Expression and regulation of the Msx1 natural antisense transcript during development.

Bidirectional transcription, leading to the expression of an antisense (AS) RNA partially complementary to the protein coding sense (S) RNA, is an emerging subject in mammals and has been associated with various processes such as RNA interference, imprinting and transcription inhibition. Homeobox genes do not escape this bidirectional transcription, raising the possibility that such AS transcription occurs during embryonic development and may be involved in the complexity of regulation of homeobox gene expression. According to the importance of the Msx1 homeobox gene function in craniofacial development, especially in tooth development, the expression and regulation of its recently identified AS transcripts were investigated in vivo in mouse from E9.