Aberrant transcription of unrearranged T‐cell receptor β gene in mouse brain

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Abstract
The nervous system and the immune system share several functional molecules involved in various cell–cell interaction events. In this study, we used in situ hybridization to identify immune molecules that are expressed by a restricted population of neurons in the mouse brain and found that mRNA for the β subunit of T-cell receptor (TCRβ) was predominantly and strongly localized to neurons in deep layers of the cerebral neocortex and weakly expressed in the thalamus. Developmentally, TCRβ mRNA expression started at embryonic day 15 in the thalamic nuclei and at postnatal day 1 in the cerebral neocortex. The level of TCRβ mRNA in the neocortex subsequently increased until postnatal day 21, and it remained high in the adult. Detailed analysis revealed that only the Cβ2 segment of TCRβ, not the Cβ1 or Vβ segments, was expressed by the brain neurons. By the 5′ rapid amplification of cDNA ends method, we determined a brain-specific transcription start site in the Jβ2 region locus, not in the Vβ region locus. Furthermore, we confirmed that the aberrant transcription around the Jβ2 region took place only in neurons and lymphocytes in transgenic mice. These results demonstrate that the transcriptional machinery for unrearranged TCRβ expression is shared by the nervous and immune systems and raise a possibility of gene rearrangement in neurons under certain circumstances. J. Comp. Neurol. 469:214–226, 2004.