C57BL/6J-Idh1^tm2Hyan/PrziJ

Stock number: 041714
Product name: Idh1^LSL:R132H
Strain synonyms: mIDH1
Research areas: Cancer Research, Developmental Biology Research, Mouse/Human Gene Homologs

Description

Idh1^LSL:R132H mice have a floxed sequence containing a STOP cassette and an FRT-flanked neo cassette downstream of exon 2 of the Idh1 gene. Endogenous exon 3 was replaced with a mutated exon 3 which has a CGA to CAC substitution, changing codon 132 from an arginine to a histidine (R132H), homologous to a missense mutation found in human gliomas. In the absence of Cre, this strain is an Idh1 knock-out. After Cre-recombination, removal of the floxed STOP cassette results in Idh1^R132H expression in Cre-expressing tissues of the offspring. Mutations in IDH1 have been identified in several cancers. This strain may be useful for studying the effect of tumor-associated mutant IDH1 (IDH1-R132H) on the various cells of origin for these cancers, as well as understanding the effect of the oncometabolite D-2HG on the microenvironment.

Detailed description

Idh1^LSL:R132H mice have a floxed sequence containing a STOP cassette and an FRT-flanked neo cassette downstream of exon 2 of the isocitrate dehydrogenase 1 (NADP+), soluble (Idh1) gene. Endogenous exon 3 was replaced with a mutated exon 3 which has a CGA to CAC substitution, changing codon 132 from an arginine to a histidine (R132H), homologous to a missense mutation found in human gliomas. Idh1 encodes an enzyme involved in the oxidative decarboxylation of isocitrate to α-ketoglutarate (α-KG) in an NADP⁺-dependent manner. IDH1 mutations have been observed in a number of cancer types, including sarcomas, hematologic malignancies, colon cancer and brain cancer, with the most frequent mutation being R132H. IDH1 mutations occur in the majority of low-grade gliomas, the most common primary malignant tumor of the central nervous system (CNS), and lead to the production of the oncometabolite, D-2-hydroxyglutarate (D-2HG).

In the absence of Cre, this strain is an Idh1 knock-out. Heterozygous Idh1^LSL:R132H/WT knock-out mice are viable and fertile. Homozygous Idh1^{LSL:R132H/LSL:R132H} mice are produced and survive at lower than the expected Mendelian ratios suggesting embryonic or perinatal lethality of homozygous knock-out mice. After Cre recombination, removal of the floxed STOP cassette results in Idh1^R132H expression in Cre-expressing tissues of the offspring.

Idh1^LSL:R132H/WT mice were subsequently bred to Nestin-Cre/ERT2 mice (see Stock No. 016261) with tamoxifen-inducible Cre recombinase expression in adult and developing mouse brain, including neuronal and glial cell precursors, and p53^fl/fl floxed mice (Stock No. 008462). Animals that harbor both the Idh1^LSL:R132H mutation and Tp53 deletion (Nestin-Cre/ERT2;Idh1^LSL:R132H/WT;Tp53^fl/fl) develop tumors at a penetrance of 15%. This is a reduction from the 50% penetrance seen in Tp53-deleted animals (Nestin-CreERT2;Tp53^fl/fl). Nestin-Cre/ERT2;Idh1^LSL:R132H/WT;Tp53^fl/fl tumor-bearing mice also display prolonged survival compared with Nestin-CreERT2;Tp53^fl/fl tumor-bearing mice. Neural stem cell (NSC) populations expressing Idh1-R132H display reduced proliferation due to p53-mediated cell-cycle arrest as well as a decreased ability to undergo neuronal differentiation.

Development

The Idh1^LSL:R132H mutant mouse line contains, from 5' to 3', a loxP site, three copies of the SV40 polyadenylation signal, a neomycin resistance (neo) cassette flanked with FRT sites, and a second loxP site downstream of exon 2 of the isocitrate dehydrogenase 1 (NADP+), soluble (Idh1) gene. Endogenous exon 3 was replaced with a mutated exon 3. Specifically, the mutated exon 3 has a CGA to CAC substitution, changing codon 132 from an arginine to a histidine (R132H), homologous to a missense mutation found in human gliomas. The construct was electroporated into C57BL/6J derived embryonic stem (ES) cells and correctly targeted ES cells were injected into blastocysts. Resulting mice were bred to C57BL/6J mice (Stock No. 000664) for at least 10 generations by the donating laboratory. Upon arrival at The Jackson Laboratory, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).

Allele

Symbol: Idh1^tm2Hyan
Name: targeted mutation 2, Hai Yan
MGI accession ID: MGI:8346388
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); Humanized sequence
Marker symbol: Idh1
Marker name: isocitrate dehydrogenase 1 (NADP+), soluble
Marker synonyms: E030024J03Rik; HEL-216; HEL-S-26; Id-1; IDCD; IDH; Idh-1; IDP; IDPC; PICD
Chromosome: 1
Strain of origin: C57BL/6J
Molecular note: This allele was created using the same construct as used in Idh1^tm1Hyan, but using the C57Bl/6 derived ES cells. The following elements were inserted into intron 2: a loxP site, a stop cassette, an FRT site flanked neomycin resistance gene cassette and a second loxP site. Exon 3 was replaced with an exon with a GA>AC substitution changing codon 132 from an arginine to a histidine codon (p.Arg132His). This creates a conditional-ready knock-in allele that will only express a transcript with the mutated exon 3 after cre recombination. The missense mutation replicates one commonly found in human gliomas.