Cell type-specific expressions of c-ras gene products in the normal rat

Age-dependent alterations in expression and co-localization of Pax6 and Ras-GAP in brain of aging mice

As the brain ages, the survival and plasticity of neurons and glia are compromised. The data-mining and in silico studies suggest interactions of Pax6 with Ras and binding sites in Ras-GAP promoter. The Pax6 also shows age-dependent alterations. Therefore, it is presumed that Pax6 may be associated with the Ras-GAP, a synaptic protein, either directly or indirectly in brain. The expression, co-localization and interaction of Pax6 and Ras-GAP in different regions of brain of mice during aging were investigated through immunofluorescence assay, co-immunoprecipitation and western blotting, respectively. The co-localization of Pax6 and Ras-GAP were observed in dentate gyrus (DG) and sub-granular zone (SGZ) of hippocampus, in glomerular (GlLa) and mitral cells (MiCe) of olfactory lobe, granular cells (GrCe), Purkinje cell (PuCe) and molecular cell layer (MoLa) of cerebellum, internal plexiform layer (InPl), molecular layer (MoLa) of cerebral cortex and in intercalated cells of amygdala (ITC), caudate nucleus regions in brain of aging mice. The expression of Pax6 and Ras-GAP was altered in hippocampus, amygdala, caudate nucleus, olfactory lobe, cerebral cortex and cerebellum from young to old mice. The Pax6 interacts with Ras-GAP in brain of mice. Results indicate impact of Pax6 on Ras-GAP-mediated activities of synapses, learning and memory, emotions and fear as well as motor functions. Alterations in expression and co-localization of Pax6 and Ras-GAP during aging may be responsible for age-associated compromised survival and plasticity of neurons and glia.

Prognostic discrimination among neuroblastomas according to Ha-ras/trk A gene expression: a comparison of the profiles of neuroblastomas detected clinically and those detected through mass screening

BACKGROUND

Neuroblastomas (NBs) exhibit a wide variety of clinical behavior. It is important to determine the biology of NB before treatment is instituted.

METHODS

One hundred six NBs detected clinically (clinical NBs) were classified according to immunohistochemical expression of the Ha-ras and trk A genes. Association of the two-gene expression with patient outcome was examined retrospectively, and the possibility of prognostic prediction was evaluated. The profile of the expression of the two genes in 85 NBs detected through mass screening (mass NBs) was compared with that in clinical NBs.

RESULTS

Ha-rasltrk A expression in clinical NBs was associated with disease free survival, even when the NBs had no amplification of the N-myc gene. Multivariate analysis demonstrated that the expression of Ha-rasl/trk A was a significant prognostic factor that was independent of stage, age at diagnosis, and N-myc amplification. Favorable outcomes of patients with advanced NB were distinguished by high Ha-ras and high trk A expression, and unfavorable outcomes were distinguished by low Ha-ras and low trk A expression. A profile of the two genes in mass NBs was different from that in clinical NBs. Greater than 50% of the mass NBs were detected as localized tumors with high Ha-ras and high trk A expression. The mass screening detected NBs with favorable and unfavorable biology.

CONCLUSIONS

The expression of Ha-ras and trk A is an excellent predictor of both favorable and unfavorable biology in NBs. The information it provides can be important in determining the appropriate therapeutic intervention for each patient.

Ras-GRF, the activator of Ras, is expressed preferentially in mature neurons of the central nervous system

In rodents, the Ras-specific guanine-nucleotide exchange factor (Ras-GRF) is expressed in different areas of the brain and, at a reduced level, also in the spinal cord. No expression of the 140 kDa Ras-GRF was detected in dorsal root ganglia and all other tissues tested. Analysis of primary cultures derived from brain reveals that this exchange factor is only present in neurons of the central nervous system. In primary hippocampal cultures, the expression of Ras-GRF increases in parallel with the onset of a neuronal network and in the whole brain it increases sharply after birth.

trk A gene expression in neuroblastoma. The clinical significance of an immunohistochemical study

BACKGROUND

Neuroblastomas display a spectrum of morphologic and cytologic features of neural cells, and the prognosis of patients with these tumors varies widely. Expression of trk A in these tumors, as documented by Northern blot analysis, is associated with a favorable prognosis. To examine the expression of trk A at the cellular level in individual tumors and apply the results to routine clinical use, the authors designed this immunohistochemical study using an antibody with a predetermined specificity on formalin fixed, paraffin embedded tumor sections.

METHODS

Expression of trk A and Ha-ras genes in 105 neuroblastomas was examined by avidin-biotin-complex immunoperoxidase staining. N-myc gene amplification was examined in 81 of the tumors by Southern blot analysis.

RESULTS

Immunohistochemical expression in tumors correlated strongly with a favorable prognosis for trk A expression (P < 0.0001) and for Ha-ras expression (P < 0.0001). N-myc amplification was found in neuroblastomas with low expression of trk A and of Ha-ras genes. Kaplan-Meier analysis resulted in a favorable outcome associated with high trk A expression and no N-myc amplification, and a poor outcome associated with low trk A expression and demonstrable N-myc amplification (P < 0.0001). Univariate analysis showed that immunohistochemical expression of trk A at the time of diagnosis was a powerful predictor of the patient's prognosis, as were N-myc amplification and Ha-ras expression. trk A expression even correlated significantly with prognosis when the analysis was restricted to Stages III and IV tumors.

CONCLUSIONS

Immunohistochemical detection of the trk A gene product in tumor cells is strongly predictive of a favorable prognosis for patients with neuroblastomas. The coexpression of trk A and Ha-ras genes with clinical behavior of the tumor may indicate close linkage of these genes in the nerve growth factor signal transduction system. Prognostic evaluation at diagnosis based on such molecular and genetic information should be important clinically.

Immunodetection of the p21-ras products in human normal and preneoplastic tissues and solid tumors: a review

Immunohistochemical detection of p21-ras to identify and characterize preneoplastic or neoplastic lesions in human tissues is reviewed. Information concerning the commercially available antibodies is presented. Antibodies DWP, Ras-10, Y13-259, YA6-172, NCC-001, and NCC-004 are fully documented with respect to their behavior in appropriate specificity tests and appear to be reliable reagents. After reviewing the data we have identified three groups of tissues or organs with respect to positive immunostaining for p21-ras as the significant criterion of malignancy. These three groups comprise (1) tissues for which no definite conclusion could be drawn (colon, lung, bladder, ovary, and neural and odontogenic tissues) despite occasional claims to the contrary, (2) tissues for which conclusions were negative (pancreas and stomach), and (3) tissues for which p21-ras staining positively discriminated malignant from normal tissues (liver, uterus, and salivary gland). Immunohistochemically detectable levels of products from a mutated ras gene could be demonstrated in a fraction of the samples from colon, lung, and bladder carcinomas, as well as in some histologically normal tissues adjacent to a colon carcinoma. The possibility that a higher relative intensity of the immunostaining reaction for p21-ras might discriminate malignant tissues from normal tissues or benign lesions in breast, pancreas, stomach, lung, uterus, or thyroid samples is suggested. Further studies now appear warranted and a strategy is proposed to validate the conclusions reached thus far.

Localization of the ras-like rab3A protein in the adult rat brain

Rab3A is a small GTP-binding synaptic vesicle protein, shown to dissociate from synaptic vesicle membranes upon depolarization-induced exocytosis. Using an antiserum raised against rab3A, we found that the antigen was localized to the neuropil of specific brain regions, but was not present in major fiber tracts or most cell bodies. For example, the neuropil of several thalamic nuclei (i.e., dorsal lateral geniculate nucleus, lateral posterior nucleus, ventroposterior nucleus), cerebral cortex, upper layers of the superior colliculus and matrix zones of the neostriatum, were strongly immunoreactive, while the anterior commissure, corpus callosum, optic tract and internal capsule were devoid of staining. The hippocampus, regions of cerebral cortex and the cerebellum exhibited striking laminar distributions of rab3A immunoreactivity. In the hippocampus, dark staining was observed in the stratum oriens, stratum radiatum and molecular layer of the dentate gyrus, while the pyramidal, stratum lacunosum moleculare and dentate granule layers were not stained. In cerebellum the molecular layer and to a lesser extent, the underlying granule cell layer showed enhanced immunoreactivity. Seven days after excitotoxic lesions of the cerebral cortex, rab3A immunoreactivity was diminished in the mirror locus in the contralateral cortical hemisphere and in certain thalamic nuclei ipsilateral to the injection site. These results show that rab3A is localized to a number of specific regions. Its absence from other areas suggests that this synaptic vesicle protein is not universal to all neuronal terminals and pathways. In addition, our lesion studies indicate that for some brain regions, much of the antigen originates in cortical neurons and is distributed within specific axonal projections.

Immunohistochemical detection of ras and myc oncogene expression in regenerating rat liver

The expression of ras and myc oncogene proteins was examined in formalin-fixed paraffin-embedded sections of male Sprague-Dawley rat liver at various times after liver regeneration was induced by either a necrogenic dose of CCl4 or a 2/3 partial hepatectomy. Antibody specific for these proteins and immunohistochemical (IHC) procedures were used to detect oncogene expression in the liver. Increased expression of both oncogene proteins was detected at times comparable to those reported by others using either Northern or Western blot methods. However, the IHC procedure provided additional information since oncogene expression was detected only in hepatocytes, mainly occupying liver lobule zones known to contain proliferating hepatocytes during regeneration. Also, ras and myc stain intensity of individual hepatocytes did not increase during regeneration. Rather, a greater number of hepatocytes were positive at several time points in the regeneration process. This suggested that the increased ras and myc expression detected in Northern and Western blot methods probably represents a greater number of hepatocytes expressing the oncogene proteins rather than increased expression by individual hepatocytes. Overall, this study provides additional information on the cells involved in the expression of the ras and myc oncogenes during regeneration and further substantiates their role in a normal physiological process.

Ontogeny of Ha-ras and c-myc mRNA levels in rabbit embryo and extraembryonic tissues by quantitative in situ hybridization

A large variety of proto-oncogenes are known to be of key importance in cellular growth and differentiation during embryonic development. Using quantitative in situ hybridization, we studied in detail the levels of the proto-oncogenes Ha-ras and c-myc mRNA in embryos and extraembryonic tissues (maternal and embryonic placentas, trophoblast, and endometrial epithelium) during prenatal life of rabbit. cDNA probes encoding for Ha-ras (fragment Kpn 1-BstE II of 883 bp) and c-myc (fragment Pst 1-Pst 1 of 490 bp) were used to detect specific transcripts in fixed cryostat sections. High levels of Ha-ras and c-myc mRNA were detected in the rabbit embryo as well as in the decidua and in the trophoblast as early as day 9 of gestation. At 12 and 15 days of gestation, Ha-ras and c-myc mRNA levels decreased in both embryonic and maternal placenta while in the embryo a significant increase of Ha-ras and c-myc expression was detected with particular evidence in the central nervous system. Finally, at 25 days of gestation the expression of the two proto-oncogenes, Ha-ras and c-myc, was greatly decreased in both the embryo and extraembryonic tissues, and was undetectable by 30 days of gestation. These results show that in rabbit the expression of the two proto-oncogenes Ha-ras and c-myc is localized in the same tissues with similar intensity and follows an unparallel temporal modulation in the embryo and in the extraembryonic tissues during prenatal development.

A significant association of Ha-ras p21 in neuroblastoma cells with patient prognosis. A retrospective study of 103 cases

To evaluate biologic characteristics of neuroblastoma, the authors examined the expression of Ha-ras gene (Ha-ras p21) in 103 primary tumors obtained at the time of diagnosis. Higher expression of the Ha-ras p21 in tumor cells showed a significant association with lower clinical stage of the tumor at diagnosis (chi-square = 35.418, degrees of freedom [df] = 9, P less than 0.001) and survival of the patients (chi-square = 37.111, df = 3, P less than 0.001). Thirty-six (84%) of 43 patients with decreased Ha-ras p21 expression died of aggressive disease. The Ha-ras DNA was examined in the 32 tumors by Southern blot analysis. Neither augmentation nor deletion of the Ha-ras DNA was observed. Amplification of the N-myc DNA was also examined in 43 cases in comparison with Ha-ras p21 expression. N-myc amplification was detected in 12 (55%) of 22 patients who died, and 19 (86%) of the 22 patients showed a low expression of the Ha-ras p21 in tumor cells. Eighteen (86%) of 21 survivors showed a high expression of the Ha-ras p21. The expression of Ha-ras p21 was thought to be a clinically important marker for prognosis in children with neuroblastoma.

Tissue and subcellular distributions of the smg-21/rap1/Krev-1 proteins which are partly distinct from those of c-ras p21s

We have made a specific antiserum recognizing both smg p21A (the rap1A/Krev-1 protein) and -B (the rap1B protein), ras p21-like GTP-binding proteins having the same putative effector domain as ras p21s and have used this antiserum to study the tissue and subcellular distributions of smg p21s by immunoblot and immunocytochemical analyses. By immunoblot analysis, smg p21s were detected in various rat tissues and at the highest level in brain. By light microscopic immunocytochemical analysis, smg p21s were also detected in various rat tissues. Particularly, smg p21s in brain were found abundantly in the cytoplasmic region of most types of neuronal cell bodies and moderately in neuropil, whereas c-ras p21s were found more abundantly in neuropil than in the cytoplasmic region of most types of neuronal cell bodies. smg p21s in testis were found in spermatogenic cells, in which c-ras p21s were not significantly detected. By subcellular fractionation analysis of cerebrum, smg p21s were detected in all of the particulate fractions but not in the cytosol fraction. Among the particulate fractions, approximately 70% of smg p21s was recovered with the highest specific content in the fraction containing mainly synaptosomes, mitochondria, and myelin. In further fractionation of this fraction, approximately 40% of smg p21s was recovered in each of the synaptosome fraction and the mitochondrial fraction. This subcellular distribution of smg p21s in cerebrum was partly distinct from that of c-ras p21s, which were mainly recovered in the synaptosome and microsome fractions but present at very low levels in the mitochondrial fraction. These tissue and subcellular distributions of smg p 21s together with the fact that smg p21s have the same putative effector domain as ras p21s exert their own specific actions in addition to the actions similar or antagonistic to those of c-ras p21s.

Messenger molecules in the cerebellum

As data accumulate, the mammalian brain reveals its complex and subtle synaptic mechanisms. In the simplest system, a neurotransmitter binds to the receptor portion of a molecular complex incorporating an ion channel and thus alters the membrane potential, leading to excitatory or inhibitory effects. In more complex systems, receptors are coupled to second messenger systems to generate signals of longer duration and to modulate more diverse molecular mechanisms. The cerebellar cortex has a relatively simple wiring diagram with the primary neurotransmitter of most inhibitory and excitatory synapses well established. The second messenger signalling systems are more complex and those of the cerebellar output, the Purkinje cells, are the best characterized. More recently, molecules that might act as neuromodulators, carrying messages between neurons and between neurons and glial cells, have been identified, such as endothelin and nitric oxide. The classic neurotransmitters and novel neuromodulators, together with second messenger-activated trophic factors, can interact in complex ways; in this review Christopher Ross, David Bredt and Solomon Snyder discuss how studies of cerebellar circuitry and biochemistry are revealing such interrelations.

Tissue and subcellular distributions of the smg-21/rap1/Krev-1 proteins which are partly distinct from those of c-ras p21s

We have made a specific antiserum recognizing both smg p21A (the rap1A/Krev-1 protein) and -B (the rap1B protein), ras p21-like GTP-binding proteins having the same putative effector domain as ras p21s and have used this antiserum to study the tissue and subcellular distributions of smg p21s by immunoblot and immunocytochemical analyses. By immunoblot analysis, smg p21s were detected in various rat tissues and at the highest level in brain. By light microscopic immunocytochemical analysis, smg p21s were also detected in various rat tissues. Particularly, smg p21s in brain were found abundantly in the cytoplasmic region of most types of neuronal cell bodies and moderately in neuropil, whereas c-ras p21s were found more abundantly in neuropil than in the cytoplasmic region of most types of neuronal cell bodies. smg p21s in testis were found in spermatogenic cells, in which c-ras p21s were not significantly detected. By subcellular fractionation analysis of cerebrum, smg p21s were detected in all of the particulate fractions but not in the cytosol fraction. Among the particulate fractions, approximately 70% of smg p21s was recovered with the highest specific content in the fraction containing mainly synaptosomes, mitochondria, and myelin. In further fractionation of this fraction, approximately 40% of smg p21s was recovered in each of the synaptosome fraction and the mitochondrial fraction. This subcellular distribution of smg p21s in cerebrum was partly distinct from that of c-ras p21s, which were mainly recovered in the synaptosome and microsome fractions but present at very low levels in the mitochondrial fraction. These tissue and subcellular distributions of smg p 21s together with the fact that smg p21s have the same putative effector domain as ras p21s exert their own specific actions in addition to the actions similar or antagonistic to those of c-ras p21s.

Developmental and regional expression of three new members of the ras-gene family in the mouse brain

We have examined the expression in the mouse nervous system of three new members of the ras protooncogene family: rab1, rab2, and rab3. Each of these genes was transcribed into messenger RNAs with different molecular weights. These transcripts has specific developmental and regional patterns of expression. In particular, for the three genes, the ratio between the heavy and light mRNAs depended strongly on developmental stage and brain region. The use of pure neuronal and glial cultures revealed that the high molecular weight transcripts were enriched in neurons and that, in the case of rab2 and rab3, their expression increased with neuronal differentiation. These results are discussed considering the sequence identities between these genes and the yeast YPTI and sec-4 genes, which are known to be implicated in post-Golgi vesicular transport and cytoskeletal stabilization. We propose that the rab genes might be of importance in the regulation of these two processes within the developing and adult nervous system.

Developmental and regional regulation of rab3: a new brain specific "ras-like" gene

Recently, the expression of rab3, a new ras-like gene, has been shown to be restricted to brain tissues (Olofsson et al., 1988). This finding has prompted us to study the expression of rab3 in different brain regions of the developing mouse. The two transcripts corresponding to rab3 (1.8 and 1.3 kb) were first detected in the brains of E13 mouse embryos and were not randomly distributed. Highest levels were found in the mesencephalon, followed by the cortex, striatum, cerebellum, and brain stem in that order. In vitro, the expression of the 1.8-kb transcript was neuron specific, whereas the small transcript was present in neurons and astrocytes. This is the first report showing developmental and regional regulation of a nervous system-restricted ras-like gene. Based on the homologies found between the rab genes and YPT1 or sec-4, we suggest that the physiological role of rab3 might be related to the stabilization of the neuronal cytoskeleton or to post-Golgi vesicle transport and fusion.

Localization and subcellular distribution of cellular ras gene products in rat brain

Localization and subcellular distribution of the cellular ras gene products (c-ras p21s) in rat brain were studied by immunofluorescence and immunoblotting using a monoclonal antibody recognizing all of Ki-, Ha- and N-ras p21s. In immunohistochemical analysis, strong immunoreactivity for ras p21s was observed in the neuropile of cerebral and cerebellar cortex. On the other hand, the immunoreactivity of the neuronal perikarya and that of white matter were weak and that of non-neuronal cells was undetectable. In subcellular fractionation analysis of cerebrum, c-ras p21s were found mostly in the particulate fractions and almost half of the particulate-bound c-ras p21s were recovered in the P2 fraction containing myelin, synaptosomes and mitochondria, approximately one-third were in the P3 fraction containing microsomes, and the rest were in the P1 fraction containing nuclei and cell debris. In further fractionation of the P2 fraction, most of c-ras p21s were associated with synaptosomal fraction. In the synaptosomal fraction, c-ras p21s were highly concentrated in the fractions rich in synaptic plasma membranes and were poorly present in the other fractions rich in synaptic vesicles, intrasynaptosomal mitochondria or postsynaptic densities. The content of c-ras p21s of the original homogenate was calculated to be 0.05% of the total protein and c-ras p21s were distributed in the fractions rich in synaptic plasma membranes with approximately 4-fold enrichment over the original homogenate. These results indicate that c-ras p21s are mainly localized in the synaptic plasma membranes and microsomes and suggest that they may participate in some specific neuronal functions at these sites.