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Functional screening of ZIP8 naturally occurring variants identifies pathogenic mutations and trafficking defects
Michael Nikolovski1, Tianqi Wang1, Aaron Sue2
1Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA.
Biorxiv : the Preprint Server for Biology
|May 25, 2026
Summary
Researchers developed a scalable assay to functionally test human metal transporter ZIP8 variants. This method identified 14 potentially pathogenic variants, highlighting the extracellular domain's role in protein expression and trafficking.
Area of Science:
- Genomics
- Molecular Biology
- Biochemistry
Background:
- Human genomic data expansion presents challenges for variant functional annotation.
- The metal transporter SLC39A8 (ZIP8) has clinically relevant variants, most lacking functional characterization.
Purpose of the Study:
- To develop and apply a scalable workflow for functional evaluation of ZIP8 variants.
- To analyze naturally occurring missense variants in the ZIP8 extracellular domain (ECD).
Main Methods:
- Integrated laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOF-MS) with scaled-up cell-based transport assays.
- Analyzed 33 naturally occurring missense variants in the ZIP8 ECD.
- Quantified intracellular metal accumulation with high throughput (∼150 samples/hour).
Main Results:
- Identified 14 potentially pathogenic ZIP8 variants with significantly reduced transport activity.
- Observed a moderate correlation (R² = 0.423) between experimental activity and AlphaMissense pathogenicity scores.
- Found that most loss-of-function variants exhibit impaired cell surface trafficking, potentially due to misfolding or instability.
Conclusions:
- Established a scalable approach for functional screening of metal transporter variants.
- Highlighted the importance of the ZIP8 ECD in protein expression and intracellular trafficking.
- Emphasized the necessity of experimental validation for computational variant pathogenicity predictions.
