Maternal immune activation alters behavior in adult offspring, with subtle changes in the cortical transcriptome and epigenome.

Maternal immune activation during prenatal development, including treatment with the viral RNA mimic, polyriboinosinic-polyribocytidilic acid (poly IC), serves as a widely used animal model to induce behavioral deficits reminiscent of schizophrenia and related disease. Here, we report that massive cytokine activation after a single dose of poly IC in the prenatal period is associated with lasting working memory deficits in adult offspring. To explore whether dysregulated gene expression in cerebral cortex, contributes to cognitive dysfunction, we profiled the cortical transcriptome, and in addition, mapped the genome-wide distribution of trimethylated histone H3-lysine 4 (H3K4me3), an epigenetic mark sharply regulated at the 5' end of transcriptional units. However, deep sequencing-based H3K4me3 mapping and mRNA profiling by microarray did not reveal significant alterations in mature cerebral cortex after poly IC exposure at embryonic days E17.5 or E12.5. At a small set of genes (including suppressor of cytokine signaling Socs3), H3K4me3 was sensitive to activation of cytokine signaling in primary cultures from fetal forebrain but adult cortex of saline- and poly IC-exposed mice did not show significant differences. A limited set of transcription start sites (TSS), including Disrupted-in-Schizophrenia 1 (Disc1), a schizophrenia risk gene often implicated in gene-environment interaction models, showed altered H3K4me3 after prenatal poly IC but none of these differences survived after correcting for multiple comparisons. We conclude that prenatal poly IC is associated with cognitive deficits later in life, but without robust alterations in epigenetic regulation of gene expression in the cerebral cortex.

White matter neuron alterations in schizophrenia and related disorders.

Increased density and altered spatial distribution of subcortical white matter neurons (WMNs) represents one of the more well replicated cellular alterations found in schizophrenia and related disease. In many of the affected cases, the underlying genetic risk architecture for these WMN abnormalities remains unknown. Increased density of neurons immunoreactive for Microtubule-Associated Protein 2 (MAP2) and Neuronal Nuclear Antigen (NeuN) have been reported by independent studies, though there are negative reports as well; additionally, group differences in some of the studies appear to be driven by a small subset of cases. Alterations in markers for inhibitory (GABAergic) neurons have also been described. For example, downregulation of neuropeptide Y (NPY) and nitric oxide synthase (NOS1) in inhibitory WMN positioned at the gray/white matter border, as well as altered spatial distribution, have been reported. While increased density of WMN has been suggested to reflect disturbance of neurodevelopmental processes, including neuronal migration, neurogenesis, and cell death, alternative hypotheses--such as an adaptive response to microglial activation in mature CNS, as has been described in multiple sclerosis--should also be considered. We argue that larger scale studies involving hundreds of postmortem specimens will be necessary in order to clearly establish the subset of subjects affected. Additionally, these larger cohorts could make it feasible to connect the cellular pathology to environmental and genetic factors implicated in schizophrenia, bipolar disorder, and autism. These could include the 22q11 deletion (Velocardiofacial/DiGeorge) syndrome, which in some cases is associated with neuronal ectopias in white matter.

Cingulate white matter neurons in schizophrenia and bipolar disorder.

BACKGROUND: Increased neuronal density in prefrontal, parietal, and temporal white matter of schizophrenia subjects is thought to reflect disordered neurodevelopment; however, it is not known if this cellular alteration affects the cingulate cortex and whether similar changes exist in bipolar disorder. METHOD: Eighty-two postmortem specimens (bipolar 15, schizophrenia 22, control 45) were included in this clinical study. Densities for two neuronal markers, neuron-specific nuclear protein (NeuN) and neuregulin 1 alpha (NRG), were determined in white matter up to 2.5 mm beneath the anterior cingulate cortex; density of NeuN immunopositive neurons (NeuN+) was also determined for a subset of cases in prefrontal cortex. Changes during normal development were monitored in a separate cohort of 14 brains. RESULTS: Both the schizophrenia and bipolar cohorts demonstrated a twofold increase in NeuN+ density in cingulate white matter; this effect could be attributed to approximately 25% of cases that exceeded the second standard deviation from control subjects. Similar changes were observed in prefrontal cortex. In contrast density of NRG expressing neurons was unaltered. Cases with increased NeuN+ densities in two-dimensional (2-D) counts also showed a pronounced, > fivefold elevation in NeuN+ nuclei per cubic millimeter. Additionally, the developmental cohort demonstrated a 75% decline in NeuN+ neuronal density during the first postnatal year but was stable thereafter. CONCLUSIONS: Increased neuronal density in white matter of cingulate cortex in schizophrenia provides further evidence that this alteration occurs in multiple cortical areas. Similar changes in some cases with bipolar illness suggest that the two disorders may share a common underlying defect in late prenatal or early postnatal neurodevelopment.

DNA methylation changes in schizophrenia and bipolar disorder.

The etiology of the major psychotic disorders, including schizophrenia and bipolar disorder, remains poorly understood. Postmortem brain studies have revealed altered expression of multiple mRNAs, affecting neurotransmission, metabolism, myelination and other functions. Epigenetic mechanisms could be involved, because for a limited number of genes, the alterations of mRNA levels have been linked to inverse DNA methylation changes at sites of the corresponding promoters. However, results from independent studies have been inconsistent, and when expressed in quantitative terms, disease-related methylation changes appear to be comparatively subtle. A recent study identified approximately 100 loci with altered CpG methylation in schizophrenia or bipolar disorder, the majority of which were gender-specific. Additional work will be necessary to clarify the origin and timing of these methylation changes in psychosis and to determine the specific cell types affected in the diseased brain.

DNA methylation in the human cerebral cortex is dynamically regulated throughout the life span and involves differentiated neurons.

The role of DNA cytosine methylation, an epigenetic regulator of chromatin structure and function, during normal and pathological brain development and aging remains unclear. Here, we examined by MethyLight PCR the DNA methylation status at 50 loci, encompassing primarily 5' CpG islands of genes related to CNS growth and development, in temporal neocortex of 125 subjects ranging in age from 17 weeks of gestation to 104 years old. Two psychiatric disease cohorts--defined by chronic neurodegeneration (Alzheimer's) or lack thereof (schizophrenia)--were included. A robust and progressive rise in DNA methylation levels across the lifespan was observed for 8/50 loci (GABRA2, GAD1, HOXA1, NEUROD1, NEUROD2, PGR, STK11, SYK) typically in conjunction with declining levels of the corresponding mRNAs. Another 16 loci were defined by a sharp rise in DNA methylation levels within the first few months or years after birth. Disease-associated changes were limited to 2/50 loci in the Alzheimer's cohort, which appeared to reflect an acceleration of the age-related change in normal brain. Additionally, methylation studies on sorted nuclei provided evidence for bidirectional methylation events in cortical neurons during the transition from childhood to advanced age, as reflected by significant increases at 3, and a decrease at 1 of 10 loci. Furthermore, the DNMT3a de novo DNA methyl-transferase was expressed across all ages, including a subset of neurons residing in layers III and V of the mature cortex. Therefore, DNA methylation is dynamically regulated in the human cerebral cortex throughout the lifespan, involves differentiated neurons, and affects a substantial portion of genes predominantly by an age-related increase.

Coagulation abnormalities in patients with single-ventricle physiology precede the Fontan procedure.

OBJECTIVE: Thromboembolic events in patients who have undergone the Fontan operation have been reported to be as high as 20% to 33%. A hypercoagulable state with deficiencies in proteins C and S has been implicated. Using age-matched control subjects, we evaluated whether an altered coagulation state is present earlier in the course of staged single-ventricle repair. METHODS: After informed consent had been obtained, coagulation factors were assayed in 36 infants (mean age, 7.7 +/- 3.6 months) with single-ventricle cardiac defects immediately before undergoing the bidirectional Glenn procedure; 34 infants (mean age, 8.4 +/- 2.6 months) without cardiac disease were assayed as control subjects. Concentration of factors II, V, VII, VIII, IX, and X; antithrombin III; plasminogen; proteins C and S; fibrinogen; serum albumin; and liver enzymes were measured. Normal reference intervals on the basis of the control subjects were determined by using 95% confidence limits. Patient demographic and hemodynamic variables were evaluated as possible predictors of coagulation abnormalities. RESULTS: Concentrations of protein C; factors II, V, VII, IX, and X; plasminogen; fibrinogen; and antithrombin III were significantly lower in the pre-Glenn infants compared with the age-matched control subjects (all P <.001, Student t test). On the basis of multiple logistic regression, no specific hemodynamic variables were predictive of a procoagulant or anticoagulant deficiency. Ventricular dysfunction did predict the presence of multiple coagulation abnormalities (P <.001). CONCLUSION: Procoagulant and anticoagulant factor abnormalities occur early in the course of single-ventricle repair and precede the cavopulmonary connection.