Member, Maternal & Child Health Research Institute (MCHRI)
Honors & Awards
Stanford Maternal and Child Health Research Institute (MCHRI) Postdoctoral Support, Stanford Maternal and Child Health Research Institute (MCHRI) (2020-2021)
School of Medicine Dean's Postdoctoral Fellowship, Stanford University School of Medicine (2017-2018)
Special Fellow, University of Tsukuba (2012-2017)
Bachelor of Science, Tsukuba University (2011)
Doctor of Philosophy, Tsukuba University (2017)
Polarizing brain organoids.
View details for PubMedID 30936565
Reliability of human cortical organoid generation.
2019; 16 (1): 75–78
The differentiation of pluripotent stem cells in three-dimensional cultures can recapitulate key aspects of brain development, but protocols are prone to variable results. Here we differentiated multiple human pluripotent stem cell lines for over 100 d using our previously developed approach to generate brain-region-specific organoids called cortical spheroids and, using several assays, found that spheroid generation was highly reliable and consistent. We anticipate the use of this approach for large-scale differentiation experiments and disease modeling.
View details for PubMedID 30573846
Differentiation and maturation of oligodendrocytes in human three-dimensional neural cultures.
Investigating human oligodendrogenesis and the interaction of oligodendrocytes with neurons and astrocytes would accelerate our understanding of the mechanisms underlying white matter disorders. However, this is challenging because of the limited accessibility of functional human brain tissue. Here, we developed a new differentiation method of human induced pluripotent stem cells to generate three-dimensional brain organoids that contain oligodendrocytes as well as neurons and astrocytes, called human oligodendrocyte spheroids. We found that oligodendrocyte lineage cells derived in human oligodendrocyte spheroids transitioned through developmental stages similar to primary human oligodendrocytes and that the migration of oligodendrocyte lineage cells and their susceptibility to lysolecithin exposure could be captured by live imaging. Moreover, their morphology changed as they matured over time in vitro and started myelinating neurons. We anticipate that this method can be used to study oligodendrocyte development, myelination, and interactions with other major cell types in the CNS.
View details for PubMedID 30692691
Physiological function of phospholipase D2 in anti-tumor immunity: regulation of CD8+ T lymphocyte proliferation.
2018; 8 (1): 6283
Two major phospholipase D (PLD) isozymes in mammals, PLD1 and PLD2, hydrolyze the membrane phospholipid phosphatidylcholine to choline and the lipid messenger phosphatidic acid. Although their roles in cancer cells have been well studied, their functions in tumor microenvironment have not yet been clarified. Here, we demonstrate that PLD2 in cytotoxic CD8+ T cells plays a crucial role in anti-tumor immunity by regulating their cell proliferation. We found that growth of tumors formed by subcutaneously transplanted cancer cells is enhanced in Pld2-knockout mice. Interestingly, this phenotype was found to be at least in part attributable to the ablation of Pld2 from bone marrow cells. The number of CD8+ T cells, which induce cancer cell death, significantly decreased in the tumor produced in Pld2-knockout mice. In addition, CD3/CD28-stimulated proliferation of primary cultured splenic CD8+ T cells is markedly suppressed by Pld2 ablation. Finally, CD3/CD28-dependent activation of Erk1/2 and Ras is inhibited in Pld2-deleted CD8+ T cells. Collectively, these results indicate that PLD2 in CD8+ T cells plays a key role in their proliferation through activation of the Ras/Erk signaling pathway, thereby regulating anti-tumor immunity.
View details for DOI 10.1038/s41598-018-24512-x
View details for PubMedID 29674728
The small G protein Arf6 expressed in keratinocytes by HGF stimulation is a regulator for skin wound healing.
2017; 7: 46649
The earlier step of cutaneous wound healing process, re-epithelialization of the wounded skin, is triggered by a variety of growth factors. However, molecular mechanisms through which growth factors trigger skin wound healing are less understood. Here, we demonstrate that hepatocyte growth factor (HGF)/c-Met signaling-induced expression of the small G protein Arf6 mRNA in keratinocytes is essential for the skin wound healing. Arf6 mRNA expression was dramatically induced in keratinocytes at the wounded skin, which was specifically suppressed by the c-Met inhibitor. Wound healing of the skin was significantly delayed in keratinocyte-specific Arf6 conditional knockout mice. Furthermore, Arf6 deletion from keratinocytes remarkably suppressed HGF-stimulated cell migration and peripheral membrane ruffle formation, but did not affect skin morphology and proliferation/differentiation of keratinocytes. These results are consistent with the notion that Arf6 expressed in skin keratinocytes through the HGF/c-Met signaling pathway in response to skin wounding plays an important role in skin wound healing by regulating membrane dynamics-based motogenic cellular function of keratinocytes.
View details for DOI 10.1038/srep46649
View details for PubMedID 28429746
ACAP3, the GTPase-activating protein specific to the small GTPase Arf6, regulates neuronal migration in the developing cerebral cortex.
Biochemical and biophysical research communications
The GTPase-activating protein (GAP) specific to the small GTPase Arf6, ACAP3, is known to regulate morphogenesis of neurons in vitro. However, physiological significance of ACAP3 in the brain development in vivo remains unclear. Here, we show that ACAP3 is involved in neuronal migration in the developing cerebral cortex of mice. Knockdown of ACAP3 in the developing cortical neurons of mice in utero significantly abrogated neuronal migration in the cortical layer, which was restored by ectopic expression of wild type of ACAP3, but not by its GAP-inactive mutant. Furthermore, morphological changes of neurons during migration in the cortical layer were impeded in ACAP3-knocked-down cortical neurons. These results provide evidence that ACAP3 plays a crucial role in migration of cortical neurons by regulating their morphological change during development of cerebral cortex.
View details for DOI 10.1016/j.bbrc.2017.09.076
View details for PubMedID 28919417
Machineries regulating the activity of the small GTPase Arf6 in cancer cells are potential targets for developing innovative anti-cancer drugs.
Advances in biological regulation
The Small GTPase ADP-ribosylation factor 6 (Arf6) functions as the molecular switch in cellular signaling pathways by cycling between GDP-bound inactive and GTP-bound active form, which is precisely regulated by two regulators, guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Numerous studies have shown that these machineries play critical roles in tumor angiogenesis/growth and cancer cell invasion/metastasis through regulating the cycling of Arf6. Here, we summarize accumulating knowledge for involvement of Arf6 GEFs/GAPs and small molecule inhibitors of Arf6 signaling/cycling in cancer progression, and discuss possible strategies for developing innovative anti-cancer drugs targeting Arf6 signaling/cycling.
View details for DOI 10.1016/j.jbior.2016.10.004
View details for PubMedID 27776975
ACAP3 regulates neurite outgrowth through its GAP activity specific to Arf6 in mouse hippocampal neurons.
2016; 473 (17): 2591-2602
ACAP3 (ArfGAP with coiled-coil, ankyrin repeat and pleckstrin homology domains 3) belongs to the ACAP family of GAPs (GTPase-activating proteins) for the small GTPase Arf (ADP-ribosylation factor). However, its specificity to Arf isoforms and physiological functions remain unclear. In the present study, we demonstrate that ACAP3 plays an important role in neurite outgrowth of mouse hippocampal neurons through its GAP activity specific to Arf6. In primary cultured mouse hippocampal neurons, knockdown of ACAP3 abrogated neurite outgrowth, which was rescued by ectopically expressed wild-type ACAP3, but not by its GAP activity-deficient mutant. Ectopically expressed ACAP3 in HEK (human embryonic kidney)-293T cells showed the GAP activity specific to Arf6. In support of this observation, the level of GTP-bound Arf6 was significantly increased by knockdown of ACAP3 in hippocampal neurons. In addition, knockdown and knockout of Arf6 in mouse hippocampal neurons suppressed neurite outgrowth. These results demonstrate that ACAP3 positively regulates neurite outgrowth through its GAP activity specific to Arf6. Furthermore, neurite outgrowth suppressed by ACAP3 knockdown was rescued by expression of a fast cycle mutant of Arf6 that spontaneously exchanges guanine nucleotides on Arf6, but not by that of wild-type, GTP- or GDP-locked mutant Arf6. Thus cycling between active and inactive forms of Arf6, which is precisely regulated by ACAP3 in concert with a guanine-nucleotide-exchange factor(s), seems to be required for neurite outgrowth of hippocampal neurons.
View details for DOI 10.1042/BCJ20160183
View details for PubMedID 27330119