The BHDflox allele (Flcnflox) has loxP sites flanking exons 3-4 of the folliculin gene. Cre recombinase-induced removal of the floxed sequence creates a null allele. These BHDflox mice are useful in studying Birt-Hogg-Dube (BHD) syndrome; a rare cancer disorder caused by Flcn mutations that manifests in lung, kidney and skin, and also exhibits characteristics of ciliopathies.
Jindong Chen, University of Rochester
Birt-Hogg-Dube (BHD) syndrome is a rare cancer disorder caused by mutations of the tumor suppressor gene folliculin (Flcn or BHD). BHD manifests in lung (cysts), kidney (polycystic kidney disease and renal cell carcinoma) and skin (fibrofolliculomas), and also exhibits characteristics of ciliopathies. The BHDflox allele (Flcnflox) has loxP sites flanking exons 3-4 of the folliculin gene. Mice homozygous for the floxed allele are viable and fertile with no reported abnormalities. When bred to mice that express Cre recombinase, the resulting offspring will have functional FLCN expression deleted in the cre-expressing tissues.
For example, when bred to germline Cre-expressing mice (C57BL/6-congenic CMV-Cre; Stock No. 006054), the resulting global knockout homozygotes die in utero between 3.5-8.5 dpc. Those mice heterozygous for the global null allele (BHDflox/-) can survive up to two years with some animals developing renal cysts, renal tumors and other neoplasia in other organs.
Flcnflox mice allow studying cell/tissue-specific FLCN deficiency in the developing kidney (specifically in distal tubules, collecting ducts, and the thick ascending limb of Henle's loop) via breeding with C57BL/6-congenic Ksp-Cre transgenic mice (Stock No. 012237). Such homozygous mice (BHDflox/flox/Ksp-Cre) develop multiple renal cysts and rapid death; affected animals die in three weeks due to uraemia.
Furthermore, breeding BHDflox mice to C57BL/6 Sglt2-Cre transgenic mice (Tg(Slc5a2-cre)1Tauc) results in offspring with FLCN deficiency specifically in the renal proximal tubule. Those homozygous mice (Flcnflox/flox/Sglt2-Cre) develop bilateral cystic kidneys (~50% by 1 month of age), a wide spectrum of kidney tumor subtypes (multiple histological forms) and survival up to two years.
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 it was first characterized. The phenotype described above was for BHDflox mice on a mixed C57BL/6;129 genetic background. It should be noted that the phenotype of C57BL/6-congenic BHDflox mice could vary from that originally described on the mixed genetic background. We may modify the strain description if necessary as published results become available.
The BHDflox allele (Flcnflox) was created by Dr. Jindong Chen (while at Van Andel Research Institute, now at University of Rochester Medical Center). First, a targeting vector was designed to insert an attB site and loxP site upstream of exon 3, and also insert (from 5' to 3') a loxP site, frt-flanked neo cassette and attB site into intron 4 of the folliculin gene (Flcn or BHD) on chromosome 11.
The construct was electroporated into 129S4/SvJaeSor-derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts, and chimeric mice were bred with C57BL/6J mice for germline transmission and to establish the colony.
Offspring were bred with ACTB-FLPe transgenic mice (on a C57BL/6 background; see Stock No. 005703) for germline deletion of the neo cassette; leaving exons 3-4 flanked by loxP sites.
The donating investigator reports that the resulting BHDflox colony was bred with C57BL/6J wildtype mice for at least six generations (and the ACTB-FLPe transgene was removed). In 2016, BHDflox males with black coat color were sent to The Jackson Laboratory Repository.
Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).
Of note, it is not known if the Y chromosome has been fixed to the C57BL/6J background during backcrossing.
|Allele Name||targeted mutation 1, Bin Tean Teh|
|Allele Type||Targeted (Conditional ready (e.g. floxed), No functional change)|
|Gene Symbol and Name||Flcn, folliculin|
|Strain of Origin||129S4/SvJaeSor|
|Molecular Note||Exons 3 and 4 were flanked by loxP sites and an frt flanked neo cassette was inserted after the second loxP site via homologous recombination. The neo cassette was subsequently removed via Flp mediated recombination.|
When maintaining a live colony, heterozygous mice may be bred together, to wildtype mice from the colony or to C57BL/6J inbred mice (Stock No. 000664). Alternatively, homozygous mice may be bred together.
When using the BHDflox (Flcnflox) mouse strain in a publication, please cite the originating article(s) and include JAX stock #028718 in your Materials and Methods section.