Dynamic Single Cell Transcriptomics Defines Kidney FGF23/KL Bioactivity and Novel Segment-Specific Inflammatory...

Area of Science:

• Molecular Endocrinology
• Renal Physiology
• Systems Biology

Background:

• Fibroblast growth factor 23 (FGF23) and its coreceptor αKlotho (KL) are critical regulators of phosphate metabolism.
• The precise spatial-temporal mechanisms of renal FGF23 action and its interaction with inflammation remain poorly understood.
• Altered FGF23 levels are implicated in rare and common metabolic syndromes, highlighting the need to understand its renal functions.

Purpose of the Study:

• To elucidate the spatial-temporal mechanisms of FGF23 bioactivity in the kidney at single-cell resolution.
• To identify specific cell populations and signaling pathways mediating FGF23's effects on phosphate metabolism.
• To investigate the interplay between FGF23 signaling and inflammatory pathways, particularly TNF/NF-κB.

Main Methods:

• Single-cell RNA sequencing (scRNAseq) of mouse kidneys following recombinant FGF23 (rFGF23) injection at multiple time points.
• Computational analysis of scRNAseq data to identify distinct cell clusters and track FGF23 bioactivity.
• Integration of ATAC-seq and RNA-seq data to pinpoint genomic regulatory elements involved in FGF23 signaling.

Main Results:

• FGF23 bioactivity was mapped to specific renal cell populations, including proximal and distal tubules, dependent on constitutive KL expression.
• Temporal FGF23 responses induced distinct cellular identities and modulated MAPK and vitamin D metabolic pathways via early and late transcriptional regulons.
• An unexpected crosstalk between FGF23-mediated MAPK signaling and TNF receptor/NF-κB inflammatory pathways was identified, which inhibited FGF23 bioactivity.

Conclusions:

• Novel FGF23-regulated pathways and cellular responses in the kidney have been uncovered at single-cell resolution.
• The findings reveal a critical interplay between FGF23 signaling and inflammatory pathways (TNF/NF-κB), impacting FGF23 bioactivity.
• These insights provide a foundation for understanding FGF23-dependent disease mechanisms and developing targeted therapeutic strategies for mineral metabolism disorders.