A fetus with severe developmental defects caused by dominant-negative and hypomorphic ATG7 alleles

Macroautophagy/autophagy is a fundamental process for neuronal homeostasis, yet its role in human development, notably brain development, remains poorly understood. Here, we report a fetus presenting severe developmental defects, including brain malformations, carrying two deleterious variants in ATG7, a gene associated with severe neurodevelopmental disorders: maternally inherited nonsense mutation Arg659Ter (hereafter R659*) and a de novo missense mutation Arg481Gln (hereafter R481Q). Functional analyses showed ATG7^R659* acting as a dominant-negative allele, whereas ATG7^R481Q was hypomorphic, revealing arginine 481 as a critical residue for ATG7-LC3 interaction in mammals. Loss of ATG7 function disrupted autophagosome formation, promoted abnormal axonal elongation and branching in neurons, and nearly abolished canonical autophagy in fetal cells. These findings highlight ATG7 as a key regulator of development and provide mechanistic insight into autophagy-related neurodevelopmental disorders.Abbreviations: ATG: autophagy related; CHX: cycloheximide; cHBSS: complete Hanks' buffered salt solution; C572A: Cys572Ala catalytically-inactive mutant; DIV: day in vitro; DMSO: dimethyl sulfoxide; EBSS: Earle's balanced salt solution; GABARAP: GABA type A receptor-associated protein; MAP1LC3: microtubule associated protein 1 light chain 3; NDD: neurodevelopmental disorder; NMD: nonsense-mediated decay; PB: permeabilization buffer; PBS: phosphate-buffered saline; RT-PCR: reverse transcriptase polymerase chain reaction; R481Q: Arg481Gln; R659*: Arg659Ter; shRNA: short hairpin RNA; siRNA: small interfering RNA.