In collaboration with the Samuel and Lichtman groups, we are mapping the wiring of the entire nervous system, from hatching to adulthood. We perform semi-automated reconstruction of the wiring diagram, or connectome by serial-section EM of individuals.
At birth, C. elegans has 218 neurons. 82 new neurons are incorporated before the end of larval development. These include sensory, motor, and interneurons that are located throughout the body, suggesting a system-wide remodeling of the juvenile circuit during post-embryonic development.
Combining partial reconstruction data of more than five different isogenic individuals, an adult connectome was mapped more than 30 years ago (The Mind of a Worm, 1986). This map served as the guide for the adult circuit functional interrogation, but is insufficient on its own to address how the circuit develops and varies among individuals.
Newly emergent technologies improve the fidelity and throughput of serial EM. With the Samuel and Lichtman groups, we have built a pipeline to reconstruct and compare the entire C. elegans nervous system across different developmental time points.
This evolving dataset
· provides answers to how anatomic remodeling takes place without interfering the circuit function
· serves as a framework to interrogate circuit underlying of sensorimotor behaviors during development.
Traces of all neurons, glia, and muscle cells entering the brain (nerve ring) of a first-stage larva, annotated using CATMAID.
Part of a scanning electron micrograph highlighting synapses in the brain (nerve ring) of a first-stage larva. Imaged by James Mitchell, the Samuel Lab.
The 3D model of a motor neuron pair undergoing remodeling
(16hr after hatching)
The complete connectome of a first-stage larva.
Nodes represent neuron and muscle classes; edges represent connections.