About
The Berghia Brain Project is funded by NIH BRAIN U01-NS108637 in collaboration with Jeff Lichtman (Harvard University), William Frost (Rosalind Franklin University), and Deirdre Lyons (University of California San Diego) and Vincent Lyzinski (UMass Math & Stats). We are developing new tools for high throughput analysis in a meso-scale brain to determine the neural basis of behavior in a species whose brain had never been studied before, the nudibranch mollusc, Berghia stephanieae.
Berghia has unique attributes facilitating neuroethological studies. First, it can be reared in the lab and has a 2-month generation time enabling developmental studies and establishment of stable transgenic lines. Second, the adult brain has only about 4000 neurons, many of which are large and accessible to direct manipulation and recording. Third, we know from other nudibranchs that behaviors are controlled by a small number of interneurons, allowing us to understand behavior at the cellular level. We have optimized protocols for generating a complete connectome of the Berghia brain at the synaptic level. The brain is being serially sectioned on the Automated Tape-collecting Ultramicrotome (ATUM) and imaged using volume electron microscopy. The resulting connectome will be aligned with a light-level atlas generated using light sheet microscopy in conjunction with CLARITY techniques and immunohistochemical labeling of neurons to identify individual cells. Identified neurons are being isolated and single neuron transcriptomes generated to determine the transmitters and receptors they express. We are characterizing behaviors performed by Berghia and have found that it readily tracks prey using olfactory cues. It also navigates using visual stimuli, indicating that it has spatial vision despite its extremely simple eyes. We have used voltage-sensitive dyes to record from many neurons simultaneously. Recordings will be aligned with the light-level atlas to identify the neurons and trace through the circuitry. We are developing tools to express bio-sensors in Berghia neurons and have successfully injected embryos with constructs to express GFP. Finally, we are developing network analysis tools to study the topology of the connectivity with rich data at each node. Among other things, this project serves as a proof-of-principle that the connectomics approach can be applied to study the neural basis of behavior in “non-model” species.