Dose-dependent expression of claudin-5 is a modifying factor in schizophrenia.
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Schizophrenia is a neurodevelopmental disorder that affects up to 1% of the general population. Various genes show associations with schizophrenia and a very weak nominal association with the tight junction protein, claudin-5, has previously been identified. Claudin-5 is expressed in endothelial cells forming part of the blood-brain barrier (BBB). Furthermore, schizophrenia occurs in 30% of individuals with 22q11 deletion syndrome (22q11DS), a population who are haploinsufficient for the claudin-5 gene. Here, we show that a variant in the claudin-5 gene is weakly associated with schizophrenia in 22q11DS, leading to 75% less claudin-5 being expressed in endothelial cells. We also show that targeted adeno-associated virus-mediated suppression of claudin-5 in the mouse brain results in localized BBB disruption and behavioural changes. Using an inducible 'knockdown' mouse model, we further link claudin-5 suppression with psychosis through a distinct behavioural phenotype showing impairments in learning and memory, anxiety-like behaviour and sensorimotor gating. In addition, these animals develop seizures and die after 3-4 weeks of claudin-5 suppression, reinforcing the crucial role of claudin-5 in normal neurological function. Finally, we show that anti-psychotic medications dose-dependently increase claudin-5 expression in vitro and in vivo while aberrant, discontinuous expression of claudin-5 in the brains of schizophrenic patients post mortem was observed compared to age-matched controls. Together, these data suggest that BBB disruption may be a modifying factor in the development of schizophrenia and that drugs directly targeting the BBB may offer new therapeutic opportunities for treating this disorder.
Published Version (Please cite this version)
Greene, C, J Kealy, MM Humphries, Y Gong, J Hou, N Hudson, LM Cassidy, R Martiniano, et al. (2018). Dose-dependent expression of claudin-5 is a modifying factor in schizophrenia. Molecular psychiatry, 23(11). pp. 2156–2166. 10.1038/mp.2017.156 Retrieved from https://hdl.handle.net/10161/25898.
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Undiagnosed and rare diseases cause significant emotional and financial distress to patients who suffer from these and their families. Duke is one of seven clinical sites to be part of the NIH Undiagnosed Diseases Network (UDN). As a principal investigator for the Duke UDN site, I am involved in arranging detailed clinical evaluation for children and adults with undiagnosed diseases and in the interpretation of the genome sequencing that is performed as part of the initiative to obtain a diagnosis in these individuals. I also currently serve as the Co-Chair of the UDN steering committee.
Chromosome 22q11.2 deletion syndrome (also known as velocardiofacial or DiGeorge syndrome: particular interests are in understanding the learning disabilities and the high risk of mental illness in these children as they get older, for which a research study is ongoing. As a clinician and researcher in this area, I run a clinic for children and adults with 22q11.2 deletion syndrome and am an investigator within the International Brain and Behavior Consortium for 22q11.2 deletion syndrome. The goal of the consortium is to conduct research to understand the genetic underpinnings of the serious mental illnesses such as schizophrenia that occur in ~25% of adolescents and adults with the condition.
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