In the healthy adult brain synapses are continuously remodelled through a process of elimination and formation known as structural plasticity1. Reduction in synapse number is a consistent early feature of neurodegenerative diseases2, 3, suggesting deficient compensatory mechanisms. While much is known about toxic processes leading to synaptic dysfunction and loss in these disorders2,3, how synaptic regeneration is affected is unknown. In hibernating mammals, cooling induces loss of synaptic contacts, which are reformed on rewarming, a form of structural plasticity4, 5. We have found that similar changes occur in artificially cooled laboratory rodents. Cooling and hibernation also induce a number cold-shock proteins in the brain, including the RNA binding protein, RBM36. The relationship of such proteins to structural plasticity is unknown. Here we show that synapse regeneration is impaired in mouse models of neurodegenerative disease, in association with the failure to induce RBM3. In both prion-infected and 5×FAD (Alzheimer-type) mice7, the capacity to regenerate synapses after cooling declined in parallel with the loss of induction of RBM3. Enhanced expression of RBM3 in the hippocampus prevented this deficit and restored the capacity for synapse reassembly after cooling. Further, RBM3 over-expression, achieved either by boosting endogenous levels through hypothermia prior to the loss of the RBM3 response, or by lentiviral delivery, resulted in sustained synaptic protection in 5×FAD mice and throughout the course of prion disease, preventing behavioural deficits and neuronal loss and significantly prolonging survival. In contrast, knockdown of RBM3 exacerbated synapse loss in both models and accelerated disease and prevented the neuroprotective effects of cooling. Thus, deficient synapse regeneration, mediated at least in part by failure of the RBM3 stress response, contributes to synapse loss throughout the course of neurodegenerative disease. The data support enhancing cold shock pathways as potential protective therapies in neurodegenerative disorders.

Particulate air pollution is associated with cardiovascular morbidity and mortality. To investigate this association, we studied the effect of ultrafine (60 nm) polystyrene particles on thrombus formation in a hamster model after intravenous and intratracheal administration of unmodified, carboxylate-polystyrene, or amine-polystyrene particles. Unmodified particles had no effect on thrombosis up to 5 mg/kg. Carboxylate-polystyrene particles significantly inhibited thrombus formation at 500 and 100 microg/kg body weight but not at 50 microg/kg body weight. In contrast, amine-polystyrene particles significantly enhanced thrombosis at 500 and 50 microg/kg body weight but not at 5 microg/kg body weight. Similarly, the intratracheal instillation of 5,000 microg of amine-polystyrene particles significantly increased thrombus formation. The unmodified particles and carboxylate-polystyrene particles had no effect. During platelet aggregation in human platelet-rich plasma, induced with 1.25 microM ADP, unmodified particles had no effect up to 100 microg/ml, and carboxylate-polystyrene particles weakly enhanced platelet aggregation at 25 to 100 microg/ml. However, amine-polystyrene particles (50 and 100 microg/ml) induced platelet aggregation themselves and strongly increased the ADP-induced aggregation. We conclude that the presence of (ultrafine) particles in the circulation may affect hemostasis. The observed in vivo prothrombotic tendency results, at least in part, from platelet activation by positively charged amine-polystyrene particles.

Cajal bodies are small nuclear organelles with a number of nuclear functions. Here we show that FLICE-associated huge protein (FLASH), originally described as a component of the apoptosis signaling pathway, is mainly localized in Cajal bodies and is essential for their structure. Reduction in FLASH expression by short hairpin RNA results in disruption of the normal architecture of the Cajal body and relocalization of its components. Because the function of FLASH in the apoptosis receptor signaling pathway has been strongly questioned, we have now identified a clear function for this protein.coiled bodies ͉ nuclear organelles C ajal bodies (CBs) are small nuclear organelles described in vertebrate cells a century ago by Ramon y Cajal and which have since been observed in a variety of animal and plant nuclei. Many components of CBs are shared with the nucleolus, and CBs frequently localize to the nucleolar periphery or within the nucleoli (1-3). CBs disappear from prophase nuclei and reappear in late G 1 after resumption of transcription in the daughter nuclei (for review see refs. 1, 4, and 5). Although their function is still in part elusive, recent work suggests that they are involved in several nuclear functions, including modification of small nuclear RNAs and small nuclear ribonucleoproteins, important for spliceosome formation, and assembly of the three eukaryotic RNA polymerases (pol I, pol II, and pol III) with their respective transcription and processing factors that are then transported as multiprotein complexes to the sites of transcription (1). More recently CBs have been implicated in replication-dependent histone gene transcription and mRNA maturation (1, 6-10), and a subset of CBs is physically associated with histone gene clusters on chromosomes 1 and 6 (11). Here we identify FLASH (FLICEassociated huge protein) (12) as a new component of CBs and show that it is essential for their structure.FLASH was initially identified as a component of the apoptosis signaling complex known as the death-inducing signaling complex (12, 13), which is associated with caspase 8 in the death-inducing signaling complex and thus essential for caspase 8 activation. However, this role of FLASH has been questioned (14). More recently it has been shown that, in response to TNF␣, FLASH translocates to the nucleus and binds the glucocorticoid receptor-interacting protein (GRIP-1), inhibiting both its interaction with, and the transcriptional activity of, the glucocorticoid receptor (15, 16). Results FLASH Has a Nuclear Localization.Despite the presence of three nuclear localization signals FLASH was originally described as a cytoplasmic protein (12,17). Staining endogenous FLASH with four different anti-FLASH antibodies, however, showed that FLASH only localized to the nucleus with a clear punctate appearance (Fig. 5a, which is published as supporting information on the PNAS web site). The specificity of the antibodies used was confirmed by the disappearance of the staining after short hairpin RNA for FLASH (Fig. 4a). West...