RBFOX3 and Nijmegen breakage syndrome: Interestingly, A‐T BOs displayed premature neuronal and astrocytic differentiation as compared to WT controls, as indicated by the early increase in RNA expression and protein expression of the mature neuronal marker NeuN and the astrocyte marker GFAP in 3‐month‐old A‐T BOs (Figure 2d and f and Figure S3a–d), a phenomenon that appears to be conserved among genome instability syndromes, such as Nijmegen Breakage Syndrome (Martins et al. 2020).