Hoxb4-ENE-GFPCre transgenic mice are viable and fertile, with expression of a GFP/Cre fusion protein directed primarily to developing spinal cord and hindbrain by the mouse homeobox B4 early neuronal enhancer (ENE) region and heat shock protein 1B minimal promoter. Cre recombinase activity is observed from embryonic day (E)9.0-13.5 throughout the neural tube in the hindbrain, the dorsal root ganglia, motor neurons, and the Xth cranial ganglia (vagus); with a sharp anterior boundary at rhombomeres 6 and 7 (r6/r7). Ectopic cre activity is reported in the Vth cranial nerve (trigeminal) of E10.5-11.5 embryos. GFP fluorescence is first detectable at E9.0, strongest at E10.5, and absent by ~E12.0. GFP fluorescence is localized to the neural tube and the hindbrain with a sharp anterior limit between rhombomeres 7 and 8 (r7/r8) at E9.5. GFP expression at the anterior r7/r8 boundary was maintained through E11.5, while the posterior boundary expanded caudally from E9.5-E11.5. When bred with mice containing loxP-flanked sequences, Cre-mediated recombination will result in deletion of the floxed sequences in the Hoxb4-expressing cells of the offspring. These Hoxb4-ENE-GFPCre transgenic mice may be useful as a Cre-lox or fluorescent tool for the fate-mapping/lineage-tracing of Hoxb4-expressing neurons in the developing neural tube.
In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. It should be noted that the phenotype could vary from that originally described. We will modify the strain description if necessary as published results become available.
