Biglycan is a novel binding partner of fibroblast growth factor receptor 3c (FGFR3c) in the human testis

Area of Science:

• Reproductive Biology
• Molecular Endocrinology
• Cell Signaling

Background:

• Spermatogonial maintenance regulation in the human testis is poorly understood.
• Fibroblast growth factor receptor 3 (FGFR3) is implicated, particularly its mesenchymal 'c' splice isoform (FGFR3c).
• FGFR3-activating mutations are found in spermatocytic seminoma, suggesting a role in spermatogonial proliferation.

Purpose of the Study:

• To identify binding partners of FGFR3c in human spermatogonia.
• To elucidate the role of potential ligands in FGFR3c signaling.
• To understand the contribution of FGFR3c to spermatogonial maintenance.

Main Methods:

• Candidate ligand identification based on expression patterns and binding site homology.
• Screening of non-FGF proteins for FGFR3c interaction.
• Cell-free system experiments to confirm binding interactions.

Main Results:

• FGF1, FGF2, and FGF9 were identified as potential natural ligands for FGFR3c.
• Biglycan (BGN), a proteoglycan, was found to bind FGFR3c and FGF1.
• BGN is expressed in peritubular cells adjacent to FGFR3-expressing spermatogonia.

Conclusions:

• Biglycan (BGN) is a novel binding partner for FGFR3c and FGF1.
• BGN, secreted by peritubular cells, may modulate FGFR3c signaling.
• These findings contribute to understanding FGFR3c's role in human spermatogonial maintenance.