Genome sequencing has revealed that primitive animals which lack nervous systems, and single-celled organisms which diverged prior to the emergence of animals, possess a striking complement of genes with crucial and specialized roles in neurons and muscle. Included in these are voltage-gated calcium (Cav) channels, which are essential for translating electrical signals at the cell membrane to intracellular events including pre-synaptic exocytosis, muscle contraction, control of ciliary beating, and changes in gene expression associated with neuronal learning and memory and synaptic plasticity.
In the Senatore lab, we are interested in how and when specific cellular processes that involve Cav channels, critical for nervous system function, evolved. Thus, we employ a broad range of techniques, including molecular biology, electrophysiology, genomics and proteomics to identify evolutionary changes in Cav structure, function and complexing associated with nervous system evolution.
Trichoplax adhaerens
One very intriguing basal animal is Trichoplax adhaerens, which lacks chemical and electrical synapses and muscle, yet is capable of coordinating cellular activities to conduct motile behavior such as feeding, chemotaxis and phototaxis (see real-time video below of Trichoplax “gliding”, viewed under 20x and 40x magnification). In our current research, we are evaluating the presence of key “synaptic” protein interactions involving Trichoplax Cav channels, which in synapses, are positioned within nanometers of the Ca2+-sensitive exocytotic machinery to ensure fast, synchronous neurotransmission.
We also interested in ctenophores (i.e. comb jellies such as Mnemiopsis leidyi), reported in recent phylogenetic studies as the most early-diverging animals. Ctenophores have fairly elaborate nervous systems and muscle cell types, which is remarkable given that two animal phyla that lack nervous systems, Porifera (sponges) and Placozoa (Trichoplax), separate them from all other animals with nervous systems (see phylogeny). Some thus suggest that ctenophores independently evolved neurons and muscle. Similar to Trichoplax, we are seeking to understand the function and complexing of Cav channels in ctenophores, especially in the context of synaptic transmission and muscle contraction.