In vitro differentiated T cells from healthy control and MND-c.o.RAG1-rescued RAG1-SCID patient HSPCs show comparable TRB diversity to healthy PBMCs. GeneScan visualization of Dβ-Jβ (left column) and Vβ-Jβ (middle and right columns) TCR gene rearrangements using DNA from week 8 ATOs. Primers covering Dβ1, Dβ2, Jβ1.1-1.6 and Jβ2.1-2.6 and all 23 Vβ families were included. The Jβ1 cluster (Jβ1.1-6) is shown in green, the Jβ2 cluster (Jβ2.1-7) in blue. For the Vβ-Jβ rearrangements, the 13 Jβ primers were divided over 2 reactions: the middle column includes the first 9, Jβ1.1-1.6 and Jβ2.2, 2.6, 2.7 and the right column includes the remaining 4 (Jβ2.1, 2.3-2.5). (A) TRB rearrangements in healthy control PBMCs (used as polyclonal assay control), ATOs with differentiated mPB and UCB CD34⁺ HSPCs and a clonal assay control (cell line⁴⁰) for comparison. (B) ATOs with differentiated patients’ CD34⁺ HSPCs, corrected (+LV) and noncorrected.