In this strain a NEO cassette replaces exon 1 of the Lrat gene. Mice homozygous for this targeted mutation exhibit vitamin A deficiency, blindness and have applications in retinoic acid synthesis, retinoid homeostasis, and vitamin A metabolism research.
Krzysztof Palczewski, University of California, Irvine
Lecithin-retinol acyltransferase (phosphatidylcholine-retinol-O-acyltransferase) catalyzes the conversion of all-trans-retinol into all-trans-retinyl esters. Allelic variants of the human LRAT gene are implicated in severe early-onset retinal dystrophy and Leber congenital amaurosis. These mice carry a targeted mutation of the Lrat gene that replaces exon 1, including the ATG start codon, with a NEO cassette. Homozygous mice are viable, but exhibit vitamin A deficiency and blindness. Homozygotes are viable and fertile. However, on a vitamin A deficient diet, male homozygotes are often infertile. Levels of all-trans-retinyl esters are diminished in liver, lung, eye and blood. At 6 to 8 weeks of age, histological analysis reveals retinal rod outer segments (ROS) are approximately 35% shorter in length than control ROS. By 4.5 months of age, ROS from homozygotes are approximately half the length of wildtype control and exhibit a decrease of less than 10% in the number of photoreceptor nuclei. There is a significant loss of sensitivity of pupillary light responses and abnormal electroretinograms in homozygotes. Homozygotes are less susceptible to diethylnitrosamine induced hepatocarcinogenesis. During backcrossing, the Y chromosome may not have been fixed to the C57BL/6J genetic background.
A targeting vector containing a NEO cassette was used to disrupt exon 1, including the ATG start codon, and 2.2 kb of upstream sequence. The construct was electroporated into 129S6/SvEvTac derived TL1 embryonic stem (ES) cells.
Correctly targeted ES cells were injected into C57BL/6J blastocysts.
The donating investigator reported that the resulting chimeric animals were crossed to C57BL/6J mice for 5 generations (see SNP note below). During backcrossing, the Y chromosome may not have been fixed to the C57BL/6J genetic background.
Upon arrival at The Jackson Laboratory, the mice were crossed to C57BL/6J (Stock No. 000664) at least once to establish the colony.
A 48 SNP (single nucleotide polymorphism) panel analysis, with 43 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. Six markers throughout the genome were segregating, suggesting 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, Krzysztof Palczewski|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Lrat, lecithin-retinol acyltransferase (phosphatidylcholine-retinol-O-acyltransferase)|
|Strain of Origin||129S6/SvEvTac|
|Molecular Note||Part of exon 1, including ATG, was replaced by a neo cassette via homologous recombination. Protein expression was abolished in the eye of homozygous mutant mice as shown by immunocytochemistry. Western blot shows no protein in homozygous mutants.|
When maintaining a live colony, these mice can be bred as homozygotes. Homozygotes are viable and fertile. However, on a vitamin A deficient diet, male homozygotes are often infertile.
When using the B6;129S6-Lrattm1Kpal/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #018866 in your Materials and Methods section.