ErbB4 alternative splicing mediates fetal mouse alveolar type II cell differentiation in vitro

Background Alternative splicing (AS) creates different protein isoforms, an important mechanism regulating cell-specific function. Little is known about AS in lung development, particularly in alveolar type II (ATII) cells. ErbB4 receptor isoforms Jma and Jmb have significant and opposing functions in the brain, heart, and lung development and/or disease. However, the regulators of ErbB4 AS are unknown. ErbB4 AS regulators in fetal mouse ATII cells control its function in ATII cell maturation. Methods Candidate ErbB4 AS regulators were found using in silico analysis. Their developmental expression was studied in fetal mouse ATII cells. The effects of splice factor downregulation and upregulation on ATII cell maturation were analyzed. Results ErbB4-Jma increased significantly in ATII cells after gestation E16.5. In silico analysis found four candidate splice factors: FOX2, CUG/CELF1, TIAR, and HUB. Fetal ATII cells expressed these factors in distinct developmental profiles. HUB downregulation in E17.5 ATII cells increased Jma isoform levels and Sftpb gene expression and decreased Jmb. HUB overexpression decreased Jma and Sftpb. Conclusions ErbB4 AS is developmentally controlled by HUB in fetal ATII cells, promoting ATII differentiation. Regulated AS expression during ATII cell differentiation suggests novel therapeutic strategies to approach human disease. Impact Alternative splicing (AS) of the ErbB4 receptor, involving mutually exclusive exon inclusion, creates Jma and Jmb isoforms with distinct differences in receptor processing and function. The Jma isoform of ErbB4 promotes differentiation of fetal lung alveolar type II cells. The AS is mediated in part by the RNA-binding protein HUB. The molecular mechanism of AS for ErbB4 has not been previously described. The regulation of ErbB4 AS has important implications in the development of organs, such as the lung, brain, and heart, and for disease, including cancer.

Automated summary

This study found that ErbB4-Jma significantly increased in fetal mouse ATII cells after E16.5. Through in silico analysis, four candidate splice factors were identified: FOX2, CUG/CELF1, TIAR, and HUB. Downregulation of the HUB gene in E17.5 ATII cells increased the levels of Jma isoform and Sftpb gene expression, while decreasing Jmb. These results suggest that the HUB gene plays a developmental regulatory role in ErbB4 AS in fetal mouse ATII cells, promoting ATII cell differentiation.