Generation and characterization of Lhx9-GFPCreER^T2 knock-in mouse line

LHX9 is a LIM-homeodomain transcription factor essential for the development of gonads, spinal cord interneurons, and thalamic neurons to name a few. We recently reported the expression of LHX9 in retinal amacrine cells during development. In this study, we generated an Lhx9-GFPCreER^T2 (GCE) knock-in mouse line by knocking-in a GCE cassette at the Lhx9 locus, thus inactivating endogenous Lhx9. Lhx9^GCE/+ mice were viable, fertile, and displayed no overt phenotypical characteristics. Lhx9^GCE/GCE mice were all phenotypically female, smaller in size, viable, but infertile. The specificity and efficacy of the Lhx9-GCE mouse line was verified by crossing it to a Rosa26-tdTomato reporter mouse line, which reveals the Cre recombinase activities in retinal amacrine cells, developing limbs, testis, hippocampal neurons, thalamic neurons, and cerebellar neurons. Taken together, the Lhx9-GCE mouse line could serve as a beneficial tool for lineage tracing and gene manipulation experiments.