Unaltered expression of Bcl-2 and TAG-1/axonin-1 precedes sensory apoptosis in Brn3a knockout mice

Neuroreport. 2003 Feb 10;14(2):173-6. doi: 10.1097/00001756-200302100-00002.


Mice lacking the POU-domain transcription factor Brn3a exhibit growth defects in trigeminal axons, undergo extensive sensory cell death in late gestation, and die at birth. Based on tissue culture studies, the mediator of apoptosis Bcl-2 has been suggested as a target of Brn3a regulation which could affect sensory viability in these mice. In addition, Bcl-2 and the neural cell adhesion molecule TAG-1/axonin-1 have both been implicated in sensory axon guidance. In this study we examined wild-type and Brn3a knockout embryos for alterations in the expression of these genes. Trigeminal ganglia were harvested from embryonic day 13.5 mouse embryos, and Bcl-2 and TAG-1 expression were measured by RT-PCR. TAG-1 expression was also examined in the embryonic trigeminal and dorsal root ganglia by immunohistochemistry. The developing trigeminal ganglia of Brn3a knockout mice exhibit similar levels of Bcl-2 and TAG-1 mRNA expression. Immunohistochemical staining of TAG-1 also appeared to be quantitatively similar in the sensory axons of wild-type and knockout embryos. It is unlikely that Bcl-2 is a regulatory target of Brn3a, or that either of these factors mediates the defects in axon guidance and neuronal survival observed in the sensory ganglia of Brn3a knockout mice.

Publication types

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

MeSH terms

  • Animals
  • Apoptosis / physiology*
  • Cell Adhesion Molecules, Neuronal / analysis
  • Cell Adhesion Molecules, Neuronal / biosynthesis*
  • Contactin 2
  • DNA-Binding Proteins / deficiency*
  • DNA-Binding Proteins / genetics
  • Gene Expression Regulation / physiology
  • Genes, bcl-2 / physiology*
  • Mice
  • Mice, Knockout
  • Transcription Factor Brn-3
  • Transcription Factor Brn-3A
  • Transcription Factors / deficiency*
  • Transcription Factors / genetics
  • Trigeminal Ganglion / chemistry
  • Trigeminal Ganglion / embryology
  • Trigeminal Ganglion / metabolism


  • Cell Adhesion Molecules, Neuronal
  • Cntn2 protein, mouse
  • Contactin 2
  • DNA-Binding Proteins
  • Pou4f1 protein, mouse
  • Transcription Factor Brn-3
  • Transcription Factor Brn-3A
  • Transcription Factors