Neuroendocrine cells release neurotransmitters and hormones to control body functions often in response to chemical or mechanical activation. However, we still lack the knowledge of how neuroendocrine cells develop, how they are activated, and the functional importance of their extrasynaptic signaling. In C. elegans, there are four uterine-vulval (
uv1) neuroendocrine cells at the ventral surface of the vulval canal which release tyramine and neuropeptides that inhibit egg-laying behavior. Our previous studies have shown these cells are mechanically activated following egg-laying events, but whether the
uv1 cells respond to vulval opening or passage of eggs through the uterus was not clear. We developed an optogenetics approach to stimulate vulval muscle contraction while recording
uv1 cell Ca2+ activity. These studies indicate that vulval opening, not egg release, drives
uv1 activity. We also discovered that mechanical prodding of the
uv1 cells was sufficient to induce calcium activity, confirming the
uv1 cells respond directly to mechanical activation. We are presently manipulating the time and speed of the mechanical stimulus in juvenile and adult animals to determine how these parameters affect
uv1 activation. [KMC1] To determine if prodding of the vulva triggers vulval muscle contraction which then drives
uv1 activation, we will analyze
uv1 activation in
unc-54 muscle myosin mutants unable to contract the vulval muscles. We have recently shown that vulval muscle contraction stimulates Ca2+ activity in the cholinergic VC neurons that innervate the vulval muscles. The
uv1 cells express muscarinic acetylcholine receptors that might modulate
uv1 activity following VC signaling. We will block VC synaptic transmission with Tetanus Toxin to test whether acetylcholine signaling from the VCs affects
uv1 activation. To identify molecules required for
uv1 activation, we identified new mutants that do not show
uv1 Ca2+ activity in response to egg laying. Some mutants affect
uv1 cell development while others affect activation. We are presently using a Hawaiian single nucleotide polymorphism mapping strategy followed by whole-genome sequencing to identify the mutant genes. We predict the genes will encode conserved factors that function generally to regulate the development and activation of neuroendocrine cells like
uv1 that regulate core body functions including reproduction and metabolism.