title: Synaptotagmin I and II are present in distinct subsets of central synapses.
abstract: Synaptotagmin 1 and 2 (syt 1, syt 2) are synaptic vesicle-associated membrane proteins that act as calcium sensors for fast neurotransmitter release from presynaptic nerve terminals. Here we show that widely used monoclonal antibodies, mab 48 and znp-1, stain nerve terminals in multiple species and, in mouse, recognize syt 1 and syt 2, respectively. With these antibodies, we examined the synaptic localization of these synaptotagmin isoforms in the mouse central nervous system. Syt 1 and syt 2 are localized predominantly to different subsets of synapses in retina, hippocampus, cerebellum, and median nucleus of the trapezoid body (MNTB). In the MNTB, syt 1 and syt 2 are present in different presynaptic terminals on the same postsynaptic principal neuron. In retina, horizontal and OFF-bipolar cell terminals contain syt 2, whereas most other terminals contain syt 1. Syt 1 localization in the immature retina resembles that seen in adult; however, syt 2 localization appears strikingly different at perinatal ages and continues to change dramatically prior to eye opening. For example, starburst amacrine cells, which lack syt 2 in adult retina, transiently express syt 2 during the first 2 postnatal weeks. In addition to differences in spatial and temporal distribution, species-specific differences in synaptotagmin localization were observed in retina and cerebellum. The cell-, temporal-, and species-specific expression of synaptotagmin isoforms suggests that each may have distinct functions in neurotransmitter release.
authors.affiliation: Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Fox
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Sanes
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D002490:Central Nervous System / Q000166:cytology / Q000378:metabolism*; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism; D002642:Chick Embryo; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D007150:Immunohistochemistry; D051379:Mice; D010786:Photoreceptor Cells / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism*; D020033:Protein Isoforms; D012160:Retina / Q000166:cytology / Q000378:metabolism*; D013045:Species Specificity; D050863:Synaptotagmin I / Q000378:metabolism*; D050861:Synaptotagmin II / Q000378:metabolism*; D014018:Tissue Distribution; D014714:Vertebrates; D015027:Zebrafish
chemical_list: D000911:Antibodies, Monoclonal; D020033:Protein Isoforms; D050863:Synaptotagmin I; D050861:Synaptotagmin II