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Objectives: Ubiquitin carboxyl-terminal esterase-L1 (UCHL1) is a protein highly selectively expressed in neurons and has been linked to neurodegenerative disease in humans. We hypothesize that UCHL1 would be an effective serum biomarker for brain injury as tested in canine models of hypothermic circulatory arrest (HCA) and cardiopulmonary bypass (CPB)., Methods: Dogs were exposed to CPB (n = 14), 1 hour of HCA (1h-HCA; n = 11), or 2 hours of HCA (2h-HCA; n = 20). Cerebrospinal fluid and serum were collected at baseline, 8 hours, and 24 hours after treatment. UCHL1 levels were measured using a sandwich enzyme-linked immunosorbent assay. Neurologic function and histopathology were scored at 24 hours, and UCHL1 immunoreactivity was examined at 8 hours., Results: Baseline UCHL1 protein levels in cerebrospinal fluid and serum were similar for all groups. In serum, UCHL1 levels were elevated at 8 hours after treatment for 2h-HCA subjects compared with baseline values (P < .01) and also compared with CPB dogs at 8 hours (P < .01). A serum UCHL1 level above 3.9 ng/(mg total protein) at 8 hours had the best discriminatory power for predicting functional disability. In cerebrospinal fluid, UCHL1 was elevated in all groups at 8 hours after treatment compared with baseline (P < .01). However, UCHL1 levels in cerebrospinal fluid remained elevated at 24 hours only in 2h-HCA subjects (P < .01). Functional and histopathologic scores were closely correlated (Pearson coefficient, 0.66; P < .01) and were significantly worse in 2h-HCA animals., Conclusions: This is the first report associating elevated serum UCHL1 with brain injury. The novel neuronal biomarker UCHL1 is increased in serum 8 hours after severe neurologic insult in 2h-HCA animals compared with CPB animals. These results support the potential for use in cardiac surgery patients and form the basis for clinical correlation in humans., (Copyright © 2011 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.)

Rett syndrome is a neurodevelopmental disorder caused by mutations in the methyl CpG binding protein 2 gene (MECP2). The MECP2 protein is expressed primarily in neurons, and mutations in the gene lead to the clinical features of Rett syndrome in human patients and neurologic deficits in murine models. Visual function is relatively preserved in Rett syndrome patients, but the cause is unknown. The eyes of two Rett syndrome patients who died of the disease were analyzed; no gross or microscopic changes were found. MECP2 expression was examined using immunohistochemistry; nuclear protein expression was largely limited to ganglion cells and the portion of the inner nuclear layer populated by amacrine cells. No significant differences in MECP2 protein level or distribution were identified in the two eyes from the Rett syndrome patients, compared with 11 controls. The findings were compared with MECP2 expression in the brain of these two subjects and in MECP2-deficient mice. The findings suggest that the normally limited expression of MECP2 in visual pathway neurons may underlie the intact vision observed in Rett syndrome.

The clinical signs of Rett syndrome, as well as neuropathology and brain imaging, suggest that the disorder disrupts neuronal circuits. Studies using receptor autoradiography demonstrate abnormalities in the density of excitatory glutamate and inhibitory gamma-aminobutyric acid (GABA) synaptic receptors in postmortem brain from young female subjects with Rett syndrome. MeCP2, the protein that is abnormal in most female individuals with Rett syndrome, is expressed predominantly in neurons and appears during development at the time of synapse formation. Studies of nasal epithelium from patients with Rett syndrome show that the maturation of olfactory receptor neurons is impeded prior to the time of synapse formation. Recent reports indicate that MeCP2 controls the expression of brain-derived neurotrophic factor and the DNA-binding homeobox protein Dlx5. Brain-derived neurotrophic factor enhances glutamate neurotransmission at excitatory synapses, whereas Dlx5 is expressed in most GABAergic neurons and stimulates the synthesis of GABA. Taken together, this information supports the hypothesis that Rett syndrome is a genetic disorder of synapse development, especially synapses that use glutamate and GABA as neurotransmitters.

β-Amyloid (Aβ) pathology is an essential pathogenic component in Alzheimer's disease (AD). However, the significance of Aβ pathology, including Aβ deposits/oligomers and glial reactions, to neurodegeneration is unclear. In particular, despite the Aβ neurotoxicity indicated by in vitro studies, mouse models with significant Aβ deposition lack robust and progressive loss of forebrain neurons. Such results have fueled the view that Aβ pathology is insufficient for neurodegeneration in vivo. In this study, because monoaminergic (MAergic) neurons show degenerative changes at early stages of AD, we examined whether the APPswe/PS1ΔE9 mouse model recapitulates progressive MAergic neurodegeneration occurring in AD cases. We show that the progression forebrain Aβ deposition in the APPswe/PS1ΔE9 model is associated with progressive losses of the forebrain MAergic afferents. Significantly, axonal degeneration is associated with significant atrophy of cell bodies and eventually leads to robust loss (~50%) of subcortical MAergic neurons. Degeneration of these neurons occurs without obvious local Aβ or tau pathology at the subcortical sites and precedes the onset of anxiety-associated behavior in the mice. Our results show that a transgenic mouse model of Aβ pathology develops progressive MAergic neurodegeneration occurring in AD cases. [ABSTRACT FROM AUTHOR]

The clinical variability of Rett syndrome, associated with mutations in the MECP2 gene, varies from classically symptomatic female patients to asymptomatic female patients, and male patients who have none of the diagnostic features considered pathognomonic of this disease. Multiple factors contribute to this variability. In our studies, mutations closer to the aminoterminus, prior to amino acid 255, led to severe clinical manifestations, such as inability to walk, severe dysphagia, and urinary organic acid abnormalities, compared with mutations toward the carboxyl-terminus. However, we found no correlation between severity and mutation type (missense versus nonsense). Despite the importance of mutation location to clinical severity, the widely varying severity within the same mutation suggests that in females, X-chromosome inactivation or other epigenetic phenomena also have roles in determining severity. We propose that stages 1 and 2 of the disease are a consequence of failed, time-linked, postnatal expression of MeCP2 in cerebellar neurons. This, in association with glutamate N-methyl-D-aspartate receptor — mediated neuroexcitotoxic injury to the differentiating neurons, results in the transient agespecific autistic-like behavior, motor, and cognitive dysfunction associated with these stages. (J Child Neural 2003;18:662-668). [ABSTRACT FROM AUTHOR]