Biology subjects

Ikawa, Y.

Publications and source records attributed to Ikawa, Y..

3 recordsLinked to original sources

bioRxiv2024

Localization and function of key axonemal microtubule inner proteins and dynein docking complex members reveal extensive diversity among vertebrate motile cilia

Vertebrate motile cilia are broadly classified as (9+2) or (9+0), based on the presence or absence of the central pair apparatus, respectively. Cryogenic electron microscopy (cryo-EM) analyses of (9+2) cilia have uncovered an elaborate axonemal protein composition; whether these features are relevant to (9+0) cilia remain unclear. We previously demonstrated that Cfap53, a key microtubule inner protein (MIP) as well as centriolar-satellites component, is essential for motility of (9+0), but not (9+2) cilia. Here, we show that in (9+2) cilia, Cfap53 functions redundantly with a paralogous MIP, Mns1. Mns1 localizes to ciliary axonemes, and combined loss of both proteins in zebrafish and mice, caused severe loss of outer dynein arms (ODAs) of (9+2) cilia, significantly affecting their motility. Moreover, using immunoprecipitation, we demonstrate that while Mns1 can self-associate and interact with Cfap53, Cfap53 is unable to self-associate. Finally, we show that multiple additional dynein interacting proteins, such as the ODA docking complex (ODA-DC) members, show strikingly distinct localization patterns between various motile cilia-types. Our findings clarify how paralogous MIPs, Cfap53 and Mns1, function in regulating motility of (9+2) versus (9+0) cilia, and establish that localization pattern of other key motility proteins also differ between these cilia-types, further emphasizing extensive structural variations among these organelles.

developmental biology↗

bioRxiv2022

Immotile cilia of the mouse node sense a fluid flow-induced mechanical force for left-right symmetry breaking

Immotile cilia of crown cells at the node of mouse embryos are required for sensing of a leftward fluid flow1 that gives rise to the breaking of left-right (L-R) symmetry2. The flow-sensing mechanism has long remained elusive, however, with both mechanosensing and chemosensing models having been proposed1, 3-5. Here we show that immotile cilia at the mouse node respond to mechanical force. In the presence of a leftward flow, immotile cilia on the left side of the node bend toward the ventral side whereas those on the right side bend toward the dorsal side. Application of mechanical stimuli to immotile cilia along the dorsoventral axis by optical tweezers induced Ca2+ transients and degradation of Dand5 mRNA--the first known L-R asymmetric molecular events--in the targeted cells. The Pkd2 channel protein was found to be preferentially localized to the dorsal side of immotile cilia on both left and right sides of the node, and the observed induction of Ca2+ transients preferentially by mechanical stimuli directed toward the ventral side could explain the differential response of immotile cilia to the directional flow. Our results thus suggest that immotile cilia at the node sense the direction of fluid flow in a manner dependent on a flow-generated mechanical force.

developmental biology↗

bioRxiv2020

Fluid flow-induced left-right asymmetric decay of Dand5 mRNA in the mouse embryo requires Bicc1-Ccr4 RNA degradation complex

Molecular left-right (L-R) asymmetry is established at the node of the mouse embryo as a result of the sensing of a leftward fluid flow by immotile cilia of perinodal crown cells and the consequent degradation of Dand5 mRNA on the left side. We here examined how the fluid flow induces Dand5 mRNA decay. We found that the 3 untranslated region (3-UTR) of Dand5 mRNA is necessary and sufficient for the left-sided decay and is responsive to the flow direction, loss of the cation channel Pkd2, and Ca2+. The 200-nucleotide proximal-most portion of the 3-UTR, which is conserved among mammals, is essential for the asymmetric mRNA decay and binds Bicc1, an RNA binding protein specifically expressed at the node. Bicc1 preferentially recognizes GAC and GACR sequences in RNA, and these motifs are enriched in the 200-nucleotide region of the Dand5 3-UTR. The Cnot3 component of the Ccr4-Not deadenylase complex interacts with Bicc1 and is also required for Dand5 mRNA decay at the node. Our results thus suggest that leftward fluid flow induces binding of Bicc1 to the 3-UTR of Dand5 mRNA in crown cells on the left side of the node, and that consequent recruitment of Ccr4-Not mediates mRNA degradation.

developmental biology↗