Localization of cathepsin x in the mouse retina

Abstract

Abstract Purpose Cathepsin X is a recently identified member of the papain‐like cysteine protease family that is expressed by many cell types. The in vivo functions of Cathepsin X are unknown. Hence, the aims of this study are to localize cathepsin X expression in the mouse retina and to compare the retinal morphology and ERG function of cathepsin X knock‐out mice (Ctsx‐/‐) to congenic wild type C57Bl/6 mice (Ctsx+/+). Methods Left eyes of adult mice were prepared for paraffin‐ and right eyes for cryo‐sections. Histology was accomplished by Hämalaun‐Eosin and PAS staining after depigmentation. Expression of cathepsin X and the proliferation marker Ki67 were investigated by immunohistochemistry. Retinal function was tested by ERG. Results Cathepsin X expression in WT mice accumulates along the external limiting membrane. Additionally, a netlike pattern of cathepsin X was found around the neuronal cells in the inner nuclear and ganglion cell layer. There is no significant difference between cathepsin X knock‐out and WT mice in retinal morphology, cell proliferation or ERG readings. Conclusion We found prominent expression of cathepsin X in WT mice retina. Normal retinal morphology and ERG function in cathepsin X knock‐out mice, however, suggest that other cathepsins might compensate for the loss of retinal cathepsin X.