Semaphorins are a family of cell surface and secreted proteins involved in neural development that are conserved from insects to humans. Members of this family are approximately 750 amino acids in length (including signal sequences) and are defined by a conserved extracellular ??semaphorin??domain of approximately 500 amino acids containing 14-16 cysteines, blocks of conserved sequences and no obvious repeats. The transmembrane semaphorins are characterized by an additional 80 amino acid transmembrane domain and an 80-110 amino acid cytoplasmic domain. SEMA6C, also known as SEMA Y, is a transmembrane protein expressed in fetal brain and adult skeletal muscle. Three isoforms of this semaphorin exist due to alternative splicing: SEMA6C 1, SEMA6C 2 and SEMA6C 3. The extracellular domain of SEMA6C induces growth cone collapse of dorsal root ganglion and plays a role in generation or stability of entorhino-hippocampal synapses.