Wataru Katano, Shunta Mori, Shun Sasaki, Yuki Tajika, Koichi Tomita, K Jun Takeuchi and Kazuko Koshiba-Takeuchi : Sall1 and Sall4 cooperatively interact with Myocd and SRF to promote cardiomyocyte proliferation by regulating CDK and cyclin genes., Development, Vol.150, No.24, 2023.
Kazunori Matsuda, Junya Fukuda, Gou Satou, Momoyo Matsuoka, Takefumi Kamakura, Atsuhiko Uno, Eiji Kondou, Takahiro Azuma, Yoshiaki Kitamura, Koichi Tomita, Tadashi Kitahara and Noriaki Takeda : The effects of continuous administration of diazepam on the recovery of lesion-induced nystagmus in unilaterally labyrinthectomised rats., Acta Oto-Laryngologica, Vol.143, No.8, 675-680, 2023.
(Summary)
These findings suggested that continuous administration of diazepam accelerates the initial process of VC; however, it does not suppress the nystagmus-driving mechanisms in rats.
Teruyoshi Hirayama, Y Kadooka, E Tarusawa, S Saitoh, H Nakayama, N Hoshino, S Nakama, T Fukuishi, Y Kawanishi, Hiroki Umeshima, Koichi Tomita, Y Yoshimura, N Galjart, K Hashimoto, N Ohno and T Yagi : CTCF loss induces giant lamellar bodies in Purkinjecell dendrites., Acta Neuropathologica Communications, Vol.10, No.1, 172, 2022.
(Summary)
CCCTC-binding factor (CTCF) has a key role in higher-order chromatin architecture that is important for establishing and maintaining cell identity by controlling gene expression. In the mature cerebellum, CTCF is highly expressed in Purkinje cells (PCs) as compared with other cerebellar neurons. The cerebellum plays an important role in motor function by regulating PCs, which are the sole output neurons, and defects in PCs cause motor dysfunction. However, the role of CTCF in PCs has not yet been explored. Here we found that the absence of CTCF in mouse PCs led to progressive motor dysfunction and abnormal dendritic morphology in those cells, which included dendritic self-avoidance defects and a proximal shift in the climbing fibre innervation territory on PC dendrites. Furthermore, we found the peculiar lamellar structures known as "giant lamellar bodies" (GLBs), which have been reported in PCs of patients with Werdnig-Hoffman disease, 13q deletion syndrome, and Krabbe disease. GLBs are localized to PC dendrites and are assumed to be associated with neurodegeneration. They have been noted, however, only in case reports following autopsy, and reports of their existence have been very limited. Here we show that GLBs were reproducibly formed in PC dendrites of a mouse model in which CTCF was deleted. GLBs were not noted in PC dendrites at infancy but instead developed over time. In conjunction with GLB development in PC dendrites, the endoplasmic reticulum was almost absent around the nuclei, the mitochondria were markedly swollen and their cristae had decreased drastically, and almost all PCs eventually disappeared as severe motor deficits manifested. Our results revealed the important role of CTCF during normal development and in maintaining PCs and provide new insights into the molecular mechanism of GLB formation during neurodegenerative disease.
Junya Fukuda, Kazunori Matsuda, Gou Satou, Tadashi Kitahara, Momoyo Matsuoka, Takahiro Azuma, Yoshiaki Kitamura, Koichi Tomita and Noriaki Takeda : Effects of Betahistine on the Development of Vestibular Compensation after Unilateral Labyrinthectomy in Rats., Brain Sciences, Vol.11, No.3, 360, 2021.
(Summary)
These findings suggest that betahistine facilitated the late, but not the initial, process of VC in UL rats.
Kazunori Matsuda, Tadashi Kitahara, Taeko Ito, Munehisa Fukushima, Junya Fukuda, Gou Satou, Yoshiaki Kitamura, Koji Abe, Atsuhiko Uno, Koichi Tomita, Hiromi Sakata-Haga, Yoshihiro Fukui and Noriaki Takeda : A new immunohistochemical method to evaluate the development of vestibular compensation after unilateral labyrinthectomy in rats., Acta Oto-Laryngologica, Vol.139, No.6, 505-510, 2019.
(Summary)
These findings suggested that the number of MK801-induced Fos-LIR neurons in contra-MVe was decreased in concordance with the restoration of ipsi-MVe-activity during the late process of VC after UL and that thioperamide accelerated the late, but not the initial process of VC.
T Sakamoto, T Nitta, K Maruno, YS Yeh, H Kuwata, Koichi Tomita, T Goto, N Takahashi and T Kawada : Macrophage infiltration into obese adipose tissues suppresses the induction of UCP1 expression in mice., American Journal of Physiology, Endocrinology and Metabolism, Vol.310, No.8, 676-687, 2016.
(Summary)
Emergence of thermogenic adipocytes such as brown and beige adipocytes is critical for whole body energy metabolism. Promoting the emergence of these adipocytes, which increase energy expenditure, could be a viable strategy in treating obesity and its related diseases. However, little is known regarding the mechanisms that regulate the emergence of these adipocytes in obese adipose tissue. Here, we demonstrated that classically activated macrophages (M1 Mϕ) suppress the induction of thermogenic adipocytes in obese adipose tissues of mice. Cold exposure significantly induced the expression levels of uncoupling protein-1 (UCP1), which is a mitochondrial protein unique in thermogenic adipocytes, in C57BL/6 mice fed a normal diet. However, UCP1 induction was significantly suppressed in adipose tissues of C57BL/6 mice fed a high-fat diet, into which M1 Mϕ infiltrated. Depletion of M1 Mϕ using clodronate liposomes eliminated the suppressive effect and markedly reduced the mRNA level of tumor necrosis factor-α (TNFα) in the adipose tissues. Importantly, consistent with the observed changes in the expression levels of marker genes for thermogenic adipocytes, combination treatment of clodronate liposome and cold exposure resulted in metabolic benefits such as lowered body weight and blood glucose level in obese mice. Moreover, intraperitoneal injection of recombinant TNFα protein suppressed UCP1 induction in lean adipose tissues of mice. Collectively, our data indicate that infiltrated M1 Mϕ suppress the induction of thermogenic adipocytes in obese adipose tissues via TNFα. This report suggests that inflammation induced by infiltrated Mϕ could cause not only insulin resistance but also reduction of energy expenditure in adipose tissues.
Y Ishino, Y Hayashi, M Naruse, Koichi Tomita, M Sanbo, T Fuchigami, R Fujiki, K Hirose, Y Toyooka, T Fujimori, K Ikenaka and S Hitoshi : Bre1a, a histone H2B ubiquitin ligase, regulates the cell cycle and differentiation of neural precursor cells., The Journal of Neuroscience, Vol.34, No.8, 3067-3078, 2014.
(Summary)
Cell cycle regulation is crucial for the maintenance of stem cell populations in adult mammalian tissues. During development, the cell cycle length in neural stem cells increases, which could be associated with their capabilities for self-renewal. However, the molecular mechanisms that regulate differentiation and cell cycle progression in embryonic neural stem cells remain largely unknown. Here, we investigated the function of Bre1a, a histone H2B ubiquitylation factor, which is expressed in most but not all of neural precursor cells (NPCs) in the developing mouse brain. We found that the knockdown of Bre1a in NPCs lengthened their cell cycle through the upregulation of p57(kip2) and the downregulation of Cdk2. In addition, the knockdown of Bre1a increased the expression of Hes5, an effector gene of Notch signaling, through the action of Fezf1 and Fezf2 genes and suppressed the differentiation of NPCs. Our data suggest that Bre1a could be a bifunctional gene that regulates both the differentiation status and cell cycle length of NPCs. We propose a novel model that the Bre1a-negative cells in the ventricular zone of early embryonic brains remain undifferentiated and are selected as self-renewing neural stem cells, which increase their cell cycle time during development.
Teppei Goto, Tomikawa Junko, Kana Ikegami, Shiori Minabe, Hitomi Abe, Tatsuya Fukanuma, Takuya Imamura, Kenji Takase, Makoto Sanbo, Koichi Tomita, Masumi Hirabayashi, Kei-ichiro Maeda, Hiroko Tsukamura and Yoshihisa Uenoyama : Identification of hypothalamic arcuate nucleus-specific enhancer region of kiss1 gene in mice., Molecular Endocrinology, Vol.29, No.1, 121-129, 2014.
(Summary)
Pulsatile secretion of GnRH plays a pivotal role in follicular development via stimulating tonic gonadotropin secretion in mammals. Kisspeptin neurons, located in the arcuate nucleus (ARC), are considered to be an intrinsic source of the GnRH pulse generator. The present study aimed to determine ARC-specific enhancer(s) of the Kiss1 gene by an in vivo reporter assay. Three green fluorescent protein (GFP) reporter constructs (long, medium length, and short) were generated by insertion of GFP cDNA at the Kiss1 locus. Transgenic female mice bearing the long and medium-length constructs showed apparent GFP signals in kisspeptin-immunoreactive cells in both the ARC and anteroventral periventricular nucleus, in which another population of kisspeptin neurons are located. On the other hand, transgenic mice bearing 5'-truncated short construct showed few GFP signals in the ARC kisspeptin-immunoreactive cells, whereas they showed colocalization of GFP- and kisspeptin-immunoreactivities in the anteroventral periventricular nucleus. In addition, chromatin immunoprecipitation and chromosome conformation capture assays revealed recruitment of unoccupied estrogen receptor-α in the 5'-upstream region and intricate chromatin loop formation between the 5'-upstream and promoter regions of Kiss1 locus in the ARC. Taken together, the present results indicate that 5'-upstream region of Kiss1 locus plays a critical role in Kiss1 gene expression in an ARC-specific manner and that the recruitment of estrogen receptor-α and formation of a chromatin loop between the Kiss1 promoter and the 5' enhancer region may be required for the induction of ARC-specific Kiss1 gene expression. These results suggest that the 5'-upstream region of Kiss1 locus functions as an enhancer for ARC Kiss1 gene expression in mice.
Koichi Tomita, M Sperling, SB Cambridge, T Bonhoeffer and M Hübener : A molecular correlate of ocular dominance columns in the developing mammalian visual cortex., Cerebral Cortex, Vol.23, No.11, 2531-2541, 2013.
(Summary)
Ocular dominance (OD) columns, alternating regions of left and right eye input in the visual cortex of higher mammals, have long been thought to develop from an initially intermingled state by an activity-dependent process. While indirect evidence points to potential alternative mechanisms based on molecular cues, direct proof for a molecular difference between left- and right eye columns is missing. Here, we show that heat shock protein 90 alpha (Hsp90α) is expressed in a clustered fashion in the developing cat visual cortex. Clusters of Hsp90α-positive cells are in register with OD columns of the ipsilateral eye as early as postnatal day 16, when OD columns have just appeared. Importantly, a periodic, clustered expression of Hsp90α is already present weeks before OD columns have started to form, suggesting that molecular differences between future left and right eye OD columns may contribute to the segregated termination of eye specific afferents in the developing visual cortex.
Koichi Tomita, H Gotoh, K Tomita, N Yamauchi and M Sanbo : Multiple patterns of spatiotemporal changes in layer-specific gene expression in the developing visual cortex of higher mammals., Neuroscience Research, Vol.73, No.3, 207-217, 2012.
(Summary)
The mammalian cerebral cortex, which is stratified into six layers, has functional domains that vertically span the six layers, thereby requiring tight interlaminar connectivity within a domain. The synaptic connections in individual layers are first broadly formed under predetermined programs and later reinforced between neurons which reside in the same functional domain via experience-dependent reorganization during the critical period. However, the molecular mechanisms that control these two processes within each layer are still unclear. Therefore, we performed a differential screen for candidates and found seven genes with layer-specific expression during postnatal development of cat visual cortex. APLP1, a transmembrane protein mediating synaptogenesis, started dual-layer expression in layers 2/3 and 5 before the critical period, suggesting that it might execute coarse synapse formation of these layers. STMN2 (SCG10), which promotes microtubule turnover, was unique, as it dramatically shifted its dual-layer distribution from layers 2/3 and 5 to the deeper layers 4 and 6 at the onset of the critical period; it lost this new expression pattern in the adult. Surprisingly, brief dark rearing disturbed the shift in its dual-layer distribution around the onset of the critical period. Thus, by accelerating structural remodeling, STMN2 (SCG10) might launch experience-dependent reorganization of particular layers.
J Tomikawa, Y Uenoyama, M Ozawa, T Fukanuma, K Takase, T Goto, H Abe, N Ieda, S Minabe, C Deura, N Inoue, M Sanbo, Koichi Tomita, M Hirabayashi, S Tanaka, T Imamura, H Okamura, K Maeda and H Tsukamura : Epigenetic regulation of Kiss1 gene expression mediating estrogen positive feedback action in the mouse brain., Proceedings of the National Academy of Sciences of the United States of America, Vol.109, No.20, 1294-1301, 2012.
(Summary)
This study aims to determine the epigenetic mechanism regulating Kiss1 gene expression in the anteroventral periventricular nucleus (AVPV) to understand the mechanism underlying estrogen-positive feedback action on gonadotropin-releasing hormone/gonadotropin surge. We investigated estrogen regulation of the epigenetic status of the mouse AVPV Kiss1 gene locus in comparison with the arcuate nucleus (ARC), in which Kiss1 expression is down-regulated by estrogen. Histone of AVPV Kiss1 promoter region was highly acetylated, and estrogen receptor α was highly recruited at the region by estrogen. In contrast, the histone of ARC Kiss1 promoter region was deacetylated by estrogen. Inhibition of histone deacetylation up-regulated in vitro Kiss1 expression in a hypothalamic non-Kiss1-expressing cell line. Gene conformation analysis indicated that estrogen induced formation of a chromatin loop between Kiss1 promoter and the 3' intergenic region, suggesting that the intergenic region serves to enhance estrogen-dependent Kiss1 expression in the AVPV. This notion was proved, because transgenic reporter mice with a complete Kiss1 locus sequence showed kisspeptin neuron-specific GFP expression in both the AVPV and ARC, but the deletion of the 3' region resulted in greatly reduced GFP expression only in the AVPV. Taken together, these results demonstrate that estrogen induces recruitment of estrogen receptor α and histone acetylation in the Kiss1 promoter region of the AVPV and consequently enhances chromatin loop formation of Kiss1 promoter and Kiss1 gene enhancer, resulting in an increase in AVPV-specific Kiss1 gene expression. These results indicate that epigenetic regulation of the Kiss1 gene is involved in estrogen-positive feedback to generate the gonadotropin-releasing hormone/gonadotropin surge.
GX Zhang, K Obata, D Takeshita, S Mitsuyama, T Nakashima, A Kikuta, M Hirabayashi, Koichi Tomita, R Vetter, WH Dillmann and M Tkaki : Evaluation of left ventricular mechanical work and energetics of normal hearts in SERCA2a transgenic rats., The Journal of Physiological Sciences, Vol.62, No.3, 221-231, 2012.
(Summary)
Cardiac sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA2a) is responsible for most of the Ca(2+) removal during diastole and a larger Ca(2+) handling energy consumer in excitation-contraction (E-C) coupling. To understand the cardiac performance under long-term SERCA2a overexpression conditions, we established SERCA2a transgenic (TG) Wistar rats to analyze cardiac mechanical work and energetics in normal hearts during pacing at 300 beats/min. SERCA2a protein expression was increased in TGI and TGII rats (F2 and F3 of the same father and different mothers). Mean left ventricular (LV) end-systolic pressure (ESP) and systolic pressure-volume area (PVA; a total mechanical energy per beat) at midrange LV volume (mLVV) were significantly larger in TGI rats and were unchanged in TGII rats, compared to those in non-TG [wildtype (WT)] littermates. Mean myocardial oxygen consumption per minute for E-C coupling was significantly increased, and the mean slope of myocardial oxygen consumption per beat (VO(2))-PVA (systolic PVA) linear relation was smaller, but the overall O(2) cost of LV contractility for Ca(2+) is unchanged in all TG rats. Mean Ca(2+) concentration exerting maximal ESP(mLVV) in TGII rats was significantly higher than that in WT rats. The Ca(2+) overloading protocol did not elicit mitochondrial swelling in TGII rats. Tolerance to higher Ca(2+) concentrations may support the possibility for enhanced SERCA2a activity in TGII rats. In conclusion, long-term SERCA2a overexpression enhanced or maintained LV mechanics, improved contractile efficiency under higher energy expenditure for Ca(2+) handling, and improved Ca(2+) tolerance, but it did not change the overall O(2) cost of LV contractility for Ca(2+) in normal hearts of TG rats.
N Usui, K Watanabe, K Ono, Koichi Tomita, N Tamamaki, K Ikenaka and H Takebayashi : Role of motoneuron-derived neurotrophin 3 in survival and axonal projection of sensory neurons during neural circuit formation., Development, Vol.139, No.6, 1125-1132, 2012.
(Summary)
Sensory neurons possess the central and peripheral branches and they form unique spinal neural circuits with motoneurons during development. Peripheral branches of sensory axons fasciculate with the motor axons that extend toward the peripheral muscles from the central nervous system (CNS), whereas the central branches of proprioceptive sensory neurons directly innervate motoneurons. Although anatomically well documented, the molecular mechanism underlying sensory-motor interaction during neural circuit formation is not fully understood. To investigate the role of motoneuron on sensory neuron development, we analyzed sensory neuron phenotypes in the dorsal root ganglia (DRG) of Olig2 knockout (KO) mouse embryos, which lack motoneurons. We found an increased number of apoptotic cells in the DRG of Olig2 KO embryos at embryonic day (E) 10.5. Furthermore, abnormal axonal projections of sensory neurons were observed in both the peripheral branches at E10.5 and central branches at E15.5. To understand the motoneuron-derived factor that regulates sensory neuron development, we focused on neurotrophin 3 (Ntf3; NT-3), because Ntf3 and its receptors (Trk) are strongly expressed in motoneurons and sensory neurons, respectively. The significance of motoneuron-derived Ntf3 was analyzed using Ntf3 conditional knockout (cKO) embryos, in which we observed increased apoptosis and abnormal projection of the central branch innervating motoneuron, the phenotypes being apparently comparable with that of Olig2 KO embryos. Taken together, we show that the motoneuron is a functional source of Ntf3 and motoneuron-derived Ntf3 is an essential pre-target neurotrophin for survival and axonal projection of sensory neurons.
N Imamura, S Sugio, WB Macklin, Koichi Tomita, KF Tanaka and K Ikenaka : Gene induction in mature oligodendrocytes with a PLP-tTA mouse line., Genesis : the journal of genetics and development, Vol.50, No.5, 424-428, 2011.
(Summary)
Mature oligodendrocytes are critical for myelin maintenance. To understand the molecular basis for this, genetic manipulation of mature oligodendrocytes is needed. Here we generated a mature oligodendrocyte tTA (tetracycline-controlled transcriptional activator) mouse line which, in combination with a tTA-dependent promoter line driving the expression of the desired transgene, can be used for gain-of-function studies. We used an oligodendrocyte promoter, the mouse proteolipid protein (PLP) promoter, to express mammalianized tTA, and generated a PLP-mtTA mouse line. In adults, mtTA mRNA was predominantly detected in brain white matter where it co-localized with PLP mRNA. mtTA-mediated gene induction was confirmed by crossing to mice with a tTA-dependent promoter driving expression of yellow fluorescent protein (tetO-YFP mice). YFP induction in PLP-mtTA::tetO-YFP mice was consistent with PLP expression in adult mature oligodendrocytes and premyelinating-stage myelinating oligodendrocytes. This PLP-mtTA mouse line is the first to enable gain-of-function studies in mature oligodendrocytes with the tet system.
Kazunori Matsuda, Junya Fukuda, Gou Satou, 北原 糺, Yoshihiro Fukui, Koichi Tomita and Noriaki Takeda : Neural Mechanisms of Vestibular Compensation and Development of Drugs for Facilitating the Processes of Vestibular Compensation, Practica Oto-Rhino-Laryngologica. Suppl., No.158, 37-50, Feb. 2022.
Investigation of the mechanisms involved in both obtainment of ocular preference of premature neurons and grouping of same ocular preference neurons during cortical development. (Project/Area Number: 26460298 )
Analysis of DNA demethylation by Glial cells missing genes (Project/Area Number: 25650005 )
Challenges to elucidate the role of ocular dominance columns for visual perception and to progress the study of OD plasticity in mouse (Project/Area Number: 22650068 )
Cell sensor and its model shift (Project/Area Number: 18077010 )