The genetic basis of the first connections in the brain
There are an estimated 100 billion neurons in the human brain, equal to the number of stars in our galaxy. These neurons are connected at specialized junctions called synapses, one type of which is electrical. Gap junction channels connect neurons at electrical synapses, allowing small molecules to pass between cells. Initial synapse formation is determined by the genetic code, which instructs where, when, and how neurons wire together to create circuits. Genetic defects believed to alter normal circuit wiring have been linked to neurodevelopmental disorders such as autism and schizophrenia, but the exact circuits and molecular mechanisms affected remain unclear. Critical to normal circuit wiring is the formation of the first synapses between neurons, as these lay the foundation upon which mature circuits are built; research has shown that these first synapses are electrical but it is unknown which genes are responsible and drive the continued development of the networks. This project aims to identify the genes required for the first synapses and investigate their roles from a genetic, neural circuit, and behavioral standpoint. We examined the first spinal cord circuits that wire together in zebrafish. These neural networks provide advantages to studying synapse formation because they wire together within 24 hours post fertilization via electrical synapses, are visualizable at the levels of neurons, circuit function, and behavior, and are genetically accessible. With this approach, we can identify the genes responsible for the first synapses formed in the brain and examine how these synapses impact early circuit wiring.