Developmental dynamics of two bipotent thymic epithelial progenitor types

Area of Science:

• Immunology
• Developmental Biology
• Cell Biology

Background:

• Thymus T cell development is vital for immunity and relies on the thymic epithelial microenvironment.
• The thymus exhibits dynamic changes in size and cellularity throughout life, impacting T cell production.
• Previous studies using single-cell RNA sequencing revealed thymic epithelial cell heterogeneity, but progenitor identities remain unclear.

Purpose of the Study:

• To identify and characterize epithelial progenitor populations in the thymus.
• To understand the developmental dynamics of the thymic epithelium over time.
• To explore strategies for modulating thymopoietic activity.

Main Methods:

• Combined single-cell RNA sequencing (scRNA-seq) with a CRISPR-Cas9-based cellular barcoding system in mice.
• Analyzed qualitative and quantitative changes in the thymic epithelium.
• Investigated the role of Fgf7 in thymic microenvironment expansion.

Main Results:

• Identified two principal bipotent progenitor populations: one biased towards cortical epithelium and another towards medullary epithelium.
• Characterized distinct early and postnatal progenitor populations.
• Demonstrated that sustained autocrine Fgf7 signaling promotes thymic microenvironment expansion without progenitor exhaustion.

Conclusions:

• The study resolves the identities and developmental dynamics of thymic epithelial progenitors.
• Findings reveal distinct progenitor populations governing cortical and medullary development.
• Suggests Fgf7 as a potential therapeutic target for modulating thymopoietic activity and immune function.