Single disruption of Jmjd3 or Utx had partial effects on S1pr1 expression in mature OT-II thymocytes (Fig. 3c,d and Supplementary Fig. 5a), and caused a combination of thymocyte accumulation and lymphopenia, similar to but less marked than in dKO mice (Fig. 2i,j and Supplementary Fig. 5b,c). Here, KDM6B is linked to lymphopenia.