Mika Sato-Maeda

Semaphorin3a1 regulates angioblast migration and vascular development in zebrafish embryos.

Semaphorins are a large family of secreted and cell surface molecules that guide neural growth cones to their targets during development. Some semaphorins are expressed in cells and tissues beyond the nervous system suggesting the possibility that they function in the development of non-neural tissues as well. In the trunk of zebrafish embryos endothelial precursors (angioblasts) are located ventral and lateral to the somites. The angioblasts migrate medially and dorsally along the medial surface of the somites to form the dorsal aorta just ventral to the notochord. Here we show that in zebrafish Sema3a1 is involved in angioblast migration in vivo. Expression of sema3a1 in somites and neuropilin 1, which encodes for a component of the Sema3a receptor, in angioblasts suggested that Sema3a1 regulates the pathway of the dorsally migrating angioblasts. Antisense knockdown of Sema3a1 inhibited the formation of the dorsal aorta. Induced ubiquitous expression of sema3a1 in hsp70:gfpsema3a1myc transgenic embryos inhibited migration of angioblasts ventral and lateral to the somites and retarded development of the dorsal aorta, resulting in severely reduced blood circulation. Furthermore, analysis of cells that express angioblast markers following induced expression of sema3a1 or in a mutant that changes the expression of sema3a1 in the somites confirmed these results. These data implicate Sema3a1, a guidance factor for neural growth cones, in the development of the vascular system.

Application of heat shock promoter in transgenic zebrafish

The heat shock promoter is useful for regulating transgene expression in small water‐living organisms. In zebrafish embryos, downstream gene expression can be greatly induced throughout the body by raising the temperature from 28.5°C to 38.0°C. By manipulating the local temperature within an embryo, spatial control of transgene expression is also possible. One such way for inducing heat shock response in targeted cells is by using a laser microbeam under the microscope. In addition, random mosaic expression by transient gene expression and transplantation of the transgenic embryo into a wild type host can be considered a powerful tool for studying gene functions using this promoter. In this paper, we review the applications of the zebrafish heat shock protein promoter as a gene expression tool and for lineage labeling and transcription enhancer screening.

Sema3a1 guides spinal motor axons in a cell- and stage-specific manner in zebrafish

In order for axons to reach their proper targets, both spatiotemporal regulation of guidance molecules and stepwise control of growth cone sensitivity to guidance molecules is required. Here, we show that, in zebrafish, Sema3a1, a secreted class 3 semaphorin, plays an essential role in guiding the caudal primary (CaP) motor axon that pioneers the initial region of the motor pathway. The expression pattern of Sema3a1 suggests that it delimits the pioneer CaP axons to the initial, common pathway via a repulsive action, but then CaP axons become insensitive to Sema3a1 beyond the common pathway. Indeed, nrp1a, which probably encodes a component of the Sema3a1 receptor, is specifically expressed by CaP during the early part of its outgrowth but not during later stages when extending into sema3a1-expressing muscle cells. To examine this hypothesis directly, expression of sema3a1 and/or nrp1a was manipulated in several ways. First, antisense knockdown of Sema3a1 induced CaP axons to branch excessively, stall and/or follow aberrant pathways. Furthermore, dynamic analysis showed they extended more lateral filopodia and often failed to pause at the horizontal myoseptal choice point. Second, antisense knockdown of Nrp1a and double knockdown of Nrp1a/Sema3a1 induced similar outgrowth defects in CaP. Third, CaP axons were inhibited by focally misexpressed sema3a1 along the initial common pathway but not along their pathway beyond the common pathway. Thus, as predicted, Sema3a1 is repulsive to CaP axons in the common region of the pathway, but not beyond the common pathway. Fourth, induced ubiquitous overexpression of sema3a1 caused the CaP axons but not the other primary motor axons to follow aberrant pathways. These results suggest that the repulsive response to Sema3a1 of the primary motor axons along the common pathway is both cell-type specific and dynamically regulated, perhaps via regulation of nrp1a.

Position fine-tuning of caudal primary motoneurons in the zebrafish spinal cord

In zebrafish embryos, each myotome is typically innervated by three primary motoneurons (PMNs): the caudal primary (CaP), middle primary (MiP) and rostral primary (RoP). PMN axons first exit the spinal cord through a single exit point located at the midpoint of the overlying somite, which is formed beneath the CaP cell body and is pioneered by the CaP axon. However, the placement of CaP cell bodies with respect to corresponding somites is poorly understood. Here, we determined the early events in CaP cell positioning using neuropilin 1a (nrp1a):gfp transgenic embryos in which CaPs were specifically labeled with GFP. CaP cell bodies first exhibit an irregular pattern in presence of newly formed corresponding somites and then migrate to achieve their proper positions by axonogenesis stages. CaPs are generated in excess compared with the number of somites, and two CaPs often overlap at the same position through this process. Next, we showed that CaP cell bodies remain in the initial irregular positions after knockdown of Neuropilin1a, a component of the class III semaphorin receptor. Irregular CaP position frequently results in aberrant double exit points of motor axons, and secondary motor axons form aberrant exit points following CaP axons. Its expression pattern suggests that sema3ab regulates the CaP position. Indeed, irregular CaP positions and exit points are induced by Sema3ab knockdown, whose ectopic expression can alter the position of CaP cell bodies. Results suggest that Semaphorin-Neuropilin signaling plays an important role in position fine-tuning of CaP cell bodies to ensure proper exit points of motor axons.

Temporal profile of the vascular anatomy evaluated by 9.4-tesla magnetic resonance angiography and histological analysis in mice with the R4859K mutation of RNF213, the susceptibility gene for moyamoya disease.

Moyamoya disease (MMD) is a chronic, occlusive cerebrovascular disease with an unknown etiology. Recent genome-wide and locus-specific association studies identified the RNF213 gene (RNF213) as an important susceptibility gene of MMD among East Asian populations; however, the mechanism by which an abnormality in RNF213 leads to MMD has not yet been elucidated. Therefore, we herein generated Rnf213-knock-in mice (RNF213-KI) expressing a missense mutation in mouse Rnf213, p. R4828K, on Exon 61, corresponding to human RNF213, p. R4859K, on Exon 60, in MMD patients, and investigated whether they developed MMD. We assessed the temporal profile of intracranial arteries by 9.4-T magnetic resonance angiography (MRA) continuously in the same mouse up to 64 weeks of age. The ratios of the outer diameter of the internal carotid artery (ICA)/basilar artery (BA) and middle cerebral artery (MCA)/BA were evaluated histopathologically. The common carotid arteries (CCA) were sectioned and arterial wall thickness/thinness was evaluated by Elastica-Masson staining before and after CCA ligation, which selectively induced vascular hyperplasia. The results obtained showed that RNF213-KI grew normally, with no significant difference being observed in MRA findings or the anatomy of the circle of Willis between homozygous RNF213-KI and wild-type (Wt) littermates. Furthermore, no significant difference was noted in the diameter of the intracranial vasculature (ICA/BA; p=0.82, MCA/BA; p=0.27) or in vascular remodeling after CCA ligation. Therefore, RNF213-KI did not spontaneously develop MMD. Multiple secondary insults such as environmental factors may contribute to the onset of MMD in addition to genetic factors.

Temporal profile of magnetic resonance angiography and decreased ratio of regulatory T cells after immunological adjuvant administration to mice lacking RNF213, a susceptibility gene for moyamoya disease

Moyamoya disease (MMD) is a chronic, occlusive cerebrovascular disease with an unknown etiology and is characterized by an abnormal vascular network at the base of the brain. Recent studies identified the RNF213 gene (RNF213) as an important susceptibility gene for MMD; however, the mechanisms underlying the RNF213 abnormality related to MMD have not yet been elucidated. We previously reported that Rnf213-deficient mice and Rnf213 p. R4828K knock-in mice did not spontaneously develop MMD, indicating the importance of secondary insults in addition to genetic factors in the pathogenesis of MMD. The most influential secondary insult is considered to be an immunological reaction because RNF213 is predominantly expressed in immunological tissues. Therefore, we herein attempted to evaluate the role of an immunological stimulation as a supplementary insult to the target disruption of RNF213 in the pathophysiology of MMD. Rnf213-deficient mice were treated with strong immunological adjuvants including muramyl dipeptide (MDP)-Lys (L18), and then underwent time-sequential magnetic resonance angiography (MRA) up to 40 weeks of age. The results obtained did not reveal any characteristic finding of MMD, and no significant difference was observed in MRA findings or the anatomy of the circle of Willis between Rnf213-deficient mice and wild-type mice after the administration of MDP-Lys (L18). The ratio of regulatory T cells after the administration of MDP-Lys (L18) was significantly decreased in Rnf213-deficient mice (p<0.01), suggesting the potential role of the RNF213 abnormality in the differentiation of regulatory T cells. Although the mechanisms underlying the development of MMD currently remain unclear, the RNF213 abnormality may compromise immunological self-tolerance, thereby contributing to the development of MMD.

Transient middle cerebral artery occlusion in mice induces neuronal expression of RNF213, a susceptibility gene for moyamoya disease.

Although recent genome-wide and locus-specific association studies revealed that the RING finger protein 213 (RNF213) gene is an important susceptibility gene for moyamoya disease (MMD), the exact mechanism by which the genetic alteration of RNF213 contributes to the development of MMD has not yet been elucidated. A quantitative reverse transcription polymerase chain reaction (PCR) analysis revealed that the constitutive expression of the RNF213 gene was very low in adult and embryonic brain tissue. However, information regarding the temporal and spatial expression patterns of the RNF213 gene under the condition of cerebral ischemia, which is one of characteristic pathologies associated with MMD, is currently limited. In order to address this critical issue, Rnf213 mRNA expression was investigated in mouse brains subjected to 60 min of transient middle cerebral artery occlusion (tMCAO). Male C57BL6/j mice underwent tMCAO through the intraluminal blockade of MCA. Expression of the Rnf213 gene in the tMCAO brain was investigated with in situ RNA hybridization and a real-time PCR analysis from 1 to 72 h after tMCAO. In situ RNA hybridization revealed a significant increase in Rnf213 mRNA levels in the cerebral cortex supplied by the affected MCA, especially at the penumbra area, as early as 6h after tMCAO, and these levels had increased further by 24 h. Rnf213 gene expression remained unchanged in the non-ischemic hemisphere or control specimens. Double staining of Rnf213 mRNA with NeuN immunohistochemistry revealed Rnf213 hybridization signal expression mostly in neurons. The real-time PCR analysis confirmed induction of the Rnf213 gene after tMCAO. Therefore, the Rnf213 gene was up-regulated in the ischemic brain, especially at the penumbra area, 6 h after tMCAO. Early increases in RNF213 gene expression in neurons after tMCAO indicate its involvement in cerebral ischemia, which is an underlying pathology of MMD. Further investigation is required to clarify its exact role in the pathophysiology of MMD.

Fibroblast growth factor-induced gene expression and cartilage pattern formation in chick limb bud recombinants

To clarify the roles of fibroblast growth factors (FGF) in limb cartilage pattern formation, the effects of various FGF on recombinant limbs that were composed of dissociated and reaggregated mesoderm and ectodermal jackets were examined. Fibroblast growth factor‐soaked beads were inserted just under the apical ectodermal ridge (AER) of recombinant limbs and the recombinant limbs were grafted and allowed to develop. Control recombinant limbs without FGF beads formed one or two cartilage elements. Recombinants with FGF‐4 beads formed up to five cartilage elements, which were aligned along the anteroposterior (AP) axis. Each cartilage element showed digit‐like segmentation. In contrast, recombinants with FGF‐2 beads showed formation of multiple thick and unsegmented cartilage rods, which elongated inside and outside the AP plane from the distal end of the recombinants. Recombinants with FGF‐8 beads formed a truncated cartilage pattern and recombinants with FGF‐10 beads formed a cartilage pattern similar to that of the control recombinants. The expression of the Fgf‐8, Msx‐1 and Hoxa‐13 genes in the developing recombinant limbs were examined. FGF‐4 induced extension of the length of the Fgf‐8‐positive epidermis, or AER, along the AP axis 5 days after grafting, at which time the digits are specified. FGF‐2 induced expansion of the Msx‐1‐positive area, first in the proximal direction and then along the dorsoventral axis. The functions of these FGF in recombinant and normal limb patterning are discussed in this paper.

De Novo Development of Moyamoya Disease in an Adult Female with a Genetic Variant of the RNF-213 Gene: Case Report

BACKGROUND The de novo development of moyamoya disease (MMD) in adults is extremely rare, with only 2 cases being previously reported. Furthermore, the mechanisms underlying the progression of adult MMD have not been elucidated yet. CASE REPORT A transient ischemic attack occurred in a 46-year-old woman, owing to progressive MMD. Magnetic resonance (MR) angiography performed 7 years before the diagnosis of MMD did not detect any steno-occlusive changes in the major intracranial vessels, including the internal carotid artery (ICA) and the middle cerebral artery (MCA). However, during the last 2 years, serial MR angiography revealed the gradual progression of left MCA stenosis and ultimately showed apparent stenosis of the bilateral terminal ICA to proximal MCA. Catheter angiography confirmed the definitive diagnosis of MMD. A genetic analysis of RING-finger protein (RNF)-213, an MMD susceptibility gene, revealed that not only the patient, but also her sister, brother, and daughter had the heterozygous variant of the RNF-213 gene. Because of hemodynamic compromise with ischemic symptoms, the patient underwent revascularization surgery on the affected hemisphere, without complications. She had no cerebrovascular event in the postoperative follow-up period of 8 months, and there was no evidence of the further progression of MMD. CONCLUSION We herein present the entire clinical course of the de novo development of MMD in a female adult. Newly developed MMD in an adult patient with a characteristic variant of the RNF-213 gene appears to be unique.

Increased serum production of soluble CD163 and CXCL5 in patients with moyamoya disease: Involvement of intrinsic immune reaction in its pathogenesis

Moyamoya disease (MMD) is a rare cerebrovascular disease characterized by a progressive stenosis at the terminal portion of the internal carotid artery and an abnormal vascular network at the base of the brain. Although its etiology is still unknown, intrinsic immune reactions such as autoimmune response has been implicated in the pathogenesis of MMD. Recently, the RING finger protein 213 (RNF213) was found to be an important risk gene for MMD, and is predominantly expressed in blood cells and the spleen. Thus, we hypothesized that patients with MMD represent an intrinsic autoimmune status mediated by M2-polarized macrophages, which play an important role in tissue remodeling and angiogenesis. We compared the serum level of soluble (s)CD163, an activating marker for CD163+ M2-polarized macrophages that has been implicated in a variety of autoimmune disorders, between MMD patients and healthy controls. We also analyzed serum levels of CXCL5, an augmented cytokines that has been correlated with the severity of autoimmune diseases. As a result, the serum sCD163 levels of MMD patients (281,465 pg/ml) were significantly higher than those of healthy controls (174,842 pg/ml) (p = .004). The serum CXCL5 levels of MMD patients (679.02 pg/ml) were significantly higher than those of healthy controls (401.79 pg/ml) (p = .046). There were no differences in the serum sCD163 and CXCL5 levels between each genotype of the RNF213 polymorphism (wild-type or variant) among MMD patients. Although this is a pilot study and further validation with larger number of samples is necessary, our results indicate that patients with MMD may have increased autoimmune activity, and our results shed light on the pathogenesis of MMD via CD163+ M2-polarized macrophages.