Deletion of CEACAM 1 does not affect retinal and choroidal morphology or transcriptome

CEACAM1 (CC1) is an important mediator of cell proliferation and adhesion and serves as an angiogenic factor through interaction with VEGF. Although the role of CC1 has been extensively studied in organs such as the heart, liver and lung in which CC1 is considered as important regulator of various pathological conditions, little is known about the function of CEACAM1 in the eye. In this study, we investigated the expression and function of CC1 in the retina and choroid of healthy adult mice using immunohistochemistry, fluorescence activated cell sorting (FACS) and RNA sequencing. We found a strong expression of CC1 in endothelial and myeloid cells of the retina and the choroid. However, deletion of CC1 did not result in vascular abnormalities of the retina and choroid or changes in retinal myeloid cell morphology and number. Furthermore, the retinal architecture was not affected and morphometric measurements of the thickness of the inner and outer retinal layers were not altered by deletion of CC1. Accordingly, we did not observe structural or transcriptomic changes in the choroid. Our data suggest that the role of CC1 in the adult eye during steady state is attenuated or can be compensated by other molecular mediators. However, one could speculate that CC1 may become functionally relevant during pathological conditions, such as in neovascular eye diseases such as proliferative diabetic retinopathy or neovascular age-related macular degeneration.