Language is an essential part to life. Without some kind of communication strategy there is a likelihood that humans could not have surpassed their caveman years. There is an over lurking question as to where speech and language stem from and how humans had the ability to talk and form complete structured and coherent sentences. There is a protein in a gene called Forkhead Box P2 (FOXP2) that was discovered in 2001 in a study of the KE family (Marcus and Fisher, 2003). Researchers were able to understand that when the gene was effectively turned on due to environmental surrounding, it enabled humans to begin to produce speech which lead to forming languages. It is proposed that this gene is relatively new to the human species only having been created by a mutation few thousand years ago (Youg, 2003). This gene was mutated so that humans could produce speech and be able to communicate with other, however if there is a mutation on the gene it could hinder the ability to produce speech thus interrupting the language process. There are many disorders that are correlated with a mutation in the FOXP2 gene like childhood apraxia of speech, but there are also other disorders that one might not think is correlated with a speech disorder at all. Evidence shows that schizophrenia and depression are linked to the FOXP2 gene.
When researching the FOXP2 gene, the KE family was mentioned in many different articled. The KE family was what helped researchers answer the questions “Why do humans have speech and language disorders and where do they come from?” “Approximately half of the members in the KE family are affected with a severe speech and language disorder which appears to be transmitted as an autosomal dominant monogenic trait” (Fisher, et. al. 1998) Their disorder shows that they have grammatical difficulty which does support further research for that there are genes specifically associated to grammar (Fisher, et. al., 1998). There have been other research findings due to the KE family study.
Childhood apraxia of speech seemed to be the one of the most associated disorders with a mutation in the FOXP2 gene. Childhood apraxia is characterized by the difficulty in motor movements of the mouth to be able to produce speech. Children do know what they want to say but because of the inability of the muscles in their mouth to coordinate correctly with the words they want to say, they have a difficult time doing so (American Speech). Parents can have a difficulty diagnosing their children because they do not know what to look for when a child begins to communicate which could lead to the child having a severe speech delay. However childhood apraxia of speech can be treated with speech therapy and children could make a remarkable improvement if treated early (Dodd, 2012). With that being said, the percentages of children who have childhood apraxia of speech could decrease if parents knew what the signs and symptoms looked like but further research would have to be done to prove that.
Disorders like schizophrenia and depression are not thought to be associated with the FOXP2 gene because these disorders are known to be psychiatric disorders and not speech and language disorders. “This discovery of a link between FOXP2 and spoken language sparked investigations into associations between the gene and vulnerability to mental disorders typified by language impairments, including schizophrenia. In fact, language deficits, such as poor verbal functioning and abnormal verbal production and comprehension, are common phenomenological traits in schizophrenia patients” (Spaniel et. al., 2011). Researchers Spaniel et. al. proposed that there is a genetic variation in the FOXP2 gene that alters grey matter concentrations in schizophrenia patients. Researchers gathered 40 patients diagnosed with schizophrenia and 36 healthy control patients. Each patient was a Caucasian of Czech and age varied from 18-years-old to 60-years-old. Each patient was subject to a magnetic resonance image (MRI) scan, genotyping and psychometric measurement (Spaniel et. al., 2011). Fisher et. al. results show that schizophrenia patients had a reduction in grey matter located near the Broca’s area. Broca’s area is highly responsible for language processing.
Another study conducted by Jones et. al. suggests that there is a link between the FOXP2 gene and childhood emotional abuse that can predict auditory verbal hallucinations in schizophrenia. Auditory verbal hallucinations (AVH) are hallucinations where the patient hears a voice, but there is no external stimuli suggesting that the voice they are hearing is from someone talking to them or around them. Participants of this study included 333 people with a schizophrenic disorder. Of these participants 116 were female with mean age 39-years-old. “There were 251 schizophrenic patients, 42 schizoaffective, 34 psychotic disorder not otherwise specified, 6 delusional disorder” (Jones et. al., 2013). Child abuse was assessed using the Childhood Adversity Questionnaire that targets the type of child abuse (sexual, physical, emotional, and neglect) each patient had received that suggests them for psychosis research. Each question was phrased as ‘I was neglected as a child’ or ‘I was sexually abused as a child’ to be specific as possible as to what kind of abuse each participant faced. Each participant was also genotyped to see if there was any ancestral relation to schizophrenia. Results show that 84% of the 25 participants that reported sexual abuse had AVH. There was a trend that showed people who were in the non-AVH category showed higher levels of negative symptoms in schizophrenia. Negative symptoms include lack of appetite, lack of empathy, and reductions in speech. However, “The study neither found a significant association between AVHs and FOXP2…” (Jones, et. al., 2013). Although, participants who have a CC genotype were more likely to experience AVH with the presence of child abuse. CC genotype is associated with schizophrenia as “C allele carriers from the schizophrenia group are prone to changes in the anatomy of, the region of the brain subservient to language functions” (Spaniel et. al., 2011). This study proves that people who experiences child abuse and have schizophrenia will likely experience AVH which is associate with the FOXP2 gene.
Other research shows that not only does the FOXP2 gene show speech and language deficits in schizophrenia, but so does the FOXP1 gene. The FOXP1 gene is important for development B cells and expressive language. Researchers, Bacon and Rappold suggest that not only does the FOXP2 gene play a significant role in cognitive disease, the FOXP1 gene does the same as well. A mutated FOXP2 gene causes difficulty with expressive and receptive language and FOXP1 causes difficulty with just expressive language (Bacon & Rappold, 2012). People who have a mutation in their FOXP1 gene can be intellectually delayed as “intellectual disability is a consistent feature of the phenotype associated with FOXP1 disruption” (Bacon & Rappold, 2012). Members of the KE family who had a mutation in the FOXP2 gene have lower IQ levels than their non-affected family members (Bacon & Rappold, 2012). However, in other studies, there has been reports of people having normal IQ levels even thought their FOXP2 gene has a mutation. “The reported IQs of patients with similarities and differences between FOXP1 and FOXP2 neuronal phenotypes with FOXP1 disruptions are much lower than those reported for people with FOXP2 variant” (Bacon & Rappold, 2012). Intelligence is more correlated in FOXP1 than in FOXP2. Bacon and Rappold suggest that the FOXP2 and FOXP1 gene do not cause a disease, but that they are both associated with the pathology of a disease. “The phenotypic spectra of FOXP1 and FOXP2 disruptions suggest that these two closely related transcription factors are involved in both shared and distinct neurodevelopmental pathways underlying cognitive diseases through the regulation of common and exclusive targets. The findings discussed in this review show that FOXP1 and FOXP2 may provide crucial insight into the molecular pathways involved in human cognitive diseases” (Bacon & Rappold, 2012). FOXP1 and FOXP2 may not directly cause a disease/disorder such as schizophrenia, but they both play a key role in how that disorder is brought about in patients. Both genes can be studied more to see exactly how FOXP1 is correlated in schizophrenia.
There is no doubt that the FOXP2 gene needs to be studied more in cognitive disorders. Schizophrenia is a major cognitive disorder that impacts millions of people every day. The fact that researchers were able to link the FOXP2 gene to auditory hallucinations in schizophrenia is astounding and can be considered a bit of a stretch. With the research that has been done, scientists could possibly develop a new medication that could directly impact that way the FOXP2 gene plays a role on schizophrenia instead of schizophrenic patients just taking first and second generation antipsychotic medication. Further research would need to be conducted on the influence medication has a genes for that to be possible. In the future with more research and the way that genes can be manipulated, the symptoms of schizophrenia could change. A medication or therapy could be developed that keeps gray matter from diminishing near the Broca’s area which could help reduce some aspects of the audio hallucinations schizophrenic patients’ experience. The FOXP2 gene does have a significant correlation with speech and language development, which could lead to some underlying causes of cognitive disorders. With further research about the FOXP2 gene, scientists could develop a cure for FOXP2 related disorders, or potentially be able to manipulate a mutated FOXP2 gene in vitro so that no one is born with a speech and language disorder.

References
A. (2017, December 12). FOXP1 gene – Genetics Home Reference. Retrieved December 13, 2017, from https://ghr.nlm.nih.gov/gene/FOXP1

American Speech-Language Hearing Association. (n.d.). Childhood apraxia of speech. Retrieved from http://www.asha.org/public/speech/disorders/ChildhoodApraxia/

Bacon, C. & Rappold, G. (2012). The distinct and overlapping phenotypic spectra of FOXP1 and FOXP2 in cognitive disorders. Hum Genet, 131:1687–1698.

Dodd, B. (2010). Differential diagnosis and treatment of children with speech disorder. Second Ed. London: Whurr, 71-82.

Fisher, E. S., Khadem, F., Watkins, E. K., Monaco, P. A., & Pembrey, E. A. (1998). Localization of a gene implicated in a severe speech and language disorder. Nature Genetics 18, 168– 170.

Marcus, G., and Fisher, S., (2003). FOXP2 in focus: what can genes tell us about speech and language?

Yong, E. (2009, November 11). Revisiting FOXP2 and the origins of language. Retrieved September 14, 2017, from http://scienceblogs.com/notrocketscience/2009/11/11/revisiting-foxp2-and-the-origins-of- language/