Low nephron number at birth is a significant contributor and predisposing factor to kidney disease and high blood pressure in adult life. Despite the strong association, currently no interventions are available to improve nephron endowment at birth. Maintenance of an abundant Nephron Progenitor Cell (NPC) population is a major determinant of nephron number at birth and is determined in part by the balance between NPC renewal and differentiation. Studies show that NPCs have a limited lifespan, with Young NPCs (E13.5) predominantly expanding the NPC pool by self-renewal and Old NPCs (P0) exiting the self-renewing pool poised to differentiate en masse. Our recent studies show cell-intrinsic differences in NPCs metabolic pathway usage with developmental age. This metabolic shift correlates spatiotemporally with the switch from NPC renewal to differentiation. The long term goal of our research program is to harness this significant difference in metabolic states to maneuver NPC fate in vitro and in vivo. The overall hypothesis to be tested is that the changing metabolite milieu within the NPCs due to the metabolic shift from glycolysis to OxPhos during development will reprogram the NPC epigenome to favor renewal shutdown and promote differentiation. The hypothesis presents a new paradigm for NPC self-renewal and differentiation decisions, linking existing knowledge on growth factor signaling in NPC to an energy metabolism driven cell-fate switch. The focus of this application is to determine how metabolic manipulations impact the NPC open chromatin landscape to regulate NPC fate. Both glycolysis and OxPhos are easily measured and easily manipulated. This proposal aims to identify fuel dependency and metabolic flexibility of young versus old NPCs. We combine genetic, epigenetic and metabolic approaches to test our hypothesis. The studies proposed in Aim1 will determine whether glycolysis is necessary and/or sufficient to promote NPC renewal, and conversely, whether OxPhos is necessary and sufficient to promote differentiation.
Aim 2 will test the hypothesis that a metabolism-epigenetic axis controls NPC lifespan and demonstrate that metabolic manipulations directly modify the open chromatin landscape to regulate gene expression and NPC fate. We combine genetic, epigenetic and metabolic approaches to test our hypothesis, using open chromatin landscape profiling (ATAC-Seq), ChIP-Seq, and metabolic manipulations on mesenchyme cultures and isolated NPCs from wild type and glycolysis-impaired mouse NPCs. Identifying the preferred fuel(s) and metabolic pathways utilized by Young versus Old NPCs, and their degree of flexibility in fuel metabolism would guide how to nutritionally modulate NPCs transcriptional program and thus their fate.
We propose to characterize how cellular metabolism controls renewal and differentiation decisions in nephron progenitor cells. Our work is expected to guide strategies to extend NPC lifespan for in vitro kidney tissue regeneration or for in vivo stimulation of nephron endowment or repair. Defining how the metabolic status of the NPC switches the cellular program from self-renewal to differentiation offers a viable treatment option to improve nephron endowment, or restrain uncontrolled NPC proliferation by inducing differentiation, and potentially inform how the maternal environment influences fetal nephrogenesis.
