Mohawk is a novel homeobox gene expressed in the developing mouse embryo

Homeodomain-containing proteins comprise a superfamily of transcription factors that participate in the regulation of almost all aspects of embryonic development. Here, we describe the mouse embryonic expression pattern of Mohawk, a new member of the TAJLE superclass of atypical homeobox genes that is most-closely related to the Iroquois class. During mouse development, Mohawk was transcribed in cell lineages derived from the somites. As early as embryonic day 9.0, Mohawk was expressed in an anterior to posterior gradient in the dorsomedial and ventrolateral lips of the dermomyotome of the somites that normally give rise to skeletal muscle. Mohawk transcription in the dorsomedial region required the expression of the transcription factor paraxis. As somites matured, Mohawk transcription was observed in the tendon-specific syndetome and the sclerotome-derived condensing mesenchyme that prefigures the proximal ribs and vertebral bodies. In the limbs, Mohawk was expressed in a pattern consistent with the developing tendons that form along the dorsal and ventral aspect of the phalanges. Finally, Mohawk was detectable in the tips of the ureteric buds in the metanephric kidneys and the testis cords of the male gonad. Together, these observations suggest that Mohawk is an important regulator of vertebrate development.