C.129-Flt1^tm1Jrt/BannJ

Stock number: 022541
Research areas: Cardiovascular Research, Developmental Biology Research, Research Tools

Description

This knock-in/knock-out reporter strain expresses beta-galactosidase in endothelial cells from the endogenous mouse Flt1 locus.

Detailed description

The Flt1 (FMS-like tyrosine kinase 1) gene encodes a receptor tyrosine kinase that binds to the VEGFR-A, VEGFR-B and placental growth factor proteins and is critical to angiogenesis and vasculogenesis. These knock-in/knock-out mice carry a mutation of the Flt1 gene in which a lacZ-NEO cassette replaces sequence encoding the signal peptide. Although heterozygous mice are viable and fertile, homozygous mice have an embryonic lethal phenotype, failing to develop past E8.5. This strain is difficult to breed with less than expected inheritance of the mutation; the Donating Investigator breeds female heterozygotes to wildtype males.

No gene product (mRNA) is detected by RT-PCR analysis of homozygous embryos, aged E8.5. Approximately 50% of gene product (mRNA) is detected by RT-PCR and real-time RT-PCR analysis of heart tissue from heterozygotes. Homozygous embryos exhibit disorganized blood islands and developing vascular structures, with increased endothelial cell proliferation and vascular density. Heterozygotes also display increased endothelial cell proliferation and vascular density during embryonic development. Beta-galactosidase staining pattern of heterozygotes mimics the endogenous Flt1 expression pattern. Adult heterozygotes exhibit reduced ischemic preconditioning-mediated cardioprotection compared to wildtype controls.

In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. This is the case for the strain above. It should be noted that the phenotype could vary from that originally described. We will modify the strain description if necessary as published results become available.

Development

A targeting vector containing a lacZ-NEO cassette with 2 polyadenylation sites was used to disrupt sequence encoding the signal peptide. The construct was electroporated into 129 derived R1 embryonic stem (ES) cells. Correctly targeted ES cells were aggregated with CD-1 morulae. The resulting chimeric animals were tested for germline transmission. The mice were then backcrossed to BALB/c for more than 10 generations. Upon arrival at The Jackson Laboratory, the mice were crossed to BALB/cJ inbred mice (Stock No. 000651) at least once to establish the colony.

Allele

Symbol: Flt1^tm1Jrt
Name: targeted mutation 1, Janet Rossant
MGI accession ID: MGI:1857717
Generation method: Targeted
Attributes: Reporter; Null/Knockout
Marker symbol: Flt1
Marker name: FMS-like tyrosine kinase 1
Chromosome: 5
Strain of origin: (129X1/SvJ x 129S1/Sv)F1-Kitl⁺
Expressed genes: lacZ,beta-galactosidase,E. coli
Site of expression: Beta-galactosidase is expressed in endothelial cells.
Molecular note: A LacZ-neomycin resistance cassette replaced sequences that encode the signal peptide. The authors predict this is a null allele because the translation start site is removed and reinitiation at the first two downstream Kozak sequences would result in out-of-frame translated products.