Dominantly acting variants in ARF3 have disruptive consequences on Golgi integrity and cause microcephaly recapitulated in zebrafish

Abstract

Vesicle biogenesis, trafficking and signaling via the ER-Golgi network support essential processes during development and their disruption can lead to neurodevelopmental disorders and neurodegeneration. We report that de novo missense variants in ARF3, encoding a small GTPase regulating Golgi structure and function, cause a neurodevelopmental disease showing microcephaly and progressive cortical atrophy, with microsomia and rib anomalies in severely affected subjects, suggesting a pleiotropic effect. All microcephaly-associated variants clustered in the guanine nucleotide binding pocket and perturbed the biochemical behavior of the protein by stabilizing it in a GTP-bound state. Functional analysis proved the disruptive consequences of the variants on Golgi integrity, and brain and body plan formation. In-depth analysis in zebrafish embryos expressing ARF3 mutants traced back the developmental alterations to defective gastrulation cell movements as the earliest detectable effect. Our findings document a role of ARF3 in Golgi homeostasis and demonstrate an obligate dependence for early development.

Teleost Fish and Organoids: Alternative Windows Into the Development of Healthy and Diseased Brains

“…For instance, recently, we identified a previously unknown Golgipathy involving dominant mutations in the new disease gene encoding for the small GTPase ARF3. We demonstrated the validity of using zebrafish to recapitulate the microcephaly observed in patients and to validate the disruptive effect on the Golgi stability in vitro and in embryos ( Fasano et al, 2021 ). Dedicated studies assessing and differentiating the mechanisms of previously discovered genetic lesions using zebrafish models also exist.…”

“…For instance, secondary microcephaly combined with periventricular heterotopia was linked to impaired Golgi assembly and trafficking affecting membrane proteins, proliferation and cell migration (e.g., ARFGEF2, Banne et al, 2013 ). Furthermore, fragmented Golgi has also been recently associated with a neurodevelopmental condition showing microcephaly and caused by mutations in the new disease-gene ARF3 , encoding a small GTPase involved in post-Golgi trafficking ( Fasano et al, 2021 ). More recently, loss of function of WDR81 which impairs endosomal trafficking of pro-proliferative signal EGFR was functionally linked to microcephaly ( Carpentieri et al, 2022 ).…”