Are high-molecular-weight glycoproteins regulators of cellular growth?

Altered adhesion, proliferation and death in neural cultures from adults with schizophrenia

The causes of schizophrenia are unknown, but there is evidence linking subtle deviations in neural development with schizophrenia. Embryonic brain development cannot be studied in an adult with schizophrenia, but neurogenesis and early events in neuronal differentiation can be investigated throughout adult life in the human olfactory epithelium. Our past research has demonstrated that neuronal cultures can be derived from biopsy of the human adult olfactory epithelium. In the present study, we examined mechanisms related to neurogenesis and neuronal differentiation in adults with schizophrenia versus well controls. Forty biopsies were collected under local anaesthesia from ten individuals with DSM III-R schizophrenia and ten age- and sex-matched well controls. All patients, except one, were receiving antipsychotic medication at the time of the biopsy. Immunostaining for neuronal markers indicated that neurogenesis occurred in the biopsies from both patients and controls since all contained cells expressing tubulin and/or olfactory marker protein. The major findings of this study are: 1. biopsies from patients with schizophrenia showed a significantly reduced ability to attach to the culture slide: 29.9% of patient biopsies attached compared to 73.5% of control biopsies; 2. biopsies from patients with schizophrenia had a significantly greater proportion of cells undergoing mitosis: 0.69% in the patients compared to 0.29% in the controls; and 3. dopamine (10 microM) significantly increased the proportion of apoptotic cells in the control cultures but significantly decreased the proportion in patients' cultures.

Altered adhesion efficiency and fibronectin content in fibroblasts from schizophrenic patients

Cultured fibroblasts from the cutaneous tissue of 16 schizophrenic patients were compared with 16 control cultured fibroblasts from the healthy subjects. The fibroblasts from the schizophrenic patients showed a decreased adhesion efficiency within 30 min after plating compared to that of the control subjects. However, after 90 min, there was no significant difference between the groups, where more than 90% of the cells from both groups had adhesed to the plate. By immunohistochemistry and western blotting using the antibodies against integrin (VLA5), talin, vinculin, fodrin, vimentin, ankyrin, plectin, fibronectin, and focal adhesion kinase (FAK), there was no significant difference in localization and amount between the groups. The amount of fibronectin released into the medium in which the fibroblast had already kept confluency showed no significant difference between the groups. However, the fibronectin content in cell lysate within 48 h after plating was significantly lower in the schizophrenic group.

In utero ethanol exposure retards growth and alters morphology of cortical cultures: GM1 reverses effects

Ethanol, a developmental neurotoxin, alters plasma membranes' physicochemical properties affecting embryogenesis, cell migration, differentiation, and synaptogenesis. In a previous study using a model for fetal alcohol effects, GM1 ganglioside treatment was shown to reduce ethanol-induced accumulation of endogenous GM1 and fatty acid ethyl esters in rat fetuses. The present study was initiated to define further the in utero effects of ethanol and the capacity of GM1 treatment to ameliorate such effects. Wistar dams were exposed to ethanol (intragastrically) on gestation day (GD) 7 and GD8 and GD13 and GD14. GM1 ganglioside (10 mg/kg, im) was given 24 hr before ethanol administration. Cortical cultures were derived from GD15 and GD20 fetuses. GM1, which is highly localized on the cellular plasma membrane outer surface of CNS cells, was used as a marker molecule to assess cell integrity. Cholera toxin/antitoxin/fluorescence immunohistochemistry was used to localize GM1. Results indicate that the brief in utero exposure to ethanol affected cell growth and morphology. A marked retardation of cell development and arborization was observed as early as 24 hr after plating. Ethanol-exposed cells evidenced considerably altered GM1 localization. Such alterations likely reflect losses of membrane integrity. These in utero ethanol-induced pathologies are remarkably diminished in cultures derived from ethanol-exposed fetuses of dams treated with GM1.

Glucose oxidation and monoamine oxidase activity from the fibroblasts of schizophrenic patients and controls

Fibroblasts have emerged as one of the best systems in which to study several genetically inherited diseases. Their use avoids the contaminating effects of medication and other environmental factors. Moreover, fibroblast cells cultured in vitro can express several biochemical parameters which are characteristic of neuronal cells. We have studied fibroblast MAO-A and glucose oxidation and platelet MAO-B from schizophrenic patients and control subjects. Fibroblasts from schizophrenics showed an increased glucose oxidation in two different experiments conducted (122% and 126% compared to controls). No changes were found in the levels of fibroblast MAO-A or platelet MAO-B activity. Possibly these alterations in glucose oxidation may be associated with a generalized membrane abnormality which has been reported in schizophrenia.

Decreased adhesiveness and altered cellular distribution of fibronectin in fibroblasts from schizophrenic patients

Relative to those from normal subjects, cultured skin fibroblasts from schizophrenic patients have been found to show abnormal growth characteristics and morphology. This study compared skin fibroblasts from 10 drug-free schizophrenic patients and 10 normal control subjects on cell adhesiveness to the substratum. Relative to fibroblasts from normal controls, those from patients showed significantly decreased cell adhesiveness, with no overlap in distribution between the groups. Since fibronectin, a major cell surface molecule, is known to be involved in the fibroblast adhesion to substratum, its extracellular and intracellular distribution was determined by immunocytochemical analysis. Both extracellular and intracellular levels of fibronectin were significantly lower, and the distribution was altered in fibroblasts from the patients.

Abnormal growth of skin fibroblasts from schizophrenic patients

Fibroblast cultures were established from skin biopsies of 18 schizophrenic patients (14 on drug and 4 off drug) and 13 normal subjects, and growth parameters (initial growth and rate of growth) and morphology were studied. Fibroblasts from patients took significantly longer to grow than did normal fibroblasts. Cell lines were established within 2 weeks for all normal controls, but for only 6 (33%) of 18 schizophrenic patients. The rate of growth (doubling time) was also significantly longer for fibroblasts from patients than from normals. Neither time to establishment of initial growth nor doubling time was related to age, sex, age at onset, duration of illness, or medication status in the patients. Fibroblasts from normals showed uniform, long (slender), characteristic spindle-like, bipolar appearance, with unidirectional orientation, both while growing from explant as well as after subculturing. By contrast, fibroblasts from patients generally showed random size (shorter and flatter), mostly spiny, multipolar cells with short stubby projections, and an irregular orientation resulting in a criss-cross pattern, and often exhibited poor attachment. Fibroblasts from skin biopsies of patients who were drug free at the time of biopsy showed similar initial growth, doubling time, and morphology to those from patients who were receiving neuroleptic treatment. In vitro challenge of skin biopsies of normal subjects with haloperidol in culture resulted in slight delay in initial growth and marginal increase in doubling time. However, the morphology remained normal. Possible molecular mechanisms that may be associated with abnormal growth of fibroblasts in schizophrenia are discussed.

Stimulation of DNA synthesis by cathepsin D digests of fibronectin

A number of studies over the past decade (reviewed in refs 1-3) have suggested an intimate link between fibronectin, proteolysis and the control of cell proliferation. So far, however, no unequivocal connection has been made. Recent evidence that gelatin-binding fragments of fibronectin enhance morphological cell transformation led to the postulate that the fibronectin molecule harbours latent properties released only on proteolysis. These findings led us to investigate the role of fibronectin fragmentation in the regulation of cell growth in vitro, and we report here that whilst fibronectin is without effect, its cathepsin D digests possess the ability to initiate DNA synthesis in serum-deprived quiescent cultures of normal hamster fibroblasts.

Fibronectin and anchorage-independent and anchorage-dependent growth of benign and malignant cell lines

The presence of fibronectin in three "malignant" (AU-471, AU-436, LT-2) and two "benign" (BHK-21, WI-38) cell lines was demonstrated with a fluorescent antibody technique; two malignant (AU-471, AU-436) cell lines were fibronectin-negative and one (LT-2) retained fibronectin expression. One "benign" cell line (WI-38) expressed fibronectin, the other (BHK-21) did not. Anchorage-independent soft agar (AISA) growth correlated better with loss of fibronectin than with malignant potential. All three fibronectin-negative cell lines (benign and malignant) grew anchorage-independently (AU-471, AU-436, BHK-21), and both fibronectin-positive cell lines were anchorage-dependent (LT-2, WI-38). Surprisingly, the addition of Clg to anchorage-independent cells increased their anchorage-independent soft-agar cloning efficiency, but had no effect on anchorage-dependent cell lines. Anti-Clg antibodies decreased AISA growth. The effect of Clg on anchorage-independent growth varied with the concentration, and also between cell lines, and a variation in effect was noted between anchorage-independent (AISA) and anchorage-dependent (in flasks) growth even in the same cell line.

Modifications of chromatin structure in control of gene expression

Repetitive sequences in intron and spacer DNA could be sites for binding of chromosomal proteins which maintain chromatin structure and control gene activity. Methylation of DNA guides the binding of acidic nonhistone proteins and maintains the differentiation state during DNA replication. Differentiation inducers modify repressor proteins permitting unfolding of chromatin. Histone H 1 must be removed for gene activity. Phosphorylation of nonhistone proteins probably induces allosteric modifications which permit unfolding of chromatin. Acetylation of nucleosomal histones is necessary to permit passage of RNA polymerase. Deacetylation quickly returns the gene to a normal histone repressed state. Chromosomal RNA attached to nonhistone proteins aids the binding of RNA polymerase to the DNA template. Carcinogens can disrupt normal gene control leading to circumvention of normal cell cycle controls.

Progress towards a unified theory of the mechanisms of carcinogenesis: role of cell cycle restriction points

Cancer is characterized by a relatively autonomous growth of cells due to a reduced responsiveness to normal controls of proliferation and differentiation. The proliferation of normal cells is regulated at arrest (restriction) points in the cell cycle. Relatively autonomous growth (tumors) can result from various mechanisms which circumvent the normal regulatory controls of the cell cycle.