Understanding the role of semaphorin3d during zebrafish fin regeneration

Connexins are components of gap junctions, which are critical for direct intercellular communication. Gap junctional intercellular communication (GJIC) is required for bone morphogenesis in mammals. Prior research has indicated that connexin43 (cx43) has two functions during zebrafish (Danio rerio) fin regeneration: it promotes cell proliferation and suppresses joint formation. Semaphorin3d (sema3d) is a gene that functions downstream of cx43 during regeneration, also promoting cell proliferation and suppressing joint formation. Semaphorins generally mediate cellular signal transduction, and may interact with receptors called Neuropilins. Neuropilin2a (Nrp2a) is a putative receptor for Sema3d, but it remains unknown whether Nrp2a is involved in the Cx43 pathway. Sema3d is extremely labile in vitro, and processing of the protein may play a role in its function. In situ hybridization revealed that both cx43 and sema3d levels transiently decrease around the time of the first joint formation in the regenerating fin. These data support that both cx43 and sema3d promote cell proliferation and suppress joint formation.