Exon 2 of the Lin28a (lin-28 homolog A (C. elegans)) gene is flanked by loxP sites in this conditional targeted mutation strain. Cre excision of the floxed segment produces a knockout allele.
George Q. Daley, Children's Hospital Boston
LIN28A (lin-28 homolog A (C. elegans)) is an RNA-binding protein that blocks biogenesis of Mirlet7 (let-7) microRNAs. Let-7 targets are known regulators of mammalian body size and metabolism.
Exon 2 of the gene is flanked by loxP sites in this conditional targeted mutation strain. Cre excision of the floxed segment produces a knockout allele.
Muscle-specific knockout mice created through crosses with Myf5 (myogenic factor 5)-cre animals display glucose intolerance and reduced Insr (insulin receptor) expression.
Mice created from crosses with germline-specific Ddx4-cre mice (see Stock No. 006954) show dwarfism as early as E13.5 and by E18.5 show 20% reduction in weight relative to heterozygous controls. Although born at expected Mendelian ratios, roughly 93% of Lin28a knockout mice die within 1 day of birth (2 out of 5 mice harboring a cardiac ventricular septal defect). Those animals that survive are 30-50% smaller in weight and 20-30% shorter in length than controls. Dual-energy x-ray absorptiometry imaging confirms the decreased fat mass and also revealed decreased bone mineral density in the knockout animals, suggesting that these animals suffer from metabolic dysregulation.
Exon 2 was flanked by loxP sites and an FRT-flanked neomycin cassette was introduced through homologous recombination in (C57BL/6 x 129S4/SvJae)F1-derived v6.5 embryonic stem (ES) cells. The neomycin cassette was excised via a Flp recombinase. This strain was backcrossed to C57BL/6 for 6 generations by the donating lab (see SNP note below).
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. Five of the 27 markers throughout the genome were segregating suggested an incomplete backcross. Also, 3 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 1.2, George Q Daley|
|Allele Type||Targeted (Conditional ready (e.g. floxed), No functional change)|
|Gene Symbol and Name||Lin28a, lin-28 homolog A (C. elegans)|
|Strain of Origin||(C57BL/6 x 129S4/SvJae)F1|
|Molecular Note||A loxP site was inserted upstream of exon 2. An FRT flanked neo cassette with a 5' loxP site was inserted downstream of exon 2 via homologous recombination. FLP-mediated recombination removed the neomycin cassette.|
Homozygous and heterozygous floxed mice are viable and fertile.
When using the STOCK Lin28atm1.2Gqda/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #023913 in your Materials and Methods section.