Inducible CreER^T2 mouse lines for study of retinal bipolar cell subtypes

Abstract

Purpose : The general development and function of retinal bipolar cells have been well-described. However, little is known about the differentiation and specific functions of retinal bipolar cell subtypes in visual processing besides its broad ON and OFF classifications. In this study, we develop CreER^T2 and reporter models for further investigation of specific ON and OFF-bipolar cell subtypes.

Methods : Three mouse lines with CreER^T2 knock-in in Vsx1, Lhx3, and Lhx4 were created and crossed with Ai32 (RCL-ChR2(H134R)/EYFP) Cre recombinase-dependent reporter mice to generate a double heterozygous CreER^T2 and ChR2/EYFP reporter line. Mice of either sex were used in all experiments. Mice were given intraperitoneal tamoxifen injection and retinas were harvested 7 or more days post-injection. Immunohistochemistry was then performed on PFA-fixed frozen retina sections and imaged with a Leica Stellaris confocal microscope.

Results : The Cre activities of Vsx1, Lhx3, and Lhx4 were all detected in BHLHB5-expressing type 2 bipolar cells. Types 1b and 6 also expressed Lhx3-CreER^T2 while types 3, 4, and 5 expressed Lhx4-CreER^T2. Consistent with previous findings, Vsx1-CreER^T2 was also expressed in type 6 and type 7 bipolar cells. Subtype-specific gene expression was ascertained using sparse-labeling 3D morphology, specific cell markers, and level of axon stratification.

Conclusions : The CreER^T2 knock-ins of Vsx1, Lhx3, and Lhx4 are specifically expressed in subtypes of bipolar cells in the retina and these inducible Cre lines are valuable tools for further study and manipulation of these subtypes.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.