Northern blot analysis of murine T-ALL cell lines reveals 2 types of aberrant Notch1 transcripts. Northern blot analyses used polyA RNAs from normal murine thymus or the indicated cells lines. Panels A, B, and C correspond to Northern blots hybridized to probes A (exon 34), B (exon 26), or C (exon 1), which are homologous to the regions shown in the cartoon of the Notch1 locus above the blots. Numbers correspond to the position of RNA size markers in kilobases. FL indicates full-length Notch1 transcript. *Short Notch1 transcripts.