Munc13s are homologues of the C. elegans unc-13 gene product. Three brain-specific isoforms, Munc 13-1, -13-2, and -13-3, are expressed in rat, where they localize to presynaptic terminals. All three isoforms share multiple regulatory domains that may mediate phorbol ester and diacylglycerol binding.
 Munc13-1 shows the broadest expression pattern and is found in cortex, cerebellum, olfactory bulb, and hippocampus. Munc13-2 is mainly expressed in cortex and hippocampus, whereas Munc13-3 exhibits highest expression levels in cerebellum and pons. Munc13-1 interacts directly with a putative coiled-coil domain in the N-terminal part of syntaxin and is involved in synaptic vesicle priming. For Munc13-2 an additional ubiquitously expressed N-terminal splice variant (ubMunc13-2) has been described.
Munc13-3 has been shown to be involved in the regulation of cerebellar synaptic transmission and motor learning.
  
 For more information on protein expression pattern, please refer to the overview image in our SYSY Antibodies ATLAS.