Homozygotes are small, and only a fraction survive to weaning and breeding age. This strain may be useful in studies of development.
David Ginsburg, University of Michigan
These mice carry a spontaneous nonsense mutation in serine 57 of the Irs1 (insulin receptor substrate 1) gene that, in the homozygous state, produces small mice. Only a fraction of smla homozygotes survive to weaning and breeding age with significant losses beginning at postnatal day 21. Repeated backcrosses to C57BL/6J contributed to marked increases in lethality. Postmortem examination identified no significant gross or microscopic abnormalities aside from proportionally decreased stature and muscle wasting in a subset of mice. Western blot analysis of quadriceps muscle tissue demonstrates no detectable protein in mice homozygous for the mutation.
A spontaneous nonsense C->A point mutation occurred in serine 57 of the Irs1 gene in cultured 129S2/SvPas-derived D3 embryonic stem (ES) cells. ES cell clones were injected into C57BL/6J blastocysts. Mice were mated to B6D2F1 hybrid animals then backcrossed to C57BL/6J six times by the donating investigator.
|Allele Name||small phenotype|
|Allele Type||Spontaneous (Null/Knockout)|
|Gene Symbol and Name||Irs1, insulin receptor substrate 1|
|Strain of Origin||129S2/SvPas|
|Molecular Note||A spontaneous mutation produced a C-to-A transition that results in an amino acid substitution of serine to stop codon at position 57 (p.S57*). The absence of protein expression was confirmed by western blot analysis on muscle extracts.|
When maintained as a live colony, heterozygotes may be bred.
When using the B6.129S2-Irs1smla/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #007240 in your Materials and Methods section.