CAS is the speech disorder identified in a multigenerational pedigree ('KE') in which half of the members have a mutation in FOXP2 that co-segregates with CAS, oromotor apraxia, and low scores on a nonword repetition task.
Here we provide comprehensive behavioural and neuroimaging data on a large novel family where one parent and 11 children presented with features of childhood apraxia of speech (the same speech disorder associated with FOXP2 variants).
The specific colocalization of FoxP1 and FoxP2 found in several structures in the bird and human brain predicts that mutations in FOXP1 could also be related to speech disorders.
After completing this paper, readers should be able to (a) identify key epidemiological findings for the three speech phenotypes that were discussed (DAS, speech delay, and stuttering); (b) summarize the findings of the behavioral genetic studies of speech disorders that were presented; (c) identify four specific challenges that may impede future molecular genetic studies of these phenotypes; (d) describe the methodological sequence that led to the discovery of the FOXP2 gene; and (e) summarize the two research strategies that were presented to potentially reduce sample heterogeneity for future molecular genetics research.
We identified three truncated genes: CDH12, DGKB and FOXP2, confirming the role of FOXP2 in severe speech disorder, and suggestive roles of CDH12 and/or DGKB for the global developmental and psychomotor delay.
Childhood apraxia of speech is the speech disorder segregating with a mutation in FOXP2 in a multigenerational London pedigree widely studied for its role in the development of speech-language in humans.
CNTNAP2 is known to be involved in the cause of language and speech disorders and autism spectrum disorder and is in the same pathway as FOXP2, another important language gene, which makes it a candidate gene for causal studies speech and language disorders such as stuttering.