STOCK Ctsl^{tm1c(EUCOMM)Hmgu}/PraagJ

Stock number: 041403
Product name: Ctsl^f
Research areas: Cancer Research, Cell Biology Research, Research Tools

Description

Ctsl^f mice possess loxP sites flanking exons 3-6 of the Ctsl gene. These mice may be useful when studying protein metabolism, specifically related to immune response pathways.

Of note, the donating laboratory has also made a Ctsb^f available as Stock No. 041401.

Detailed description

CTSL (cathepsin L or Cat L) is a member of the C1 family of peptidases and functions as a lysosomal cysteine protease. Cat L has been implicated in antigen processing for immunity, particularly in MHC Class II presentation for T-cell selection. Mutations in the cathepsin L (Ctsl) gene have been associated with progression of certain cancers, autoimmune disease such as myasthenia gravis and also cardiac development issues. These Ctsl^f mice have loxP sites flanking exons 3-6 of the Ctsl gene.

Heterozygous and homozygous Ctsl^f mice are viable and fertile with no overt phenotype. When bred to mice that express tissue-specific Cre recombinase, resulting offspring will have exons 3-6 deleted, leading to complete loss of Cat L in the cre-expressing tissues. These mice may be useful when studying protein homeostasis, specifically related to proteins involved in immune pathways and certain cancers.

Of note, the donating laboratory has also made a Ctsb^f available as Stock No. 041401.

Development

Dr. Masaki Ohmuraya purchased C57BL/6N-derived JM8A3.N1 embryonic stem (ES) cells bearing the Ctsl^{tm1a(EUCOMM)Hmgu} targeted allele from the International Mouse Phenotyping Consortium (IMPC). The targeting cassette is composed of an FRT site followed by lacZ sequence and an initial loxP site upstream of exon 3 of the cathepsin L (Ctsl) gene. The first loxP site is followed by a neomycin resistance gene under the control of the human beta-actin promoter, SV40 polyA, a second FRT site and a second loxP site. A third loxP site is inserted downstream of exon 6. Targeted ES cells were injected into recipient blastocysts. The resulting chimeric mice were bred with FLP-Recombinase mice to excise the FRT-flanked lacZ-loxP-neo cassette. Some Ctsl floxed (Ctsl^f) mice, with the lacZ-loxP-neo cassette removed and floxed exons 3-6 intact, were bred with Ctsb floxed (Ctsb^f) mice (for details please see Stock No. 041401) until a double homozygous Ctsb floxed/Ctsl floxed (referred as Ctsb^f/f;Ctsl^f/f v1) mouse line was achieved.

This Ctsb^f/f;Ctsl^f/f v1 mouse line was transferred to Dr. Henriette van Praag. One Ctsb^f/f;Ctsl^f/f v1 male mouse was bred with a C57BL/6J female mouse (Stock No. 000664), and the resulting progeny were intercrossed for several generations until a double homozygous Ctsb floxed/Ctsl floxed (referred as Ctsb^f/f;Ctsl^f/f v2) mouse line was again established in the van Praag lab. This mouse line was then bred with a Ckmm-Cre mouse line (Stock No. 029100, wild-type for the Fxn allele) resulting in triple heterozygous offspring (Ctsb f/-; Ctsl f/-; Ckmm-Cre +/-). Triple heterozygous mice (F1) were intercrossed to produce F2 offspring, resulting in multiple genotype combinations, in which mice carrying specific genotypes were selected and maintained as independent colonies. Specifically, the Ctsl^f mice (Stock No. 041403) was isolated to generate a homozygous Ctsl^f/f mouse line. Ctsl^f homozygous mice were continually bred to Ctsl^f/f;Ckmm-Cre^+/- mice at each generation by the donating laboratory. Males that were homozygous for Ctsl^f and wildtype for Ckmm-Cre allele were provided to The Jackson Laboratory for sperm cryopreservation. To establish a live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes.

In 2026, 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 males sent to The Jackson Laboratory Repository. Two of the 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating, including the rd8 recessive mutation associated with retinal degeneration on Chromosome 1 within the Crb1 locus.

Allele

Symbol: Ctsl^{tm1c(EUCOMM)Hmgu}
Name: targeted mutation 1c, Helmholtz Zentrum Muenchen GmbH
MGI accession ID: MGI:6489575
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed)
Synonyms: Ctsl^f; Ctsl^fl
Marker symbol: Ctsl
Marker name: cathepsin L
Marker synonyms: 1190035F06Rik; Cat L; CATHL; CatL; CATL2; Ctsl1; CTSL2; CTSU; major excreted protein; MEP
Chromosome: 13
Strain of origin: C57BL/6N
Molecular note: The L1L2_Pgk_P cassette was inserted at position 64514008 of Chromosome 13 upstream of the third to sixth exon(s) (Build GRCm39). The cassette is composed of an FRT site followed by lacZ sequence and a loxP site. This first loxP site is followed by a neomycin resistance gene under the control of the PGK promoter, SV40 polyA, a second FRT site and a second loxP site. A third loxP site is inserted downstream of the targeted third to sixth exon(s) at position 64516516. The critical hird to sixth exon(s) is/are thus flanked by loxP sites. A "conditional ready" (floxed) allele was created by flp recombinase expression in mice carrying this allele to remove the lacZ sequence and neo selection cassette, leaving loxP sites flanking the critical exon(s). Further information on targeting strategies used for this and other IKMC alleles can be found at http://www.informatics.jax.org/mgihome/nomen/IKMC_schematics.shtml