Germline transcription from T-cell receptor Vβ gene is uncoupled from allelic exclusion

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Abstract
Allelic exclusion operates in B and T lymphocytes to ensure clonal expression of antigen receptors after V(D)J recombination. Germline transcription, which proceeds V(D)J recombination, has been postulated to provide an instructive signal for allelic exclusion. Here, we use a genetic marker to track germline transcription from a Vβ gene within the TCRβ locus. We find that developing thymocytes exhibit uniformed, bi‐allelic activation of the Vβ gene before V‐DJ recombination, a process subject to allelic exclusion. We further show that V‐DJ rearrangement promotes activation rather than silencing of germline transcription from the remaining Vβ genes on either the functionally or non‐functionally rearranged chromosome. Results presented here suggest that germline transcription, although necessary for V(D)J recombination, is not sufficient to instruct allelic exclusion.