Mutations tested included six class I mutations, which destabilize the NRR; one class II mutation (from the T-ALL cell line P12-Ichikawa) consisting of a direct repeat in exon 27 of Notch1 that duplicates a 14 amino acid sequence containing the S2 cleavage site [26]; one juxtamembrane class III mutation (from the T-ALL cell line Jurkat) consisting of a direct repeat in exon 28 of Notch1 that inserts a 17 amino acid sequence [58]; and VSV, an artificial mutation that inserts 14 amino acids into the juxtamembrane region [58]. Here, NOTCH1 is linked to acute lymphoblastic leukemia.