Zebrafish nephrogenesis is regulated by interactions between retinoic acid, mecom, and Notch signaling.
The zebrafish pronephros provides a conserved model to study kidney development, in particular to delineate the poorly understood processes of how nephron segment pattern and cell type choice are established. Zebrafish nephrons are divided into distinct epithelial regions that include a series of proximal and distal tubule segments, which are comprised of intercalated transporting epithelial cells and multiciliated cells (MCC). Previous studies have shown that retinoic acid (RA) regionalizes the renal progenitor field into proximal and distal domains and that Notch signaling later represses MCC differentiation, but further understanding of these pathways has remained unknown. The transcription factor mecom (mds1/evi1 complex) is broadly expressed in renal progenitors, and then subsequently marks the distal tubule. Here, we show that mecom is necessary to form the distal tubule and to restrict both proximal tubule formation and MCC fate choice. We found that mecom and RA have opposing roles in patterning discrete proximal and distal segments. Further, we discovered that RA is required for MCC formation, and that one mechanism by which RA promotes MCC fate choice is to inhibit mecom. Next, we determined the epistatic relationship between mecom and Notch signaling, which limits MCC fate choice by lateral inhibition. Abrogation of Notch signaling with the γ-secretase inhibitor DAPT revealed that Notch and mecom did not have additive effects in blocking MCC formation, suggesting that they function in the same pathway. Ectopic expression of the Notch signaling effector, Notch intracellular domain (NICD), rescued the expansion of MCCs in mecom morphants, indicating that mecom acts upstream to induce Notch signaling. These findings suggest a model in which mecom and RA arbitrate proximodistal segment domains, while MCC fate is modulated by a complex interplay in which RA inhibition of mecom, and mecom promotion of Notch, titrates MCC number. Taken together, our studies have revealed several essential and novel mechanisms that control pronephros development in the zebrafish.
['Li|Yue|Y|', 'Cheng|Christina N|CN|', 'Verdun|Valerie A|VA|', 'Wingert|Rebecca A|RA|']
D000818:Animals D002454:Cell Differentiation D019070:Cell Lineage D004268:DNA-Binding Proteins D004843:Epistasis, Genetic D018507:Gene Expression Regulation, Developmental D023281:Genomics D007668:Kidney D000074008:MDS1 and EVI1 Complex Locus Protein D009399:Nephrons D038081:Organogenesis D060910:Pronephros D017434:Protein Structure, Tertiary D018075:RNA, Complementary D051880:Receptors, Notch D015398:Signal Transduction D013997:Time Factors D014212:Tretinoin D015027:Zebrafish D029961:Zebrafish Proteins
Nephrogenesis Retinoic acid Retinoic acid mecom Notch Pronephros Segmentation multiciliated cell MCC RA mds1/evi1 complex Notch intracellular domain NICD 4-diethylamino-benzaldehyde CS DE DEAB DL G IM MET N PCT PD PM PST RARE corpuscle of Stannius days post-fertilization distal early distal late dpf glomerulus hours post-fertilization hpf intermediate mesoderm mesenchymal to epithelial transition neck paraxial mesoderm pronephric duct proximal convoluted tubule proximal straight tubule retinoic acid retinoic acid response element