Genotype-phenotype association and functional analysis of hnRNPA1 mutations in amyotrophic lateral sclerosis

Abstract

Background

Pathogenic variants in hnRNPA1 have been reported in amyotrophic lateral sclerosis (ALS) patients. However, studies on hnRNPA1 mutant spectrum and pathogenicity of variants were rare.

Methods

We performed whole exome sequencing of ALS-associated genes and subsequent verification of rare variants in hnRNPA1 in our ALS patients. The hnRNPA1 mutations reported in literature were reviewed and combined with our results to determine the genotype-phenotype relationship. Functional analysis of the novel variant p.G195A was performed in vitro by transfection of mutant hnRNPA1 into 293T cell.

Results

Among 207 ALS patients recruited, 3 rare hnRNPA1 variants were identified (mutant frequency 1.45%), including two recurrent mutations (p.P340S and p.G283R), and a novel rare variant p.G195A. In combination with previous reports, there are 27 ALS patients with 15 hnRNPA1 mutations identified. Disease onset age was 47.90 ± 1.52 years with predominant limb onset. The p.P340S mutation caused flail arm syndrome (FAS) in two independent families with extended life expectancy. The newly identified p.G195A mutation, lying at the start of the PrLD (“prion-like” domain)/LCD (low-complexity domain), causes local structural changes in 3D protein prediction. Upon sodium arsenite exposure, mutant hnRNPA1 retained in the nucleus but deficit of cytoplasmic G3BP1-positive stress granule clearance was observed. This is different from the p.P340S mutation which caused both cytoplasmic translocation and stress granule formation. No cytoplasmic TDP-43 translocation was observed.

Conclusion

Mutations in hnRNPA1 are overall minor in ALS patients. The p.P340S mutation is associated with manifestation of FAS. Mutations in LCD of hnRNPA1 cause stress granule misprocessing.

Keywords:

• Amyotrophic lateral sclerosis
• hnRNPA1
• mutation
• genotype-phenotype association
• stress granule

Authors’ contributions

Xinyi Zhang, Ye Sun, and Xinzhe Zhang performed the experiments, analyzed the data and each wrote part of the manuscript; Dongchao Shen recruited and followed up the patients; Shi Shu performed cellular transfection test for the P340S mutation reported previously; Xunzhe Yang, Mingsheng Liu and Liying Cui recruited the patients; Liying Cui, Qing Liu, and Xue Zhang supervised the study; Qing Liu revised the manuscript.

Disclosure statement

The authors report there are no competing interests to declare.

Additional information

Funding

This work was financially supported by the National High Level Hospital Clinical Research Funding under Grant [2022-PUMCH-B-017]; National Key Research and Development Program of China under Grant [2022YFC2703900, 2022YFC2703904]; National Natural Science Foundation of China under Grant [81971293, 82394420, 82394423]; Strategic Priority Research Program (Pilot study) “Biological basis of aging and therapeutic strategies” of the Chinese Academy of Sciences (XDB39040000); and the CAMS Innovation Fund for Medical Sciences under Grant [2021- I2M-1-034, 2021-I2M-1-018 and 2022-I2MJB- 004].