Objective: To functionally characterize WDR45-mediated BPAN (Beta-propeller protein-associated neurodegeneration).

Background: BPAN patients usually present with global developmental delay and autistic features in early childhood and regression in early adulthood with movement disorders, speech problems, and dementia. BPAN is a form of neurodegeneration with brain iron accumulation (NBIA) caused by mutations in the WDR45 gene. The encoded protein has been linked to autophagy. However, the molecular pathways linking mutant WDR45 and iron accumulation remain elusive.

Method: We included a novel BPAN patient who underwent a detailed clinical examination, MRI, and genetic testing. For functional characterization, we used fibroblast cultures from this patient, a previously reported BPAN patient [1], and three controls. Western blotting was performed to evaluate autophagy and lysosomal homeostasis using LC3-II, p62, and GBA. We conducted GRP75-immunostaining to evaluate the mitochondrial network (form factor analysis). Iron storage, iron recycling, and ferroptosis were investigated by determining FTH, and GPX4 levels under basal conditions and upon RSL3 treatment (inducing ferroptosis) using Western blotting.

Results: The novel patient carried the missense variant p.(Asn61Lys) in WDR45 (NM_007075.3: c.183C>A). Clinical examination and MRI were consistent with BPAN including generalized brain atrophy, predominantly of the cerebellum. In WDR45-mutant fibroblasts, Western blotting showed decreased levels of the autophagosome marker LC3-II (under basal condition and upon Bafilomycin A1 treatment) and lysosomal enzymes (e.g., GBA) when compared to controls. Form factor analyses confirmed decreased mitochondrial branching and interconnectivity in WDR45-mutant fibroblasts. We detected reduced protein levels of FTH, GPX4, and p62 in WDR45-mutant fibroblasts in comparison to controls. Upon RSL3 treatment, we observed highly increased protein levels of GPX4 and p62 and no change in FTH levels in WDR45-mutant fibroblasts when compared to the same cell lines under basal conditions.

Conclusion: We investigated iron homeostasis in WDR45 mutant fibroblasts to better understand the link between impaired autophagy, mitochondrial dysfunction, and iron accumulation. We here highlight that dysfunctional WDR45 leads to autophagic defects accompanied by altered iron recycling and storage, and affects the regulation of the ferroptosis pathway.

References: [1] Seibler, P.; Burbulla, LF.; Dulovic, M.; Zittel, S.; Heine, J.; Schmidt, T. et al. Iron overload is accompanied by mitochondrial and lysosomal dysfunction in WDR45 mutant cells. Brain 2018, 10(141):3052–3064.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/mutant-wdr45-leads-to-altered-ferroptosis-in-%ce%b2-propeller-protein-associated-neurodegeneration/