Cytogenetic and molecular characterization of a congenital mesoblastic nephroma.

A newborn baby boy was diagnosed with the mixed form of congenital mesoblastic nephroma (CMN) representing both classic and cellular histology features in the renal tumor. Additionally, the patient had skin and bone lesions consistent with multifocal involvement of a generalized infantile fibromatosis (IFS). Both skin and bone lesions were distinctly different from CMN and did not represent metastasis. The primary tumor cell line (MCH-MN-1), established from the resected right kidney tumor, had a diploid DNA content. Cytogenetic studies revealed deletion on the long arm of chromosome 3 (q21q24) and duplication on the short arm of chromosome 11 (p15). MCH-MN-1 cells expressed ETV6-NTRK3 gene fusion transcripts, characteristic of cellular and mixed forms of CMNs. The cells had high p21 and low Bax mRNA expression in the reverse transcriptase-polymerase chain reaction (RT-PCR) assay. The high level of proliferative marker (Ki67) mRNA expression correlated well with the pluripotent nature of MCH-MN-1 in tissue culture (cell doubling time = 12.4 h). Our results showed that MCH-MN-1 might be a good model cell line for investigations on mesoblastic nephroma.

Expression of apoptosis, cell proliferation, and drug resistance genes in pediatric Wilms' tumors.

The expression of genes associated with apoptosis, cell proliferation and drug resistance in tumor cells was investigated in two pediatric Wilms' tumor patients (MCH-WT-1 and MCH-WT-3) for their association with cell cycle, daunorubicin accumulation and clinical data. DNA content, cell cycle and drug accumulation were analyzed immediately after surgery by flow cytometry and mRNA expression by reverse transcriptase-polymerase chain reaction (RT-PCR) assay. Primary cell cultures were established from tumor specimens and tumor cells in both cases showed epithelial morphology. Although cell proliferation markers (Ki67 and PCNA) were expressed in both cases, MCH-WT-3 showed higher levels of mRNA expression, which corresponded, with metastatic behavior of the tumor in the patient. While p53 and p21 mRNAs were expressed at low levels in MCH-WT1, MCH-WT-3 showed high levels of p21 mRNA only. The increased expression of cyclin kinase inhibitor (p21) in MCH-WT-3 compared to MCH-WT-1 correlated with a higher percentage of G0/G1 cell population in the tumor specimen. Despite the expression of multidrug resistance markers (MDR1 and LRP) in MCH-WT-1, flow cytometric analysis showed tumor cell populations with very low and high daunorubicin accumulation and with the absence of any effect for verapamil and dipyridamole on daunorubicin accumulation of tumor cells.

Sulfamidase deficiency in a family of Dachshunds: a canine model of mucopolysaccharidosis IIIA (Sanfilippo A).

Mucopolysaccharidosis IIIA (MPS IIIA or Sanfilippo A, McKusick 25290) was diagnosed in two adult wire-haired Dachshund littermates. Clinical and pathologic features paralleled the human disorder; both dogs exhibited progressive neurologic disease without apparent somatic involvement. Pelvic limb ataxia was observed when the dogs were 3 y old and progressed gradually within 1-2 y to severe generalized spinocerebellar ataxia. Mentation remained normal throughout the course of the disease. A mucopolysaccharide storage disorder was indicated in both dogs by positive toluidine blue spot tests of urine. The diagnosis of MPS IIIA was confirmed by documentation of urinary excretion and tissue accumulation of heparan sulfate and decreased sulfamidase activity in fibroblasts and hepatic tissue. Mild cerebral cortical atrophy and dilation of the lateral ventricles were grossly evident in both dogs. Light microscopically, fibroblasts, hepatocytes, and renal tubular epithelial cells were vacuolated. Within the nervous system, cerebellar Purkinje cells, neurons of brainstem nuclei, ventral and dorsal horns, and dorsal ganglia were distended with brightly autofluorescent, periodic acid-Schiff-positive, sudanophilic material. Ultrastructurally, visceral storage presented as membrane-bound vacuoles with finely granular, variably electron-lucent contents. Neuronal storage appeared as membranous concentric whorls, lamellated parallel membrane stacks, or electron-dense lipid-like globules. This represents the first reported animal disease homolog of the human Sanfilippo A syndrome.

Tyrosine phosphorylation in early embryonic growth cones.

A large and growing body of evidence suggests that the regulation of tyrosine phosphorylation is important in the induction of axon growth. We have examined the subcellular distribution of enzymes regulating tyrosine phosphorylation in early embryonic brain, employing a preparation of isolated growth cone particles (GCPs). Because of the early developmental age and well-characterized nature of our tissue source, our GCP preparation offers some advantages over those described previously. As was found with other GCPs, our GCPs had relatively high levels of both the growth-associated protein GAP-43 and the intracellular tyrosine kinase pp60c-arc. In addition, we found that both total tyrosine kinase activity and total tyrosine phosphatase activity were concentrated two- to threefold in the GCPs relative to a neuronal membrane fraction. Two other nonreceptor tyrosine kinases, YES and FYN, were concentrated in the GCPs to a similar degree as that seen for SRC. In addition, we examined the developmental expression in brain of the three tyrosine kinases, using both a quantitative ELISA and Western blot analysis. Our results show that FYN, like SRC, reaches a peak of expression early in development, and declines thereafter. In contrast, expression of YES peaks later, and remains high in the adult brain. Immunofluorescence staining suggests that FYN is expressed both by neurons and by glia, and possibly by neuronal precursor cells. Our results implicate multiple tyrosine kinases as well as tyrosine phosphatases in growth cone function. In addition, the concentration of FYN in early embryonic growth cones combined with its early peak of expression suggests an important role for FYN in early neuronal development.

Inhibition of tyrosine phosphorylation potentiates substrate-induced neurite growth.

Protein tyrosine kinases (PTKs) have major roles in signal transduction and growth control. There are several lines of evidence implicating PTKs in the regulation of axon growth, and this has led to the suggestion that they are centrally involved in the transduction of neuronal growth signals. To test this idea, we assayed the effect of the compounds genistein and lavendustin, specific inhibitors of PTKs, on neurite growth. We find that genistein greatly reduces phosphotyrosine in neurons, as expected from its action on other cells. Surprisingly, administration of genistein or lavendustin potentiated substrate-induced neurite growth in at least several different neuronal types. Stimulation of neurite growth by genistein was abolished by vanadate, providing additional evidence that inhibition of PTKs is responsible for this effect. The potentiation of growth is rather general, in that it occurs on several different extracellular matrix substrates and on two different cell adhesion molecules. Both the initiation of neurite growth and the rate of neurite elongation appear to be potentiated. Our results do not provide evidence for models of substrate-induced signal transduction that involve PTKs as a positive and necessary step, but suggest that such kinases play a regulatory role in neurite elongation.

Extracellular matrix molecules and cell adhesion molecules induce neurites through different mechanisms.

It has recently become clear that both extracellular matrix (ECM) glycoproteins and various cell adhesion molecules (CAMs) can promote neurite outgrowth from primary neurons, though little is known of the intracellular mechanisms through which these signals are transduced. We have previously obtained evidence that protein kinase C function is an important part of the neuronal response to laminin (Bixby, J.L. 1989. Neuron. 3:287-297). Because such CAMs as L1 (Lagenauer, C., and V. Lemmon. 1987. Proc. Natl. Acad. Sci. USA. 84:7753-7757) and N-cadherin (Bixby, J.L. and R. Zhang. 1990. J. Cell Biol. 110:1253-1260) can be purified and used as substrates to promote neurite growth, we have now tested whether the response to CAMs is similarly dependent on protein kinase C. We find that inhibition of protein kinase C inhibits growth on fibronectin or collagen as well as on laminin. In contrast, C kinase inhibition actually potentiates the initial growth response to L1 or N-cadherin. The later "phase" of outgrowth on both of these CAMs is inhibited, however. Additionally, phorbol esters, which have no effect on neurite growth when optimal laminin concentrations are used, potentiate growth even on optimal concentrations of L1 or N-cadherin. The results indicate that different intracellular mechanisms operate during initial process outgrowth on ECM substrates as compared to CAM substrates, and suggest that protein kinase C function is required for continued neurite growth on each of these glycoproteins.

Characterization of the proteins of intracisternal type A and extracellular oncornavirus-like particles produced by MOPC-460 myeloma cells.

The mouse plasmacytoma cell line, MOPC-460, produces both intracisternal and intracytoplasmic A-type particles when grown as a solid tumor. When these cells are grown either as an ascites tumor or in tissue culture, a third type of particle is produced extracellularly. This particle, the "myeloma-associated virus," is closely related to, and probably an alternate form of, the intracisternal A-type particle. The proteins present in these two types of particles were compared by tryptic peptide mapping. Both types of particles were found to contain essentially the same major proteins of 76,000 (p76), 68,000 to 70,000 (p68-70), and 45,000 (p45) daltons, in addition to varying amounts of smaller proteins. The relative proportions of all these proteins varied from preparation to preparation in an unpredictable way. The p45, p68, and p70 proteins all contained sequences found in p76, suggesting precursor-product relationships of p76 leads to p70 leads to p45 for solid tumor A-type particles and p76 leads to p68 leads to p45 for extracellular myeloma-associated virus. In addition, immune precipitation experiments have established that p76 contains at least some of the antigenic determinants characteristic of murine leukemia virus p30. This confirms earlier nucleic acid hybridization studies which indicated a moderate degree of relatedness between MOPC-460 A-type particles and several standard murine leukemia and sarcoma viruses. Taken together, our results provide evidence supporting the concept that MOPC-460 A-type particles may represent aberrant forms of C-type murine viruses.

Characterization of infectious oncornaviruses from MOPC-460 plasmacytomas: their relation to A-type particles.

MOPC-460 mouse plasmacytoma cells produce intracellular A-type particles and extracellular oncornavirus-like particles ("myeloma-associated virus," abbreviated MAV). The genomes of these two particles are closely related. During attempts to establish infections with MOPC-460 extracellular particles, we isolated ecotropic and xenotropic infectious forms of murine leukemia virus. We have investigated the relation of these isolates to A-type particles and to MAV by nucleic acid hybridization. Using complementary DNA probes prepared from the two isolates, we found that these infectious murine leukemia viruses differ from A-type particles and from MAV. Moreover, we found that MAV is the predominant extracellular component: the ecotropic and xenotropic forms of murine leukemia virus were present at only low levels (less than 5%) in MAV preparations. Neither the SC-1 cells infected with ectropic murine leukemia virus nor the mink cells infected with xenotropic murine leukemia virus showed any A-type particles in their cytoplasm when examined by electron microscopy. Our inability to demonstrate infection by the A-type particle-related component, MAV, suggests that these may be defective.