The Isl1fl floxed allele has loxP sites flanking the homeodomain (exon 4) of the LIM-homeodomain factor Islet1 gene. Homozygous removal of the floxed sequences results in a phenotype consistent with complete loss of Isl1 function. These mice may be useful in studying cardiac development and early development of motor neurons/sensory neurogenesis.
Sylvia M Evans, University of California, San Diego
The Isl1fl allele has loxP sites flanking the homeodomain (exon 4) of the Isl1 gene.
The Isl1 gene encodes the LIM-homeodomain factor Islet1; critical for early development of motor neurons/sensory neurogenesis and essential for cardiac development. When bred to mice that express Cre recombinase, the resulting offspring may be useful in generating a tissue-specific Isl1 knockout. The donating investigator reports that homozygous removal of the floxed sequences results in a phenotype consistent with complete loss of Isl1 function.
For example, when bred to mice expressing Cre recombinase in Isl1 cells, the resulting Isl1 knockout homozygotes die during the perinatal period.
Similar lethality is observed when Isl1 ablation is directed to developing dorsal neural tube and neural crest cells by breeding to Wnt-1/GAL4/cre-11 mice (see Stock Nos. 003829/009107).
When Isl1fl mice are bred to have Isl1-ablation in differentiated cardiomyocytes (via Troponin T-Cre transgenic mice; Stock No. 024240), the resulting cTnT-Cre Isl1fl/fl mutants have severe bradycardia, increased heart-rate variability with long pauses and die from embryonic day (E)9.5-E11.5.
When Isl1fl mice are bred to have Isl1 ablation in sinoatrial node cells from E9.5 (via Hcn4-CreERT2 transgenic mice; Stock No. 024283), the resulting Hcn4-CreERT2 Isl1fl/fl mutants have sinus arrhythmia, fewer sinoatrial node cells and embryonic lethality by E11.5.
Mice homozygous for the Isl1fl allele are viable and fertile with no reported abnormalities.
A targeting vector was designed by Dr. Sylvia M. Evans (University of California, San Diego) to have the homeodomain (exon 4) of the ISL1 transcription factor, LIM/homeodomain gene (Isl1) on chromosome 13 flanked by a loxP site on one side, and a second loxP site and an frt-flanked neo cassette on the other side. The construct was electroporated into (129X1/SvJ x 129S1/Sv)F1-Kitl+-derived R1 embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts. The donating investigator reprts that chimeric males were bred with Black Swiss females to establish the colony.
Offspring were bred with the FLPeR deleter strain (Gt(ROSA)26Sortm1(FLP1)Dym on an outbred background; see Stock Nos. 009086 / 003946) for germline deletion of the neo cassette.
The resulting Isl1fl colony was maintained by breeding together and/or with Black Swiss mice for several generations (and the Flp-expressing transgene was removed). The Isl1fl colony was also bred to R26-LSL-tdTomato reporter mice (Ai14 mice six generations onto the Black Swiss genetic background ; see Stock No. 007914), and then later bred to Black Swiss to remove the R26-LSL-tdTomato allele.
In 2016, Isl1fl male mice with black coat color were sent to The Jackson Laboratory Repository.
Upon arrival, mice were bred to C57BL/6J inbred mice (Stock No. 000664) for at least one generation to establish our live Isl1fl colony.
|Allele Name||targeted mutation 2, Sylvia M Evans|
|Allele Type||Targeted (Conditional ready (e.g. floxed), No functional change)|
|Gene Symbol and Name||Isl1, ISL1 transcription factor, LIM/homeodomain|
|Strain of Origin||(129X1/SvJ x 129S1/Sv)F1-Kitl+|
|Molecular Note||Exon 4, which encodes the homeodomain of the protein product, was floxed by the insertion of a loxP site on one end and a loxP site and frt-flanked neo cassette on the other end. After germline integration, the frt-flanked neo cassette was removed from Isl1tm4Sev by crossing with FLPe transgenic strain.|
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 Isl1fl mouse strain in a publication, please cite the originating article(s) and include JAX stock #028501 in your Materials and Methods section.