The forkhead box protein p2, otherwise known as FOXP2, is a protein that is encoded by the FOXP2 gene. The FOXP2 gene is commonly referred to as the “language gene” (Gillespie, 2017). It was first referred to as the “language gene” because of the KE family’s speech disorder and the genetic mix-up on chromosome 7. It was determined that the FOXP2 gene was causing this mutation on chromosome 7 (Enard, 2002). After the study on the KE family came out, numerous studies have surfaced questioning whether the FOXP2 gene is specifically the “language gene”. Some studies found the FOXP2 protein is present in organisms such as yeast. Studies have also shed light on how similar the human FOXP2 gene is to the finch FOXP2 gene, they are only different in 8 of 200,000 positions (Gillespie, 2017). The topic is still heavily debated to this day, does FOXP2 gene have other functions that it is responsible for, or is it specifically for language and speech?

The FOXP2 gene was first noted as the language gene because of the study done on a family in London. This family is known as the KE family and have gained much publicity because of the study. The KE family has a long history of family members being affected with similar language deficits. In fact, the language deficits spanned three generations of this family, affecting 15 members. Language deficits in the family include articulation errors, impaired processing and problems with “mastering the coordinated movement sequences that underlie fluent speech” (Enard, 2002). What caught the eye of researchers is that the language deficits weren’t due to cognitive deficits. The affected family members and non-affected family members all had around the same nonverbal IQ when they were tested. Because the language impairments weren’t due to cognitive deficits, researchers were speculating about a “language gene” even before the neuropsychological studies began (Enard, 2002).

Scientific studies on the family first began in 1998. Not all members of the KE family had severe language deficits and because of this, researchers were able to compare unaffected members with affected members. This ultimately lead to the discovery of the FOXP2 gene. The FOXP2 gene was determined to be the gene that was causing the language deficits in the KE family when neuroimaging was examined between the affected family members and the non-affected family members. Researchers recognized that the affected family members had mutations on the chromosome 7 while the non-affected family members had no mutations present (Enard, 2002). Researchers were able to pinpoint that the mutations on chromosome 7 were coming from the FOXP2 gene because of an analysis on the “SPCH1 interval” (Enard, 2002). The researchers also included two other individuals (related to eachother) that were not part of the KE family but had language deficits of their own. Results were identical to those found in the KE family, the language deficits in the two individuals were stemming from the FOXP2 gene.

Although there is strong evidence that shows the FOXP2 gene is associated with language and speech, there is even stronger evidence that shows the FOXP2 gene is not specifically the “language gene”. According to Mueller (2016), the study on the KE family should not have gained as much attention as it did for many reasons. FOXP2 was labeled as the “language gene” after a number of small studies were done on families similar to the KE family. However, there has been no research done on “genome-wide nor gene-specific” studies (Mueller, 2016). In other words, there is no current research that provides evidence that a common polymorphism in a gene is what is causing individual differences in language development in a general population. Mueller et al. (2016) provided evidence in their 2016 study that shows there is no common polymorphism in the FOXP2 gene that causes individual differences in language development.

Mueller et al. (2016) looked at common variants of the FOXP2 gene that are seen in individuals and requested that these individuals take a test that measured language ability. This study included 812 participants that were of European decent, these participants were all school aged children. DNA samples were taken from the individuals, this gave researchers the ability to look at their FOXP2 gene and the variants that were associated with it. A quantitative test was given to the individuals, which measured individuals language ability (Mueller, 2016). The results revealed that there was no QTL (quantitative trait loci) variance above .02 for an associated allele with MAF (minor allele frequency) above .02 (Mueller, 2016). In other words, if there is a common variant associated with language ability in the FOXP2 gene, the common variant has very little effect on language in individuals.

This study is of significance for several reasons. For one, the population size in this study is substantially more than previous studies that were done on the FOXP2 gene. Having such a large sample size is important because the results show more inclusiveness and reliability when compared to a study with a smaller population size. Previous studies done were small family studies that often looked at 10-20 individuals that were related, this is not inclusive to the general population. This is the reason why people should never have named the FOXP2 gene the “language gene”. The research was based of a small population, the population was all related, which is not inclusive to the general population. The results to this study were also of importance. Results to the study were important because it proved that variants in the FOXP2 gene have very little effect on language on individuals in the general population. If the FOXP2 gene just solely had to do with language than the variants in the gene would have had a substantial effect on language in the individuals. This shows that the FOXP2 gene serves other purposes within the human body.

Another study done by Shu et al. (2007) looked at mice that had no FOXP2 gene present. Researchers purposely developed mice that had no FOXP2 gene. The researchers chose mice for a number of reasons. For one, it is not ethical to test this on humans, and the second reason is because the mice FOXP2 gene only differs from humans in three of 200,000 positions (Shu, 2007). So, the human FOXP2 gene and the mice FOXP2 gene are very similar. It is important to note that previous studies have been done that mutated the gene in mice but not completely take it out. The results were very similar to what happens in a human with a mutated FOXP2 gene, the mice had abnormal vocalizations. Shu et al. (2007) reported that the mice with no FOXP2 gene had severe lung defects that ultimately made them die 21 days earlier than mice that had the FOXP2 gene.

The results of the Shu et al. study is important because it shows that the FOXP2 gene is not specifically for language. This makes sense because FOXP2 is a transcription factor, a transcription factor is a “protein that that binds to the promoter region of other genes and facilitates their transcription from DNA to RNA” (MacAndrew, 2004). Without FOXP2 present, the information that it normally transcribes doesn’t get transcribed anymore which can be seen to affect humans and animals in more ways than just language. This is seen in the Shu et al. study, without FOXP2 present the mice have severe lung defects as well as deficits with their communication.

FOXP2 is found in simple organisms such as yeast (Gillespie, 2017). This is another reason that the FOXP2 gene can’t just be responsible for language. Yeast is an organism that uses no type of communication or language so why would FOXP2 be present in yeast? The answer is simple, FOXP2 is responsible for a lot of things because it is a transcription factor. It just so happens that a small duty of FOXP2 has to do with language and communication in humans and animals.

The FOXP2 gene is still commonly referred to as the “language gene”. It was dubbed the “language gene” because of small family studies. These studies looked into individuals that had severe language deficits. Researchers found that the language deficits were stemming from mutations on chromosome 7, these mutations were due to the FOXP2 gene. Researchers then prematurely named it the “language gene” because they thought that’s what the gene’s sole purpose was. It was premature to name it the “language gene” because the initial studies were done on small, specialized populations that were not inclusive to a general population. After looking at more recent studies done on the FOXP2 gene it becomes clear the FOXP2 gene is not specifically for speech and language.

References

Enard, W., Przeworksi, M., Fisher, S., Lai, C., Wiebe, V., Kitano, T., . . . Paabo, S. (2002). Molecular evolution of FOXP2, a gene involved in speech and language. Nature 418, 869-872. doi:10.1038/nature01025.

Gillespie, M. (2017, September 13). Evolution and Language. Lecture presented at Psychology of Language Class in McConnell Hall, Durham.

MacAndrew, A. (2004, March 27). FOXP2 and Evolution of Language. Retrieved December 12, 2017, from http://www.evolutionpages.com/FOXP2_language.htm

Mueller, K. L., Murray, J. C., Michaelson, J. J., Christiansen, M. H., Reilly, S., & Tomblin, J. B. (2016). Common Genetic Variants in FOXP2 Are Not Associated with Individual Differences in Language Development. Plos One, 11(4). doi:10.1371/journal.pone.0152576

Shu, W., Lu, M. M., Zhang, Y., Tucker, P. W., Zhou, D., & Morrisey, E. E. (2007). Foxp2 and Foxp1 cooperatively regulate lung and esophagus development. Development, 134(10), 1991-2000. doi:10.1242/dev.02846