Genetic pathways implicated in speech and language

Disorders of speech and language are highly heritable, providing strong support for a genetic basis. However, the underlying genetic architecture is complex, involving multiple risk factors. This chapter begins by discussing genetic loci associated with common multifactorial language-related impairments and goes on to detail the only gene (known as FOXP2) to be directly implicated in a rare monogenic speech and language disorder. Although FOXP2 was initially uncovered in humans, model systems have been invaluable in progressing our understanding of the function of this gene and its associated pathways in language-related areas of the brain. Research in species from mouse to songbird has revealed effects of this gene on relevant behaviours including acquisition of motor skills and learned vocalisations and demonstrated a role for Foxp2 in neuronal connectivity and signalling, particularly in the striatum. Animal models have also facilitated the identification of wider neurogenetic networks thought to be involved in language development and disorder and allowed the investigation of new candidate genes for disorders involving language, such as CNTNAP2 and FOXP1. Ongoing work in animal models promises to yield new insights into the genetic and neural mechanisms underlying human speech and language.