Fuchs endothelial corneal dystrophy (FECD) is a progressive and debilitating disorder of the corneal endothelium (CE) that affects approximately 4% of individuals over the age of 40. Despite the burden of the disease, the pathogenesis of FECD remains poorly understood, and treatment options are limited, highlighting the need for deeper investigation into its underlying molecular mechanisms. Over the past decade, studies have indicated independent contributions of endoplasmic reticulum (ER) and mitochondrial stress to the pathogenesis of FECD. However, there are limited studies suggesting ER-mitochondria crosstalk in FECD. Recently, our lab established the role of chronic ER stress in inducing mitochondrial dysfunction for corneal endothelial cells (CEnCs), indicating the existence of ER-mitochondria crosstalk in FECD. This paper aims to provide a comprehensive overview of the current understanding of how ER and mitochondrial stress contribute to FECD pathogenesis. The paper also reviews the literature on the mechanisms of ER-mitochondria crosstalk in other diseases relevant to FECD.

Cells respond to metabolic and environmental challenges through the integrated stress response (ISR), a cellular process that maintains homeostasis under diverse stressors. ATF4 is a key player in this ISR, as it is activated via the PERK–eIF2α–ATF4 pathway. ATF4 induction can elicit adaptive responses, including the regulation of genes involved in metabolism and autophagy, to maintain homeostasis. However, ATF4 activation can also induce apoptosis, leading to a wide spectrum of diseases, including metabolic, neurologic, and ocular pathologies. This duality reflects the highly context-dependent nature of ATF4 signaling. This review aims to synthesize the role of ATF4 in metabolic dysfunction, neurodegenerative diseases, and ocular pathology; the mechanisms underlying its protective versus pathologic effects; and future directions to refine ATF4’s potential as a clinical therapeutic target across different diseases.