Abstract
BackgroundThe blood filtering organ in zebrafish embryos is the pronephros, which consists of two functional nephrons. Segmentation of a nephron into different domains is essential for its function and is well conserved among vertebrates. Zebrafish has been extensively used as a model to understand nephron segmentation during development. Here, we have identified EF-hand domain containing 2 (Efhc2) as a novel component of genetic programme regulating nephron segmentation in zebrafish. Human EFHC2 is a protein with one predicted calcium-binding EF-hand motif and three DM10 domains, whose function is unknown. EFHC2 has been implicated in several brain-related genetic diseases like Turner syndrome and juvenile myoclonic epilepsy. However, there is limited information on its normal physiological function.Resultsefhc2 mRNA is primarily expressed in the pronephros of zebrafish embryos. Other sites of expression include olfactory placode, notochord, otic vesicle, epiphysis and neuromast cells. Morpholino antisense oligonucleotide-mediated knock-down of Efhc2 resulted in defects in pronephros development and function in zebrafish embryos. Efhc2 knock-down leads to expansion of distal early segment of pronephros, whereas, the corpuscle of stannius and distal late segments were reduced. The number of multi-ciliated cells (MCC) that are present in a salt-and-pepper fashion throughout the middle of each nephron and vital for fluid flow were also reduced. It is known that retinoic acid (RA) signaling regulates pronephros segmentation in vertebrates and we show that Efhc2 function is crucial for nephron segmentation in zebrafish. Our data suggests that RA and Efhc2 function independent of each other in pronephros segmentation. However, Efhc2 and RA synergistically regulate MCC development.ConclusionIn this study, we have identified Efhc2 as a regulator of segmentation of the distal part of nephron and pronephros function during zebrafish development.
Highlights
The blood filtering organ in zebrafish embryos is the pronephros, which consists of two functional nephrons
In 24 hpf embryos, efhc2 is expressed in pronephros, olfactory placode, notochord, otic vesicle, epiphysis, and tail bud. efhc2 is not expressed in the glomerulus and neck segments of the pronephros, but its expression starts at the proximal convoluted tubule (PCT)
We sought to address the function of efhc2 in pronephros development in zebrafish
Summary
The blood filtering organ in zebrafish embryos is the pronephros, which consists of two functional nephrons. Kidney organogenesis in zebrafish is under the control of several transcription factors (TFs) and signaling pathways [8]. These regulatory molecules are important for specification and proper segmentation of pronephros in zebrafish. Transcriptional factor irx3b, evi, and pou3f3a/pou3f3b are required for the development of distal segments of pronephros [6]. The hnf1ba and hnf1bb are required for proper nephron patterning by regulating the expression of other genes, like pax2a establishes boundary of podocyte and the neck by directly inhibiting wt mediated podocyte formation [11]. The transcription factor mecom and sim1a are required for formation of the distal tubule and restriction of proximal segments of the nephron [14]
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