MybF/F floxed mutant mice possess loxP sites flanking exon 6 of the myeloblastosis oncogene (Myb). MYB is a transcription factor involved in the proliferation and differentiation of hematopoietic progenitor cells. Mice that are homozygous for this allele are viable and fertile. When these mutant mice are bred to mice that express Cre recombinase, resulting offspring will have exon 6 deleted in cre-expressing tissues.
When crossed to B6.Cg-Tg(Lck-cre)548Jxm/J mice (Stock No. 003802) expressing Cre recombinase T lymphocytes, T cells in resulting mybF/F/LckCre mice did not progress from the DN3 stage to the DN4 stage of thymocyte development. Thymic cellularity is decreased to 11% of that seen in controls. Double positive (DP) thymocytes are reduced by 62% compared to littermate controls.
When crossed to B6.Cg-Tg(Mx1-cre)1Cgn/J mice (Stock No. 003556) expressing Cre recombinase in adult bone marrow, resulting mybF/F/MxCre mice have reductions of hematopoietic lineages including neutrophilic, monocytic, B lymphoid, erythroid, and, megakaryocytic cells after polyinosinic-polycytidylic acid (pIpC) administration.
Stock No. 035170, a similar strain with loxP sites flanking exon 2, takes into account that splicing of nascent Myb mRNA between exon 1 and 2 occurs in the first reading frame, whereas all other known splices between coding exons are in the second and third reading frames. Thus, there
are no known splicing events that could occur in frame down stream of exon 1 after Cre mediated deletion of exon 2. c-Myb proteins are not detected using antibodies that
recognize epitopes in the N- or C-terminal ends after cre recombination in this line.
This Stock No. 028881 with exon 6 floxed, targets the c-Myb DNA binding domain, rather than exon 2. Due to a variety of c-My splice variants expressed from different promoters, deletion of exon 6 may still produce a truncated protein driven by a promoter that is still present upstream of exon 2. This includes 2 major variants that involve exons 9 and 9A.
