Symmetric arrangement of mitochondria:plasma membrane contacts between adjacent photoreceptor cells regulated by Opa1

Significance Mitochondria play an essential role in the homeostasis of the highly energy-demanding photoreceptors and enable normal vision. We used 3D electron microscopy to show that the mitochondria in the photoreceptor inner segment are tethered to the plasma membrane in a highly specialized arrangement. This includes mitochondria running alongside each other in neighboring inner segments, with evidence of alignment of the cristae openings. The cristae structure was not greatly affected in photoreceptors of a heterozygous Opa1 knockout mouse model, but the mitochondria were enlarged and had reduced alignment to neighboring inner-segment mitochondria. This leads us to propose that mitochondria are arranged to share metabolites and assist in maintaining homeostasis across the photoreceptor cell layer.