The Zebrafish Kupffer’s Vesicle: A Special Organ in a Model Organism to Study Human Diseases

Abstract

The Kupffer's vesicle (KV) is a small, ciliated organ transiently present during embryogenesis of the zebrafish and other teleosts. The KV is required to the establishment of visceral laterality, such as the heart on the left side, being also known by the name left-right organizer (LRO). The LRO is found in other vertebrates, including mice, rabbits, frogs and human embryos. Among these, the KV became an excellent model organ to investigate the early left-right events during development and in disease. Many ciliary molecular players associated to the human disease primary ciliary dyskinesia have been tested in the zebrafish looking at KV cilia and its downstream effects on flow and left-right markers. Additionally, given its morphology and molecular features, we proposed the KV as a model organ to study the molecular mechanisms of the renal cyst inflation that occurs in the autosomal dominant polycystic kidney disease. Although having no connection to the kidney, the KV mimics a renal cyst because it is a fluid-filled vesicle, lined by monociliated epithelial cells that express polycystin-2, which knockdown leads to the organ luminal enlargement through changes in ion/water epithelial transport. Here, we explore the usefulness of the zebrafish KV to model these diseases. Keywords: Kupffer's vesicle (KV), left-right (LR), left-right organizer (LRO), primary ciliary dyskinesia (PCD), autosomal dominant polycystic kidney disease (ADPKD) Zebrafish in Biomedical Research

Animal and Cell Culture Models for Cystic Fibrosis

“…The Kupffer vesicle is a ciliated organ transiently present during zebrafish embryogenesis that is inflated by Cftr-dependent fluid secretion, thereby providing a rapid assay of Cftr activity. 21,68 Pulmonary ionocytes have recently been identified in humans and are a major source of CFTR expression in the airway epithelium. 69,70 Gene expression profile of zebrafish ionocytes resembles that of human pulmonary ionocytes, 69 and thus CF zebrafish could prove useful in investigating the role of ionocytes in disease physiology and pathogenesis, as well as in strategies for targeting these cells in therapies.…”

Pkd2 Affects Cilia Length and Impacts LR Flow Dynamics and Dand5

“…The cation channel Pkd2 together with the mechanosensor Pkd1 (Polycystin 1) form a complex which, in the kidney, has the ability to sense the urine flow and induce an intracellular Ca 2+ signal ( Nauli et al, 2003 ). Pkd2 and its new partner Pkd1-like-1 have also been proposed as the mechanosensor-channel complex responsible for sensing the flow in the LROs of mice, medaka, and zebrafish and conveying the information into the adjacent tissues ( Field et al, 2011 ; Kamura et al, 2011 ; Roxo-Rosa and Lopes, 2019 ). Despite working as a complex, it has been shown that decreasing Pkd2 alone is sufficient for a strong LR randomization both in mice and in zebrafish ( Pennekamp et al, 2002 ; Bisgrove et al, 2005 ; Schottenfeld et al, 2007 ; Yoshiba et al, 2012 ).…”

Zebrafish Motile Cilia as a Model for Primary Ciliary Dyskinesia

“…Even though the zebrafish is transparent, and the LRO is accessible by light microscopy, a more detailed analysis using conventional TEM can be problematic. The organ itself is not bigger than 70 µm in diameter (measured by TEM), but its presence is transient during the zebrafish development [16,17,56]. In addition, the LRO has an ovoid shape, leading to cilia with many different orientations when imaged by TEM from ultrathin cross-sections.…”

“…In addition, the LRO has an ovoid shape, leading to cilia with many different orientations when imaged by TEM from ultrathin cross-sections. Furthermore, the LRO is only composed of around 50 monociliated cells (assessed by light microscopy) [16,17]. Altogether, these features make the LRO a challenging organ to study by conventional TEM.…”

“…On the other hand, motile cilia lacking CP (9 + 0) have a specific movement pattern, described as planar rotation, circling or twisting. These 9 + 0 monocilia are present in the LRO in vertebrates such as mice or zebrafish [16][17][18], but reports on LRO cilia with 9 + 2 cilia and 9 + 4 also exist [7,18,19]. In cases of disease, multiciliated cells with cilia wholly or partially lacking the CP are frequently accounted as one of the phenotypes of Primary Ciliary Dyskinesia, an autosomal recessive disease of the motile cilia [20,21].…”