Blast related traumatic brain injury (TBI) has been a major cause of injury in the wars in Iraq and Afghanistan. A striking feature of the mild TBI (mTBI) cases has been the prominent association with post-traumatic stress disorder (PTSD). However, because of the overlapping symptoms, distinction between the two disorders has been difficult. We studied a rat model of mTBI in which adult male rats were exposed to repetitive blast injury while under anesthesia. Blast exposure induced a variety of PTSD-related behavioral traits that were present many months after the blast exposure, including increased anxiety, enhanced contextual fear conditioning, and an altered response in a predator scent assay. We also found elevation in the amygdala of the protein stathmin 1, which is known to influence the generation of fear responses. Because the blast overpressure injuries occurred while animals were under general anesthesia, our results suggest that a blastrelated mTBI exposure can, in the absence of any psychological stressor, induce PTSD-related traits that are chronic and persistent. These studies have implications for understanding the relationship of PTSD to mTBI in the population of veterans returning from the wars in Iraq and Afghanistan.

Identifying genes involved in social behavior is important for autism research. Williams-Beuren syndrome (WBS) is a developmental syndrome with unique neurocognitive features, including low IQ, deficits in visuospatial and visual-motor abilities, hypersensitivity to sounds, hypersociability, and increased general anxiety. The syndrome is caused by a recurrent hemizygous deletion of the 7q11.23 region, containing about 28 genes. One of genes in the region, GTF2I, has been implicated in the hypersociability and visuospatial deficits of WBS based on genotype-phenotype correlation studies of patients with atypical deletions. In order to clarify the involvement of GTF2I in neurocognitive function, especially social behavior, we have developed and characterized Gtf2i-deficient mice. We found that homozygous deletion of Gtf2i causes lethality during embryonic development with neural tube closure defects and exencephaly, consistent with other reports. Gtf2i heterozygous animals show no gross changes in brain structure or development. Furthermore, heterozygous animals show no alterations in learning and memory, including spatial memory as assessed by the Morris water maze, but show alterations in the recognition of novel objects. Interestingly, they show increased social interaction with unfamiliar mice and do not show typical social habituation processes, reminiscent of the hypersociability observed in WBS patients. The mice do not appear to show increased anxiety, supporting a specific effect of Gtf2i on defined domains of the WBS phenotype. These data indicate that Gtf2i is involved in several aspects of embryonic development and the development of social neurocircuitry and that GTF2I haploinsufficiency could be a contributor to the hypersociability in WBS patients.

BackgroundCopy number variation (CNV) at the 15q11.2 region, which includes a gene that codes for CYFIP1 (cytoplasmic FMR1 interacting protein 1), has been implicated in autism, intellectual disability and additional neuropsychiatric phenotypes. In the current study we studied the function of Cyfip1 in synaptic physiology and behavior, using mice with a disruption of the Cyfip1 gene.Methodology/Principal FindingsWe observed that in Cyfip1 heterozygous mice metabotropic glutamate receptor (mGluR)-dependent long-term depression (LTD) induced by paired-pulse low frequency stimulation (PP-LFS) was significantly increased in comparison to wildtype mice. In addition, mGluR-LTD was not affected in the presence of protein synthesis inhibitor in the Cyfip1 heterozygous mice, while the same treatment inhibited LTD in wildtype littermate controls. mGluR-agonist (RS)-3,5-dihydroxyphenylglycine (DHPG)-induced LTD was also significantly increased in hippocampal slices from Cyfip1 heterozygous mice and again showed independence from protein synthesis only in the heterozygous animals. Furthermore, we observed that the mammalian Target of Rapamycin (mTOR) inhibitor rapamycin was only effective at reducing mGluR-LTD in wildtype animals. Behaviorally, Cyfip1 heterozygous mice showed enhanced extinction of inhibitory avoidance. Application of both mGluR5 and mGluR1 antagonist to slices from Cyfip1 heterozygous mice reversed the increase in DHPG-induced LTD in these mice.Conclusions/SignificanceThese results demonstrate that haploinsufficiency of Cyfip1 mimics key aspects of the phenotype of Fmr1 knockout mice and are consistent with the hypothesis that these effects are mediated by interaction of Cyfip1 and Fmrp in regulating activity-dependent translation. The data provide support for a model where CYFIP1 haploinsufficiency in patients results in intermediate phenotypes increasing risk for neuropsychiatric disorders.

BackgroundBlast-related traumatic brain injury (TBI) has been a significant cause of injury in the military operations of Iraq and Afghanistan, affecting as many as 10-20% of returning veterans. However, how blast waves affect the brain is poorly understood. To understand their effects, we analyzed the brains of rats exposed to single or multiple (three) 74.5 kPa blast exposures, conditions that mimic a mild TBI.ResultsRats were sacrificed 24 hours or between 4 and 10 months after exposure. Intraventricular hemorrhages were commonly observed after 24 hrs. A screen for neuropathology did not reveal any generalized histopathology. However, focal lesions resembling rips or tears in the tissue were found in many brains. These lesions disrupted cortical organization resulting in some cases in unusual tissue realignments. The lesions frequently appeared to follow the lines of penetrating cortical vessels and microhemorrhages were found within some but not most acute lesions.ConclusionsThese lesions likely represent a type of shear injury that is unique to blast trauma. The observation that lesions often appeared to follow penetrating cortical vessels suggests a vascular mechanism of injury and that blood vessels may represent the fault lines along which the most damaging effect of the blast pressure is transmitted.

Endothelin‐converting enzyme (ECE)‐2 is a metalloprotease that possesses many properties consistent with it being a neuropeptide‐processing enzyme. This protease is found primarily in neural tissues, with high levels of expression in midbrain, cerebellum, hypothalamus, frontal cortex and spinal cord and moderate levels in hippocampus and striatum. To evaluate its role in neural function, mice have been generated lacking this enzyme. Physical appearance, autonomic reflexes, motor co‐ordination, balance, locomotor activity and spontaneous emotional responses appear normal in these knockout (KO) mice. However, these mutants display deficits in learning and memory as evidenced by marked impairment in the Morris water maze. Knockout mice are also deficient in object recognition memory where they show delays in discerning changes in object location and in recognizing the introduction of a novel object. In this study, perseveration appears to interfere with learning and memory. Finally, mutants are impaired in social transmission of food preference where they show poor short‐term memory and perturbations in long‐term memory; the latter can be ameliorated by reminder cues. As ECE‐2 has been implicated in Alzheimer’s disease, the deficits in learning and memory in the KO mice may provide unique insights into processes that may contribute to this disease and possible other disorders of cognition.