Transcriptional codes and the control of neuronal identity

Annu Rev Neurosci. 2002;25:251-81. doi: 10.1146/annurev.neuro.25.112701.142916. Epub 2002 Mar 27.


The topographic assembly of neural circuits is dependent upon the generation of specific neuronal subtypes, each subtype displaying unique properties that direct the formation of selective connections with appropriate target cells. Studies of motor neuron development in the spinal cord have begun to elucidate the molecular mechanisms involved in controlling motor projections. In this review, we first describe the actions of transcription factors within motor neuron progenitors, which initiate a cascade of transcriptional interactions that lead to motor neuron specification. We next highlight the contribution of the LIM homeodomain (LIM-HD) transcription factors in establishing motor neuron subtype identity. Importantly, it has recently been shown that the combinatorial expression of LIM-HD transcription factors, the LIM code, confers motor neuron subtypes with the ability to select specific axon pathways to reach their distinct muscle targets. Finally, the downstream targets of the LIM code are discussed, especially in the context of subtype-specific motor axon pathfinding.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Cell Differentiation / physiology
  • Efferent Pathways / cytology
  • Efferent Pathways / embryology*
  • Efferent Pathways / metabolism
  • Gene Expression Regulation, Developmental / physiology
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism*
  • Humans
  • Motor Neurons / cytology*
  • Motor Neurons / metabolism
  • Muscle, Skeletal / embryology
  • Muscle, Skeletal / innervation*
  • Muscle, Skeletal / metabolism
  • Spinal Cord / cytology
  • Spinal Cord / embryology*
  • Spinal Cord / metabolism
  • Stem Cells / cytology*
  • Stem Cells / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*


  • Homeodomain Proteins
  • Transcription Factors