ATP5F1A deficiency causes developmental delay and motor dysfunction in humans and zebrafish.

Background: The ATP synthase F1 subunit α (ATP5F1A) gene encodes a critical structural subunit of mitochondrial complex V. ATP5F1A mutations are linked to mitochondrial complex V deficiency diseases. Although only 14 cases have been reported globally, the genotype-phenotype correlations and underlying molecular mechanisms remain poorly understood.

Objective: To investigate the pathogenic mechanisms of ATP5F1A deficiency through functional analysis of a recurrent missense variant.

Method: A Han Chinese family with developmental delay and motor dysfunction was studied. Whole-exome sequencing and trio analysis identified the causative variant. Pathogenicity was evaluated using bioinformatic predictions and structural modeling. HEK293T cells were transfected with wild-type or mutant-type ATP5F1A plasmids for Western blot and immunofluorescence analysis. Morpholino (MO) oligonucleotides were microinjected into zebrafish embryos for gene knockdown. Motor neuron development was observed in Tg(mnx1:eGFP) zebrafish, with accompanying behavioral assessments. RNA sequencing was conducted to explore the underlying molecular pathways.

Results: A de novo missense variant (c.1252G > A, p.Gly418Arg) in ATP5F1A was identified and shown to segregate with the disease phenotype. The mutation reduced protein stability and expression. In HEK293T cells, the mutant protein exhibited reduced expression without affecting mitochondrial localization. In zebrafish, atp5fa1 knockdown caused growth retardation, motor dysfunction, and impaired motor neuron axon development. Rescue experiments with human wild-type ATP5F1A mRNA partially restored motor neuron morphology. Transcriptomic analysis identified 2,261 differentially expressed genes, enriched in neurotransmission and apelin signaling pathways. qPCR confirmed downregulation of autophagy-related genes (apln, becn1, map1lc3b) in knockdown larvae. Western blot showed that atp5fa1 knockdown increased P62 and decreased Lc3b-II expression in zebrafish models.

Conclusion: This study is the first to report pathogenic ATP5F1A mutations in the Chinese population. Atp5fa1 dysfunction leads to multi-system defects and disease phenotypes in a zebrafish model, possibly mediated through inhibiting autophagy activation mechanisms.