“…5 B ). Motifs of other TFs, including many critical to B cell development (ETS1, RUNX1, RUNX2, EBF1, SPIB, and GABPA) and/or already implicated in human primary immunodeficiencies (TCF3, IRF3, IRF4, and IRF8; Hambleton et al, 2011 ; Boisson et al, 2013 ; Andersen et al, 2015 ; Bravo García-Morato et al, 2018 ; Tangye et al, 2020 ), were also significantly overrepresented. Hence, PU.1 haploinsufficiency specifically limits the access of nonpioneer TFs, including those relevant to B cell development and/or associated with primary immunodeficiencies, to pro–B cell open chromatin.…”