Biallelic germline variants in the hematologic malignancy predisposition gene DDX41 cause retinal dystrophy through dysregulation of retinal homeostasis.

Abstract

Leber congenital amaurosis (LCA) and Early-onset severe retinal dystrophy (EOSRD) manifest within the first months and the first years of life, respectively. They are the leading cause of severe vision impairment in childhood. Using next generation sequencing, we identified eight families of patients with LCA/EOSRD carrying biallelic combination of six germline variants in DDX41, encoding a DEAD-box ATPase RNA helicase involved in RNA splicing, innate immunity and hematopoiesis. In fibroblasts from a patient carrying the homozygous missense variant c.1187T>C (p. Ile396Thr) and in the retina of Ddx41I396T/I396T mice, DDX41 protein expression was decreased. Electroretinogram recordings in these animals also revealed significant visual dysfunction since the first month of age, supporting a pathogenic role of DDX41 in retinal physiology. Immunohistochemical staining showed that the protein localized to nuclei in all major retinal cell types and to photoreceptor synapses, while biochemical assays showed that LCA/EOSRD variants disrupt DDX41 interactions with RNA through misfolding or the formation of non-productive aggregates, resulting in loss-of-function. Transcriptomic profiling of mutant mouse retinas revealed dysregulation of gene networks associated with Muller cells (MCs), glial cells essential for maintaining retinal structure, metabolic balance, and immune surveillance. The dysregulated pathways chiefly involved cell morphogenesis and junction formation, consistent with immunohistological analyses of widespread architectural disruption and nuclear disorganization, identifying MCs as a site of dysfunction. Together, these findings establish for the first time the involvement of DDX41 in LCA/EOSRD and provide new insights into the role of helicases in retinal homeostasis.