Somatic muscle development in Sepia officinalis (cephalopoda - mollusca): a new role for NK4

Cephalopods are emerging as new developmental models. These lophotrochozoans exhibit numerous morphological peculiarities among molluscs, not only regarding their nervous system but also regarding their circulatory system, which is closed and includes three hearts. However, the molecular control of cardiac myogenesis in lophotrochozoans is largely unknown. In other groups, cardiac development depends on numerous different genes, among them NK4 seems to have a well-conserved function throughout evolution. In this study, we assessed the expression pattern of SoNK4, the Sepia officinalis NK4 homologue, during Sepia officinalis development by whole-mount in situ hybridization. SoNK4 expression begins before morphogenesis, is not restricted to prospective cardiac muscles but above all concerns mesodermal structures potentially rich in muscles such as arms and mantle. These results suggest an important role of SoNK4 in locomotory (somatic) muscles development of Sepia officinalis, and thus a new role for NK4.