A strong candidate gene for schizophrenia and major mental disorders, disrupted-inschizophrenia 1 (DISC1) was first described in a large Scottish family in which a balanced chromosomal translocation segregates with schizophrenia and other psychiatric illnesses. The translocation mutation may result in loss of DISC1 function via haploinsufficiency or dominant-negative effects of a predicted mutant DISC1 truncated protein product. DISC1 has been implicated in neurodevelopment, including maturation of the cerebral cortex. To evaluate the neuronal and behavioral effects of mutant DISC1, the Tet-off system under the regulation of the CAMKII promoter was used to generate transgenic mice with inducible expression of mutant human DISC1 (hDISC1) limited to forebrain regions, including cerebral cortex, hippocampus and striatum. Expression of mutant hDISC1 was not associated with gross neurodevelopmental abnormalities, but led to a mild enlargement of the lateral ventricles and attenuation of neurite outgrowth in primary cortical neurons. These morphological changes were associated with decreased protein levels of endogenous mouse DISC1, LIS1 and SNAP-25. Compared to their sex-matched littermate controls, mutant hDISC1 transgenic male mice exhibited spontaneous hyperactivity in the open field and alterations in social interaction, and transgenic female mice showed deficient spatial memory. The results show that the neuronal and behavioral effects of mutant hDISC1 are consistent with a dominant-negative mechanism, and are similar to some features of schizophrenia. The present mouse model may facilitate the study of aspects of the pathogenesis of schizophrenia.

Blood coagulation in vivo is a spatially nonuniform, multistage process: coagulation factors from plasma bind to tissue factor (TF)-expressing cells, become activated, dissociate, and diffuse into plasma to form enzymatic complexes on the membranes of activated platelets. We studied spatial regulation of coagulation using two approaches: 1), an in vitro experimental model of clot formation in a thin layer of plasma activated by a monolayer of TF-expressing cells; and 2), a computer simulation model. Clotting in factor VIII- and factor XI-deficient plasmas was initiated normally, but further clot elongation was impaired in factor VIII- and, at later stages, in factor XI-deficient plasma. The data indicated that clot elongation was regulated by factor Xa formation by intrinsic tenase, whereas factor IXa was formed by extrinsic tenase on activating cells and diffused into plasma, thus sustaining clot growth. Far from the activating cells, additional factor IXa was produced by factor XIa. Exogenously added TF had no effect on the clot growth rate, suggesting that plasma TF does not contribute significantly to the clot propagation process in a reaction-diffusion system without flow. Addition of thrombomodulin at 3-100 nM caused dose-dependent termination of clot elongation with a final clot size of 2-0.2 mm. These results identify roles of specific coagulation pathways at different stages of spatial clot formation (initiation, elongation, and termination) and provide a possible basis for their therapeutic targeting.

To cite this article: Ovanesov MV, Ananyeva NM, Panteleev MA, Ataullakhanov FI, Saenko EL. Initiation and propagation of coagulation from tissue factor-bearing cell monolayers to plasma: initiator cells do not regulate spatial growth rate. J Thromb Haemost 2005; 3: 321-31.Summary. Exposure of tissue factor (TF)-bearing cells to blood is the initial event in coagulation and intravascular thrombus formation. However, the mechanisms which determine thrombus growth remain poorly understood. To explore whether the procoagulant activity of vessel wall-bound cells regulates thrombus expansion, we studied in vitro spatial clot growth initiated by cultured human cells of different types in contact pathway-inhibited, non-flowing human plasma. Human aortic endothelial cells, smooth muscle cells, macrophages and lung fibroblasts differed in their ability to support thrombin generation in microplate assay with peaks of generated thrombin of 60 ± 53 nmol L , 218 ± 55 nmol L )1 and 407 ± 59 nmol L )1 (mean ± SD), respectively. Real-time videomicroscopy revealed the initiation and spatial growth phases of clot formation. Different procoagulant activity of cell monolayers was manifested as up to 4-fold difference in the lag times of clot formation. In contrast, the clot growth rate, which characterized propagation of clotting from the cell surface to plasma, was largely independent of cell type (£ 30% difference). Experiments with factor VII (FVII)-, FVIII-, FX-or FXI-deficient plasmas and annexin V revealed that (i) cell surface-associated extrinsic Xase was critical for initiation of clotting; (ii) intrinsic Xase regulated only the growth phase; and (iii) the contribution of plasma phospholipid surfaces in the growth phase was predominant. We conclude that the role of TF-bearing initiator cells is limited to the initial stage of clot formation. The functioning of intrinsic Xase in plasma provides the primary mechanism of sustained and far-ranging propagation of coagulation leading to the physical expansion of a fibrin clot.