One particular target that is directly downregulated by FOXP2 in human neurons is the CNTNAP2 gene, a member of the neurexin family; variants in this target gene have been associated with common forms of language impairment.
A Pitt–Hopkins like phenotype has been assigned to autosomal recessive mutations of the contactin associated protein like 2 (CNTNAP2) gene on the long arm of chromosome 7 (7q33-q36) and the neurexin 1 alpha (NRXN1) gene on the short arm of chromosome 2 (2p16.3).
Splice variants a, b, and e, in Figures 5 and 6 have >99% structural similarity to the protein neurexin 1-alpha(NRXN1).