Multiple transcription start sites for FOXP2 with varying cellular specificities

FOXP2 is a forkhead transcription factor implicated in developmental verbal dyspraxia, a human speech and language disorder. FOXP2 is expressed in complex patterns during brain, lung, heart, and gut development and on into adulthood. Both the protein sequence and brain expression patterns are highly conserved through much of vertebrate evolution. FOXP2 also contains six ultraconserved regions in its introns, consistent with the idea that FOXP2 is tightly regulated. Previous evidence suggested the presence of three transcription start sites for FOXP2, and we sought to characterize them and determine their cell and tissue specificity. We used 5′ RNA ligase-mediated rapid amplification of cDNA ends (RLM-RACE) and RT-PCR to identify four transcription start sites for human FOXP2, the fourth being in a novel exon. Two of the transcription start sites, including the one in the novel exon, appear to be more cell line specific and lie in an area of remarkably high conservation. We propose that these two transcription start sites may be of great interest in future studies of FOXP2 regulation.