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Engrailed-1 expression marks a primitive class of inhibitory spinal interneuron
Shin-ichi Higashijima1, Mark A Masino, Gail Mandel
1Department of Neurobiology and Behavior, State University of New York at Stony Brook, Stony Brook, New York 11794-5230, USA.
Summary
Engrailed-1 marks a specific type of spinal cord interneuron in zebrafish that inhibits other neurons and is active during swimming. This finding reveals a primitive functional organization in the developing spinal cord.
Area of Science:
- Neuroscience
- Developmental Biology
- Genetics
Background:
- Transcription factors are hypothesized to define functional interneuron subtypes in the developing spinal cord.
- Previous studies in chicks and mice suggest a link between transcription factors and interneuron function.
Purpose of the Study:
- To investigate the role of Engrailed-1 in zebrafish spinal cord development.
- To determine if Engrailed-1 marks specific interneuron populations and their functions.
Main Methods:
- Genetic analysis to identify Engrailed-1 expressing cells.
- Morphological studies to analyze axonal projections.
- Physiological recordings (patch clamp) to assess neuronal activity and synaptic connections.
Main Results:
- Engrailed-1 expression uniquely identifies circumferential ascending (CiA) interneurons with ipsilateral projections.
- CiA interneurons express glycine transporter 2 and are rhythmically active during swimming.
- Engrailed-1 neurons provide monosynaptic inhibition to sensory interneurons, motoneurons, and descending interneurons.
Conclusions:
- Engrailed-1 marks a class of inhibitory interneuron essential for ipsilateral glycinergic inhibition in the zebrafish spinal cord.
- These multifunctional interneurons play roles in sensory gating and motor pattern generation.
- The Engrailed-1-positive interneuron subtype represents a primitive functional organization with evolutionary significance.