NKX2-5 is a transcription factor involved in the formation/development of the heart and other developing structures (including pharyngeal arch, thymus and spleen). Mutations of NKX2-5 have been implicated in familial cases of atrial septal defect (ASD) with severe atrioventricular conduction block.

The Nkx2.5-Cre knock-in/knock-out allele has a Cre recombinase gene inserted in-frame into exon 2 of the Nkx2-5 locus - this abolishes endogenous gene function and results in the Nkx2-5 promoter/enhancer regions directing cre expression. When Nkx2.5-Cre mice are bred with mice containing lox-flanked (floxed) sequences, Cre-mediated recombination will result in deletion of the floxed sequences in NKX2-5-expressing cells in the offspring.

The donating investigator summarizes that Nkx2.5-Cre mice express Cre recombinase in a pattern consistent with the endogenous gene in embryonic heart, as well as developing tongue, thymus and spleen. Earliest heart expression is observed at embryonic day (E)7.5 in cardiac progenitor cell pools that form the cardiac crescent - therefore cre expression is reported in cardiomyocytes, endocardium, dorsal mesocardium, pericardial mesoderm, epithelium of the first pharyngeal arch and second heart field. Whereas the original publication (Moses et al. 2001 Genesis 31:176) claimed no Cre recombinase activity was reported in endocardial cells or the endocardial cushions, the donating investigator now states that cre expression should be observed in both myocardium and endocardium - the endocardium may be mosaic. The donating investigator did not examine the presence/absence of cre expression in tissues other than those described above.

Heterozygotes are viable and fertile with no reported phenotype abnormalities. Mice homozygous for Nkx2.5-Cre are embryonic lethal due to cardiac malformation (similar to other published knock-out alleles). Although no Nkx2.5 expression is expected from this Nkx2.5-Cre knock-in/knock-out allele, the absence of Nkx2.5 mRNA or protein has not been examined to date (December 2016).

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Nkx2.5-Cre knock-in/knock-out allele was designed to both abolish endogenous gene function and allow the Nkx2-5 promoter/enhancer regions to direct Cre recombinase expression to embryonic heart, as well as developing tongue, thymus and spleen. These mice may be useful for recombining lox-flanked (floxed) alleles in studying cardiac development.

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Our minimum guarantee for cryorecovery orders is 2 carriers. To ensure that your colony can be rapidly expanded upon arrival, additional carriers may be added to your order.

B6129S1-Nkx2-5<tm1(cre)Rjs>/J Frozen Embryo