Kupffer's vesicle is a ciliated organ of asymmetry in the zebrafish embryo that initiates left-right development of the brain, heart and gut

Abstract

SummaryKupffer's vesicle is a ciliated organ of asymmetry in the zebrafish embryo that initiates left-right development of the brain, heart and gut Research article Development 1248However, genes implicated in ciliated node cell function are also expressed in non-node cells, and mutations of these genes give rise to a variety of laterality phenotypes and more pleiotropic phenotypes, making it impossible to exclude other mechanisms for LR development during early embryogenesis (for reviews, see Tabin and Vogan, 2003;Wagner and Yost, 2000;Yost, 2003). Furthermore, it is not known whether nodal flow is a murine-specific mechanism. Cilia formation and expression of lrd homologues have recently been observed in structures analogous to the node in chick, frog (Xenopus laevis) and zebrafish embryos (Essner et al., 2002), but the existence of motile cilia and nodal flow has not been demonstrated in non-murine embryos. Further confounding the issue, there are molecular asymmetries that precede the appearance of lrd expression and monocilia in Xenopus Levin et al., 2002) and perhaps in chick (Levin et al., 1995;Stern et al., 1995). This raises the issue of whether ciliated cells in other vertebrate embryos generate fluid flow and have a conserved function for ciliogenesis genes in LR development. In zebrafish, ciliated cells arise in the tailbud at the end of gastrulation (Essner et al., 2002) in a transient spherical organ called Kupffer's vesicle (KV). KV, first described in 1868 (Kupffer, 1868), is a conserved structure among teleost fishes. Electron microscopy studies in the bait fish Fundulus heteroclitus have shown that a single cilium (i.e. monocilium) protrudes from each cell lining KV into the lumen (Brummett and Dumont, 1978). In zebrafish, KV is formed from a group of approximately two-dozen cells, known as dorsal forerunner cells (DFCs), that migrate at the leading edge of the embryonic shield (the zebrafish equivalent of the mouse node) during gastrulation. In contrast to other cells in this region, DFCs do not involute during gastrulation, but remain at the leading edge of epibolic movements. At the end of gastrulation, DFCs migrate deep into the embryo and organize to form KV (Cooper and D'Amico, 1996; D'Amico and Cooper, 1997;Melby et al., 1996). During subsequent somite stages, KV is found ventral to the forming notochord in the tailbud and adjacent to the yolk cell. Although KV was first described well over 100 years ago, it remains unknown whether DFCs and KV are mesodermal or endodermal in origin, and it is unclear what role they play during development, leading to the categorization of KV as an embryonic 'organ of ambiguity ' (Warga and Stainier, 2002).Recently, using a novel technique to knockdown gene expression specifically in DFCs, we reported the first evidence that DFCs and/or KV function in LR patterning (Amack and Yost, 2004). Here, we show that cilia that arise inside KV are motile and generate a consistent counterclockwise fluid flow. A combination of laser ablations, embryological manipul...

Three types of cilia including a novel 9+4 axoneme on the notochordal plate of the rabbit embryo

“…Homologous structures are found in amphibian (gastrocoel roof plate; GRP; Essner et al, 2002;Shook et al, 2004;Blum et al, 2006) and teleost fish embryos (Kupffer's vesicle; KV; Essner et al, 2002Essner et al, , 2005KramerZucker et al, 2005;Okada et al, 2005;Hirokawa et al, 2006). This structure is characterized by a number of distinctive features that distinguishes it from any other ciliated tissue in the animal kingdom: (1) it is directly derived from the embryonic organizer, and (2) harbors motile monocilia of the 9ϩ0 and/or 9ϩ2 type.…”

“…It has become increasingly clear that almost any defect in ciliary components that disturbs the function of the PNC monocilia disrupts correct situs specification in mice as well as humans Fliegauf and Omran, 2006;Hirokawa et al, 2006;Marshall and Nonaka, 2006;Raya and Belmonte, 2006;Shiratori and Hamada, 2006). In zebrafish and medaka, a homologous cilia-driven fluid flow was discovered in Kupffer's vesicle, which was required for laterality determination as well, indicating an evolutionary conserved mechanism of LR axis determination (Essner et al, 2005;Kramer-Zucker et al, 2005;Okada et al, 2005). Interestingly, Kupffer's vesicle cilia, while performing rotational beat patterns in all cases, display 9ϩ2 axonemes in zebrafish (KramerZucker et al, 2005) and 9ϩ0 axonemes in medaka (Okada et al, 2005).…”

A mutation in the zebrafish Na,K‐ATPase subunit atp1a1a.1 provides genetic evidence that the sodium potassium pump contributes to left‐right asymmetry downstream or in parallel to nodal flow

“…The cells lining Kupffer's vesicle (KV) form cilia that have been demonstrated to induce an asymmetric fluid flow (Essner et al, 2002(Essner et al, , 2005b. To investigate whether the defects in Na,K-ATPase function in m883 may exert their effect on laterality through affecting KV formation or function, we compared the morphology of Kupffer's vesicle in wild-type and mutant embryos.…”

“…Monocilia in Kupffer's vesicle in whole embryos were visualized with anti-acetylated tubulin antibody (Sigma) as described in Essner et al (2005a). Cilia were documented in 80% glycerol using a confocal microscope.…”

“…Monocilia occur in a small group of cells in the Xenopus organizer, the node in chick, and shield in zebrafish. The zebrafish dorsal forerunner cells (DFC) in the shield later form the inner lining of Kupffer's vesicle (KV), and mutational analysis eliminating DFCs disturbs LR axis formation (Essner et al, 2005b). Knock down of both polycystin-2 and polaris, necessary for cilia assembly in zebrafish, causes disruption of the left-right asymmetry (Bisgrove et al, 2005).…”