Homozygous Isl1 (ISL1 transcription factor, LIM/homeodomain) targeted mutation embryos are arrested in their development soon after embryonic day 9.5 (E9.5) and demonstrate abnormalities in the organization of the vascular endothelium and its surrounding mesenchyme. Motor neurons are not generated without ISL1 protein and a population of interneurons that express engrailed 1 (EN1) also fails to differentiate in these mutant embryos.
Samuel L Pfaff, The Salk Institute
Homozygous embryos are arrested in their development soon after embryonic day 9.5 (E9.5) but exhibit an overtly normal organization of neural, mesodermal, and endodermal tissues. Histological analysis of embryos reveals abnormalities in the organization of the vascular endothelium and its surrounding mesenchyme, notably a disruption in the formation of the dorsal aorta. An impairment in vascular development is therefore a possible cause of the embryonic lethality in homozygous mutants. Motor neurons are not generated without ISL1 protein, although many other aspects of cell differentiation in the neural tube occur normally. A population of interneurons that express engrailed 1 (EN1), however, also fails to differentiate in these mutant embryos. ISL1 is required for the generation of motor neurons and motor neuron generation is required for the subsequent differentiation of certain interneurons.
Homozygote embryos analyzed at E9.5 express a modified transcript in mesodermal cells, but no expression is detected in neural tissues. No ISL1 immunoreactivity is detected in any tissues in homozygous mutant embryos, indicating that the targeted mutation eliminates expression of ISL1 protein.
Exon 3 (LIM domain 2) of the gene was replaced by a neomycin resistance cassette. The targeting vector was electroporated into 129S1/Sv Oca2+ Tyr+ Kitl +-derived W9.5/W95 embryonic stem (ES) cells. The line was initially backcrossed to C57BL/6 and then to CB6F1/J mice for 12 years by the donating laboratory.
|Allele Name||targeted mutation 1, Thomas M Jessell|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Isl1, ISL1 transcription factor, LIM/homeodomain|
|Strain of Origin||129S1/Sv-Oca2+ Tyr+ Kitl+|
|Molecular Note||A neomycin selection cassette was inserted such that the exon encoding the second LIM domain was deleted and that splicing from the exon encoding the first LIM domain to the exon encoding the homeodomain would result in a frameshift mutation. In situ hybridization did not detect transcript produced from this allele in the neural tube of homzygous mutant mice, but message was detected in the mesoderm ventral to the neural tube. Immunohistochemical analysis of homozygous mutant embryonic sections showed a lack of protein in all analyzed tissues.|
|Mutations Made By|| |
Thomas Jessell, Columbia University/HHMI
When maintained as a live colony, heterozygotes may be bred. Homozygotes are embryonic lethal.
When using the CB6-Isl1tm1Tmj/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #009645 in your Materials and Methods section.