Expression and regulation of mouse Mtsh1 during limb and branchial arch development

The mouse genome contains at least two genes, Mtsh1 and Mtsh2, related in sequence to the Drosophila homeotic gene teashirt (tsh). In this paper, we report the characterization of Mtsh1 expression in the developing branchial arches and forelimbs during mouse embryogenesis. Mtsh1 was found predominantly transcribed in the mesenchymal tissue of branchial arches and forelimbs. Surgical removal of the epithelium of both forelimb and branchial arch significantly decreased the expression of Mtsh1 in the mesenchymal cells of these tissues. Upon implantation of FGF8-soaked beads into arches and limbs, Mtsh1 transcription was up-regulated. In contrast, when BMP4-soaked beads were implanted, Mtsh1 expression was inhibited. Together, these results suggest that mouse Mtsh1 gene may be involved in the outgrowth of limbs and arches and may be functioning downstream of BMP and FGF signaling pathways.