Nodal·Gdf1 heterodimers with bound prodomains enable serum-independent nodal signaling and endoderm differentiation

Area of Science:

• Stem cell biology
• Developmental biology
• Molecular signaling

Background:

• The TGFβ family member Nodal is crucial for controlling pluripotent stem cell fate but has limited specific activity for differentiation.
• Nodal's developmental functions, including left-right axis asymmetry, depend on Growth and Differentiation Factor 1 (Gdf1) and the co-receptor Cryptic.

Purpose of the Study:

• To investigate whether Gdf1 can augment the functionality and potency of Nodal as a stem cell differentiation factor.
• To elucidate the mechanism by which Gdf1 influences Nodal signaling and its interaction with receptors.

Main Methods:

• Co-immunoprecipitation assays to detect Nodal-Gdf1 interactions.
• Biochemical purification and characterization of Nodal-Gdf1 complexes.
• Analysis of Activin receptor (Acvr) signaling potentiation and receptor binding affinities.
• Assessment of soluble Acvr2 inhibition and differentiation of human embryonic stem cells (ES cells).

Main Results:

• Gdf1 suppresses Nodal's dependence on serum proteins and is essential for non-autonomous signaling.
• Nodal and Gdf1 form a heterodimeric complex that significantly stimulates Acvr signaling compared to Nodal alone.
• Gdf1 potentiation of Nodal activity involves stabilizing a low molecular weight fraction susceptible to soluble Acvr2 neutralization.
• The Nodal·Gdf1 complex more efficiently induced endodermal markers in differentiating human ES cells than Nodal alone.

Conclusions:

• Gdf1 acts as a critical enhancer for Nodal signaling, forming a potent heterodimeric complex.
• The Nodal·Gdf1 complex represents a novel and effective reagent for directing stem cell differentiation, particularly towards endodermal lineages.
• Understanding the mechanism of Gdf1 potentiation provides insights into regulating stem cell fate and developmental processes.