Year: 2010
Type: dissertation
Abstract: dbx1 is a homeobox gene that is expressed in neuronal progenitors located in the intermediate region of the developing spinal cord.Neurons that derive from dbx1-expressing progenitors (V0 neurons) are predominantly commissural in amniotes, but their fine morphological and physiological properties are still largely unknown.Thus, I am attacking this issue using the zebrafish model system.Using transgenic zebrafish lines that express fluorescent proteins in dbx1-expressing cells and/or their progeny, I show that zebrafish V0 neurons are all commissural, consisting of both excitatory and inhibitory neurons.Morphologically, excitatory neurons are heterogeneous.Based on the trajectories of axons on the contralateral side of the body, V0 excitatory neurons can be subdivided into three groups: ascending, bifurcating and descending neurons.According to their dendritic morphologies, ascending and descending neurons can be further subdivided into two groups: multipolar and unipolar.By contrast, V0 inhibitory neurons are relatively homogeneous in morphology.Morphological features of V0 inhibitory neurons include: unipolar somata with dendrites coming off from the primary process, and bifurcating axons on the contralateral side of the body.The axonal length of V0 inhibitory neurons, on average, is shorter than that of V0 excitatory neurons.I also examined the firing patterns of V0 inhibitory neurons during fictive swimming.They tend to fire in phase with ventral root activity, suggesting that they are involved in reciprocal inhibition of body movements during swimming.The results of the present study will provide useful information for comparative studies of spinal neuronal circuits in other vertebrate species, including amniotes.
Author: Chie Satou
Language: English
Subfield: Cell Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W180022817