STOCK Rbbp8^tm2Rjbr/J

Stock number: 037396
Product name: Ctip^T855A
Research areas: Cancer Research, Cell Biology Research, Research Tools

Description

The Ctip^T855A allele has a single amino acid substitution (Threonine-855 to Alanine) in the mouse Retinoblastoma Binding Protein 8 (Rbbp8, also called Ctip) gene. This point mutation removes an ATM/ATR phosphorylation site that regulates the DNA resection activity of the Ctip/MRN complex. These mice may be useful for studying DNA resection and homology-directed repair after DNA damage, as well as cancer biology.

Detailed description

The Rbbp8 gene codes for Retinoblastoma-Binding Protein 8 (RB Protein 8), also known as Ctip. Ctip complexes with many other proteins to facilitate DNA resection and homology-directed repair of double-strand DNA breaks (DSBs), regulate cell cycle progression and transcription. The Ctip^T855A allele has a point mutation at position 855 from Threonine to Alanine in the Rbbp8 gene, corresponding to the T859A mutation in humans. This mutation eliminates a phosphorylation site that regulates DNA resection activity of the Ctip/MRN complex.

Utilizing Ctip^T855A/T855A mice, the donating laboratory and their collaborators, investigated the role this specific Ctip residue (T855A) plays in B-cell development, class-switch recombination (CSR), V(D)J recombination, and initiation of DNA resection. Results indicated that phosphorylation of Ctip-T855 is essential for the induction of DNA resection in response to DNA damage, but is not required for CSR, V(D)J recombination, and lymphocyte viability in vivo.

Ctip^T855A/T855A homozygous mice are viable and fertile but are hypersensitive to radiation.

Development

The Ctip^T855A mutation was created by introducing a threonine to alanine substitution at residue 855 (T855A) into exon 18, followed by a loxP-neo-loxP cassette, in the Rbbp8 gene. The construct was electroporated into (129XB6)F1-derived KV1 embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts and the resulting chimeric mice were identified by genotyping and bred to C57BL/6J mice (Stock No. 000664). The resulting colony of Ctip^T855A mice were then crossed to B6.FVB-Tg(EIIa-cre)C5379Lmgd/J (Stock No. 003724) to remove the neo cassette. The Cre transgene was removed by selective breeding back to C57BL/6J mice. Heterozygous males with agouti coat color were sent to The Jackson Laboratory in 2022. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes.

Allele

Symbol: Rbbp8^tm2Rjbr
Name: targeted mutation 2, Richard J Baer
MGI accession ID: MGI:6764591
Generation method: Targeted
Attributes: Not Applicable
Marker symbol: Rbbp8
Marker name: retinoblastoma binding protein 8, endonuclease
Chromosome: 18
Strain of origin: (C57BL/6J x 129S6/SvEvTac)F1
Molecular note: A threonine to alanine substitution at residue 855 (T855A) was introduced into exon 18. The T855 in mouse corresponds to T859 in human which is phosphorylated by ATM/ATR.