Cilia-driven fluid flow in the zebrafish pronephros, brain and Kupffer's vesicle is required for normal organogenesis

Abstract

Cilia, as motile and sensory organelles, have been implicated in normal development, as well as diseases including cystic kidney disease, hydrocephalus and situs inversus. In kidney epithelia, cilia are proposed to be nonmotile sensory organelles, while in the mouse node, two cilia populations, motile and non-motile have been proposed to regulate situs. We show that cilia in the zebrafish larval kidney, the spinal cord and Kupffer's vesicle are motile, suggesting that fluid flow is a common feature of each of these organs. Disruption of cilia structure or motility resulted in pronephric cyst formation, hydrocephalus and left-right asymmetry defects. The data show that loss of fluid flow leads to fluid accumulation, which can account for organ distension pathologies in the kidney and brain. In Kupffer's vesicle, loss of flow is associated with loss of left-right patterning, indicating that the 'nodal flow' mechanism of generating situs is conserved in non-mammalian vertebrates.

Laterality defects are influenced by timing of treatments and animal model

“…A considerable number of studies have reported complete absence of nodal, lefty, or pitx2 expression (Field et al, 2011; Oki et al, 2010; Sakano et al, 2010; Gaio et al, 1999; Takeuchi et al, 2007; Zhang et al, 2001; Yan et al, 1999; Tsukui et al, 1999; Collignon et al, 1996; Kramer-Zucker et al, 2005; Krebs et al, 2003; Pennekamp et al, 2002), with some reporting 100% absent expression for all three genes. What does complete absence of gene expression mean?…”

“…I have also asked, is there any effect of animal model on the penetrance of LR defects? Importantly, when collecting this data, it was also apparent that many studies examine only asymmetric gene expression and use this data to make conclusions about organ position [see for example (Oki et al, 2010; Antic et al, 2010; Vick et al, 2009; Pathak et al, 2007; Houde et al, 2006; Kramer-Zucker et al, 2005; Zhang et al, 2001)]. A few studies have proposed that gene expression can be used to predict organ laterality, but the mathematical models produced to date have only been applied to extremely limited datasets (Ibanes and Izpisua Belmonte, 2009; Lohr et al, 1997; Mogi et al, 2003).…”

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

“…However, different types of axonemes have been described at the teleost KV, namely 9ϩ0 cilia in medaka (Okada et al, 2005) and 9ϩ2 cilia in zebrafish (Kramer-Zucker et al, 2005). In mouse, only 9ϩ0 cilia were published at the PNC (Sulik et al, 1994;Nonaka et al, 1998), yet the knockout of Foxj1, a gene that selectively affects 9ϩ2 cilia, revealed laterality defects nevertheless (Blatt et al, 1999;Brody et al, 2000).…”

“…PNC ("node") cilia in the mouse lack the central pair microtubules (Sulik et al, 1994), while cilia of the homologous Kupffer's vesicle in zebrafish display axonemes of the 9ϩ2 type (Kramer-Zucker et al, 2005). In order to investigate the PNC axonemes in rabbit, we performed an ultrastructural TEM analysis.…”

“…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).…”