B6.129S1-Tpp1^tm1Plob/J

Stock number: 039036
Product name: Tpp1 KO
Research areas: Metabolism Research, Mouse/Human Gene Homologs, Neurobiology Research, Research Tools

Description

Tpp1 knock-out (KO) mice possess a loxP-flanked neomycin cassette in intron 11 of the tripeptidyl peptidase I gene (Tpp1), as well as a point mutation in exon 11, resulting in an arginine to histidine amino acid substitution (R446H). These Tpp1 KO mice demonstrate a null mutant phenotype prior to Cre-recombination. Removal of the floxed cassette with Cre recombinase generates an allele that expresses only the amino acid substitution (R446H), which yields a TPP1 hypomorph. These mice may be useful for studying the lysosomal storage disease, classical late-infantile neuronal ceroid lipofuscinosis (cLINCL).

Detailed description

The tripeptidyl peptidase I (Tpp1) gene codes for a lysosomal peptidase that cleaves N-terminal tripeptides from proteins. Mutations of this gene results in a build-up of cellular waste that leads to a neurological disorder, classical late-infantile neuronal ceroid lipofuscinosis (cLINCL). cLINCL patients display epileptic seizures, ataxia, vision loss and show developmental regression.

These Tpp1 knock-out (KO) mice carry a loxP-flanked neomycin cassette inserted into intron 11, as well as an arginine to histidine (R446H) missense mutation in exon 11. Prior to Cre-mediated recombination, homozygous Tpp1 KO mice demonstrate onset of tremors around 7 weeks of age along with progressive ataxia and neurodegeneration. The median lifespan for these Tpp1 KO mice, prior to Cre-recombination, is ~4 months of age. The donating laboratory notes that some homozygous mice, prior to Cre-recombination, may succumb to the disease possibly due to spontaneous seizure activity. After Cre-mediated recombination, only the R446H mutation is expressed, resulting in a TPP1 hypomorph with a later disease onset and median survival of ~9 months.

Heterozygous Tpp1 KO mice are viable and fertile with no overt phenotype. These mice may be useful for studying classical late-infantile neuronal ceroid lipofuscinosis (cLINCL).

It is important to note that the donating investigator has found differences in survival based on genetic background. They indicate that homozygous mice, prior to Cre-recombination, on a congenic 129SvEv background demonstrate extended survival by an average of 30 days, compared to those on a mixed B6;129 or congenic C57BL/6 background.

Development

The Tpp1 knock-out (KO) allele was generated using a targeting vector composed of an loxP-flanked neomycin cassette in intron 11 of the tripeptidyl peptidase I (Tpp1) gene. The construct also contains a missense mutation causing an arginine to histidine substitution (R446H) within exon 11. The construct was electroporated into 129S1/Sv-Oca2⁺ Tyr⁺ Kitl⁺-derived W9.5 embryonic stem (ES) cells. Targeted ES cells were injected into C57BL/6 blastocysts. The resulting chimeric mice were bred with C57BL/6 to establish germline transmission. The resulting heterozygous Tpp1 KO mice, with floxed neo cassette intact, were back-crossed to C57BL/6J mice for at least 10 generations by the donating laboratory. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).

Allele

Symbol: Tpp1^tm1Plob
Name: targeted mutation 1, Peter Lobel and David Sleat
MGI accession ID: MGI:3521972
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); Null/Knockout
Synonyms: CLN2^-; neo^insArg446His; Tpp1^-
Marker symbol: Tpp1
Marker name: tripeptidyl peptidase I
Marker synonyms: Cln2; GIG1; LPIC; SCAR7; TPP-1
Chromosome: 7
Strain of origin: 129S1/Sv-Oca2⁺ Tyr⁺ Kitl⁺
Molecular note: A floxed neo cassette was inserted into intron 11 and a missense mutation causing Arg446His was engineered within exon 11. Northern blot and RT-PCR analysis revealed that most of the mutant transcripts were mis-spliced and an enzyme assay for the gene product (tripeptidyl peptidase I) revealed no detectable activity.