The FOXP2 gene provides instructions for making a protein known as Forkhead box protein P2. This protein acts as a transcription factor, meaning it controls the activity of other genes. It is present in various bodily tissues, including the brain, heart, lungs, and digestive system, both before and after birth. The FOXP2 protein is thought to influence the development and function of nerve cells and their connections, which are important for learning and memory.
Its Role in Human Language
The connection between the FOXP2 gene and human language was first identified in 1998 through studies of a British family, known as the KE family, where about half of its members across three generations experienced a severe speech and language disorder. This condition, termed developmental verbal dyspraxia or childhood apraxia of speech (CAS), makes it difficult to produce the sequences of sounds and syllables needed to form words. Affected individuals typically begin speaking their first words later than other children, often between 18 months and 7 years of age.
Mutations in the FOXP2 gene disrupt its normal activity, leading to an abnormal FOXP2 protein. This disruption affects other genes in the developing brain involved in speech and language. These mutations can impair the planning and coordination of movements of the lips, mouth, and tongue, which are necessary for clear speech. The disorder can manifest as difficulties with speech articulation, stuttering, and poor pronunciation, along with challenges in verbal comprehension and language production.
Brain imaging studies on affected KE family members suggest that the speech and language impairments are linked to developmental defects in neural networks involved in speech and language function, particularly in motor-related circuits like corticostriatal and corticocerebellar circuits. The FOXP2 gene is located on chromosome 7, and changes affecting this gene or neighboring genes on the same chromosome can result in a related condition called FOXP2-plus-related speech and language disorder.
Functions Beyond Human Speech
While FOXP2 is recognized for its connection to human language, its functions extend to other species and developmental processes. This gene is found in many vertebrates, indicating a conserved role across different animals.
For instance, in birds, FOXP2 plays a part in song learning and vocal imitation. In mice, the gene influences vocalizations, with mutations leading to simpler calls. In bats, FOXP2 is implicated in echolocation, a complex sensorimotor process involving vocal signals for navigation and prey capture. Beyond vocalization, FOXP2 also contributes to general brain development and motor coordination in humans.
How FOXP2 Works
The FOXP2 protein binds directly to specific regions of DNA, effectively controlling whether other genes are “turned on” or “off.” By regulating the expression of many other genes, the FOXP2 protein influences the development and function of various brain regions and neural circuits. Researchers estimate that the FOXP2 protein may regulate the activity of hundreds of genes. This broad regulatory role allows FOXP2 to impact diverse processes, including the formation and function of synapses—the connections between nerve cells where communication occurs—and synaptic plasticity, the ability of these connections to adapt over time, important for learning and memory.