Skeletal stem cell fate defects caused by Pdgfrb activating mutation

Area of Science:

• Skeletal biology
• Stem cell research
• Connective tissue disorders

Background:

• Autosomal dominant PDGFRβ gain-of-function mutations cause skeletal and connective tissue abnormalities.
• The cellular origin of these PDGFRβ-related disorders is currently unknown.

Purpose of the Study:

• To investigate the cellular and molecular mechanisms underlying PDGFRβ gain-of-function mutations in skeletal stem cells (SSCs).
• To determine the impact of PDGFRβ mutations on SSC differentiation and skeletal development.

Main Methods:

• Isolation and culture of mouse skeletal stem cells (SSCs) with PDGFRβ gain-of-function mutations.
• Single-cell RNA transcriptomics to analyze gene expression changes in mutant SSCs.
• In vitro differentiation assays to assess osteogenic and chondrogenic potential.
• Phenotypic analysis of mice with PDGFRβ gain-of-function mutations.

Main Results:

• PDGFRβ gain-of-function mutations in SSCs lead to defects in colony formation, mirroring mouse wasting or overgrowth phenotypes.
• Mutant SSCs show altered osteogenic and chondrogenic precursor development, with impaired osteogenesis and increased chondrogenic marker expression (e.g., Sox9).
• Mice with PDGFRβ mutations exhibit osteopenia, linked to increased STAT5 phosphorylation and overexpression of Igf1 and Socs2, suggesting activation of the STAT5-IGF1 axis.

Conclusions:

• PDGFRβ gain-of-function mutations directly impact SSCs, causing intrinsic cellular changes that favor chondrogenesis over osteogenesis.
• These intrinsic SSC changes result in osteopenic skeletal phenotypes observed in mice.
• The study identifies PDGFRβ mutations as a cause of skeletal disorders through altered SSC behavior and differentiation pathways.