These targeted mutation mice carry a floxed allele of transcriptional co-repressor Tgif1 (TGFB-induced factor homeobox 1). Cre excision of floxed exons 2 and 3 creates a gene knockout.
Christopher Walsh, Boston Children's Hospital
Tgif1 (TGFB-induced factor homeobox 1) is a member of the evolutionarily-conserved three-amino-acid loop extension (TALE) superclass of atypical homeodomain proteins. It acts as a transcriptional co-repressor that modulates responses to TGFB signaling and plays a role in regulating retinoic-acid-mediated gene expression. Mutation of the mouse gene results in relatively mild developmental phenotypes on most strain backgrounds. Knockout of both Tgif1 and Tgif2 results in a failure of embryonic gastrulation. Mutations in the human TGIF1 gene have been associated with holoprosencephaly.
Exons 2 and 3, encoding 98% of the amino acids in one isoform of the protein and 100% of the other, are flanked by loxP sites in this conditional knockout allele. Cre excision of the floxed segment can direct tissue-specific knockouts of the gene. Animals made homozygous for a widespread knockout via crosses with a human β-actin-driven Cre deleter line are viable and fertile without discernible derangements in any of the major organ systems, including the forebrain.
A targeting vector was constructed by inserting a loxP site 75 bp upstream of exon 2 and an inverted PGK-Neo cassette flanked by FRT-loxP sites 181 bp downstream of exon 3 after the poly(A) signal. The targeting construct was electroporated into 129/SvEv-derived embryonic stem (ES) cells. G418 resistant ES cell clones were screened for homologous recombination by Southern hybridization. Desired recombinant ES clones were selected and injected into C57BL/6J blastocysts. The resultant chimeras were crossed with C57BL/6J mice for germline transmission. The conditional allele was generated by crossing animals with human β-actin FLP deleter mice of mixed genetic background to remove the PGK-Neo cassette and one loxP site, leaving two loxP sites flanking exons 2 and 3. Mice with the conditional allele were backcrossed with C57BL/6J for at least 6 generations by the donating lab (see SNP note below).
A 32 SNP (single nucleotide polymorphism) panel analysis, with 27 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. Ten markers throughout the genome were found to be segregating with 129, suggesting an incomplete backcross.
|Allele Name||targeted mutation 1, Christopher A Walsh|
|Allele Type||Targeted (Conditional ready (e.g. floxed), No functional change)|
|Gene Symbol and Name||Tgif1, TGFB-induced factor homeobox 1|
|Strain of Origin||129S/SvEv|
|Molecular Note||A targeting vector was used to flank exons 2 and 3 with loxP sites. An FRT-flanked neomycin resistance gene was inserted downstream of the floxed sequence. Crossing with FLPe deleter mice removed the neo.|
Homozygous and heterozygous mice are viable and fertile.
When using the B6;129S-Tgif1tm1Caw/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #021443 in your Materials and Methods section.