A hedgehog-like signal is involved in slow muscle differentation in Sepia officinalis (Mollusca)

Abstract

In the tentacle of Sepia officinalis, smooth-like, helical and cross-striated fibres deriving from
different populations of myoblasts are present. Myoblasts appear at different times during the
development and express two muscle-specific transcription factors: Myf5-like and MyoD-like factors.
Myoblasts expressing Myf5 give rise to slow fibres, whereas fast fibres derive from MyoD+ myoblasts.
We found that a Hedgehog (Hh)-like signal was present in the central nerve cord of the tentacle from
the early stages of development and in a specific population of myoblasts which are the precursors of
slow muscle fibres. The model showed interesting similarities with vertebrates, in which Sonic
hedgehog is a protein secreted by axial structures (the notochord and neurotube) and is involved in
slow muscle differentiation and in survival of muscle precursors.