Fetal thymic organ cultured cells expressed multiple DJβ rearrangements. Genomic DNA was isolated from thymocytes generated from CD34⁺ CB cells (lobes D35/control) or from CD34⁺ γc transduced BM patient cells (lobes D35/γ + S1) after 35 days of organ culture. DNA was then amplified by PCR using TBF1 and TBR1 primers to detect Dβ1-Jβ1 rearrangements. PCR products were blotted and hybridized with the TBR3 probe. Total thymocytes and fibroblasts served as positive and negative controls, respectively. (Right) Positions of the genomic fragment and the specific rearrangements of Dβ1 to the Jβ1-1-Jβ1-6 elements.