Biology subjects

Mochizuki, N.

Publications and source records attributed to Mochizuki, N..

10 recordsLinked to original sources

bioRxiv2025

Endothelial-zippering proceeds by sensing heartbeat-driven force through Cadherin-6 during heart-vessel connection in zebrafish

The connection between the heart and great vessels established during embryogenesis is essential for circulation. However, how great veins adhere to the endocardium lining the inside lumen of the beating heart remains unknown. Here, using zebrafish, we demonstrate that the endocardium and great veins are sealed in a zipper-closing manner outside the beating heart. The gradual elongation of the endocardium, driven by convergent extension, organized this adhesion by pulling venous ECs along the anterior-posterior axis. Time-specific manipulation of the heart rate revealed that this endocardial elongation proceeds against heartbeat-driven force. From time-lapse imaging of adherens junctions, which would counterbalance mechanical forces, we found a specific contribution of Cadherin-6 instead of Cadherin-5 in sensing endocardium-specific mechanical force. This specificity was confirmed by the depletion of Cadherin-6 that caused endocardium deformation. Altogether, we propose Cadherin-6 mediated EC-zippering as a novel mechanism that updates the understanding of Cadherin usage in dynamic morphogenesis.

developmental biology↗

bioRxiv2025

Chemokine induces phase transition from non-directional to directional migration during angiogenesis

During angiogenesis, sprouting endothelial cells (ECs) migrate and eventually connect to target vessels to form new vessel branches. However, it remains unclear how these sprouting vessels migrate toward the target vessels in three-dimensional space. We performed in vivo imaging of the cerebral capillary network formation in zebrafish to investigate how sprouting tip cells migrate toward their targets. Of note, we found that tip cells reach the target vessels through two phases: a non-directional phase and a directional phase. In the non-directional phase, sprouting tip cells dynamically extend and retract their protrusions at the leading front and have less directionality in their movement. In contrast, once tip cells enter the directional phase, they migrate directly toward the anastomotic targets. Chemokine receptor Cxcr4a and its ligand Cxcl12b are important for the phase transition to the directional phase. In cxcr4a mutants, sprouting tip cells lose their directionality and tend to connect to nearby sprouting ECs, resulting in altered capillary network patterning. Furthermore, in wild-type (WT) larvae, local Ca2+ oscillations were detected in protrusions of tip cells, specifically in the non-directional phase, but almost disappeared in the directional phase as a result of the Cxcr4-dependent phase transition. Thus, this study provides evidence of a chemokine-induced phase transition in migrating tip cells, which is important for proper vascular network formation in the zebrafish brain.

cell biology↗

bioRxiv2023

Angpt1 binding to Tie1 regulates the signaling required for lymphatic vessel development in zebrafish

Development of the vascular system is regulated by multiple signaling pathways mediated by receptor tyrosine kinases (RTKs). Among them, Angiopoietin (Ang)/Tie signaling regulates lymphatic and blood vessel development in mammals. Of the two Tie receptors, Tie2 is well known as a key mediator of Ang/Tie signaling, but unexpectedly, recent studies reveal that the Tie2 locus has been lost in many vertebrate species, while the Tie1 gene is more commonly present. However, Tie1-driven signaling pathways, including ligands and cellular functions, are not well understood. Here, we performed comprehensive mutant analyses of Angiopoietins and Tie receptors in zebrafish and found that only angpt1 and tie1 mutants show defects in trunk lymphatic vessel development. Among zebrafish Angiopoietins, only Angpt1 binds to Tie1 as a ligand. We indirectly monitored Ang1/Tie1 signaling and detected Tie1 activation in sprouting endothelial cells (ECs), where Tie1 inhibits nuclear import of EGFP-Foxo1a. Angpt1/Tie1 signaling functions in EC migration, proliferation, and lymphatic specification during early lymphangiogenesis, at least in part by modulating Vegfc/Vegfr3 signaling. Thus, we show Angpt1/Tie1 signaling to constitute an essential signaling pathway for lymphatic development in zebrafish. Brief Summary StatementZebrafish Angpt1/Tie1 signaling is characterized as an essential signaling pathway for trunk lymphatic development, with Tie1 regulating Foxo1 localization and modulating Vegfc/Vegfr3 signaling.

developmental biology↗

bioRxiv2021

Proper migration of lymphatic endothelial cells requires survival and guidance cues from arterial mural cells

The migration of lymphatic endothelial cells (LECs) is key for the development of the complex and vast lymphatic vascular network that pervades most of the tissues in an organism. In zebrafish, arterial intersegmental vessels together with chemokines have been shown to promote lymphatic cell migration from the horizontal myoseptum (HM). Here we found that LECs departure from HM coincides with the emergence of mural cells around the intersegmental arteries, raising the possibility that arterial mural cells promote LEC migration. Our live imaging and cell ablation experiments revealed that LECs migrate slower and fail to establish the lymphatic vascular network in the absence of arterial mural cells. We determined that mural cells are a source for the C-X-C motif chemokine 12 (Cxcl12a and Cxcl12b) and vascular endothelial growth factor C (Vegfc). We showed that ERK, a downstream component of Vegfc-Vegfr3 singling cascade, is activated in migrating LECs and that both chemokine and growth factor signalling is required for the robust migration. Furthermore, Vegfc-Vegfr3 has a pro-survival role in LECs during the migration. Together, the identification of mural cells a source for signals that guide LEC migration and survival will be important in the future design for rebuilding lymphatic vessels in the disease contexts.

developmental biology↗

bioRxiv2021

Field Potential Image Classification of Pacemaker Micro-coordination in the Intestine of the Mouse

The flexible and sophisticated movement of the gastrointestinal (GI) tract implies the involvement of mechanisms other than enteric neural circuits, to coordinate excitation in microregions. We thus performed microimaging of pacemaker dynamics in the small intestine of mice since it contains typical network-forming pacemaker cells. A dialysis membrane-reinforced low-impedance microelectrode array (MEA) enabled field potentials over a wide frequency range to be stably measured in microregions. The pacemaker dynamics were classified into basic patterns despite large variations. In the developmental process, pacemaker activity was categorized as either an expanding or a migrating pattern that was initiated in or propagated to the MEA sensing area, respectively. The intercellular current of the volume conductor complicated the waveform of both activities. The existence of expanding and migrating patterns was attributable to duplicated pacemaker systems such as intracellular Ca2+ oscillation-activated and voltage-gated mechanisms. Additionally, from the spatio-temporal feature during the period of pacemaker events, the bumpy/aberrant pattern was defined by aberrant, incoherent propagation, and associated with local impairment of excitability, while the colliding/converging pattern involved the interaction of multiple activities in the MEA area. Interconversion between the four micro-coordination patterns occurred in the same microregion. 5-Hydroxytryptamine (5-HT) promoted migrating activity, implying an improvement or restoration of spatial conductivity. These results agree well with the action of 5-HT to change GI movement toward propulsion. In conclusion, our MEA method of microimaging classification enables the quantitative assessment of spatio-temporal electric coordination underlying GI motility, suggesting its application to small model animals.

physiology↗

bioRxiv2021

Conserved and context-dependent roles for Pdgfrb signaling during zebrafish vascular mural cell development

Platelet derived growth factor beta and its receptor, Pdgfrb, play essential roles in the development of vascular mural cells, including pericytes and vascular smooth muscle. To determine if this role was conserved in zebrafish, we analyzed pdgfb and pdgfrb mutant lines. Similar to mouse, pdgfb and pdgfrb mutant zebrafish lack brain pericytes and exhibit anatomically selective loss of vascular smooth muscle coverage. Despite these defects, pdgfrb mutant zebrafish did not otherwise exhibit circulatory defects at larval stages. However, beginning at juvenile stages, we observed severe cranial hemorrhage and vessel dilation associated with loss of pericytes and vascular smooth muscle cells in pdgfrb mutants. Similar to mouse, pdgfrb mutant zebrafish also displayed structural defects in the glomerulus, but normal development of hepatic stellate cells. We also noted defective mural cell investment on coronary vessels with concomitant defects in their development. Together, our studies support a conserved requirement for Pdgfrb signaling in mural cells. In addition, these mutants provide an important model for definitive investigation of mural cells during early embryonic stages without confounding secondary effects from circulatory defects. Summary statementGenetic analysis in zebrafish demonstrates the conserved role of Pdgfb/Pdgfrb signaling in pericyte and vascular smooth muscle cell formation during vascular development in vertebrates.

developmental biology↗

bioRxiv2020

Marcksl1 modulates endothelial cell mechanoresponse to haemodynamic forces to control blood vessel shape and size

The formation of vascular tubes is driven by extensive changes in endothelial cell (EC) shape. Here, we have identified a novel role of the actin-binding protein, Marcksl1, in modulating the mechanical properties of EC cortex to regulate cell shape and vessel structure during angiogenesis. Increasing and depleting Marcksl1 expression level in vivo resulted in an increase and decrease, respectively, in EC size and the diameter of microvessels. Furthermore, endothelial overexpression of Marcksl1 induced ectopic blebbing on both apical and basal membranes, during and after lumen formation, that is suppressed by reduced blood flow. High resolution imaging revealed that Marcksl1 promotes the formation of linear actin bundles and decreases actin density at the EC cortex. Our findings demonstrate that a balanced network of linear and branched actin at the EC cortex is essential in conferring cortical integrity to resist the deforming forces of blood flow to regulate vessel structure.

cell biology↗

bioRxiv2019

Periosteum-derived Osteocrin regulates bone growth through both endochondral ossification and intramembranous ossification

During development of long bones, two mechanistically distinct processes contribute to long- and short-axis growth. Endochondral ossification in the growth plate leads to the long-axis growth, while intramembranous ossification including apposition in the periosteum regulates the short axis growth. Here, we show that periosteal osteoblast-derived secretory peptide, Osteocrin (OSTN), promotes both types of long bone growth through potentiation of signaling by C-type natriuretic peptide (CNP), because OSTN inhibits the clearance of CNP by binding to natriuretic peptide receptor 3 (NPR3). The mice lacking OSTN showed less bone mass in trabecular and cortical regions than the control mice, suggesting the dual functions of OSTN in long bone growth. We found that OSTN regulated trabecular bone formation by inducing proliferation and maturation of chondrocytes possibly through enhancing CNP-dependent signaling. Besides the contribution of OSTN to long axis growth, we demonstrated that OSTN together with CNP induced osteoblast differentiation of periosteum-derived multipotent progenitor cells expressing NPR3. These data suggest that OSTN induces long bone growth through endochondral ossification and osteoblast specification of multipotent progenitor cells in the periosteum.

developmental biology↗

bioRxiv2019

GUN1 regulates tetrapyrrole biosynthesis

The biogenesis of the photosynthetic apparatus in developing chloroplasts requires the assembly of proteins encoded on both nuclear and chloroplast genomes1. To co-ordinate this process there needs to be communication between these organelles, and while we have a good understanding of how the nucleus controls chloroplast development, how the chloroplast communicates with the nucleus at this time is still essentially unknown2. What we do know comes from pioneering work in which a series of genomes uncoupled (gun) mutants were identified that show elevated nuclear gene expression after chloroplast damage3. Of the six reported gun mutations, five are in tetrapyrrole biosynthesis proteins4-6 and this has led to the development of a model for chloroplast-to-nucleus retrograde signaling in which ferrochelatase 1 (FC1)-dependent heme synthesis generates a positive signal promoting expression of photosynthesis-related genes6. However, the molecular consequences of the strongest of the gun mutants, gun17, is unknown, preventing the development of a unifying hypothesis for chloroplast-to-nucleus signaling. Here, we show that GUN1 directly binds to heme and other metal-porphyrins, affects flux through the tetrapyrrole biosynthesis pathway and can increase the chelatase activity of FC1. These results raise the possibility that the signaling role of GUN1 may be manifested through changes in tetrapyrrole metabolism and supports a role for tetrapyrroles as mediators of a single biogenic chloroplast-to-nucleus retrograde signaling pathway.

plant biology↗

bioRxiv2017

Hippo signaling restricts cells in the second heart field that differentiate into Islet-1-positive atrial cardiomyocytes

AbstractCardiac precursor cells (CPCs) in the first heart field (FHF) and the second heart field (SHF) present at both arterial and venous poles assemble to form a cardiac tube in zebrafish. Hippo kinase cascade is essential for proper heart formation; however, it remains elusive how Hippo signal contributes to early cardiac fate determination. We here demonstrate that mutants of large tumor suppressor kinase 1/2 (lats1/2) exhibited an increase in a SHF marker, Islet1 (Isl1)-positive and hand2 promoter-activated venous pole atrial cardiomyocytes (CMs) and that those showed expansion of the domain between between the anterior and the posterior lateral plate mesoderm. Consistently, TEAD-8 dependent transcription was activated in caudal region of the left ALPM cells that gave rise to the venous pole atrial CMs. Yap1/Wwtr1-promoted bmp2b expression was essential for Smad-regulated hand2 expression in the left ALPM, indicating that Hippo signaling restricts the SHF cells originating from the left ALPM that move toward the venous pole.

developmental biology↗