ZFIN ID: ZDB-PUB-040625-12
Engrailed-1 expression marks a primitive class of inhibitory spinal interneuron
Higashijima, S., Masino, M.A., Mandel, G., and Fetcho, J.R.
Date: 2004
Source: The Journal of neuroscience : the official journal of the Society for Neuroscience   24(25): 5827-5839 (Journal)
Registered Authors: Fetcho, Joseph R., Higashijima, Shin-ichi
Keywords: interneuron, spinal cord, transcription factor, zebrafish, circuitry, inhibition
MeSH Terms:
  • Amino Acid Transport Systems, Neutral/metabolism
  • Animals
  • Embryo, Nonmammalian
  • Glycine/metabolism
  • Glycine Plasma Membrane Transport Proteins
  • In Situ Hybridization
  • Interneurons/metabolism*
  • Interneurons/physiology
  • Interneurons/ultrastructure
  • Larva
  • Microscopy, Confocal
  • Nerve Tissue Proteins/biosynthesis*
  • Nerve Tissue Proteins/genetics
  • Patch-Clamp Techniques
  • Spinal Cord/embryology
  • Spinal Cord/growth & development
  • Spinal Cord/metabolism*
  • Time Factors
  • Transcription Factors/biosynthesis*
  • Transcription Factors/genetics
  • Zebrafish
  • Zebrafish Proteins/biosynthesis*
  • Zebrafish Proteins/genetics
PubMed: 15215305 Full text @ J. Neurosci.
Studies in chicks and mice have suggested that transcription factors mark functional subtypes of interneurons in the developing spinal cord. We used genetic, morphological, and physiological studies to test this proposed association in zebrafish. We found that Engrailed-1 expression uniquely marks a class of ascending interneurons, called circumferential ascending (CiA) interneurons, with ipsilateral axonal projections in both motor and sensory regions of spinal cord. These cells express the glycine transporter 2 gene and are the only known ipsilateral interneurons positive for this marker of inhibitory transmission. Patch recordings show that the CiA neurons are rhythmically active during swimming. Pairwise recordings from the CiA interneurons and postsynaptic cells reveal that the Engrailed-1 neurons produce monosynaptic, strychnine-sensitive inhibition of dorsal sensory interneurons and also inhibit more ventral neurons, including motoneurons and descending interneurons. We conclude that Engrailed-1 expression marks a class of inhibitory interneuron that seems to provide all of the ipsilateral glycinergic inhibition in the spinal cord of embryonic and larval fish. Individual Engrailed-1-positive cells are multifunctional, playing roles in both sensory gating and motor pattern generation. This primitive cell type may have given rise to several, more specialized glycinergic inhibitory interneurons in birds and mammals. Our data support the view that the subdivision of spinal cord into different regions by transcription factors defines a primitive functional organization of spinal interneurons that formed a developmental and evolutionary foundation on which more complex systems were built.