Genomic imprinting refers to an epigenetic marking of genes that results in monoallelic expression. This parent-of-origin dependent phenomenon is a notable exception to the laws of Mendelian genetics. Imprinted genes are intricately involved in fetal and behavioral development. Consequently, abnormal expression of these genes results in numerous human genetic disorders including carcinogenesis. This paper reviews genomic imprinting and its role in human disease. Additional information about imprinted genes can be found on the Genomic Imprinting Website at http://www.geneimprint.com.

Genomic Imprinting: Implications for Human Disease

Genetic basis of schizophrenia

OBJECTIVE: The major cognitive theories of persecutory delusion formation and maintenance are critically examined in this article. METHOD: The authors present a comprehensive review of the literature, citing results of relevant functional neuroimaging and neural network studies. RESULTS: People with persecutory delusions selectively attend to threatening information, jump to conclusions on the basis of insufficient information, attribute negative events to external personal causes, and have difficulty in envisaging others’ intentions, motivations, or states of mind. Presence of the “reality distortion” cluster of psychotic symptoms correlates with cerebral blood flow in the left lateral prefrontal cortex, ventral striatum, superior temporal gyrus, and parahippocampal region. Social cognitive processing (selective attention to threat, attribution of causation or mental states) in normal subjects involves similar areas. Neural network models of persecutory delusions highlight the importance of disordered ne...

https://ajp.psychiatryonline.org/doi/pdfplus/10.1176/appi.ajp.158.4.527

Cognitive neuropsychiatric models of persecutory delusions.

Parent-of-origin effects were first recorded >3000 years ago by mule breeders in Asia Minor. There are now several different types of evidence suggesting the presence of a large number of imprinted genes, many of which have not yet been identified. Here, we catalogue a wide range of evidence and phenomena which indicate or suggest the presence of genomic imprinting in animals. This evidence includes: the direct documentation of parent-of-origin-specific gene transcription; human disease inheritance patterns which suggest the involvement of imprinted genes; and older, less well studied animal models which may show parent-of-origin effects.

A Catalogue of Imprinted Genes and Parent-of-Origin Effects in Humans and Animals

Many people with severe schizophrenia have increased cerebral ventricular size and diffuse reduction in cortical volume; recent attention has focused on subtle malformations of the cytoarchitecture in the hippocampus and parahippocampal cortex. Sufferers also show an excess of dermatoglyphic and minor physical abnormalities, and a significant proportion had psychomotor deficits, cognitive or behavioural problems as children. Such findings suggest that the form of schizophrenia most akin to Kraepelin's original description of dementia praecox results from neurodevelopmental impairment. This may have its origin in genetic defects in the control of early brain growth, or in early environmental hazards such as prenatal exposure to maternal influenza or perinatal complications. How foetal or neonatal lesions produce hallucinations and delusions two or three decades later remains a mystery, but maturational changes in the brain may be important.

Neurodevelopmental schizophrenia: the rediscovery of dementia praecox

Among 29 multiply affected pedigrees, age of onset among parents and offspring was examined for evidence of both anticipation and genomic imprinting. The results do not suggest that either mechanism is operating in schizophrenia, but only very large effects can be confidently excluded.

Cathy Walsh

Papers

Imprinting and anticipation. Are they relevant to genetic studies of schizophrenia

Familiality of symptom dimensions in schizophrenia

Familiality of clinical characteristics in schizophrenia.

Familial schizophrenia shows no gender difference in age of onset

Clinical dimensions in schizophrenic families