Investigation of the cellular pathology underlying the optic neuropathy in a mouse model of familial Dysautonomia

Abstract

Familial dysautonomia (FD) is a rare, recessive, progressive autosomal disorder that affects the nervous system. This neurological disorder is caused by a splice mutation in the Elongator complex I (ELP1) gene. The mutation results in a tissue-specific reduction of ELP1 protein due to unstable mRNA targeted for nonsense-mediated decay. ELP1 is a highly conserved scaffolding protein and core subunit of the six-subunit Elongator complex required for normal translation, neuronal development, and survival. Insufficient ELP1 leads to the developmental death of neurons in the peripheral and autonomic nervous systems in addition to central and peripheral nervous system neurodegeneration. Patients suffer from congenital and progressive neuropathies, such as cardiovascular dysfunction, reduced peripheral sensory function, poor growth, and digestive and respiratory problems. Outside of the risk of death in early adulthood, one of the most debilitating conditions affecting patients' quality of life is progressive blindness marked by continual loss of retinal ganglion cells (RGCs). Within the FD community, there is a concerted effort to develop treatments to prevent the loss of RGCs, thereby improving patients' quality of life. This study aims (1) to elucidate mechanisms underlying the death of RGCs in the absence of Elp1 and (2) to obtain pre-clinical intervention data that can eventually be translated into therapeutics for rescuing RGCs in FD. Using histology and confocal microscopy in conjunction with biochemistry, this study provides evidence for disrupted cellular homeostasis and inflammation preceding RGC death, and as the disease progresses, the retinal cells fail to mount a correct stress response to restore neuronal homeostasis. Furthermore, this study provides first-of-its-kind pre-clinical data using targeted gene therapies to rescue RGCs. Understanding the biological crosstalk and signaling mechanisms underlying the death of RGCs in the absence of Elp1 will allow for more targeted and effective therapeutics that will benefit not only the FD community but also individuals affected by other retinal diseases and neurological diseases that result from a faulty Elongator complex. This study provides a novel characterization of the FD retina and establishes baseline methods to further investigate rescuing RGCs.