Fig. 1

Differential XPB steady state levels in the Xpb^y/y knock-in mouse model. a Low magnification confocal image mosaic of a cortex cryosection (Xpb^y/y mouse), showing the YFP signal in green and Dapi in red to enhance contrast in the merged image. Individual cells are singled out by the strictly nuclear XPB-YFP and/or Dapi signals. Background and auto-fluorescence limits the YFP detection of weakly expressing cells that appear orange/red in the merged image. b Neurons and a Glial cell imaged within a living organotypic slice of cortex (Xpb^y/y mouse). The Glial cell is easily distinguished from the neurons by its smaller nucleus size and condensed chromatin [32] dyed with the supravital DNA marker Draq5 (Biostatus, UK). The measured average nuclear YFP signal in both cell types (N = 24) is plotted in the accompanying graph, which shows a fivefold difference in the TFIIH concentration between these two cell types. c Plot of the total XPB-YFP signal per cell versus the reconstructed volume occupied by the YFP signal of each analysed cell. In each of these tissues, cell to cell variations of the total quantity of XPB-YFP and of the nuclear volume cancel out in a non-trivial fashion, resulting in cells with the same nuclear XPB-YFP concentration. Radial dotted lines represent constant XPB-YFP concentrations