Generation and characterization of Lhx4tdT reporter knock-in and Lhx4loxP conditional knockout mice.

LHX4 is a LIM-homeodomain transcription factor essential for the development of spinal cord and pituitary gland. Mice with homozygous Lhx4-null mutation suffer early postnatal death from lung defect. In this study, to facilitate the research on Lhx4 function, we designed a targeting construct to generate two novel Lhx4 mouse lines: Lhx4 loxP conditional knockout and Lhx4 tdT reporter knock-in mice. Lhx4 tdT/+ , Lhx4 loxP/+ , and Lhx4 loxP/loxP were viable, fertile, and did not display any gross abnormalities. By breeding Lhx4 loxP line with Cre-expressing mice, the Exon 3 of Lhx4 was efficiently removed, resulting in a shift in the reading frame and the inactivation of Lhx4. The expression of tdTomato knock-in reporter recapitulated the endogenous LHX4 expression and was detected in the retina, spinal cord, pituitary gland, and hindbrain of Lhx4 tdT mice. Thus, Lhx4 tdT and Lhx4 loxP mouse lines provide valuable tools for unraveling the tissue-specific role of Lhx4 at postnatal stages in mice.