V_H14-2 mediated nuclear speckles association contributes to radial positioning of the Igh locus and regulates VDJ recombination

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Presentation Time: 03:15 PM - 04:30 PM
Poster Board Number: B700
Abstract ID: 4651

Presenting Author:
Saurabh Priyadarshi , Research Assistant Professor at Univ. of Illinois Col. of Med.

Abstract:

The Igh locus undergoes large-scale contraction and repositions to the nuclear center prior to V(D)J recombination. However, little is known about the mechanisms that mediate these processes. We recently identified a chromatin loop anchor which corresponds to a highly transcribed V_H gene promoter (V_H14-2 Pr) (Nat Commun 14:1225, 2023). Here we report that V_H14-2 deletion increased locus contraction which was expected to increase VDJ recombination. However, deletion of the V_H14-2 gene severely reduced VDJ recombination. This implied that another mechanism may contribute to VDJ recombination. Strikingly, Igh loci accumulated toward nuclear periphery in Rag2^-/-V_H14-2^-/- pro-B cells indicating the failure of radial repositioning. Thus, efficient VDJ recombination is linked to repositioning of the Igh locus and implies that the V_H14-2 gene anchors the locus in the nuclear center. Highly transcribed genes often associate with nuclear speckles that tend to locate to the nuclear center. As V_H14-2 is highly transcribed we asked whether it associates with nuclear speckles. We found that the Igh locus overlaps with nuclear speckles and this association was significantly reduced in Rag2^-/-V_H14-2^-/- pro B cells as visualized using a combination of DNA and immuno-fluorescence in situ hybridization (FISH). This study identified the V_H14-2 gene as a tether that anchors the locus to nuclear speckles and in turn contributes to radial positioning and VDJ recombination.