Proteins in this family are multi-pass membrane proteins including SPEC3 and Stum. The Stum protein was identified in Drosophila and has orthologues in animals ranging from nematodes to mammals. It is required for transduction of mechanical stimuli [].Purple sea urchin SPEC3 was found at the cilia and Golgi complexes of embryonic ectoderm cells. It has been suggested that this protein involves in ectodermal ciliogenesis [, ].
