B6.129-Myb^tm1Epr/J

Stock number: 028881
Product name: Myb^F
Research areas: Developmental Biology Research, Hematological Research, Research Tools

Description

Myb^F/F floxed mutant mice possess loxP sites flanking exon 6 of the myeloblastosis oncogene gene. This strain may be useful for studying the proliferation and differentiation of hematopoietic progenitor cells.

Detailed description

Myb^F/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 myb^F/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 myb^F/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.

Development

A targeting vector was designed to insert a loxP-flanked neomycin resistance (neo) cassette upstream of exon 6, and a single loxP site downstream of exon 6 of the myeloblastosis oncogene (Myb) gene. The construct was electroporated into (129X1/SvJ x 129S1/Sv)F1-Kitl⁺-derived R1 embryonic stem (ES) cells. Correctly targeted ES cells were transiently transfected with a pPGKcre-bpA expression plasmid to delete the neo cassette. Resulting ES cells contained multiple gene rearrangments; intact floxed-exon 6, intact floxed-neo cassette, or excision of both exon 6 and the neo cassette. Correctly targeted ES cells, containing only the floxed-exon 6, were injected into C57BL/6 x DBA2 blastocysts and resulting chimeric males were bred with C57BL/6J females. Resulting Myb^F/F offspring were bred to C57BL/6J mice for at least 10 generations. Upon arrival at The Jackson Laboratory, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).

Allele

Symbol: Myb^tm1Epr
Name: targeted mutation 1, E Premkumar Reddy
MGI accession ID: MGI:3497746
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); No functional change
Marker symbol: Myb
Marker name: myeloblastosis oncogene
Chromosome: 10
Strain of origin: (129X1/SvJ x 129S1/Sv)F1-Kitl⁺
Molecular note: Exon 6 encoding the high-affinity DNA-binding domain was flanked with loxP sites by homologous recombination of a construct that also contained a PGK-neo and thymidine kinase selection markers. The PGK-neo-thymidine kinase marker was excised by transient transfection of properly targeted ES cells with a cre-expressing plasmid and left exon 6 flanked by loxP sites.