Mice homozygous for this Ift20flox allele are viable and fertile, with loxP sites flanking exons 2-3 of the Ift20 locus. When bred to mice that express Cre recombinase, the resulting offspring will have sequences encoding the first 71 codons (including the start codon) deleted in the cre-expressing tissues; this is expected to produce a null allele.
Gregory J Pazour, University of Massachusetts Medical Sch.
These Ift20flox mice harbor loxP sites flanking exons 2-3 (encoding the first 71 codons including the start codon) of the intraflagellar transport 20 homolog (Chlamydomonas) locus. The primary cilium is a microtubule-based antenna-like structure that emanates from the surface of virtually all cells in the mammalian body. The primary cilium functions as a sensory organelle (mechano-, chemo-, photo-receptor) that receives signals from other cells/the environment, and transmits these signals to the nucleus to elicit a cellular response. Most types of eukaryotic cilia and flagella are assembled and maintained by the process of intraflagellar transport (IFT). During IFT, large protein complexes (IFT particles) are transported along the ciliary microtubules under the ciliary membrane. IFT particle proteins organize into at least three distinct complexes called complex A, complex B and the Golgi IFT complex. The unique role of Ift20 in both complex B as well as the Golgi IFT complex is particularly noteworthy. Because of the widespread presence of primary cilia in multiple organ systems, these Ift20flox mutant mice may be useful in generating conditional mutations for studying IFT proteins in eukaryotic ciliary assembly, primary cilium in cell signaling pathways associated with embryonic development and tissue homeostasis in adults, as well as carcinogenesis/cancer, cystic kidney disease, retinal degeneration/blindness, obesity, and other diseases.
For example, when Ift20flox mice are bred with mice expressing Cre recombinase in the male germline (Prm-Cre: see Stock No. 003328), the resulting offspring have pan-deletion of Ift20 function; resulting in embryonic lethality. In addition, when Ift20flox mice are bred with mice expressing Cre recombinase in during embryonic kidney development (HoxB7-Cre: see Stock No. 004692), the resulting offspring have deletion of Ift20 function in the mechanoreceptors of the kidney tubule epithelium/collecting ducts; resulting in polycystic kidney disease.
A targeting vector was designed to insert a frt-flanked neomycin cassette and loxP site upstream of exon 2, and a second loxP site (together with an NdeI site) downstream of exon 3 of the Ift20 (intraflagellar transport 20 homolog (Chlamydomonas)) locus. The construct was electroporated into 129S7/SvEvBrd-Hprtb-m2 derived AB2.2 embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts and chimeric mice were bred with C57BL/6J mice to establish the Ift20neo colony. The Ift20neo mice were then bred to FLPeR mice (on a C57BL/6J;129S4 genetic background; see Stock No. 003946) to remove the frt-flanked neo cassette. The resulting Ift20flox mice (with a single frt site and loxP site remaining upstream of exon 2, and a second loxP site downstream of exon 3) were selected. The dontating investigator reported that these Ift20flox mice were backcrossed to C57BL/6J (see SNP note below) for ten generations (and the FLPe-expressing mutation was removed) prior to sending to The Jackson Laboratory Repository. Upon arrival, mice were bred to C57BL/6J (Stock No. 000664) for at least one generation to establish the colony.
A 32 SNP (single nucleotide polymorphism) panel analysis, with 27 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the rederived living colony at The Jackson Laboratory Repository. While the 27 markers throughout the genome suggested a C57BL/6 genetic background, 1 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6J ; C57BL/6N genetic background.
|Allele Name||targeted mutation 1.1, Gregory J Pazour|
|Allele Type||Targeted (Conditional ready (e.g. floxed), No functional change)|
|Gene Symbol and Name||Ift20, intraflagellar transport 20|
|Strain of Origin||129S7/SvEvBrd-Hprtb-m2|
|Molecular Note||An frt flanked neo cassette followed by a loxP site were inserted into intron 1 and a second loxP site was inserted into intron 3 via homologous recombination. The neo cassette was then removed via in vivo Flp mediated recombination.|
|Mutations Made By|| |
Gregory Pazour, University of Massachusetts Medical Sch.
When maintaining a live colony, homozygous mice may be bred together.
When using the B6.129S7(129S4)-Ift20tm1.1Gjp/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #012565 in your Materials and Methods section.