WT1 mutants reveal SRPK1 to be a downstream angiogenesis target by altering VEGF splicing

Area of Science:

• Molecular Biology
• Developmental Biology
• Oncology

Background:

• Angiogenesis, the formation of new blood vessels, is crucial for development and disease.
• The balance between proangiogenic VEGF(165) and antiangiogenic VEGF(165)b splice isoforms regulates angiogenesis.
• Mutations in the Wilms' tumor suppressor gene (WT1) are linked to developmental abnormalities and cancer, including Wilms' tumors.

Purpose of the Study:

• To investigate the mechanism by which WT1 mutations lead to altered VEGF splicing and promote angiogenesis.
• To identify therapeutic targets for WT1-associated malignancies by understanding the role of SRPK1 and SRSF1 in VEGF regulation.

Main Methods:

• Analysis of WT1 binding to the SRPK1 promoter.
• Assessment of SRPK1 expression and SRSF1 phosphorylation in WT1 mutant cells.
• Investigating the effect of WT1, SRSF1, and SRPK1 manipulation on VEGF splicing.
• Evaluating the impact of SRPK1 inhibition on in vitro and in vivo angiogenesis and tumor growth.

Main Results:

• WT1 normally represses the expression of SRPK1, a splicing-factor kinase.
• In WT1 mutant cells, reduced repression of SRPK1 leads to its overexpression.
• SRPK1 hyperphosphorylates SRSF1, promoting proangiogenic VEGF(165)b splicing.
• Inhibition of SRPK1 or SRSF1, or restoration of WT1, normalized VEGF splicing and reduced angiogenesis.

Conclusions:

• WT1-mediated repression of SRPK1 is essential for maintaining the balance of VEGF splice isoforms.
• SRPK1 and SRSF1 are key mediators of aberrant VEGF splicing in WT1 mutant cells.
• Targeting the SRPK1/SRSF1 pathway offers a potential therapeutic strategy for WT1-associated cancers and related angiogenic disorders.