Apolipoprotein E4 increases the risk of depression recurrence

BACKGROUND

Possession of the ε4 allele of apolipoprotein E (APOE4) is related to the incidence of depression in old age. We investigated whether the presence of APOE4 is also associated with subsequent depression recurrence in a wide range of age groups.

METHODS

Altogether, 163 patients with major depressive disorder (MDD) after remission were recruited between August 2004 and March 2016 and followed up prospectively. The patients were divided into two groups: APOE4 carriers and non-carriers. We compared the time to recurrence of depression between the two groups. Kaplan-Meier survival curves, log-rank test for trend for survivor functions, and Cox proportional hazard ratio estimates for a multivariate model were conducted to examine the effect of the APOE4 allele on risk of a depression recurrence.

RESULTS

Cumulative probability of developing a depression recurrence was higher in APOE4 carriers than non-carriers. Presence of an APOE4 allele remained significantly associated with the incidence of depression recurrence.

LIMITATIONS

All patients were treated with one or two different antidepressants, which may have had different effects on patients with MDD. Second, participants in the present study comprised patients with both first and multiple episodes of MDD. Third, we did not have the statistical power to perform a stratified analysis in consideration of heterozygous or homozygous genotypes of APOE4.

CONCLUSION

Possession of an APOE4 allele may increase the risk of depression recurrence.

Management of a Mass Casualty Event Caused by Electrocution Using Doctor Helicopters

OBJECTIVE

This is the first report to show the use of doctor helicopters in a mass casualty event induced by electrocution.

METHODS

We performed a narrative review.

RESULTS

Two children obtained electrocution burns by breaking an electric fence. Five adults also received electrocution burns. Emergency medical technicians at the scene requested additional dispatch of an ambulance and the doctor helicopter. Two adult men with cardiopulmonary arrest were transported by 2 ambulances to a nearby hospital. One adult woman was in a restless confusional state, intubated, and transferred to another hospital using the doctor helicopter. One boy, who was initially in a coma, and his mother were transferred to our hospital by 1 ambulance. Another boy, who had finger amputation, was transferred to the other hospital by another doctor helicopter. A remaining elderly woman was transported to the other local hospital by ambulance. All the victims, except the 2 fathers who fell into cardiac arrest, survived.

CONCLUSION

Early confirmation of the safety of the scene, early establishment of command and control, early request for dispatch of other parties and the doctor Helicopter, appropriate triage, appropriate treatment at the scene, selecting appropriate medical facilities, and dispersion transportation were crucial.

A patient with clear consciousness even with a glucose level of 5 mg/dL (0.2 mmol/L)

A 74-year-old man noted dysarthria and right hemiparesis. His history included a gastric ulcer 2 years previously, and he had gradually lost 10 kg over a 2-year period due to appetite loss. He daily consumed 120 mg of alcohol. Upon arrival, he had clear consciousness and stable vital signs. He was malnourished. Neurologic findings included a positive finding of Barre sign in the right hand and dysarthria. A venous blood gas analysis demonstrated the following: pH 7.059; PCO2, 21.5 mm Hg; PO2, 59.1 mm Hg; HCO(3-), 5.8 mmol/L; base excess, -22.7 mmol/L; lactate,17 mmol/L; and glucose, 4 mg/dL. After the administration of an infusion of thiamine and glucose, his abnormal neurologic findings subsided completely. Head magnetic resonance image (MRI; diffusion weighted image) disclosed 3 spotty, high-intensity signals in the brain. The main results of biochemical analyses of the blood collected on arrival were as follows: hemoglobin, 5.5 g/dL; glucose, 5 mg/dL; aspartate aminotransferase, 89 IU/L. He was admitted for further examination and was diagnosed as having alcoholic ketoacidosis with hypoglycemic encephalopathy and anemia due to colon cancer.

Pregnant Woman Bitten by a Japanese Mamushi (Gloydius blomhoffii)

We herein report the fourth case of a pregnant woman bitten by a mamushi. A 33-year-old pregnant woman in the 25th week of gestation was bitten by a mamushi. Her vital signs were stable; however, biochemical analyses of the blood showed mild deterioration of anemia and hypoproteinemia. The effects of envenomation were limited to the extremities, the administration of supportive therapy without antivenom fortunately resulted in a favorable outcome. As there are differences in the maternal medical condition and weeks of gestation, further research is needed to clarify the optimal management strategy for administering antivenom in pregnancy.

A case of the vacuum phenomenon as a mechanism of gas production in the abdominal wall

A 40-year-old man experienced a collision with a car while driving a motorcycle in which the car was in the opposite lane and made a right turn. The patient was thrown approximately 10 m from the point of collision and, as he exhibited a consciousness disturbance, was transferred to our department. He had a score of 13 on the Glasgow Coma Scale with sinus tachycardia on arrival. He showed guarding of the abdomen. A pan scan disclosed traumatic subarachnoid hemorrhage, intraventricular hemorrhage, fractures of the atlas, thoracic spine, sternum and left femur, and gas in the abdomen located just in front of the stomach. As the gas in the abdomen was initially judged to be free air, the patient underwent emergency laparotomy. However, no signs of perforation or injury were detected throughout the entire digestive tract. The accumulation of minute gas (vacuum phenomenon) occurs as traumatic impact. As representative mimics of free air were not observed during surgery in the present case, we believe that the traumatic impact to the patient's abdomen as a result of the collision caused the accumulation of gas in the abdominal wall due to vacuum phenomenon. Physicians should be aware of this clinical entity to accurately recognize the mechanism of gas formation in patients showing negative laparotomy findings for gas in the abdomen. This unique case adds additional information regarding the documented etiologies of mimics of pneumoperitoneum.

A patient with refractory shock induced by several factors, including obstruction because of a posterior mediastinal hematoma

A 44-year-old man who drove a motorcycle experienced a collision with the side of another motorcycle. Because he had sustained a high-energy injury to the spinal cord, he was transferred to our hospital. His circulation was unstable, and received tracheal intubation in addition to thoracostomy for the hemothorax. Whole-body computed tomography (CT) revealed multiple fractures, right hemopneumothorax with pulmonary contusion, and minor liver injury. After infusing 5000 mL of lactated Ringer's solution and 10 units of blood, his circulation remained unstable. On a repeat CT examination, the left atrium was found to be compressed by a posterior mediastinal hematoma induced by the fracture of the thoracic spine, and a diagnosis of shock induced by multiple factors, including hemorrhagic, neurogenic, and obstructive mechanisms, was made. After obtaining stable circulation and respirations, internal fixation of the extremities and extubation were performed on the 12th hospital day. Chest CT performed on the 27th day showed the disappearance of compression of the left atrium by the hematoma.

Introduction of a physician-staffed helicopter emergency medical service in eastern Shizuoka prefecture in Japan

OBJECTIVE

To analyze the operating situation of a physician-staffed helicopter emergency medical service in eastern Shizuoka prefecture.

METHODS

A retrospective analysis was performed using the conveyance records reported by staff members of the physician-staffed helicopter. A comparison between 2007 (n = 619) and 2012 (n = 678) was performed.

RESULTS

There were no significant differences between the 2 groups with regard to the sex, ratio of cardiopulmonary arrest, and survival ratio. In contrast, the duration from the request of dispatch to arrival at the hospital in 2007 was significantly longer than that in 2012 (53.7 vs 48.2 minutes, P < 0.0001). The average age in 2007 was significantly younger than in 2012 (55.7 vs 59.4 years, P < 0.01). The ratio of trauma case in the 2012 was higher than that in 2007 (47 vs 37%, P < 0.001). The ratio of severe cases in 2007 was higher than in 2012 (45 vs 39%, P < 0.05).

CONCLUSION

Japan is an aging society. In eastern Shizuoka prefecture, the increase in the number of trauma and minor injury cases may have increased due to the emphasis on the importance of early medical intervention by the fire department.

p51/p63 Inhibits ultraviolet B-induced apoptosis via Akt activation

The epidermis must be protected against excess apoptotic cell death in response to ultraviolet-B (UV-B) irradiation. p53 is known to be critical for this protection. Although the p53 family member DeltaNp51B/DeltaNp63alpha (an N terminal-deleted form of p51/p63) is abundantly expressed in keratinocytes, its contribution to UV-B-dependent apoptosis is largely unknown. We found that, after a transient increase, DeltaNp51B is downregulated in UV-B-irradiated keratinocytes undergoing apoptosis, whereas p53 is upregulated with delayed kinetics. Furthermore, the reduction of DeltaNp51B by small interfering RNAs augmented UV-B-dependent apoptosis in keratinocytes, indicating that DeltaNp51B blocks keratinocyte apoptosis. Although the exogenous expression of DeltaNp51B in keratinocytes did not further block the UV-B-dependent apoptosis, to our surprise the expression of TAp51B (an isoform with a full NH(2)-terminal transactivation domain that is structurally and functionally similar to p53) decreased apoptosis significantly. The blockade of keratinocyte apoptosis by the p51 was dependent on the phosphorylation of Akt, resulting in the activation of a survival pathway. Thus, in addition to its indispensable roles in epithelial development, p51 acts in adult cells to protect the epidermis against UV-B irradiation by preventing excess depletion of keratinocytes.

p53 homologue, p51/p63, maintains the immaturity of keratinocyte stem cells by inhibiting Notch1 activity

p53 homologue, p51/p63, predominantly expressed in keratinocyte stem cells, is indispensable for the formation of epidermis. Notch1, another such gene indispensable for the process, induces growth arrest and differentiation in keratinocytes. We found that exogenous expression of DeltaNp51B (DeltaNp63alpha), one of the isoforms of p51 specifically expressed in basal keratinocytes, blocked Notch 1-dependent growth arrest and differentiation in mouse keratinocytes by inhibiting p21 expression and maintaining integrins expression. Furthermore, DeltaNp51B by itself was found to have ability to induce expression of integrin alpha6beta4, which promotes attachment of basal cells to basal membrane thereby keeping the cells in immature state. Therefore, we conclude that DeltaNp51B expression warrants integrin expression even under the influence of Notch1 and that DeltaNp51B is a long-sought factor required to maintain basal cell keratinocytes immaturity by inhibiting Notch1 activity. We will postulate a plausible model explaining the maintenance of the squamous epithelium architectures as well as offering mechanistic explanations for pathological features of skin diseases, including cancers, psoriasis along with physiological wound healings.

A novel neuronal cell line derived from the ventrolateral region of the suprachiasmatic nucleus

The suprachiasmatic nucleus of the anterior hypothalamus is the center of an internal biological clock in mammals. Glutamate is the neurotransmitter of retino-hypothalamic tract responsible for mediating the circadian actions of light in rodents. N-methyl-d-aspartate receptors, particularly NR2B subunit are reported to be principally involved in photic resetting of the biological clock in vivo and in slice culture. But, the precise cellular mechanisms of the resetting are not elucidated, because no adequate neuronal cell lines derived from the suprachiasmatic nucleus have been established. We established a neuronal cell line, N14.5, derived from the suprachiasmatic nucleus of a transgenic rat harboring the temperature-sensitive simian virus 40 large T-antigen gene. When the cells were cultured at 39 degrees C, the morphological features were turned fibroblastic into neuronal round cell body with neurite extensions. These cells showed immunoreactivities for neuronal markers (betaIII-tubulin, microtubule-associated protein 2 and TAU2) and as well as for vasoactive intestinal peptide which is expressed in the ventrolateral region of the suprachiasmatic nucleus. The cells expressed N-methyl-d-aspartate receptors, particularly NR1 and NR2B subunits as revealed by quantitative PCR. N-methyl-d-aspartate activated phosphorylation of p44/42 mitogen-activated protein kinase and increased expression level of Per1 and Per2 mRNA. These results suggest that the N14.5 is a novel neuronal cell line derived from the ventrolateral region of the suprachiasmatic nucleus, and that N-methyl-d-aspartate receptors expressed in the cells are a functional receptor. The N14.5 cells may be a useful tool to elucidate numerous chronobiological processes, especially resetting mechanism induced by an external light signal.

A novel oligodendrocyte cell line OLP6 shows the successive stages of oligodendrocyte development: late progenitor, immature and mature stages

The successive stages of development from oligodendrocyte progenitor to mature oligodendrocyte have been investigated in detail by using stage-specific antibodies. However, no cell lines are available that show stepwise differentiation from oligodendrocyte progenitors to mature oligodendrocytes. Here we show the establishment of an immortalized oligodendrocyte cell line, OLP6, from adult transgenic rats harboring the temperature-sensitive simian virus 40 large T-antigen gene. The OLP6 cells had a fibroblastic morphology and continuously proliferated at 33 degrees C. They displayed growth arrest and multipolar morphology when they were cultured at 39 degrees C. They express the oligodendrocytic markers O4, 2'-3'-cyclic-nucleotide 3'-phosphodiesterase, galactocerebroside and second endothelial differentiation gene receptor-2 at 39 degrees C. The OLP6 cells underwent apoptosis upon serum withdrawal at 39 degrees C. Lysophosphatidic acid inhibited this apoptosis and promoted the expression of myelin basic protein. These results demonstrate that the activation of endothelial differentiation gene receptor-2 exerts anti-apoptosis and myelinogenesis effects on the OLP6 cells. Taken together, the OLP6 cells in the late oligodendrocyte progenitor stage can progress to the immature oligodendrocyte stage by shifting culture temperature. Furthermore, lysophosphatidic acid promoted the maturation of OLP6 cells in the immature oligodendrocyte stage. Such OLP6 cells should provide a potent model system for studying the precise mechanism involved in stepwise differentiation of oligodendrocytes.

Establishment of tendon-derived cell lines exhibiting pluripotent mesenchymal stem cell-like property

Development of the musculoskeletal system requires coordinated formation of distinct types of tissues, including bone, cartilage, muscle, and tendon. Compared to muscle, cartilage, and bone, cellular and molecular bases of tendon development have not been well understood due to the lack of tendon cell lines. The purpose of this study was to establish and characterize tendon cell lines. Three clonal tendon cell lines (TT-E4, TT-G11, and TT-D6) were established using transgenic mice harboring a temperature-sensitive mutant of SV40 large T antigen. Proliferation of these cells was significantly enhanced by treatment with bFGF and TGF-beta but not BMP2. Tendon phenotype-related genes such as those encoding scleraxis, Six1, EphA4, COMP, and type I collagen were expressed in these tendon cell clones. In addition to tendon phenotype-related genes, expression of osteopontin and Cbfal was observed. These clonal cell lines formed hard fibrous connective tissue when implanted onto chorioallantoic membrane in ovo. Furthermore, these cells also formed tendon-like tissues when they were implanted into defects made in patella tendon in mice. As these tendon cell lines also produced fibrocartilaginous tissues in tendon defect implantation experiments, mesenchymal stem cell properties were examined. Interestingly, these cells expressed genes related to osteogenic, chondrogenic, and adipogenic lineages at low levels when examined by RT-PCR. TT-G11 and TT-E4 cells differentiated into either osteoblasts or adipocytes, respectively, when they were cultured in cognate differentiation medium. These observations indicated that the established tendon cell line possesses mesenchymal stem cell-like properties, suggesting the existence of mesenchymal stem cell in tendon tissue.

Establishment of Leydig cell line, TTE1, from transgenic mice harboring temperature-sensitive simian virus 40 large T-antigen gene

A Leydig cell line, TTE1, has been established from transgenic mice harboring a temperature-sensitive simian virus 40 (tsSV40) large T-antigen gene. The cells grew at a permissive temperature (33 degrees C), but growth was markedly prevented at a nonpermissive temperature (39 degrees C). T-antigen was expressed in the nuclei at 33 degrees C but disappeared at 39 degrees C, indicating that the cells show a temperature-sensitive growth phenotype reflected by the tsSV40 large T-antigen. TTE1 cells did not show any colony-forming activity in soft agar and form tumors in subcutaneous tissue in nude mice, indicating that the cells were not transformed. Alkaline phosphatase and 3beta-hydroxysteroid dehydrogenase (HSD) activities or expression of cytokeratin and vimentin were observed. Reverse transcription-polymerase chain reaction (RT-PCR) analysis indicated that TTE1 cells expressed mRNAs encoding 17beta-HSD types 1 and 3, and inhibin-alpha. The cells with unique characteristics, therefore, should serve useful model study the function of Leydig cell.

Oncostatin m regulates mesenchymal cell differentiation and enhances hematopoietic supportive activity of bone marrow stromal cell lines

Bone marrow stromal cell lines (TBR cell lines) established from temperature-sensitive Simian Virus 40 T-antigen gene transgenic mice exhibited myogenic, osteogenic, and adipogenic differentiation. The effect of oncostatin M (OSM) on such mesenchymal cell differentiation of marrow stromal cell lines was examined. One of those stromal cell lines, TBRB, differentiated into skeletal muscle, and its differentiation was stimulated by OSM, whereas differentiation of TBR10-1 into smooth muscle was inhibited by OSM. TBR31-2 is a bipotent progenitor for adipocytes and osteoblasts, and OSM stimulated osteogenic differentiation while inhibiting adipogenic differentiation. On the other hand, TBR cell lines exhibited various potentials for supporting hematopoiesis in culture. When hematopoietic progenitor cells were cocultured with OSM-stimulated stromal cell lines, TBR10-1 and TBR31-2 exhibited enhanced hematopoietic supportive activity. As responsible molecules for stromal cell dependent hematopoiesis, expression of stem cell factor (SCF) (a ligand of c-Kit), vascular cell adhesion molecule (VCAM-1) (a ligand of VLA-4), and secretion of interleukin (IL)-6 were increased by OSM. OSM affected mesenchymal cell differentiation and promoted the hematopoietic supportive activity of marrow stromal cell lines. As OSM production is induced by cytokines from hematopoietic cells, OSM may be a key factor in mutual regulation between hematopoietic cells and stromal cells in the bone marrow. OSM may play a role as a regulator in maintaining the hematopoietic microenvironment in marrow by coordinating mesenchymal differentiation.

Overexpression of AML1 transcription factor drives thymocytes into the CD8 single-positive lineage

To understand the gene regulation involved in the development of single-positive (SP) thymocytes, we generated transgenic mice in which the AML1 transcription factor is overexpressed. In these mice the number of CD8 SP thymocytes was greatly increased, and this continued to be true even when MHC class I was absent. This promotion to the CD8 SP lineage was not, however, observed when both class I and class II were absent. Furthermore, even thymocytes carrying MHC class II-restricted TCR differentiated into the CD8 SP lineage when AML1 was overexpressed. The selected CD8 SP cells were, however, unable to mature, as judged by the expression level of heat-stable Ag. Thus, overexpression of AML1 is able to skew class II-restricted thymocytes into the CD8 SP lineage, but not to drive the maturation of resulting selected CD8 SP cells.

Up-regulation of p27Kip1 by progestins is involved in the growth suppression of the normal and malignant human endometrial glandular cells

Progestins are known to suppress the growth of normal human endometrial glands and endometrial carcinomas possessing PRs. To elucidate the molecular mechanisms of progestin-induced growth inhibition, the expression and functional involvement of p27Kip1 (p27), a cyclin-dependent-kinase inhibitor, was investigated using cultured normal endometrial glandular cells and endometrial carcinoma cell lines (Ishikawa; PR-positive, KLE; PR-negative). Growth of the normal endometrial glandular cells and Ishikawa cells was suppressed by treatment with progesterone and medroxyprogesterone acetate, respectively, in association with an increase in p27 protein expression. Immunoprecipitation revealed that progestins accelerated the complex formation of p27 and cdk2 in both types of cells. However, treatment with progestins did not show any marked alterations in the mRNA expression of p27 in either normal glandular cells or Ishikawa cells. On the other hand, p27 protein degradation experiments indicated that treatment with progesterone and medroxyprogesterone acetate prolonged the degradation time of the normal endometrial glandular cells and Ishikawa cells, respectively. Forced expression of the p27 protein using a p27 expression plasmid reduced the growth activity of normal endometrial glandular cells. These findings suggest that p27 is functionally involved in progestin-induced growth suppression of normal and malignant endometrial epithelial cells and that up-regulation of the p27 protein by progestins possibly occurs via posttranslational mechanisms.

Possible applications of conditionally immortalized tissue cell lines with differentiation functions

If all individual cell types of the body could be clonally isolated and stocked, similar to cDNA or genomic DNA libraries, they would be invaluable for studying the tissue and cellular functions. We developed a new method of establishing conditionally immortalized cell lines that retain differentiated cell functions similar to the original tissues, using temperature-sensitive (ts) simian virus 40 large tumor antigen gene transgenic animals. In this review the properties of such conditionally immortalized cell lines and their possible applications are discussed.

Acidic amino acid transport characteristics of a newly developed conditionally immortalized rat type 2 astrocyte cell line (TR-AST)

To characterize acidic amino acid transport in type 2 astrocytes, we established conditionally immortalized rat astrocyte cell lines (TR-AST) from newly developed transgenic rats harboring temperature-sensitive SV40 large T-antigen gene. TR-AST exhibited positive immunostaining for anti-GFAP antibody and A2B5 antibody, characteristics associated with type 2 astrocytes, and expressed glutamine synthetase. Acidic amino acid transporters, GLT-1 and system xc-, which consists of xCT and 4F2hc, were expressed in all TR-ASTs by RT-PCR. On the other hand, GLAST expression was found in TR-AST3 and 5. The characteristics of [3H]L-glutamic acid (L-Glu) uptake by TR-AST5 include an Na+-dependent and Na+-independent manner, concentration-dependence, and inhibition by L-aspartic acid (L-Asp) and D-aspartic acid (D-Asp). The corresponding Michaelis-Menten constants for the Na+-dependent and Na+-independent process were 36.3 microM and 155 microM, respectively. [3H]L-Asp and [3H]D-Asp uptake by TR-AST5 had an Na+-dependent and Na+-independent manner. This study demonstrated that GLT-1, system xc-, and GLAST were expressed in TR-AST, which has the characteristics of type 2 astrocytes and is able to transport acidic amino acids.

mRna expression and transport characterization of conditionally immortalized rat brain capillary endothelial cell lines; a new in vitro BBB model for drug targeting

Brain capillary endothelial cell lines (TR-BBB) were established from a recently developed transgenic rat harboring temperature-sensitive simian virus 40 (ts SV 40) large T-antigen gene (Tg rat) and used to characterize the endothelial marker, transport activity, and mRNA expression of transporters and tight-junction strand proteins at the blood-brain barrier (BBB). These cell lines expressed active large T-antigen and grew well at 33 degrees C with a doubling-time of about 22-31 hr, but did not grow at 39 degrees C. TR-BBBs expressed the typical endothelial marker, von Willebrand factor, and exhibited acetylated low-density lipoprotein uptake activity. Although the gamma-glutamyltranspeptidase activity in TR-BBBs was approximately 13% of that of the brain capillary fraction of a normal rat, it was localized in the apical side, suggesting that it reflects the functional polarity of the in vivo BBB. The mRNA of tight-junction strand proteins such as claudine-5, occludin, and junctional adhesion molecule are expressed in TR-BBB13. Drug efflux transporter, P-glycoprotein, with a molecular weight of 170 kDa was expressed in all TR-BBBs and mdr 1a, mdr 1b, and mdr 2 mRNA were detected in TR-BBBs using RT-PCR. Moreover, mrp1 mRNA was expressed in all TR-BBBs. Influx transporter, GLUT-1, expressed at 55 kDa was revealed by Western blot analysis. It had 3-O-methyl-D-glucose (3-OMG) uptake activity which was concentration-dependent with a Michaelis-Menten constant of 9.86 +/- 1.20 mM. The mRNA of large neutral amino acid transporter, which consists of LAT-1 and 4F2hc was expressed in TR-BBBs. In conclusion, the conditionally immortalized rat brain capillary endothelial cell lines (TR-BBB) had endothelial makers, expressed mRNA for tight-junction strand proteins and the influx and efflux transporters and produced GLUT-1, which is capable of 3-OMG transport activity.

Establishment and characterization of chondrocyte cell lines from the costal cartilage of SV40 large T antigen transgenic mice

Complete understanding of the physiology and pathology of the cartilage is essential to establish treatments for a variety of cartilage disorders and defects such as rheumatoid arthritis, congenital malformations, and tumors of cartilage. Although synthetic materials have been used in many cases, they possess inherent problems including wear of the materials and low mechanical strength. Autograft has been considered very effective to overcome these problems. However, the limitation of the transplant volume is a major problem in autograft to be overcome. The costal cartilage is the most serious candidate for donor site transplantation, since it is the largest permanent hyaline cartilage in the body. To investigate the possibility using the costal cartilage as a transplant source, we have established and characterized three mouse chondrocyte cell lines (MCC-2, MCC-5, and MCC-35) derived from the costal cartilage of 8-week-old male SV40 large T-antigen transgenic mice. At confluence, all the cell lines formed nodules that could be positively stained with alcian blue (pH 2.5). The size of nodules gradually increased during culturing time. After 2 and 6 weeks of culture, RT-PCR analysis demonstrated that all three cell lines expressed mRNA from the cartilage-specific genes for type II collagen, type XI collagen, aggrecan, and link protein. Furthermore, type X collagen expression was detected in MCC-5 and MCC-35 but not in MCC-2. Any phenotypic changes were not observed over 31 cell divisions. Immunocytochemistry showed further that MCC-2, MCC-5, and MCC-35 produced cartilage-specific proteins type II collagen and type XI collagen, while in addition MCC-5 and MCC-35 produced type X collagen. Treatment with 1alpha, 25-dihydroxyvitamin D(3) inhibited cell proliferation and differentiation of the three cell lines in a dose-dependent manner. These phenotypic characteristics have been found consistent with chondrocyte cell lines established from cartilage tissues other than costal cartilage. In conclusion, costal cartilage shows phenotypic similarities to other cartilages, i.e., articular cartilage and embryonic limbs, suggesting that costal cartilage may be very useful as the donor transplantation site for the treatment of cartilage disorders. Furthermore, the cell lines established in this study are also beneficial in basic research of cartilage physiology and pathology.

Establishment of gingival epithelial cell lines from transgenic mice harboring temperature sensitive simian virus 40 large T-antigen gene

We established two gingival epithelial cell lines (GE1 and GE6), originating from transgenic mice harboring the temperature-sensitive simian virus 40 large T-antigen gene. GE1 and GE6 grew at a permissive temperature (33 degrees C) in a pavement arrangement and solely formed multilayers that exhibited morphological features similar to those of the stratified oral epithelium, with neither the use of stromal equivalents nor feeder layers. Both GE cells underwent apoptosis at a non-permissive temperature (39 degrees C). Characteristic keratin peptides, keratin 4 and 13, for mucosal epithelium were obviously expressed in the suprabasal cells, and keratohyalin granules and involucrin were present in the surface flat cells in the multilayered culture. Keratin 10 (one of the markers for higher keratinized gingival epithelium) was rarely found in some uppermost cells, and filaggrin (a component of keratohyalin granules) appeared sparsely in uppermost desquamating cells in the older cultures. These observations indicated that GE1 and GE6 cells exhibited the phenotype characterizing nonkeratinized sulcular epithelium, which possessed the potency undergoing keratinization in such highly stratified cultures as oral gingival epithelium. GE cells increased the expression levels of mRNA of interleukin-1beta and tumor necrosis factor alpha by the stimulation of lipopolysaccharide and extracellular substances of oral streptococci. The GE cell lines thus could serve as an excellent experimental system for further studies on the physiology of gingival epithelium and corresponding diseases, such as periodontal disease, epithelial hyperplasia, and gingival tumors.

Stromal cells provide signals different from cytokines for STAT5 activation in hematopoietic cells

After detachment from the stromal cells, hematopoietic stem cells are thought to differentiate to the cytokine-dependent stages where their growth and differentiation are promoted by these cytokines. To examine the stromal regulation of hematopoietic stem cells, we previously established a primitive hematopoietic stem-like cell line, THS119, whose growth was dependent on the bone marrow stromal cell line, TBR59, and from which IL-3- (THS119/IL-3) or IL-7- (THS119/IL-7) dependent cell lines were then generated. Using these cell lines, we examined the difference in signals mediated by the stromal cells and cytokines. The cytokine-dependent cell lines (THS119/IL-3 and THS119/IL-7) showed induction of STAT5 phosphorylation and target genes for STAT5 such as CIS, pim-1, p21 and bcl-xL upon addition of IL-3 or IL-7. IL-3 or IL-7 also induced STAT5 phosphorylation and STAT5 target genes of the stromal cell-dependent cell line, THS119, in the absence of stromal cells at levels similar to the cytokine-dependent cell lines. However, quite interestingly, TBR59 stromal cells could not induce STAT5 phosphorylation of THS119 cells, although they did induce STAT5 target genes in THS119 cells. In addition, the mRNAs for STAT5 target genes in THS119 cells on the stromal cells seemed to be more stable than those in the cytokine-dependent cell lines. Expression of the antiapoptotic genes bcl-2 and bcl-xL was higher in the stromal cell-dependent cell line than in the cytokine-dependent cell lines. These results suggested that stromal cells and cytokines may provide different signals for growth and differentiation of the hematopoietic cells.

Stage-specific tissue and cell interactions play key roles in mouse germ cell specification

Primordial germ cells (PGCs) in mice have been recognized histologically as alkaline phosphatase (AP) activity-positive cells at 7.2 days post coitum (dpc) in the extra-embryonic mesoderm. However, mechanisms regulating PGC formation are unknown, and an appropriate in vitro system to study the mechanisms has not been established. Therefore, we have developed a primary culture of explanted embryos at pre- and early-streak stages, and have studied roles of cell and/or tissue interactions in PGC formation. The emergence of PGCs from 5.5 dpc epiblasts was observed only when they were co-cultured with extra-embryonic ectoderm, which may induce the conditions required for PGC formation within epiblasts. From 6.0 dpc onwards, PGCs emerged from whole epiblasts as did a fragment of proximal epiblast that corresponds to the area containing presumptive PGC precursors without neighboring extra-embryonic ectoderm and visceral endoderm. Dissociated epiblasts at these stages, however, did not give rise to PGCs, indicating that interactions among a cluster of a specific number of proximal epiblast cells is needed for PGC differentiation. In contrast, we observed that dissociated epiblast cells from a 6.5-b (6.5+15-16 hours) to 6.75 dpc embryo that had undergone gastrulation gave rise to PGCs. Our results demonstrate that stage-dependent tissue and cell interactions play key roles in PGC determination.

Conditionally immortalized retinal capillary endothelial cell lines (TR-iBRB) expressing differentiated endothelial cell functions derived from a transgenic rat

The objective of this study was to establish and characterize a retinal capillary endothelial cell line (TR-iBRB) from a newly developed transgenic rat harboring the temperature-sensitive simian virus 40 (SV 40) large T-antigen gene (Tg rat). Retinal capillary endothelial cells were isolated from a Tg rat and cultured in collagen-coated dishes at 37 degrees C for a period of 48 hr. Cells were subsequently cultured at 33 degrees C to activate the large T-antigen. At the third passage, cells were cloned by colony formation and isolated from other cells. Nine immortalized cell lines of retinal capillary endothelial cells (TR-iBRB1 approximately 9) were obtained from a Tg rat. These cell lines had a spindle-fiber shape morphology, expressed the typical endothelial marker, von Willebrand factor, and internalized acetylated-low density lipoprotein. Moreover, vascular endothelial growth factor (VEGF) receptor-2 was expressed in TR-iBRBs. TR-iBRBs expressed a large T-antigen and grew well at 33 degrees C with a doubling time of 19-21 hr. In contrast, cells did not grow at 37 and 39 degrees C due to the reduced expression of large T-antigen, supporting temperature-dependent cell growth. TR-iBRBs expressed GLUT1 and exhibited 3- O -methyl- D -glucose (3-OMG) uptake activity. This 3-OMG uptake was saturable with a Michaelis-Menten constant of 5.56 +/- 0.51 m M and a maximum uptake rate of 45.3 +/- 2.6 nmol min(-1) mg protein(-1). P-Glycoprotein, with a molecular weight of approximately 180 KDa, was expressed in TR-iBRBs. In addition, mdr 1a, mdr 1b and mdr 2 were detected in TR-iBRB2 using RT-PCR. In conclusion, conditionally immortalized retinal capillary endothelial cell lines were established from a transgenic rat harboring the temperature-sensitive SV 40 large T-antigen gene and these lines were shown to exhibit the properties of retinal capillary endothelial cells.

Establishment of bone marrow-derived endothelial cell lines from ts-SV40 T-antigen gene transgenic rats

PURPOSE

Postneonatal neovascularization is thought to result exclusively from the proliferation, migration, and remodeling of fully differentiated endothelial cells (ECs). Recently, it has been reported that bone marrow contains cells which can differentiate into ECs and contribute to neoangiogenesis in adult species. In this study, we tried to establish conditionally immortalized endothelial cell lines (TR-BME) derived from rat bone marrow.

METHODS

Mononuclear cells were isolated and differentiated into ECs at 37 degrees C from the bone marrow of a transgenic rat harboring temperature-sensitive SV40 large T-antigen (ts T-Ag) gene. Then, the cells were transferred and incubated at 33 degrees C, a permissive temperature for ts T-Ag. Expression of vascular endothelial growth factor (VEGF) receptor (VEGFR)-1, 2, Tie-1, 2 and von Willebrand factor (VWF) were assayed by reverse transcriptase-mediated polymerase chain reaction (RT-PCR).

RESULTS

We have established three cell lines incorporating 1,1'-dioctadecyl-3,3,3',3-tetramethylindo-carbocyanine perchlorate (DiI-Ac-LDL) with a spindle shape. One of these, clone 2, strongly expressed VEGFR-2, and weakly expressed VEGFR-1 and VWF. In contrast, clone 8 showed strong expression of Tie-1, 2, and VWF, and weak expression of VEGFR-1,2. All markers were expressed strongly in clone 3.

CONCLUSIONS

These data confirm that the above three TR-BME cells are novel ECs derived from bone marrow progenitors.

Bcl-2 inhibits apoptosis of spermatogonia and growth of spermatogonial stem cells in a cell-intrinsic manner

The growth, differentiation, and death/survival of spermatogonia are precisely regulated for the proper production of spermatozoa. We have previously shown that Bcl-2 ectopically expressed in spermatogonia caused the inhibition of normal spermatogonial apoptosis and the subsequent failure of differentiation in transgenic mice. In addition, the growth of spermatogonial stem cells seemed to be temporally arrested in the transgenic mice. In the present study, we attempted to examine whether the abnormality of spermatogonia described above was caused by Bcl-2 misexpression in the spermatogonia or by an abnormal spermatogenic environment of the transgenic mice. We transplanted testicular cells of transgenic mice to seminiferous tubules of W/Wv mice in which transplanted normal testicular cells can undergo spermatogenesis. We found that the transplanted spermatogonia of the transgenic mice reproduced a series of abnormal changes including temporal growth arrest of spermatogonial stem cells and abnormal accumulation of spermatogonia in tubules, which were also observed in the testes of the transgenic mice. The results indicated that Bcl-2 inhibited apoptosis of spermatogonia and growth of spermatogonial stem cells in a cell-intrinsic manner. We also cultured testicular cells of transgenic mice and found that the spermatogonia of the transgenic mice were better able to survive than were those of wild-type mice but that their differentiation was not affected. The result suggested that failure of differentiation of the accumulated spermatogonia in the transgenic testes is not due to the abnormality of the bcl-2 misexpressing spermatogonia, but may be caused by extrinsic problems including improper interaction of spermatogonia with supporting cells.

Characterization of the amino acid transport of new immortalized choroid plexus epithelial cell lines: a novel in vitro system for investigating transport functions at the blood-cerebrospinal fluid barrier

PURPOSE

To establish and characterize a choroid plexus epithelial cell line (TR-CSFB) from a new type of transgenic rat harboring the temperature-sensitive simian virus 40 (ts SV 40) large T-antigen gene (Tg rat).

METHODS

Choroid plexus epithelial cells were isolated from the Tg rat and cultured on a collagen-coated dish at 37 degrees C during the first period of 3 days. Cells were subsequently cultured at 33 degrees C to activate large T-antigen. At the third passage, cells were cloned by colony formation and isolated from other cells using a penicillin cup.

RESULTS

Five immortalized cell lines of choroid plexus epithelial cells (TR-CSFB 1 approximately 5) were obtained from two Tg rats. These cell lines had a polygonal cell morphology, expressed the typical choroid plexus epithelial cell marker, transthyretin, and possessed Na+, K+-ATPase on their apical side. TR-CSFBs cells expressed a large T-antigen and grew well at 33 degrees C with a doubling-time of 35 approximately 40 hr. [3H]-L-Proline uptake by TR-CSFB cells took place in an Na+-dependent, ouabain-sensitive, energy-dependent, and concentration-dependent manner. It was also inhibited by alpha-methylaminoisobutylic acid, suggesting that system A for amino acids operates in TR-CSFB cells. When [3H]-L-proline uptake was measured using the Transwell device, the L-proline uptake rate following application to the apical side was five-fold greater than that following application to the basal side. In addition, both Na+-dependent and Na+-independent L-glutamic acid (L-Glu) uptake processes were present in TR-CSFB cells.

CONCLUSIONS

Immortalized choroid plexus epithelial cell lines were successfully established from Tg rats and have the properties of choroid plexus epithelial cells, and amino acid transport activity was observed in vivo.

Establishment and characterization of a colonic epithelial cell line MCE301 from transgenic mice harboring temperature-sensitive simian virus 40 large T-antigen gene

We produced an immortalized colonic epithelial cell line, MCE301, using fetal mice transgenic for the temperature-sensitive simian virus 40 large T-antigen gene. MCE301 cells showed epithelial-like morphology and maintained tight connections with neighboring cells. The cells grew at a permissive temperature (33 degrees C), but the growth of the cells was significantly prevented at the nonpermissive temperature (39 degrees C). The cells expressed large T-antigen at 33 degrees C but not at 39 degrees C. MCE301 cells were not transformed, as judged by the absence of anchorage-independent growth in soft agar gel and lack of tumor formation in nude mice. Electron microscopic studies showed that the cells formed microvilli-like structures on the cell surface and junctional complexes such as tight junctions and desmosomes between the cells. The cells expressed cytosketal (acidic cytokeratins and actin), basement membrane (laminin and collagen type IV) and junctional complex proteins (ZO-1 and desmoplakin I + II), as judged by specific antibodies. Fetal bovine serum, epidermal growth factor, insulin-like growth factor and insulin significantly increased the cell growth at 33 degrees C. Moreover, MCE301 cells expressed colonic mucin Muc2 mRNA as demonstrated by reverse transcriptase-polymerase chain reaction, indicating that the cells originate from mucus-secreting cells. Alkaline phosphatase, a brush border-associated enzyme, was detected in the cells. Sodium butyrate (2 mM), an inducer of cellular differentiation, markedly elevated alkaline phosphatase activity. Thus, the present mouse colonic epithelial cell line MCE301 possessing these unique characteristics should provide a useful in vitro model of colonic epithelium.

A mouse bone marrow stromal cell line, TBR-B, shows inducible expression of smooth muscle-specific genes

We established an in vitro culture system which mimicked the differentiation pathway of smooth muscle cell, using TBR-B, a bone marrow stromal cell line derived from transgenic mice harboring temperature-sensitive SV40 large T-antigen gene. TBR-B cells have the potential to express smooth muscle-specific genes including h1-calponin, h-caldesmon, SM22alpha and alpha-actin, only after cultured in the differentiation medium for 2 weeks. The differentiation state of TBR-B was well controlled by using different culture medium. Using this cell line, we also found that ascorbic acid is a potent factor inducing the expression of h1-calponin and alpha-actin. TBR-B cells will serve as a useful tool for elucidating the regulatory mechanisms of smooth muscle-specific gene expression, and for identifying compounds that regulate the differentiation state of vascular smooth muscle cells.

MIDA1 is a sequence specific DNA binding protein with novel DNA binding properties

BACKGROUND

Id proteins not only regulate cell differentiation negatively, but they also promote growth and apoptosis. To know the mechanism of how Id regulates cell fate, we previously isolated an Id-associating protein, MIDA1, which positively regulates cell growth. Its predicted amino acid sequence contains tryptophan-mediated repeats (Tryp-med repeats) similar to the DNA binding region of the c-Myb oncoprotein. We determined whether MIDA1 can bind to DNA in a sequence specific manner by PCR-assisted binding site selection.

RESULTS

We identified a 7-base sequence (GTCAAGC) surrounded by a 1-3 bp palindromic sequence as the DNA sequence recognized by the Tryp-med repeats of MIDA1. This motif is located within the 5'-flanking sequence of several growth regulating genes. Gel shift assays revealed that this sequence and a certain length of flanking DNA are necessary for MIDA1 to bind DNA in a stable manner. Methylation interference and DNase I footprint analysis suggested that the DNA binding of MIDA1 is resistant to DNA methylation and that MIDA1 does not specifically localize on this particular motif.

CONCLUSIONS

We concluded that MIDA1 is a novel sequence-specific DNA binding protein with some different properties from the usual transcription factors and that MIDA1 may act as a mediator of Id-mediated growth-promoting function through its DNA binding activity.

Sphingosine-1-phosphate and lysophosphatidic acid trigger invasion of primitive hematopoietic cells into stromal cell layers

A new primitive hematopoietic cell line (THS119), exhibiting Lin(-)/Sca-1(+)/c-Kit(+) a surface phenotype, grew and survived underneath stromal cells (TBR59). The ability of the THS119 cells to invade these stromal cell layers was dependent on the inclusion of serum in the culture medium. This was apparently due to a requirement for lipids contained in serum. Their invasion of the stromal cell layers in serum-free cultures could be triggered by addition of sphingosine-1-phosphate (S1P) or lysophosphatidic acid (LPA) and was dependent on both Rho- and Ras-signaling pathways. Between the 2 possible receptors of S1P and LPA, edg-1 and edg-2, expression of edg-2 only was found to be correlated with immaturity and/or invasive activity of the primitive hematopoietic cells. These results suggest the importance of specific lipids and their specific receptors on the invasive activity of primitive hematopoietic cells in the hematopoietic microenvironment.

Self-renewal and differentiation of a novel bipotent myeloid progenitor clone in the stroma-dependent culture

To understand regulation of myeloid development, it is necessary to obtain the myeloid progenitor cell lines with self-renewal and differentiation capacities. Because prolonged hematopoiesis occurs with the production of myeloid cells at all stages of differentiation in the Dexter-type long-term bone marrow cultures, we tried to obtain stroma-dependent myeloid progenitor cells starting from the long-term bone marrow culture. Murine cobblestone areas generated in long-term bone marrow cultures were serially passaged every 10 days. After 4 months, the resultant hematopoietic cells, designated as DFC, were passaged on a monolayer of established spleen stromal cell line, MSS62. After 10-12 passages of DFC cells on MSS62, several clones were obtained by colony formation on MSS62 cell layer. Among these clones, DFC-a cells could be maintained for a long period by coculturing with the established stromal cell line, MSS62.DFC-a cells proliferated by forming cobblestones and contained blast cells, granulocytes, and macrophages. Cell sorting and coculture experiments indicated that the blast type cells exhibiting c-Kit(+) Gr-1(-) Mac-1(-), stroma-dependently self-renewed, and spontaneously differentiated toward granulocytes (c-Kit(+) Gr-1(+) Mac-1(+)) and macrophages (c-Kit(low/+) Gr-1(-) Mac-1(high)). Although most of DFC-a cells expressed c-Kit, SCF-c-Kit interaction was not always necessary for their growth. In the presence of stromal cells, growth and differentiation of DFC-a cells were stimulated by GM-CSF or IL-3. Without stromal cells, DFC-a was transiently expanded by GM-CSF or IL-3 but could not be maintained constantly by these cytokines. The present study demonstrated that DFC-a is a novel bipotent myeloid progenitor cell clone as a simple model system of stroma-dependent myeloid development. It may reflect distinct properties for the earliest myeloid progenitor cells in vivo. It is of interest to know what signals are provided by MSS62 stromal cells to maintain the myeloid progenitor cells.

Isolation of a novel PDZ-containing myosin from hematopoietic supportive bone marrow stromal cell lines

Stromal cells in bone marrow provide an optimal microenvironment for hematopoiesis. The established stromal cell lines from bone marrow showed various cellular heterogeneities and differed in their hematopoietic supportive ability. By a differential display method, we cloned a gene whose expression levels were correlated with the hematopoietic supportive ability of stromal cells. Its deduced amino acid sequence shows a structure similar to myosins, except that it lacks an actin binding site. Interestingly, it contains a KE-rich sequence and a PDZ domain in the NH(2)-terminal, which are protein-protein interaction domains; therefore we termed this novel myosin Myosin containing PDZ domain (MysPDZ). Western blot analysis showed that its protein levels positively correlated with the supportive ability of stromal cells and immunostaining suggested that MysPDZ was present at cytoskeleton in a filamentous and/or network form. Thus MysPDZ may be involved in the maintenance of the stromal cell architectures required for cell to cell contact.

Stroma-dependent maintenance of cytokine responsive hematopoietic progenitor cells derived from long-term bone marrow culture

Hematopoietic cells maintained for long periods on primary cultures of bone marrow stromal cells formed cobblestone colonies (Dexter's long-term bone marrow culture, LTBC). These stably maintained hematopoietic cells (for 4 months) were transferred to a coculture on an established spleen stromal cell line (MSS62), and maintained under stromal cell layer, where they retained their invasive ability in the restricted space between the stromal cell layer and culture substratum (DFC culture). DFC contained lineage-negative (Lin-), c-Kit+, Sca-1- cells and spontaneously produced Mac-1+, Gr-1+ cells. DFC could not grow in the absence of MSS62 stromal cells, although, GM-CSF, IL-3, or IL-7 stimulated its growth. Production of granulocyte and monocytic cells was maintained by GM-CSF or IL-3 while it was decreased by IL-7. RT-PCR analysis showed that the IL-7 responsive cell population expressed early lymphoid markers (Ikaros, Pax-5, Oct-2, Rag-1, TdT, IL-7R and Imu), while lacking expression of receptors for G-CSF (G-CSFR) and for M-CSF (M-CSFR), or myeloperoxidase (MPO). These results suggested that DFC simultaneously contained lymphoid-committed progenitors and myeloid-committed progenitors, and that cytokines may expand their responding progenitor cells under the influence of signals provided by the stromal cells. Such a stromal cell-dependent culture system may be useful to analyze the switching mechanism from constitutive to inducible hematopoiesis in vitro.

Effect of human granulocyte-macrophage colony stimulating factor (hGM-CSF) on lymphoid and myeloid differentiation of sorted hematopoietic stem cells from hGM-CSF receptor gene transgenic mice

Bone marrow lineage-negative (Lin(-)) c-Kit(+) Sca-1(+) hematopoietic cells from human GM-CSF receptor gene transgenic mice were cultured on established bone marrow stromal cell (TBR59) layers and on semisolid medium. In the semisolid assay, an increasing number of larger colonies were observed in the presence of hGM-CSF. By coculture with the stromal cells, cobblestones containing myeloid and lymphoid lineages of cells were formed from the stem cell enriched fraction, and addition of hGM-CSF strongly stimulated formation of the cobblestones containing both lineages. Repeating passages of the cobblestones on TBR59 stromal cells in the presence of hGM-CSF gradually decreased cobblestone formation and inversely increased macrophages and granulocytes, while mast cells were generated when the cells derived from the semisolid assay were cultured in a liquid medium containing hGM-CSF. These results consistently suggest that cytokines such as GM-CSF may costimulate the immature hematopoietic cells at their stroma-dependent phase before lineage commitment, and after commitment that occurs by an intrinsic program of the cells, they may stimulate maintenance and maturation of progenitor cells.

Apoptosis of fetal testicular cells is regulated by both p53-dependent and independent mechanisms

A portion of fetal germ cells undergoes apoptosis in the physiological context, but the molecular mechanisms of their apoptosis are largely unknown. Because p53 tumor suppressor gene product promotes apoptosis in various types of cells, we have investigated the expression of p53 in fetal gonads and examined the influence of loss of p53 function in fetal gonad cells using mice deficient in the p53 gene. We found that the expression of p53 protein in fetal testis was induced after 15.5 dpc (days post coitum), while the expression was not detected in fetal ovary. The number of apoptotic cells found in the seminiferous tubules of fetal testes was not significantly different between p53-deficient and wild-type mice until 16.5 dpc. At 17.5 dpc, however, more apoptotic cells were observed in wild-type testes than in the p53-deficient mice. In contrast, a similar number of apoptotic cells was found in fetal ovaries throughout these developmental stages. These observations indicate that p53 promotes apoptosis of fetal testicular cells after 16.5 dpc.

Multipotency of a bone marrow stromal cell line, TBR31-2, established from ts-SV40 T antigen gene transgenic mice

Bone marrow is believed to contain multipotential stromal stem cells which can differentiate into osteoblasts, chondrocytes, adipocytes, and myoblasts (Prockop, D. J. Science 276, 71-74, 1997). Therefore, characterization and identification of the stem-like cell within the stromal cells are important to understand bone marrow function in relation to the hematopoietic microenvironment, and repair/regeneration of tissue defects. TBR31-2 cell, a bone marrow stromal cell line established from bone marrow of transgenic mice harboring temperature-sensitive (ts) simian virus (SV) 40T-antigen gene for immortality, is induced toward both adipocytic and osteogenic cells under conditions of the inactivation of T-antigen (Okuyama, R., Yanai, N., Obinata, M. Exp. Cell Res. 218, 424-429, 1995). In this work, using a semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, mRNA expressions of tissue-specific differentiation markers for adipocyte (lipoprotein lipase), osteoblast (type I collagen and osteocalcin), chondrocyte (type II and X collagen), and muscle cell (desmin) were examined during a long-term culture of the cell. In addition, histochemical studies showed the appearance of adipocytic, osteoblastic, chondrocytic, and muscle cells during this long-term culture. Thus, TBR31-2, which has characteristics of an undifferentiated cell, has the potential to express the multipotential cell lineages. These results indicated that a multipotential progenitor cell including potential to differentiate into a muscle cell and which is situated in the mesenchymal cell lineage was first obtained.

MIDA1, an Id-associating protein, has two distinct DNA binding activities that are converted by the association with Id1: a novel function of Id protein

Id proteins not only regulate cell differentiation negatively, but they also promote growth, immortalization, and apoptosis. To know the mechanism of how Id regulates cell fate, we previously isolated an Id-associating protein, MIDA1, which positively regulates cell growth (1). Its predicted amino acid sequence consists of a Zuotin (a Z-DNA binding protein in yeast) homology region and tryptophan-mediated repeats (Tryp-med repeats). MIDA1 exhibits a sequence-specific DNA binding activity through the Tryp-med repeats (manuscript in preparation). In this study, we revealed that, like Zuotin, MIDA1 can specifically bind to Z-DNA. This suggested that MIDA is a novel DNA binding protein that has two different DNA binding activities. Furthermore, association of Id1 with MIDA1 stimulated the sequence-specific DNA binding activity, while it inhibited the Z-DNA binding activity. Therefore, we concluded that MIDA1 may act as a mediator of the growth-promoting function of Id, by switching the two DNA binding activities of MIDA1.

Effects of p51/p63 missense mutations on transcriptional activities of p53 downstream gene promoters

The p51/p63 gene is a homologue of p53, the product of which acts as a transcriptional activator by binding to p53-responsive elements in the promoter regions of several p53 downstream genes. Recently, we identified four distinct mutations in the p51/p63 gene after screening >200 human tumors and cell lines. Because all of the detected p51/p63 mutations were missense mutations, the pathogenic effect of these mutations is difficult to determine without performing a functional analysis. In this study, we examined the transcriptional activity of tumor-derived p51/p63 missense mutations using a yeast-based assay and compared the data with that of artificial p51/p63 missense mutations at residues corresponding to the positions and substituted residues of p53 mutation "hotspots." Although most of the p51/p63 missense mutations at the p53 hotspot residues were unable to transactivate the promoters used in this study, the tumor-derived p51/p63 missense mutations retained their ability to transactivate the MDM2 and/or the BAX promoter but not the p21/WAF1 promoter. These results suggest that the p51/p63 mutation might be involved in an unknown tumor suppression pathway distinct from that of p53.

Germline-specific expression of the Oct-4/green fluorescent protein (GFP) transgene in mice

The Pic-1, Oct-1,2, Unc-86 (POU) transcription factor Oct-4 is specifically expressed in the germ cell line, and a previous study has indicated that the expression of the lacZ gene inserted into an 18 kb genomic fragment encompassing the Oct-4 gene can come close to mimicking the endogenous embryonic expression pattern of Oct-4 in transgenic mice. In the present study transgenic mice expressing green fluorescent protein (GFP) in the germ cell line were generated using the same Oct-4 genomic fragments and the expression pattern was analyzed in detail through all stages of germ cell development. The GFP expressing primordial germ cells were first detected as early as 8.0 days post-coitum (d.p.c.; early head fold stage) at the base of the allantois in living embryos. The GFP expression was thereafter found in both male and female germ cells at all developmental stages except in male germ cells after differentiating into type A spermatogonia in the postnatal testis. There was also a lower level of expression in female germ cells in the prophase of the first meiotic division. These transgenic mice therefore proved to be powerful tools for isolating living germ cells at various developmental stages to study their nature and to isolate new genes.