Otx1 function overlaps with Otx2 in development of mouse forebrain and midbrain

BACKGROUND

We previously reported that the homozygous mutation of Otx2 gene, a mouse cognate of the Drosophila head gap gene orthodenticle, causes failure in the development of the rostral head anterior to rhombomere 3, which may correspond to earlier Otx2 expression in cells destined for the anterior mesoendoderm. At the same time, the Otx2 heterozygous mutation displayed a phenotype characterized as otocephaly, probably related to expression in the anterior neuroectoderm at the subsequent pharyngula stage. Defects were characteristic in the most anterior and posterior regions of Otx2 expression where Otx1, another mouse cognate of orthodenticle, is not or weakly expressed. They were not found in the region where Otx1 is expressed.

RESULTS

In the present work, Otx1 null mutant mice were generated by gene targeting in embryonic stem cells. No defects were apparent in the regionalization of the early embryonic rostral brain. The newborn brain defects were subtle and most likely related to later Otx1-unique expression. Otx1 and Otx2 double heterozygous mutant brains, however, exhibited marked defects throughout the fore- and midbrains, where defects were not apparent with a single mutation alone.

CONCLUSIONS

Otx1 and Otx2 play synergistic roles in the development of the forebrain and midbrain where both genes are expressed.

Mitochondrial encephalomyopathies preceded by de-Toni-Debré-Fanconi syndrome or focal segmental glomerulosclerosis

We report two rare cases of mitochondrial encephalomyopathies which were preceded by renal diseases. One occurred in an 11-year-old girl diagnosed with Kearns-Sayre syndrome, which was preceded by de-Toni-Debré-Fanconi syndrome 8 years previously. The other occurred in a 14-year-old girl diagnosed with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes, who developed focal segmental glomerulosclerosis 3 years prior to confirmation of the diagnosis. Tissue from both patient demonstrated morphological abnormalities of the mitochondria in the distal renal tubular epithelium and leiomyocytes of the small renal artery. The present cases illustrate various clinical and morphologic evidence of renal diseases which may further our understanding of mitochondrial encephalomyopathies.

Fracture healing is a process independent of p53 function

We studied the role of the tumor suppressor gene p53 in the process of fracture healing using mice with a p53 gene deficiency. Fractures produced in femoral shafts of mice without a functional p53 gene (p53-/-) healed as well as those in wildtype mice (p53 +/+), and no tumor development was observed at the fracture site even after complete bone union. Formation of granulation tissue and cartilage, ossification and remodeling into mature trabecular and cortical bone showed no abnormalities in p53-/- mice. Apoptotic cells were found to be sparse in the ossifying zone of the fracture callus using in situ DNA nick end-labeling in mice of both genotypes, without any significant difference. These results indicate that apoptosis in fracture healing, even if it does play a significant role, occurs through a p53-independent pathway.

Establishment of a therapeutic model for retroviral infection using the genetic resistance mechanism of the host

Resistance to retroviral infection is often regulated by multiple genes that control different aspects of the host-virus interaction. Genetically distinct inbred strains of mice differ in their susceptibility to retrovirus and have allowed the identification of several host-resistant loci that regulate the host defense mechanism to retroviral infection. Using the murine retrovirus infection system, a therapeutic model has been developed of retrovirus infection in association with the resistant mechanism of host genes. The most effective result achieved with the model was when using bone marrow transplantation of retrovirus-resistant cells with receptor interference function, which was genetically defined by the Fv-4 resistant gene. The possible application of these findings to the gene therapy of retrovirus-induced disease of humans is discussed.

A variant CD30 protein lacking extracellular and transmembrane domains is induced in HL-60 by tetradecanoylphorbol acetate and is expressed in alveolar macrophages

We identified and cloned cDNAs for two novel CD30 mRNAs of 2.3 kb that are induced by 12-O-tetradecanoylphorbol 13-acetate (TPA) in the human myeloid leukemia cell line HL-60. These transcripts were transcribed from the intronic region just upstream of the exon coding for the transmembrane domain of the CD30 protein. The shorter cDNA had a deletion of 54 nucleotides corresponding to the 3' region of the transmembrane domain of the CD30 and which was probably caused by alternative splicing. Translation of these transcripts appeared to start from the internal methionine codon at nucleotide position 289 that corresponds to that of 1612 in the CD30 cDNA, and encode a protein of 132 amino acid residues which corresponds exactly to the C-terminal cytoplasmic domain of CD30 protein. The calculated molecular mass of this variant CD30 (CD30v) protein was 14,087. Thus, the predicted CD30v protein retains most of the cytoplasmic region, but lacks the extracellular and transmembrane domains. Northern blots detected the expression of CD30v transcripts only in the lung and the TPA-stimulated HL-60 cell line. Translation of this mRNA in vitro produced a protein of 25 kD. Immunoblotting analysis with HCD30C1, a rabbit polyclonal antibody raised against the cytoplasmic domain of CD30 protein, detected proteins with an apparent Mr 25 kD expressed in TPA-stimulated HL-60 and COS-7 cells that were transfected with both types of CD30v cDNAs. Constitutive phosphorylation of the CD30v protein was demonstrated by in vitro labeling with [32P]. Immunohistochemical studies demonstrated CD30v protein was in alveolar macrophages. Cotransfection experiments using a kappa B-site-dependent reporter construct showed that CD30v can transactivate gene expression through activation of NF kappa B, as was noted on the authentic CD30 protein. Overexpression of the CD30v induced differentiation of HL-60 cells as evidenced by an increased NBT reduction activity. These observations provided new insights into the molecular heterogeneity and biological function of CD30 in myeloid cells.

Distribution of Fv-4 resistant gene product in Friend leukemia virus-resistant Fv-4r mouse strain

Fv-4 is a mouse gene that dominantly confers resistance to infection by ecotropic murine leukemia virus (MuLV). We demonstrated previously that the Fv-4 resistant (Fv-4r) gene product, Fv-4r env antigen, is released from Fv-4r-bearing BALB/c-Fv-4Wr (C4W) mouse-derived cells into serum in vivo and binds to cells expressing surface receptors for ecotropic MuLV, thereby protecting them from infection with Friend leukemia virus (FLV) by receptor interference. This unique resistance mechanism against retroviral infection might provide a possible therapeutic model system of human retroviral infection such as AIDS. To further investigate the Fv-4r gene action in vivo, we examined the distribution and character of Fv-4r env antigen in serum and systemic organs from C4W mice. The Fv-4r env antigen was immunohistochemically localized to the lympho-hematopoietic cells and exocrine glandular cells, such as those of the salivary gland and pancreas. Using immunoprecipitation followed by Western blotting, we determined two types of gp70-related Fv-4r env antigen in the serum of C4W mice, showing molecular weights of either 70-75 kDa and 80-85 kDa. When thymocytes from Fv-4 susceptible gene (Fv-4r)-bearing C3H mouse were mixed with C4W mouse serum, the 70-75k Da molecule of the C4W serum dominantly bound to C3H thymocytes and thus contributed to receptor interference function. Using immunoelectron microscopy, Fv-4r env antigen was mainly localized to the cell surface membrane of thymic lymphoid cells, while acinar cells of the salivary gland possessed Fv-4r env antigen in the endoplasmic reticulum (ER) as well as on the cell surface membrane. These data indicate that several glandular organs, as well as lymphohematopoietic organs of C4W mice, may contribute to the production of cell-free Fv-4r env antigen, resulting in protection of cells from infection with FLV by receptor interference.

[Clinicopathological study on patients with chromophobe cell renal carcinoma]

BACKGROUND

Reports on the patients with chromophobe cell renal carcinoma were very few. Therefore, the clinical features of this disease are uncertain. Based upon this background, we have studied on the clinicopathological characteristics of chromophobe cell renal carcinoma.

PATIENTS AND METHODS

From 1957 to 1995, seven hundred and fifty-one patients with renal cell carcinoma (RCC) were treated at the Jikei University Hospitals. Of these patients, 36 (4.8%) with chromophobe cell renal carcinoma were diagnosed by histopathological examination. Of these 36 patients, the objective patients were 34 who could be followed-up along with long interval.

RESULTS

The age distribution was 28 to 83 years old (mean was 54.1 years). Regarding to the sex difference, there observed male in 22 patients and female in 12 patients (sex ratio was 1.8: 1). Furthermore, the affected side was even, but there observed the symptoms of urinary tract mainly of haematuria in 24 patients (76.5%). As to the laboratory examination, there observed the abnormality of the acute phase reactants in 20% of patients. The greater diameter of the tumour was distributed from 1.5 to 17 cm (mean: 6.9 cm), and no consistent tendency of tumour localization was observed. Regarding the preoperative angiography, there observed the hypovascular/ avascular pattern in 15 patients (44.1%). As to the stage and grade, there observed the low stage patients in 30 (88.2%) and low grade patients in 27 (79.4%). With respect to the prognosis, the 1, 3, 5, 10, 15 and 20 years survival rates for chromophobe cell renal carcinoma were 97.1%, 81.6%, 81.6%, 70.2%, 61.9% and 46.7% respectively. After comparing the survival rate of the same stage and grade patients between the objected patients and the common types of RCC, there observed a favourable prognosis in the patients with chromophobe cell renal carcinoma. Especially in patients with eosinophilic variant, no cancer related death was observed.

CONCLUSION

The clinicopathological characteristics of chromophobe cell renal carcinoma show the hypovascular/avascular in angiography, low rate of laboratory abnormality, low stage/ low grade and a favourable prognosis compared with the common types of RCC.

Mice with disrupted GM2/GD2 synthase gene lack complex gangliosides but exhibit only subtle defects in their nervous system

Gangliosides, sialic acid-containing glycosphingolipids, are abundant in the vertebrate (mammalian) nervous system. Their composition is spatially and developmentally regulated, and gangliosides have been widely believed to lay essential roles in establishment of the nervous system, especially in neuritogenesis and synaptogenesis. However, this has never been tested directly. Here we report the generation of mice with a disrupted beta 1,4-N-acetylgalactosaminyltransferase (GM2/GD2 synthase; EC 2.4.1.92) gene. The mice lacked all complex gangliosides. Nevertheless, they did not show any major histological defects in their nervous systems or in gross behavior. Just a slight reduction in the neural conduction velocity from the tibial nerve to the somatosensory cortex, but not to the lumbar spine, was detected. These findings suggest that complex gangliosides are required in neuronal functions but not in the morphogenesis and organogenesis of the brain. The higher levels of GM3 and GD3 expressed in the brains of these mutant mice may be able to compensate for the lack of complex gangliosides.

UV-induced mutations of supF gene on a shuttle vector plasmid in p53-deficient mouse cells are qualitatively different from those in wild-type cells

To verify the genetic instability of p53-deficient cells, UV-induced mutation of the supF gene on a shuttle vector was analyzed. UV-irradiated or non-irradiated shuttle vector plasmid carrying the supF gene as a target of mutation (pYZ289) was introduced into p53-deficient and p53-proficient mouse embryonic fibroblasts, and then the plasmid DNA replicated in mouse cells was recovered. Survival of UV-irradiated plasmid was almost equivalent in both p53-deficient and p53-proficient cells. The frequencies of UV-induced mutation of the supF gene were also the same in both types of cells. However, the distributions of base change mutations in the supF sequence were different between p53-deficient and p53-proficient cells; especially the locations of tandem CpC to TpT changes exhibited a marked difference. Since DNA repair activities of these two types of cell were almost the same, these qualitative differences in UV-induced mutations were probably caused by as yet unidentified differences in other than DNA repair activity.

Involvement of p53 in DNA strand break-induced apoptosis in postmitotic CNS neurons

The tumour suppressor p53 gene serves as a critical regulator of the cell cycle and of apoptosis following the exposure of normal cells to DNA damage. To examine the role of p53 in postmitotic CNS neurons, we cultured cerebellar neurons from normal wild-type mice and mutant p53-null mice under various conditions inducing neuronal death. When cerebellar neurons from 15- to 16-day postnatal wild-type mice were treated with ionizing radiation or DNA-damaging agents, massive neuron death occurred after 24-72 h. In contrast, neurons from p53-/- mice evidently resisted gamma-irradiation and some DNA-damaging agents, such as etoposide and bleomycin. On the other hand, low-K+ medium-induced apoptosis of cerebellar neurons was not affected by p53 status. Neither cell cycle progression nor DNA synthesis occurred during cell death induced by gamma-irradiation and low-K+ medium, as well as in normal cultures of p53+/+ and p53-/- neurons. These results suggest that p53 is required for the apoptotic death of postmitotic cerebellar neurons induced by DNA strand breaks.

Replication errors in hematological neoplasias: genomic instability in progression of disease is different among different types of leukemia

Genetic alteration, including genomic instability, is an ultimate step toward the malignant process. One approach to delineating replication errors in cancer cells is to determine the alterations of microsatellites, which are short, repeated nucleotide sequences existing throughout the genomes. We used a fluorescent system to assess microsatellite changes in seven loci (D2S123, D3S643, D5S107, LPL, D17S261, TP53, and D18S34) of 73 consecutive patients with various hematological neoplasias. De novo acute leukemia patients had a low frequency (<1%) of microsatellite alterations at each locus, and none of them demonstrated multiple microsatellite changes. In chronic myeloid leukemia patients, no microsatellite instability was detected in the chronic phase, whereas a relatively high frequency (25%) of multiple microsatellite changes was evident in the blastic phase, and half of these patients had multiple microsatellite changes. About 50% of the patients with myelodysplastic syndrome (MDS) and post-MDS acute myeloid leukemia (post-MDS AML) had microsatellite alterations. We next compared microsatellite alterations in two different hematological phases (MDS and post-MDS AML phases); 5 of 11 patients with post-MDS AML had de novo appearance of microsatellite instability during disease progression. This indicates that genomic instability at multiple microsatellite loci could occur either before or after leukemic transformation in MDS patients. We concluded that genomic instability in chronic myeloid leukemia might be linked to blastic transformation in combination with cytogenetic changes. In contrast, MDS patients had replication errors as a relatively early genetic event as well as a late genetic event. These results suggest that the involvement of genomic instability in the progression of disease is different among various types of leukemia.

Insulin resistance and growth retardation in mice lacking insulin receptor substrate-1 and identification of insulin receptor substrate-2

To clarify the physiological roles of insulin receptor substrate-1 (IRS-1) in vivo, we made mice with a targeted disruption of the IRS-1 gene locus. Mice homozygous for targeted disruption of the IRS-1 gene were born alive but were retarded in embryonal and postnatal growth. They also had resistance to the glucose-lowering effects of insulin, insulin-like growth factor-1 (IGF-1) and factor-2 (IGF-2). These data suggest the existence of both IRS-1-dependent and IRS-1-independent pathways for signal transduction of insulin and IGFs. Moreover, we identified tyrosine phosphorylation of a 190-kDa protein (pp 190) as a novel substrate (IRS-2) for insulin receptor kinase in livers of IRS-1 deficient mice which can bind both P13-kinase and Ash/Grb2.

Cooperation of the tumour suppressors IRF-1 and p53 in response to DNA damage

Normally growing cells promptly cease DNA synthesis when exposed to genotoxic stresses, such as radiation, and this cell-cycle arrest prevents the accumulation of mutations. The transcription factor interferon regulatory factor (IRF)-1 is essential for the regulation of the interferon system, inhibits cell growth, and manifests tumour-suppressor activities. Here we show that mouse embryonic fibroblasts (EFs) lacking IRF-1 are deficient in their ability to undergo DNA-damage-induced cell-cycle arrest. A similar phenotype has been observed in EFs lacking the tumour suppressor p53 (refs 8, 9), although the expression of IRF-1 and p53 are independent of one another. Furthermore, we show that transcriptional induction of the gene encoding p21 (WAF1, CIP1), a cell-cycle inhibitor, by gamma-irradiation is dependent on both p53 and IRF-1, and that the p21 promoter is activated, either directly or indirectly, by both in a transient cotransfection assay. These two tumour-suppressor transcription factors therefore converge functionally to regulate the cell cycle through the activation of a common target gene.

P53 protein expression in pancreatic tumors and its relationship to clinicopathological factors and prognosis

We examined the expression of p53 protein by immunohistochemical method in a series of pancreatic tumors and evaluated its relationships to the clinicopathological factors and prognosis. The study involved 108 cases of pancreatic tumors (79 ductal carcinomas, 1 acinar cell carcinoma, 14 endocrine tumors, 6 solid cystic tumors, 8 benign ductal tumors) and 8 chronic pancreatitides. Thirty-nine cases of pancreatic ductal carcinoma (49.4%) were positive for p53 protein. Analysis of the Cox hazards model identified p53 positivity and stage at the initial operation as an independent prognostic factor. Patients with p53 positive ductal carcinomas had a greater risk of death compared to p53 negative cases (P < 0.05). There was, however, no statistically significant correlation between p53 protein expression and other clinicopathological factors. Cases of stage III and IVb with positive p53 showed a bleak prognosis compared to p53 negative cases (P < 0.05). Our results suggest that p53 expression is common in invasive pancreatic ductal carcinomas and may have a prognostic value.

[Image cytometric DNA analysis in bladder tumors]

We studied image cytometric DNA analysis of bladder tumors to evaluate malignant potentials of bladder tumors.

METHODS

Thirty nine samples were obtained by TUR from 37 patients. Nuclear DNA content of all samples were measured by image cytometer and were determined ploidy pattern by DNA histogram.

RESULTS

Of 39 TCC non-diploid pattern was recognized in 50% of grade 1 cases, 73% of grade 2 cases and 100% of grade 3 cases. DNA ploidy was strictly correlated with histological grading in TCC. DNA non-diploid pattern was present in 67% of papillary tumors, 87.5% of non-papillary tumors and 100% in CIS. In diploid pattern 2 of 7 cases with grade 1 and 2 of 4 cases with grade 2 recurred. In non-diploid pattern 1 of 4 cases with grade 1, 4 of 10 cases with grade 2 and 4 of 6 cases with grade 3 recurred. There was no significant correlation between diploid and non-diploid pattern in grade 1, 2, 3.

CONCLUSION

Image cytometric DNA analysis may be useful in addition to the classic and prognostic parameters of stage and grade, especially in TCC. The differences between image analysis system and flow cytometric analysis for DNA measurement were discussed.

Clinicopathologic and mucin histochemical analyses of 90 cases of ovarian mucinous borderline tumors of intestinal and müllerian types

Clinicopathologic and mucin histochemical characteristics of 90 cases of ovarian mucinous borderline tumors (MBT) of intestinal (IMBT) and müllerian types (MMBT) were studied to determine whether IMBT and MMBT constitute distinct tumor subtypes. The IMBT (77 cases, 78 lesions) contained goblet cells, absorptive cells and endocrine cells, which represented intestinal differentiation. The average diameter of IMBT was 13.4 cm. Five patients (6.5%) had stage III disease with pseudomyxoma peritonei and one of them died from tumor. Approximately 50% of IMBT demonstrated gastrointestinal characteristics on mucin histochemistry. The MMBT (13 cases, 14 lesions) consisted of mucous columnar cells and eosinophilic cells, with no intestinal differentiation. MMBT accounted for 15.2% of MBT. MMBT averaged 8.4 cm in diameter, and 29% were associated with endometriosis of the Ipsilateral ovary. All patients with MMBT had stage I disease, and none suffered from pseudomyxoma peritonei. All patients whose follow-up data were available were alive and well, without evidence of tumor recurrence. The mucin histochemical findings in MMBT resembled those of normal endocervix. Results of the present study suggest that IMBT and MMBT have different characteristics and constitute distinct subtypes of MBT.

Analysis of CSK homologous kinase (CHK/HYL) in hematopoiesis by utilizing gene knockout mice

CHK/HYL is a non-receptor tyrosine kinase that belongs to CSK (C-terminal Src kinase) family. Northern blotting and RT-PCR analyses showed that CHK/HYL was expressed in large spectrum of hematopoietic cells except for erythroid cells and brain. To explore the function of CHK/HYL in hematopoietic cells, we generated CHK/HYL deficient mice. The mutant mice were apparently normal and fertile, while CSK knockout mice died until E11.5 from a defect in the neural tube formation. Hematological observations including blood counts and FACS analysis showed no significant abnormalities in CHK/HYL mutant mice. CHK/HYL did not affect the activity of Src, Hck, and Fgr in cultured bone marrow cells, although CSK negatively regulates Src family kinases. These results suggest that CHK/HYL might not have the same function as CSK.

Impaired development of CD4+ CD8+ thymoyctes by csk-'knock-in' into fyn locus

p59fyn is one of the Src-family kinases thought to play an important role in signaling through T cell receptor. However, Fyn deficiency has caused no overt defects in vivo on T cell development, nor has it caused any changes in the phosphorylation status of molecules such as ZAP-70 which have been proposed as p59fyn substrates. This could be explained as being due to compensation of Fyn deficiency by other Src-family kinases. Here, we have 'knocked-in' the csk gene, a negative regulator of Src-family kinases, into fyn locus to challenge the problem of redundant functions among Src-family kinases. The csk-'knock-in' mice displayed atrophy of the thymic cortex and impaired development of CD4+ CD8+ thymocytes. This was concomitant with decrease in tyrosine phosphorylation of ZAP-70 and p120cbl.

P53 gene deficiency does not enhance instability of mouse minisatellites in somatic cells of normal tissues

The effect of p53-deficiency on somatic mutation of minisatellites in normal tissues was examined using p53-deficient (-/-) mice. In total, 248 mice consisting of three different genotypes, +/+, +/ -and -/-, were obtained and DNA from their embryos was probed with two minisatellites, Pc-1 and Pc-2. The somatic mutation was detected by Southern blot hybridization as the presence of a third nonparental band reflecting mosaicism in tissues. Mutation frequency of Pc-1 for (+/+) and (+/-) was 1.3% and 1.4%, respectively, which is consistent with previous studies. On the other hand, none of the mice lacking the p53 gene (-/-) exhibited mutation. The Pc-2 probe did not show any somatic mutation in the three groups. These results suggest that the p53 deficiency does not enhance the genomic instability of the minisatellite loci in normal somatic cells.

Application of primary hepatocytes from p53-knockout mice for studies of expression of Cyp3a

CYP3A rapidly disappears in primary hepatocytes, although the primary cells are suitable for studies of the regulation of CYP3A genes. In the present study, we found that Cyp3a mRNA could be expressed in the primary hepatocytes from p53-knockout mice for at least 2 weeks when the cells were cultured in the presence of dexamethasone. Propoxycoumarin O-depropylase activity, which is known to be mainly catalyzed by CYP3A, was maintained at a level of 50% of the initial activity even after 5 days of culture, and the activity correlated with the expression level of Cyp3a mRNA in the primary hepatocytes from p53-knockout mice. The cells remained morphologically intact during 4 weeks. These results suggest that hepatocytes from p53-knockout mice are a useful tool for studies of the expression of Cyp3a.

Introduction of p130cas signaling complex formation upon integrin-mediated cell adhesion: a role for Src family kinases

Integrin-mediated cell adhesion triggers intracellular signaling cascades, including tyrosine phosphorylation of intracellular proteins. Among these are the focal adhesion proteins p130cas (Cas) and focal adhesion kinase (FAK). Here we identify the kinase(s) mediating integrin-induced Cas phosphorylation and characterize protein-protein interactions mediated by phosphorylated Cas. We found that expression of a constitutively active FAK in fibroblasts results in a consecutive tyrosine phosphorylation of Cas. This effect required the autophosphorylation site of FAK, which is a binding site for Src family kinases. Integrin-mediated phosphorylation of Cas was not, however, compromised in fibroblasts lacking FAK. In contrast, adhesion-induced tyrosine phosphorylation of Cas was reduced in cells lacking Src, whereas enhanced phosphorylation of Cas was observed Csk- cells, in which Src kinases are activated. These results suggest that Src kinases are responsible for the integrin-mediated tyrosine phosphorylation of Cas. FAK seems not to be necessary for phosphorylation of Cas, but when autophosphorylated, FAK may recruit Src family kinases to phosphorylate Cas. Cas was found to form complexes with Src homology 2 (SH2) domain-containing signaling molecules, such as the SH2/SH3 adapter protein Crk, following integrin-induced tyrosine phosphorylation. Guanine nucleotide exchange factors C3G and Sos were found in the Cas-Crk complex upon integrin ligand binding. These observations suggest that Cas serves as a docking protein and may transduce signals to downstream signaling pathways following integrin-mediated cell adhesion.

Immunohistochemical localization of the epidermal growth factor-receptor in rhesus-monkey prostate

Epidermal growth-factor receptor (EGF-r), a membrane-bound glycoprotein activated by EGF, is important in maintaining the integrity and function of the prostate. To investigate EGF-r presence in the prostate of the rhesus monkey, monoclonal-antibody immunohistochemical examination was performed. The monkey prostate consisted of the cranial and caudal lobes, and the prostatic epithelial cells were composed of the secretory and basal cells. The distribution patterns of EGF-r in the prostatic epithelial cells were quite different between the cranial and caudal lobes. In the caudal lobe, EGF-r was seen in both secretory and basal cells, whereas, in the cranial lobe, the EGF-r was seen exclusively in the basal cells. The stromal cells of both lobes did not show EGF-r. This study revealed that each prostatic lobe contains specific binding sites for EGF, indicating a biological difference between the two lobes of the prostate of the rhesus monkey.

Insulin signalling and insulin actions in the muscles and livers of insulin-resistant, insulin receptor substrate 1-deficient mice

We and others recently generated mice with a targeted disruption of the insulin receptor substrate 1 (IRS-1) gene and demonstrated that they exhibited growth retardation and had resistance to the glucose-lowering effect of insulin. Insulin initiates its biological effects by activating at least two major signalling pathways, one involving phosphatidylinositol 3-kinase (PI3-kinase) and the other involving a ras/mitogen-activated protein kinase (MAP kinase) cascade. In this study, we investigated the roles of IRS-1 and IRS-2 in the biological action in the physiological target organs of insulin by comparing the effects of insulin in wild-type and IRS-1-deficient mice. In muscles from IRS-1-deficient mice, the responses to insulin-induced PI3-kinase activation, glucose transport, p70 S6 kinase and MAP kinase activation, mRNA translation, and protein synthesis were significantly impaired compared with those in wild-type mice. Insulin-induced protein synthesis was both wortmannin sensitive and insensitive in wild-type and IRS-1 deficient mice. However, in another target organ, the liver, the responses to insulin-induced PI3-kinase and MAP kinase activation were not significantly reduced. The amount of tyrosine-phosphorylated IRS-2 (in IRS-1-deficient mice) was roughly equal to that of IRS-1 (in wild-type mice) in the liver, whereas it only 20 to 30% of that of IRS-1 in the muscles. In conclusion, (i) IRS-1 plays central roles in two major biological actions of insulin in muscles, glucose transport and protein synthesis; (ii) the insulin resistance of IRS-1-deficient mice is mainly due to resistance in the muscles; and (iii) the degree of compensation for IRS-1 deficiency appears to be correlated with the amount of tyrosine-phosphorylated IRS-2 (in IRS-1-deficient mice) relative to that of IRS-1 (in wild-type mice).

Src kinase plays an essential role in integrin-mediated tyrosine phosphorylation of Crk-associated substrate p130Cas

A novel signaling molecule p130Cas has been shown to undergo tyrosine phosphorylation in response to integrin-mediated cell adhesion. In this study, we have attempted to identify kinases that mediate Cas phosphorylation in integrin signaling by examining various mutant cell lines that do not express either p125FAK, c-Scr, c-Fyn or c-Abl. We found that deficiency of c-Src but not of other kinases completely abrogated integrin-mediated Cas phosphorylation. Importantly, paxillin phosphorylation was not compromised in each mutant cell line examined. These results suggest that c-Src primarily mediates adhesion-dependent Cas phosphorylation. As for paxillin phosphorylation, there may exist substantial redundancy amongst multiple kinases. Finally, adhesion-induced Cas phosphorylation resulted in its association with c-Crk adapter protein via the Crk-SH2 domain. Thus, Cas plays a role in the transmission of integrin-initiated signals through tyrosine phosphorylation and subsequent binding to c-Crk.

A follistatin-like gene, mac25, may act as a growth suppressor of osteosarcoma cells

mac25, a retinoic acid-inducible gene that is expressed at high levels in senescent epithelial cells, was initially cloned as a gene that is differentially expressed in meningioma. Although the homology of its product with members of family of insulin-like growth factor-binding proteins was suggested, the product also exhibits strong homology to follistatin, an activin-binding protein. However, a domain corresponding to the carboxyl terminus of follistatin is not found in mac25. The carboxyl-terminally truncated form of follistatin, generated by alternative splicing, has stronger activin-binding activity than the complete form. This result suggests that mac25 might act as an activated follistatin. Clonal growth of a p53-deficient osteosarcoma cell line was strongly inhibited when the murine mac25 gene, as well as the p53 gene, was introduced. Resembling activins that belong to the transforming growth factor-beta (TGF-beta) superfamily, mac25 and p53 might associate with similar but distinct targets, namely cyclin-dependent kinase inhibitors. However, there is no evidence for compensation of p53 function by mac25 in the development of p53-deficient mice, as judged from the pattern of expression of mac25 in mice. mac25 might act as a tumor suppressor, modulating signaling of the TGF-beta family, as does alpha-inhibin.