Biomedical subjects

Takashi Tada

Publications and source records attributed to Takashi Tada.

At least 19 recordsLinked to original sources

PubMed2006

Targeted chromosome elimination from ES-somatic hybrid cells.

To engineer a stem cell genome, we developed a technology for targeted elimination of chromosomes from mouse embryonic stem (ES)-somatic hybrid cells. Here we demonstrate the use of a universal chromosome elimination cassette (CEC) for elimination of a single embryonic stem cell (ESC)-derived chromosome 11 or 12, and also both copies of chromosome 6, which harbor pluripotency-associated genes including Nanog. We attribute hybrid-cell pluripotency to the expression of Nanog from the reprogrammed somatic-cell nuclei.

Animals↗

PubMed2006

Attenuated spread of X-inactivation in an X;autosome translocation.

X inactivation in female mammals involves transcriptional silencing of an entire chromosome in response to a cis-acting noncoding RNA, the X inactive-specific transcript (Xist). Xist can also inactivate autosomal sequences, for example, in X;autosome translocations; but here, silencing appears to be relatively inefficient. This variation has been attributed to either attenuated spreading of Xist RNA at the onset of X inactivation or inefficient maintenance of autosomal silencing. Evidence to date has favored the latter. Here, we demonstrate attenuated spreading of Xist RNA at the onset of X inactivation in the T(X;4)37H X;autosome translocation. Our findings provide direct evidence that underlying chromosome/chromatin features can disrupt spreading of the primary inactivating signal.

Animals↗

PubMed2006

Testatin transgenic and knockout mice exhibit normal sex-differentiation.

Testatin is identified as a member of the Cystatin family and expressed in germ cells and somatic cells in reproductive tissues. Testatin transcription detectable in males and females at 9.5 days post coitum, before sex-differentiation, is up-regulated just after the onset of sry expression in the male gonads, while is down-regulated to undetectable levels in the female gonads. These expression patterns suggest that Testatin might have some roles in sex-differentiation. To address Testatin function in sex-differentiation, we analyzed the effects of ectopic-expression in females and null-expression in males with testatin transgenic and knockout mice. In the transgenic females, testatin expression was constitutively elevated from embryonic gonad to adult ovary, and its expression was as high as the wild-type male gonads. However, both types of mice were fertile and did not exhibit detectable abnormalities. This suggests that the decrease of endogenous testatin in female gonad is not critical, and the increase of testatin in male gonad is dispensable for sex-differentiation.

Animals↗

PubMed2006

NANOG maintains self-renewal of primate ES cells in the absence of a feeder layer.

Nanog is a homeodomain transcription factor that is expressed specifically in undifferentiated embryonic stem (ES) cells and has been shown to be essential in the maintenance of pluripotency in mouse ES cells. To examine the function of NANOG in primate ES cells, we generated transgenic monkey ES cell lines expressing three- to seven-fold higher levels of NANOG protein compared to wild-type ES cells. These NANOG over-expressing cell lines retained their undifferentiated state in the absence of a feeder layer, as shown by expression of undifferentiated ES cell markers such as alkaline phosphatase (ALP) and OCT-4. We also demonstrated that in vitro differentiation of transgenic cell lines was mostly restricted to the ectodermal lineage, as examined by reverse transcriptase-polymerase chain reaction (RT-PCR). Knockdown experiments using NANOG small interfering (si) RNA resulted in induction of differentiation markers such as AFP, GATA4 and GATA6 for the endoderm and CDX2 for the trophectoderm. These results suggest that NANOG plays a crucial role in maintaining the pluripotent state of primate ES cells.

Animals↗

PubMed2006

Toti-/pluripotential stem cells and epigenetic modifications.

Nuclear reprogramming induces global changes of epigenetic profile and confers pluripotency on specialized somatic nuclei. Embryonic stem (ES) cells retain nuclear reprogramming activity as shown by cell fusion with adult somatic cells. The reprogrammed somatic nuclei resemble ES cell nuclei in pluripotential competence. Changes of histone tail modifications in somatic cell-derived genome by cell fusion demonstrate that the molecular process of nuclear reprogramming is separable at least in two steps: erasure of somatic epigenetic modification (genome-wide reprogramming) and establishment of pluripotential epigenetic modification (gene-specific reprogramming). In the latter step, the newly identified transcriptional factor Nanog functions in maintaining pluripotency in cooperation with other key gene Oct4. Somatic-derived Nanog is reactivated in the reprogrammed nuclei in hybrid cells and also in cloned blastocysts. It is unclear which key molecules are responsible for the nuclear reprogramming. It is, however, evident that adult somatic cell nuclei are capable of being reprogrammed in vitro by cell fusion with ES cells. A technological innovation for eliminating ES-derived chromosomes from the hybrid nuclei could make the production of personalized pluripotential stem cells without the need for therapeutic cloning possible.

Animals↗

PubMed2006

Epigenetic reprogramming of somatic genomes by electrofusion with embryonic stem cells.

Cell fusion is an approach for combining genetic and epigenetic information between two different types of cells. Electrofusion for generating hybrid cells between mouse embryonic stem cells and somatic cells, which is a type of nonchemically induced and nonvirus-mediated cell fusion, is introduced here as a highly effective, reproducible, and biomedically safe in vitro system. Under optimized electrofusion conditions, cells are ligned and form pearl chains between electrodes in response to AC pulse stimulation, and subsequently adjacent cytoplasmic membranes are fused by DC pulse stimulation. Hybrid cells survive as drug-resistant colonies in selection medium. Cell fusion is a technique that is applied widely in the life sciences. A recent topic of great interest in the field of stem cell research is the successful production of cloned animals via epigenetic reprogramming of somatic nuclei. Interestingly, nuclear reprogramming for conferring pluripotency on somatic nuclei also occurs via cell fusion between pluripotential stem cells and somatic cells. Furthermore, it has been shown that spontaneous cell fusion contributes to generating the intrinsic plasticity of tissue stem cells. Cell fusion technology may make important contributions to the fields of regenerative medicine and epigenetic reprogramming.

Animals↗

PubMed2006

Nuclear reprogramming of somatic nucleus hybridized with embryonic stem cells by electrofusion.

Cell fusion is a powerful tool for understanding the molecular mechanisms of epigenetic reprogramming. In hybrid cells of somatic cells and pluripotential stem cells, including embryonic stem (ES) and embryonic germ cells, somatic nuclei acquire pluripotential competence. ES and embryonic germ cells retain intrinsic trans activity to induce epigenetic reprogramming. For generating hybrid cells, we have used the technique of electrofusion. Electrofusion is a highly effective, reproducible, and biomedically safe in vitro system. For successful cell fusion, two sequential steps of electric pulse stimulation are required for the alignment (pearl chain formation) of two different types of cells between electrodes in response to alternating current stimulation and for the fusion of cytoplasmic membranes by direct current stimulation. Optimal conditions for electrofusion with a pulse generator are introduced for ES and somatic cell fusion. Topics in the field of stem cell research include the successful production of cloned animals via the epigenetic reprogramming of somatic cells and contribution of spontaneous cell fusion to generating intrinsic plasticity of tissue stem cells. Cell fusion technology may make important contributions to the fields of epigenetic reprogramming and regenerative medicine.

Animals↗

PubMed2006

Nuclear reprogramming: an overview.

Nuclear reprogramming is an intriguing phenomenon, in which specialized somatic cells reacquire pluripotency through the global resetting of epigenetic modifications without changes occurring to their nuclear DNA information. The nuclear reprogramming activity retained by unfertilized eggs and embryonic stem cells is readily observable through the techniques of nuclear transplantation and cell fusion, respectively. Furthermore, researches involving somatic stem cells have provided evidence that spontaneous cell fusion functions, at least in part, in maintaining the homeostasis of various tissues through the generation of replacement cells in vivo. Novel approaches by application of the nuclear reprogramming activity may open new avenues producing genetically matched personalized pluripotential stem cells derived from patient somatic cells.

Animals↗

PubMed2006

[A case of advanced gastric cancer treated by TS-1 for 3 years and 7 months].

A 72-year-old man was diagnosed as gastric cancer with pyloric stenosis by an upper gastorintestinal endoscopy for anemia in July 2001. Computed tomography (CT) of the abdomen showed multiple liver metastases. Serum CEA was 6.2 ng/ml. At laparotomy to improve anemia and pyloric stenosis in September 2001, lymphnode metastases invaded the stomach and the pancreatic body. Gastro-jejunostomy was performed without gastrectomy. Oral administration of 100 mg of TS-1 for 28 consecutive days followed by a 14-day rest was given postoperatively. The response assessment of chemotherapy after 1 year was no change (NC) of the primary lesion on endoscopic examination, and liver metastases showed a partial response (PR) on CT. Serum CEA was raised to 86.1 ng/ml in April 2004. The treatment was changed to weekly paclitaxel. The patient died in July 2005. This case with unresectable gastric cancer had been treated by oral administration of TS-1 as an outpatient for 3 years and 7 months.

Administration, Oral↗

PubMed2005

Tertiary structure and spectral tuning of UV and violet pigments in vertebrates.

Many vertebrate species use ultraviolet (UV) vision for such behaviors as mating, foraging, and communication. UV vision is mediated by UV-sensitive visual pigments, which have the wavelengths of maximal absorption (lambda max) at approximately 360 nm, whereas violet (or blue) vision is mediated by orthologous pigments with lambda max values of 390-440 nm. It is widely believed that amino acids in transmembrane (TM) I-III are solely responsible for the spectral tuning of these SWS1 pigments. Recent molecular analyses of SWS1 pigments, however, show that amino acids in TM IV-VII are also involved in the spectral tuning of these pigments through synergistic interactions with those in TM I-III. Comparisons of the tertiary structures of UV and violet pigments reveal that the distance between the counterion E113 in TM III and amino acid sites 87-93 in TM II is narrower for UV pigments than for violet pigments, which may restrict the access of water molecules to the Schiff base pocket and deprotonate the Schiff base nitrogen. Both mutagenesis analyses of E113Q and quantum chemical calculations strongly suggest that unprotonated Schiff base-linked chromophore is responsible for detecting UV light.

Amino Acid Sequence↗

PubMed2005

Nanog expression in mouse germ cell development.

Nanog is a newly identified transcriptional factor bearing a homeodomain and expressed in pluripotential cells of preimplantation and early postimplantation embryos, and embryonic stem (ES) and embryonic germ (EG) cells. Knockout experiments indicate that Nanog functions as a key player in maintaining the pluripotency of stem cells. Importantly, Nanog expression is highly expressed in primordial germ cells (PGCs) of E11.5 and E12.5 mouse embryos. However, its temporal and spatial expression pattern and function in germ cells are largely unknown. To address these issues, whole embryos and cryosections of embryos were immunostained with anti-NANOG and anti-STELLA/PGC7 antibodies. NANOG expression, repressed in colonized PGCs of E7.25-E7.5 embryos, became detectable in migrating PGCs of E7.75-E8.0 embryos. Both male and female PGCs migrating in E9.5 and E10.5 embryos and colonizing the genital ridges of E11.5 and E12.5 embryos were positive for NANOG immunostaining, while the NANOG expression pattern differed between the sexes in the later developmental stage. In female gonadal PGCs of E13.5 and E14.5 embryos, NANOG became undetectable in germ cells positive for the synaptonemal complex-specific protein SCP3, while in male PGCs of E14.5-E16.5 embryos, the number of NANOG-positive germ cells drastically decreased during the mitotic arrest. No germ cells positive for NANOG were detectable in testes and ovaries of adult mice. Thus, in germ cell development, NANOG is expressed in proliferating germ cells, in which nuclear reprogramming is progressing.

Animals↗

PubMed2005

Pluripotential competence of cells associated with Nanog activity.

Nanog is a novel pluripotential cell-specific gene that plays a crucial role in maintaining the undifferentiated state of early postimplantation embryos and embryonic stem (ES) cells. We have explored the expression pattern and function of Nanog and a Nanog-homologue, Nanog-ps1.Nanog-ps1 was mapped on Chromosome 7 and shown to be a pseudogene. Immunocytochemical analysis in vivo showed that the NANOG protein was absent in unfertilized oocytes, and was detected in cells of morula-stage embryos, the inner cell mass of blastocysts and the epiblast of E6.5 and E7.5 embryos, but not in primordial germ cells of early postimplantation embryos. In monkey and human ES cells, NANOG expression was restricted to undifferentiated cells. Furthermore, reactivation of the somatic cell-derived Nanog was tightly linked with nuclear reprogramming induced by cell hybridization with ES cells and by nuclear transplantation into enucleated oocytes. Notably, mouse Nanog (+/-) ES cells, which produced approximately half the amount of NANOG produced by wild-type ES cells, readily differentiated to multi-lineage cells in culture medium including LIF. The labile undifferentiated state was fully rescued by constitutive expression of exogenous Nanog. Thus, the activity of Nanog is tightly correlated with an undifferentiated state of cells even in nuclear reprogrammed somatic cells. Nanog may function as a key regulator for sustaining pluripotency in a dose-dependent manner.

Amino Acid Sequence↗

PubMed2005

Octamer and Sox elements are required for transcriptional cis regulation of Nanog gene expression.

The pluripotential cell-specific gene Nanog encodes a homeodomain-bearing transcription factor required for maintaining the undifferentiated state of stem cells. However, the molecular mechanisms that regulate Nanog gene expression are largely unknown. To address this important issue, we used luciferase assays to monitor the relative activities of deletion fragments from the 5'-flanking region of the gene. An adjacent pair of highly conserved Octamer- and Sox-binding sites was found to be essential for activating pluripotential state-specific gene expression. Furthermore, the 5'-end fragment encompassing the Octamer/Sox element was sufficient for inducing the proper expression of a green fluorescent protein reporter gene even in human embryonic stem (ES) cells. The potential of OCT4 and SOX2 to bind to this element was verified by electrophoretic mobility shift assays with extracts from F9 embryonal carcinoma cells and embryonic germ cells derived from embryonic day 12.5 embryos. However, in ES cell extracts, a complex of OCT4 with an undefined factor preferentially bound to the Octamer/Sox element. Thus, Nanog transcription may be regulated through an interaction between Oct4 and Sox2 or a novel pluripotential cell-specific Sox element-binding factor which is prominent in ES cells.

5' Flanking Region↗

PubMed2004

X-inactivation is stably maintained in mouse embryos deficient for histone methyl transferase G9a.

One of the two X chromosomes becomes inactivated during early development of female mammals. Recent studies demonstrate that the inactive X chromosome is rich in histone H3 methylated at Lys-9 and Lys-27, suggesting an important role for these modifications in X-inactivation. It has been shown that in the mouse Eed is required for maintenance of X-inactivation in the extraembryonic lineages. Interestingly, Eed associates with Ezh2 to form a complex possessing histone methyltransferase activity predominantly for H3 Lys-27. We previously showed that G9a is one of the histone methyltransferases specific for H3 Lys-9 and is essential for embryonic development. Here we examined X-inactivation in mouse embryos deficient for G9a. Expression of Xist, which is crucial for the initiation of X-inactivation, was properly regulated and the inactivated X chromosome was stably maintained even in the absence of G9a. These results demonstrate that G9a is not essential for X-inactivation.

Animals↗

PubMed2004

What is the predictor for invasion in non-palpable breast cancer with microcalcifications?

PURPOSE: To assess the presence of invasion in non-palpable breast cancer with microcalcifications. MATERIAL AND METHODS: We investigated 157 patients with non-palpable breast cancer with microcalcifications, who had undergone stereotactic core biopsy or vacuum-assisted breast biopsy and operation at the Cancer Institute Hospital between 1995 and 2001. We investigated the correlation between the area of calcification (maximum range of microcalcifications measured in mm by direct mammography), morphology of calcification on mammography, histological subtype of intraductal carcinoma (comedo or non-comedo) and frequency of invasion, and lymph node metastasis. The chi-square test was used in the statistical analysis and p values less than 0.05 were considered statistically significant. RESULTS: Invasion was observed in 33 of 157 pts (21%), of whom 23 showed minimal invasion, which is less than 0.5 cm in greatest diameter. The risk of invasion was 13% within 10 mm of the microcalcifications (n =70), 25% from 11 to 30 mm (n =59), and 32% more than 31 mm from the microcalcifications (n =28). The risk of invasion was 16% for punctate-round and amorphous type (n =87) microcalcifications, and 27% for pleomorphic and linear-branching types (n =70)(p =0.092). In addition, invasion was found 10% of the time within 10 mm of punctate-round and amorphous type microcalcifications, and 20% of the time at 11 mm or more. On the other hand, invasion was found 15% of the time within 10 mm of pleomorphic and linear-branching type microcalcifications, and 37% of the time at 11 mm or more. In 72 cases of intraductal carcinoma diagnosed by pathological examination, invasion was found in 10 of 31 (32%) comedo type intraductal carcinomas and in 5 of 41 (12%) non-comedo types (p =0.0379). There were 5 cases (3.2%) with axillary lymph node metastasis, all of which widely extended more than 21 mm from the microcalcifications. CONCLUSION: The risk of invasion was 10% within 10 mm of punctate-round and amorphous type microcalcifications, and 37% at more than 11 mm of pleomorphic, linear-branching microcalcifications.

Biopsy↗

PubMed2004

Clinical study on the metastasis to the eyes from breast cancer.

In our hospital, 24 patients who underwent surgery for breast cancer during 1980 to 2001 were diagnosed with metastasis to the eye. Metastasis to the choroid was found most frequently, making the choroid the most common site of metastasis. A few patients had metastasis to the orbit. Decreased visual acuity and tunnel vision were frequently found in patients who had metastasis to the choroid, and ocular floaters and blurred vision were also found in a few patients. Patients with metastasis to the orbit showed diplopia caused by ocular dyskinesia and eyelid swelling. The mean postoperative period until the diagnosis with metastasis to the eye was 3 years and 2 months, with most cases diagnosed between 20 and 40 months postoperatively, a relatively long period. We performed radiotherapy in 21 of the 24 patients, and more than half of the patients showed improvement. The mean survival period after diagnosis with metastasis to the eye was 10 months, and some of them already had recurrence to other organs such as the bones or lungs. Examination with consideration of metastasis to the eyes is required to improve the quality of life of cancer patients,.

Breast Neoplasms↗

PubMed2004

Radioguided sentinel node detection in breast cancer patients: comparison of 99mTc phytate and 99mTc rhenium colloid efficacy.

BACKGROUND: Radioguided sentinel node biopsy (SNB) of breast cancer patients has become a standard method for detecting early stage breast cancer. However, no standard radiopharmaceutical exists. METHODS: 99mTc rhenium colloid or 99mTc phytate SNB was used to aid detection in breast cancer patients. For each radiopharmaceutical, 100 patients were examined. The following points were compared: (1) scintigraphic detection rate of axillary sentinel nodes (detectability and number when detectable) and internal mammary sentinel nodes; (2) the number of nodes detected scintigraphically and the number detected during surgery; (3) sensitivity, specificity, accuracy, negative predictive value, and positive predictive value for axillary sentinel nodes. RESULTS: Axillary sentinel nodes of patients were biopsied using either 99mTc rhenium or 99mTc phytate. The number of axillary nodes surgically removed from patients given 99mTc rhenium was 2.28+/-1.08 (mean+/-SD), and the number of axillary nodes surgically removed from patients given 99mTc phytate was 1.68+/-0.82. Some patients given 99mTc rhenium showed a spill-over of radioactivity from sentinel nodes. Concordance of scintigraphically detected nodes and surgical removed nodes was superior for 99mTc phytate compared to that with 99mTc rhenium, with a statistically significant difference. The sensitivity and negative predictive value was superior with 99mTc phytate compared to that with 99mTc rhenium, even though no statistical difference was detectable. However, visualization of internal mammary nodes was superior with 99mTc rhenium. CONCLUSION: In breast cancer patients, 99mTc phytate is a better choice for the detection of axillary SNB than 99mTc rhenium colloid. However, 99mTc rhenium colloid is a better choice for the detection of internal mammary nodes.

Adult↗

PubMed2004

Histone code modifications on pluripotential nuclei of reprogrammed somatic cells.

Following hybridization with embryonic stem (ES) cells, somatic genomes are epigenetically reprogrammed and acquire pluripotency. This results in the transcription of somatic genome-derived tissue-specific genes upon differentiation. During nuclear reprogramming, it is expected that DNA and chromatin modifications, believed to function in cell-type-specific epigenotype memory, should be significantly modified. Indeed, current evidence indicates that acetylation and methylation of histone H3 and H4 amino termini play a major role in the regulation of gene activity through the modulation of chromatin conformation. Here, we show that the reprogrammed somatic genome of ES hybrid cells becomes hyperacetylated at H3 and H4, while lysine 4 (K4) of H3 becomes globally hyper-di- and -tri-methylated. In the Oct4 promoter region, histones H3 and H4 are acetylated and H3-K4 is highly tri-methylated on both the ES and reprogrammed somatic genomes, which correlates with gene activation and DNA demethylation. However, H3-K4 is also di- and tri-methylated in the promoter regions of Neurofilament-M (Nfm), Nfl, and Thy-1, which are all silent in both ES and hybrid cells. Thus, H3-K4 di- and tri-methylation of reprogrammed somatic genomes is independent of gene activity and represents one of the major events that occurs during somatic genome reprogramming towards a transcriptional activation-permissive state.

Acetylation↗