(a) Top: schematic representation of the Sµ region of CH12F3-2A cells. Bottom: schematic representation of the Sµ region of CH12F3-2A cells. The 5′ Sµ region analyzed for SHM is underlined. The genomic DNA isolated from WT or Samhd1 KO CH12F3-2A cells from three independent experiments were pooled prior to SHM analysis. 