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Dive into the research topics where Chiyomi Sakamoto is active.

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Featured researches published by Chiyomi Sakamoto.


Scientific Reports | 2015

Computational image analysis of colony and nuclear morphology to evaluate human induced pluripotent stem cells

Kazuaki Tokunaga; Noriko Saitoh; Ilya G. Goldberg; Chiyomi Sakamoto; Yoko Yasuda; Yoshinori Yoshida; Shinya Yamanaka; Mitsuyoshi Nakao

Non-invasive evaluation of cell reprogramming by advanced image analysis is required to maintain the quality of cells intended for regenerative medicine. Here, we constructed living and unlabelled colony image libraries of various human induced pluripotent stem cell (iPSC) lines for supervised machine learning pattern recognition to accurately distinguish bona fide iPSCs from improperly reprogrammed cells. Furthermore, we found that image features for efficient discrimination reside in cellular components. In fact, extensive analysis of nuclear morphologies revealed dynamic and characteristic signatures, including the linear form of the promyelocytic leukaemia (PML)-defined structure in iPSCs, which was reversed to a regular sphere upon differentiation. Our data revealed that iPSCs have a markedly different overall nuclear architecture that may contribute to highly accurate discrimination based on the cell reprogramming status.


Molecular Biology of the Cell | 2012

The distribution of phosphorylated SR proteins and alternative splicing are regulated by RANBP2

Noriko Saitoh; Chiyomi Sakamoto; Masatoshi Hagiwara; Lourdes Teresa Agredano-Moreno; Luis Felipe Jiménez-García; Mitsuyoshi Nakao

SR splicing factors are distributed in the speckled pattern in the nucleus. Alternative pre-mRNA splicing is regulated through nuclear distribution of phosphorylated SR splicing factors, which is specifically regulated by the RANBP2 system in mammalian cell lines, as well as in mouse tissues.


Cancer Science | 2012

Hmga1 is differentially expressed and mediates silencing of the CD4/CD8 loci in T cell lineages and leukemic cells.

Yang Xi; Sugiko Watanabe; Yuko Hino; Chiyomi Sakamoto; Yuko Nakatsu; Seiji Okada; Mitsuyoshi Nakao

High‐mobility group A1 (Hmga1) protein is an architectural chromatin factor, and aberrant Hmga1 expression in mice causes hematopoietic malignancies with defects in cellular differentiation. However, the functional involvement of Hmga1 in hematopoietic development and leukemic cells remains to be elucidated. Using Hmga1‐green fluorescent protein (GFP) knock‐in mice that endogenously express an Hmga1‐GFP fusion protein, we examined Hmga1 expression in undifferentiated and differentiated populations of hematopoietic cells. During early T cell development in the thymus, Hmga1 is highly expressed in CD4/CD8‐double negative (DN) cells and is transiently downregulated in CD4/CD8‐double positive (DP) cells. Consistently, Hmga1 directly binds to cis‐regulatory elements in the CD4/CD8 loci and the heterochromatin foci in DN‐stage cells, but not in DP cells. Interestingly, CD4/CD8 expression in DN‐stage leukemic cells is induced by inhibition of Hmga1 binding to nuclear DNA or RNA interference‐mediated Hmga1 knockdown. In addition, Hmga1‐depleted leukemic T cells markedly diminish proliferation, with transcriptional activation of cyclin‐dependent kinase inhibitor genes as a direct target of Hmga1. The data in the present study reveal a role of Hmga1 in transcriptional silencing in T cell lineages and leukemic cells. (Cancer Sci 2012; 103: 439–447)


Molecular Biology of the Cell | 2017

Condensin II plays an essential role in reversible assembly of mitotic chromosomes in situ

Takao Ono; Chiyomi Sakamoto; Mitsuyoshi Nakao; Noriko Saitoh; Tatsuya Hirano

A modified protocol for inducing reversible assembly of mitotic chromosomes in situ is developed. As judged by this assay, which is combined with quantitative morphological analyses using a supervised machine-learning algorithm, condensin II plays a crucial role in both the recovery of chromatin shapes and the reorganization of chromosome axes.


Nucleus | 2016

Loss of the integral nuclear envelope protein SUN1 induces alteration of nucleoli.

Ayaka Matsumoto; Chiyomi Sakamoto; Haruka Matsumori; Jun Katahira; Yoko Yasuda; Katsuhide Yoshidome; Masahiko Tsujimoto; Ilya G. Goldberg; Nariaki Matsuura; Mitsuyoshi Nakao; Noriko Saitoh; Miki Hieda

ABSTRACT A supervised machine learning algorithm, which is qualified for image classification and analyzing similarities, is based on multiple discriminative morphological features that are automatically assembled during the learning processes. The algorithm is suitable for population-based analysis of images of biological materials that are generally complex and heterogeneous. Here we used the algorithm wndchrm to quantify the effects on nucleolar morphology of the loss of the components of nuclear envelope in a human mammary epithelial cell line. The linker of nucleoskeleton and cytoskeleton (LINC) complex, an assembly of nuclear envelope proteins comprising mainly members of the SUN and nesprin families, connects the nuclear lamina and cytoskeletal filaments. The components of the LINC complex are markedly deficient in breast cancer tissues. We found that a reduction in the levels of SUN1, SUN2, and lamin A/C led to significant changes in morphologies that were computationally classified using wndchrm with approximately 100% accuracy. In particular, depletion of SUN1 caused nucleolar hypertrophy and reduced rRNA synthesis. Further, wndchrm revealed a consistent negative correlation between SUN1 expression and the size of nucleoli in human breast cancer tissues. Our unbiased morphological quantitation strategies using wndchrm revealed an unexpected link between the components of the LINC complex and the morphologies of nucleoli that serves as an indicator of the malignant phenotype of breast cancer cells.


Journal of Cell Science | 2018

Ki-67 and condensins support the integrity of mitotic chromosomes through distinct mechanisms

Masatoshi Takagi; Takao Ono; Toyoaki Natsume; Chiyomi Sakamoto; Mitsuyoshi Nakao; Noriko Saitoh; Masato T. Kanemaki; Tatsuya Hirano; Naoko Imamoto

ABSTRACT Although condensins play essential roles in mitotic chromosome assembly, Ki-67 (also known as MKI67), a protein localizing to the periphery of mitotic chromosomes, had also been shown to make a contribution to the process. To examine their respective roles, we generated a set of HCT116-based cell lines expressing Ki-67 and/or condensin subunits that were fused with an auxin-inducible degron for their conditional degradation. Both the localization and the dynamic behavior of Ki-67 on mitotic chromosomes were not largely affected upon depletion of condensin subunits, and vice versa. When both Ki-67 and SMC2 (a core subunit of condensins) were depleted, ball-like chromosome clusters with no sign of discernible thread-like structures were observed. This severe defective phenotype was distinct from that observed in cells depleted of either Ki-67 or SMC2 alone. Our results show that Ki-67 and condensins, which localize to the external surface and the central axis of mitotic chromosomes, respectively, have independent yet cooperative functions in supporting the structural integrity of mitotic chromosomes. Highlighted Article: Ki-67 and condensins, which localize to the external surface and the central axis of mitotic chromosomes, respectively, have independent yet cooperative functions in supporting the structural integrity of mitotic chromosomes.


Scientific Reports | 2018

Endocrine therapy-resistant breast cancer model cells are inhibited by soybean glyceollin I through Eleanor non-coding RNA

Tatsuro Yamamoto; Chiyomi Sakamoto; Hiroaki Tachiwana; Mitsuru Kumabe; Toshiro Matsui; Tadatoshi Yamashita; Masatoshi Shinagawa; Koji Ochiai; Noriko Saitoh; Mitsuyoshi Nakao

Long-term estrogen deprivation (LTED) of an estrogen receptor (ER) α-positive breast cancer cell line recapitulates cancer cells that have acquired estrogen-independent cell proliferation and endocrine therapy resistance. Previously, we have shown that a cluster of non-coding RNAs, Eleanors (ESR1 locus enhancing and activating non-coding RNAs) formed RNA cloud and upregulated the ESR1 gene in the nuclei of LTED cells. Eleanors were inhibited by resveratrol through ER. Here we prepared another polyphenol, glyceollin I from stressed soybeans, and identified it as a major inhibitor of the Eleanor RNA cloud and ESR1 mRNA transcription. The inhibition was independent of ER, unlike one by resveratrol. This was consistent with a distinct tertiary structure of glyceollin I for ER binding. Glyceollin I preferentially inhibited the growth of LTED cells and induced apoptosis. Our results suggest that glyceollin I has a novel role in LTED cell inhibition through Eleanors. In other words, LTED cells or endocrine therapy-resistant breast cancer cells may be ready for apoptosis, which can be triggered with polyphenols both in ER-dependent and ER-independent manners.


The Molecular Biology Society of Japan | 2016

Unbiased morphological quantitation strategies using wndchrm revealed an unexpected link between the LINC complex and the morphologies of nucleoli

Ayaka Matsumoto; Chiyomi Sakamoto; Haruka Matsumori; Jun Katahira; Yoko Yasuda; Nariaki Matsuura; Mitsuyoshi Nakao; Noriko Saitoh; Miki Hieda


The Molecular Biology Society of Japan | 2016

Discrimination between normal and cancer gastric tissue images using machine learning algorithms, wndchrm

Yoko Yasuda; Kazuaki Tokunaga; Iiya Goldberg; Chiyomi Sakamoto; Noriko Saitoh; Mitsuyoshi Nakao


The Molecular Biology Society of Japan | 2016

Physico-chemical properties of condensin-based chromosome axes as revealed by an in-situ reorganization assay

Takao Ono; Chiyomi Sakamoto; Noriko Saitoh; Tatsuya Hirano

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Takao Ono

Cold Spring Harbor Laboratory

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Tatsuya Hirano

University of California

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