Synaptogyrin-1 is an integral membrane protein associated with presynaptic vesicles in neuronal cells. The exact function of this protein is unclear, but studies of a similar murine protein suggest that it functions in synaptic plasticity without being required for synaptic transmission. Three alternatively spliced variants encoding three different isoforms have been identified.The predicted 1a, 1b, and 1c proteins contain 234, 191, and 192 amino acids, respectively. Northern blot analysis revealed that the 4.5-kb SYNGR1a mRNA is expressed at high levels in brain. The other transcript forms are expressed at low levels in nonneuronal tissues. In situ hybridization to embryonic and adult mouse tissues confirmed that SYNGR1a, the most abundant transcript form, shows predominantly neuronal expression.