
Genderblind and SLC7A11
Genderblind has a homologous gene in the human genome named SLC7A11, also known as cysteine/glutamate transporter or xCT. SLC7A11 is in the solute carrier family 7 and encodes a protein that has the same function as genderblind in flies (6). It is located on the fourth chromosome in humans, represented by the red line as can be seen below (5).
What This Means
If the SLC7A11 gene in humans has a similar function as the genderblind gene has in Drosophilia, reverberations will be felt throughout not only science but society as a whole. Sexual orientation remains a controversial topic throughout the world and especially in the United States, where President Barack Obama recently became the first American president to ever publicly support gay marriage (3). A major part of the debate over LGBT social equality is whether homosexuality is a learned trait or has a genetic basis.
The search for a "gay gene" has been going on since the 90's (7) but has yet to produce any meaningful results. If a genetic basis for homosexuality could be found it would hopefully change public perception to be more accepting of the LGBT community and lead to equal rights for everyone regardless of sexual orientation. There are downsides to possibly identifying the gay gene however. This discovery could open the doors to screening offspring for the gene to determine their sexual orientation and possibly even gene therapies designed to "cure" homosexuality.
References
Danbolt, Niels C. "Glutamate as a Neurotransmitter." The Neurotransporter Group. Centre For Molecular Biology and Neuroscience. Web. 23 May 2012. <http://www.neurotransporter.org/glutamate.html>.