Estrogen modulation of fate choice during kidney development

Abstract

Vertebrate kidney formation is a nuanced process that directs renal progenitors to form the functional units of the kidney, known as nephrons, which are comprised of specialized cell types organized into discrete functional segments. The zebrafish embryo forms two nephrons by 24 hours post fertilization (hpf) and offers a simple but tractable genetic model to study nephron patterning. A chemical screen carried out by our lab coupled with whole mount in situ hybridization (WISH) identified 17ß‐estradiol (E2), the dominant form of estrogen in vertebrates, as a potential regulator of segmentation. Further investigation has revealed that E2 results in an expansion of the distal early (DE) and decrease of the distal late (DL) nephron segments due to alterations in cell number that were quantified with fluorescent ISH. Furthermore, E2 treated animals had expanded expression of the essential DE lineage transcription factor irx3b and its target, irx1a, suggesting E2 affects specification of DE precursors. To delineate the possible mechanism of action of E2’s renal effects, we conducted a targeted chemical screen with selective estrogen receptor modulators (SERMs) that exhibit preferential binding for known E2 receptors. The esr2 antagonist PHTPP similarly reduced the DE segment, suggesting that Esr2 may be involved in nephrogenesis. Consistent with this hypothesis, esr2a and esr2b transcripts are expressed during renal progenitor specification. To investigate which of these receptors (or both) are a major player in distal cell fate choice, we have created CRISPR/Cas9 mutants using guides designed for esr2a and esr2b, respectively. With additional genetic studies, we hope to further our understanding of the role of estrogen signaling in kidney development. Combined, these preliminary findings have relevance for understanding kidney disease models, as well as efforts to recapitulate development in vivo for drug discovery and regenerative therapies.Support or Funding InformationR01DK100237