PDGFRα signaling regulates Srsf3 transcript binding to affect PI3K signaling and endosomal trafficking

Area of Science:

• Molecular Biology
• Developmental Biology
• Genetics

Background:

• Platelet-derived growth factor receptor alpha (PDGFRα) signaling is crucial for craniofacial development, with mutations linked to cleft lip/palate.
• Phosphatidylinositol 3-kinase (PI3K)/Akt pathway is a key effector of PDGFRα signaling in skeletal development.
• Serine/arginine-rich splicing factor 3 (Srsf3) is phosphorylated by Akt downstream of PDGFRα signaling, translocating to the nucleus and affecting alternative RNA splicing (AS).

Purpose of the Study:

• To elucidate the molecular mechanisms by which Srsf3 activity is regulated by PDGFRα signaling.
• To understand how Srsf3 controls AS of transcripts essential for craniofacial development.

Main Methods:

• Enhanced UV-crosslinking and immunoprecipitation (eCLIP) in mouse embryonic palatal mesenchyme (MEPM) cells.
• RNA sequencing (RNA-seq) to analyze alternative splicing changes.
• Functional validation studies.

Main Results:

• PDGF-AA stimulation altered Srsf3 binding to RNA, favoring exons over canonical motifs.
• Srsf3 activity promoted exon inclusion with higher GC content and shorter introns.
• Affected transcripts commonly encoded regulators of PI3K signaling and endosomal trafficking.
• Srsf3 activity retained PDGFRα in early endosomes, enhancing PI3K/Akt signaling.

Conclusions:

• Growth factor-mediated phosphorylation of Srsf3 is a key mechanism for regulating gene expression in craniofacial development.
• This pathway controls alternative splicing to ensure proper cell proliferation, survival, and receptor trafficking.
• Findings reveal a novel link between growth factor signaling, RNA binding proteins, and developmental processes.