The RMCE cassette of the TI{CRIMIC.TG4.0}escCR00712-TG4.0 insertion in the third intron of esc has been replaced by a sequence cassette containing a splice acceptor, mutated esc exon 4 sequence, a polyadenylation signal and a Disc\RFPDsRed.3xP3.cUa marker, resulting in the expression of the mutant esc protein under the control of endogenous regulatory sequence. The mutated esc sequence contains a G235D amino acid replacement, which is equivalent to a G255D change in the orthologous human EED gene, a variant that is associated with hematological malignancy.