A novel surfactant protein C mutation resulting in aberrant protein processing and altered subcellular localization causes infantile interstitial lung disease.
BACKGROUND
Mutations in the surfactant protein C gene (SFTPC) result in interstitial lung disease (ILD). Our objective was to report a novel SFTPC mutation and evaluate the effect of this mutant on protein synthesis and processing.


METHODS
Genomic DNA was extracted from whole blood of a Chinese infant with ILD and candidate genes associated with ILD were sequenced by next-generation sequencing. Subclones of wild-type and mutant SFTPC were transiently transfected into A549 cells. The functional characterization of mutant surfactant protein C (SP-C) was evaluated by Western blotting, transmission electron microscopy, and immunofluorescence.


RESULTS
A novel heterozygous mutation SFTPC: c.337T>T/C, p.Y113H was identified in this ILD infant. Neither of the parents carries this mutation. Using A549 cells expressing wild-type and mutant SP-C isoforms, Western blotting revealed a significant reduction of proSP-C and a band with abnormal molecular weight in the mutant SP-C compared to the wild-type. Ultrastructural analysis showed abnormal cytoplasmic organelles. Immunofluorescence demonstrated mutant SP-C was scarcely trafficked to lamellar bodies but localized well to early endosomes, which was in marked contrast to the wild type protein.


CONCLUSIONS
We detected a novel mutation in SFTPC causing ILD in infancy. The mutation results in aberrant proSP-C processing and altered subcellular localization.
Department of Respiratory Medicine, Children's Hospital of Fudan University, Shanghai, China.
Da
D
Hong
Department of Respiratory Medicine, Children's Hospital of Fudan University, Shanghai, China.
Yuanyuan
Y
Qi
Department of Respiratory Medicine, Children's Hospital of Fudan University, Shanghai, China.
Jing
J
Liu
The Molecular Genetic Diagnosis Center, Shanghai Key Lab of Birth Defects, Institute for Pediatric Research, Children's Hospital of Fudan University, Shanghai, China.
Huijun
H
Wang
Department of Respiratory Medicine, Children's Hospital of Fudan University, Shanghai, China.
Libo
L
Wang
Department of Respiratory Medicine, Children's Hospital of Fudan University, Shanghai, China.
Liling
L
Qian
D000072283:A549 Cells; D000595:Amino Acid Sequence; D005260:Female; D006801:Humans; D007223:Infant; D017563:Lung Diseases, Interstitial / Q000235:genetics*; D009154:Mutation; D011499:Protein Processing, Post-Translational; D037721:Pulmonary Surfactant-Associated Protein C / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000378:metabolism*
D037721:Pulmonary Surfactant-Associated Protein C; C489679:SFTPC protein, human