Katsutoshi Mizuno

University of Fukui · School of Medical Sciences

Immotile cilia at the ventral node of mouse embryos are required for sensing leftward fluid flow that breaks left-right symmetry of the body. However, the flow-sensing mechanism has long remained elusive. In this work, we show that immotile cilia at the node undergo asymmetric deformation along the dorsoventral axis in response to the flow. Applica...

For left-right symmetry breaking in the mouse embryo, the basal body must become positioned at the posterior side of node cells, but its precise mechanism has remained unknown. We here examined the role of microtubules (MTs) and actomyosin in this basal body positioning. Exposure of mouse embryos to agents that stabilize or destabilize MTs or F-act...

Immotile cilia of crown cells at the node of mouse embryos are required for sensing of a leftward fluid flow ¹ that gives rise to the breaking of left–right (L–R) symmetry ² . The flow–sensing mechanism has long remained elusive, however, with both mechanosensing and chemosensing models having been proposed 1,3–5 . Here we show that immotile cilia...

Light-responsive regulation of ciliary motility is known to be conducted through modulation of dyneins, but the mechanism is not fully understood. Here, we report a novel subunit of the two-headed f/I1 inner arm dynein, named DYBLUP, in animal spermatozoa and a unicellular green alga. This subunit contains a BLUF (sensors of blue light using FAD) d...

Axonemal dynein ATPases direct ciliary and flagellar beating via adenosine triphosphate (ATP) hydrolysis. The modulatory effect of adenosine monophosphate (AMP) and adenosine diphosphate (ADP) on flagellar beating is not fully understood. Here, we describe a deficiency of cilia and flagella associated protein 45 (CFAP45) in humans and mice that pre...

Immotile cilia sense extracellular signals such as fluid flow, but whether Ca ²⁺ plays a role in flow sensing has been unclear. Here, we examined the role of ciliary Ca ²⁺ in the flow sensing that initiates the breaking of left-right (L-R) symmetry in the mouse embryo. Intraciliary and cytoplasmic Ca ²⁺ transients were detected in the crown cells a...

Unidirectional fluid flow generated by motile cilia at the left–right organizer (LRO) breaks left–right (L–R) symmetry during early embryogenesis in mouse, frog and zebrafish. The chick embryo, however, does not require motile cilia for L–R symmetry breaking. The diversity of mechanisms for L–R symmetry breaking among vertebrates and the trigger fo...

Cluap1/IFT38 is a ciliary protein that belongs to the IFT‐B complex and is required for ciliogenesis. In this study, we have examined the behaviors of Cluap1 protein in non‐ciliated and ciliated cells. In proliferating cells, Cluap1 is located at the distal appendage of the mother centriole. When cells are induced to form cilia, Cluap1 is found in...

Sperm chemotaxis toward a chemoattractant is very important for the success of fertilization. Calaxin, a member of the neuronal calcium sensor protein family, directly acts on outer-arm dynein and regulates specific flagellar movement during sperm chemotaxis of ascidian, Ciona intestinalis. Here, we present the crystal structures of calaxin both in...

Through their coordinated alignment and beating, motile cilia generate directional fluid flow and organismal movement. While the mechanisms used by multiciliated epithelial tissues to achieve this coordination have been widely studied, much less is known about regulation of monociliated tissues such as those found in the vertebrate node and swimmin...

Changes in protein activity driven by post translational modifications comprise an important mechanism for the control of many cellular processes. Several flagellar proteins are methylated on arginine residues during flagellar resorption; however, the function is not understood. To learn more about the role of protein methylation during flagellar d...

The complex waveforms characteristic of motile eukaryotic cilia and flagella are produced by the temporally and spatially regulated action of multiple dynein subforms generating sliding between subsets of axonemal microtubules. Multiple protein complexes have been identified that are associated with the doublet microtubules and that mediate regulat...

Sperm motility is driven by motile cytoskeletal elements in the tail, called axonemes. The structure of axonemes consists of 9 + 2 microtubules, molecular motors (dyneins), and their regulatory structures. Axonemes are well conserved in motile cilia and flagella through eukaryotic evolution. Deficiency in the axonemal structure causes defects in sp...

Sperm chemotaxis is widely seen both in animals and plants and is considered to be necessary for efficient success of fertilization. Although intracellular Ca2+ is known to play important roles in sperm chemotaxis, the molecular mechanism causing the change in flagellar waveform that drives sperm directed toward the egg is still unclear. Several Ca...

Sperm chemotaxis occurs widely in animals and plants and plays an important role in the success of fertilization. Several studies have recently demonstrated that Ca(2+) influx through specific Ca(2+) channels is a prerequisite for sperm chemotactic movement. However, the regulator that modulates flagellar movement in response to Ca(2+) is unknown....

Metazoan spermatozoa, especially those from marine invertebrates and fish, are excellent sources for isolating axonemal dyneins because of their cellular homogeneity and the large amounts that can be collected. Sperm flagella can be easily isolated by homogenization and subsequent centrifugation. Axonemes are obtained by demembranation of flagella...

Spermatozoa show several changes in flagellar waveform, such as upon fertilization. Ca(2+) has been shown to play critical roles in modulating the waveforms of sperm flagella. However, a Ca(2+)-binding protein in sperm flagella that regulates axonemal dyneins has not been fully characterized. We identified a novel neuronal calcium sensor family pro...

A juevinile of the ascidian Ciona intestinalis expressing RFP. The RFP cassette was used as a marker of the transgene expressing Minos transposase in the male germ cells. RFP was expressed in the endostyle, peripharyngeal band, retropharyngeal band, and muscle. See Sasakura et al., Developmental Dyanmics 237:39–50.

Germline transgenesis with a Tc1/mariner superfamily Minos transposon was achieved in the ascidian Ciona intestinalis. Transgenic lines that express transposases in germ cells are very useful for remobilizing transposon copies. In the present study, we created transposase-expressing lines of Minos in Ciona. A Ciona gene encoding protamine (Ci-prm)...