Abstract: Anna Brandtjen and Hannah Lehman
Mentor: Dr. Karen F. Greif
Neurotransmitters allow nerve cells to communicate with more than one target cell through synaptic connections. Synaptotagmin-1 (Syt-1), a synaptic protein, is a calcium sensor at the synapse that regulates the release of neurotransmitters. It is also found on synaptic vesicles. Previous studies show the presence of Syt-1 in neurons prior to development of synapses; this suggests that Syt-1 may have other functions.
During neuron development, axons extend short, orthogonal structures, known as filopodia, which can later become branches. In order for neurons to communicate with more than one target cell, they depend on these branches, which are thus central to the complete interworking of the network. Elaborating filopodia and branches requires additional membrane due to increased surface area, which further leads us to question how a cell may deliver such membrane to help these structures develop.
Research from other labs suggests that calcium can have an effect on filopodia and branch outgrowth, which is significant because of the relationship Syt-1 has with calcium. We hypothesized that Syt- 1 might contribute to the membrane added in presynaptic neurons using a similar mechanism to what happens at the synapse.
Thus far, we know from research done in our lab that in embryonic day 8 chick forebrain neurons grown in culture, Syt-1 is present, even though synapses are not formed until days later. If the amount of Syt-1 is increased, more filopodia and branches are observed and as the amount is decreased, fewer filopodia and branches are observed. Syt-1 might serve to couple local calcium signals to filopodial outgrowth. In order to ultimately identify the mechanism by which Syt-1 is associated with filopodia, we first intend to alter Ca2+ levels (using Calcium ionophores and Calcium blockers) and observe the effects on filopodia and branch growth and lifespan.