Role of Ca ²⁺ transients at the node of the mouse embryo in breaking of left-right symmetry

Abstract

Immotile cilia sense extracellular signals such as fluid flow, but whether Ca2+ plays a role in flow sensing has been unclear. Here, we examined the role of ciliary Ca2+ in the flow sensing that initiates the breaking of left-right (L-R) symmetry in the mouse embryo. Intraciliary and cytoplasmic Ca2+ transients were detected in the crown cells at the node. These Ca2+ transients showed L-R asymmetry, which was lost in the absence of fluid flow or the PKD2 channel. Further characterization allowed classification of the Ca2+ transients into two types: cilium-derived, L-R-asymmetric transients (type 1) and cilium-independent transients without an L-R bias (type 2). Type 1 intraciliary transients occurred preferentially at the left posterior region of the node, where L-R symmetry breaking takes place. Suppression of intraciliary Ca2+ transients delayed L-R symmetry breaking. Our results implicate cilium-derived Ca2+ transients in crown cells in initiation of L-R symmetry breaking in the mouse embryo.

Bicc1 and Dicer regulate left-right patterning through post-transcriptional control of the Nodal inhibitor Dand5

“…Thereby, Dand5 synthesis and Nodal inhibition are secured. During flow, left-sided Pkd2 channel activation results in a cytoplasmic Ca 2+ signal, which has been described in mouse and zebrafish 10 , 11 , 38 , 45 , 46 . It represents the intracellular second messenger of the initially extracellular flow signal.…”

“…In mice and fish, left-asymmetric calcium spikes in lateral LRO cells were reported, which were depending on a ciliary Pkd2 function. Calcium influx, therefore, seems to represent the initial response to flow sensing 10 , 11 .…”

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

“…Furthermore, R > L asymmetric expression of the NDE-Hsp-dsVenu’-3 ′ -UTR transgene at the node in the present study was impaired by thapsigargin treatment and by the absence of Pkd2. The decay of Dand5 mRNA may therefore be induced by the Ca 2+ influx triggered by sensing of nodal flow by the immotile cilia of crown cells 6 . The resulting increase in the cytosolic concentration of Ca 2+ may influence, directly or indirectly, either the interaction with a component (X in Fig.…”

“…Genetic studies have indicated that nodal flow is sensed by the transient receptor potential (TRP) cation channel Pkd2 3 and its partner protein Pkd1l1 4 present in immotile cilia of crown cells at the periphery of the node 5 . Flow sensation by Pkd2 is thought to result in the entry of Ca 2+ 6 and the consequent degradation through an unknown mechanism of the mRNA for Dand5 (also known as Cerl2 or Cer2) in crown cells on the left side of the node 1 , 7 . Given that Dand5 is an antagonist of the extracellular signaling molecule Nodal, which is required for correct L-R patterning 8 , suppression of Dand5 mRNA on the left side results in increased Nodal activity in crown cells on this side 9 .…”

Disrupting polycystin-2 EF hand Ca2+ affinity does not alter channel function or contribute to polycystic kidney disease

“…They are privileged cellular organelles comprising fewer than 500 unique protein components, and are found in all organ systems, including cells of the kidney nephron ( Ostrowski et al, 2002 ; Pazour et al, 2005 ). Primary cilia house specific receptors and downstream effectors, which are capable of modulating morphogenic gene transcription responsible for left-right axis determination in developing vertebrate embryos ( Braun and Hildebrandt, 2017 ; Mizuno et al, 2020 ; Nachury and Mick, 2019 ). Dysregulation of cilia- and centrosome-localized proteins results in ciliopathies conditions that often affect specific organ systems but commonly share cystic kidney diseases as a comorbidity ( Hildebrandt et al, 2011 ; Hildebrandt and Zhou, 2007 ).…”