Generation of mice with a conditional null allele for Tbx2.

The T-box transcription factor Tbx2 plays important roles in patterning and development, and has been implicated in cell-cycle regulation and cancer. Conventional disruption of Tbx2 results in abnormalities of the heart, limbs, eye and other structures, and early fetal lethality. To gain insight into the role of Tbx2 in different tissues and at different stages of development, we have generated a conditional null allele of Tbx2 by flanking Exon 2 with loxP sites (Tbx2(fl2)). Homozygous Tbx2(fl2) mice are viable and fertile, indicating that the Tbx2(fl2) allele is a fully functional Tbx2 allele. Cre-mediated recombination, using a ubiquitously active CMV-Cre line, results in deletion of Exon 2 and loss of protein expression. Embryos homozygous for the recombined allele (Tbx2(Delta2)) show the same heart and limb defects as conventional Tbx2-deficient embryos. This Tbx2 conditional null allele will be a valuable tool to uncover tissue-specific roles of Tbx2 in development and disease.