Parental origin of the deletion 22q11.2 and brain development in velocardiofacial syndrome: a preliminary study

22q11.2 Deletion Syndrome: Influence of Parental Origin on Clinical Heterogeneity

22q11.2 deletion syndrome (22q11.2DS) shows significant clinical heterogeneity. This study aimed to explore the association between clinical heterogeneity in 22q11.2DS and the parental origin of the deletion. The parental origin of the deletion was determined for 61 individuals with 22q11.2DS by genotyping DNA microsatellite markers and single-nucleotide polymorphisms (SNPs). Among the 61 individuals, 29 (47.5%) had a maternal origin of the deletion, and 32 (52.5%) a paternal origin. Comparison of the frequency of the main clinical features between individuals with deletions of maternal or paternal origin showed no statistically significant difference. However, Truncus arteriosus, pulmonary atresia, seizures, and scoliosis were only found in patients with deletions of maternal origin. Also, a slight difference in the frequency of other clinical features between groups of maternal or paternal origin was noted, including congenital heart disease, endocrinological alterations, and genitourinary abnormalities, all of them more common in patients with deletions of maternal origin. Although parental origin of the deletion does not seem to contribute to the phenotypic variability of most clinical signs observed in 22q11.2DS, these findings suggest that patients with deletions of maternal origin could have a more severe phenotype. Further studies with larger samples focusing on these specific features could corroborate these findings.

Lessons Learned From Neuroimaging Studies of Copy Number Variants: A Systematic Review

Pathogenic copy number variants (CNVs) and aneuploidies alter gene dosage and are associated with neurodevelopmental psychiatric disorders such as autism spectrum disorder and schizophrenia. Brain mechanisms mediating genetic risk for neurodevelopmental psychiatric disorders remain largely unknown, but there is a rapid increase in morphometry studies of CNVs using T1-weighted structural magnetic resonance imaging. Studies have been conducted one mutation at a time, leaving the field with a complex catalog of brain alterations linked to different genomic loci. Our aim was to provide a systematic review of neuroimaging phenotypes across CNVs associated with developmental psychiatric disorders including autism and schizophrenia. We included 76 structural magnetic resonance imaging studies on 20 CNVs at the 15q11.2, 22q11.2, 1q21.1 distal, 16p11.2 distal and proximal, 7q11.23, 15q11-q13, and 22q13.33 (SHANK3) genomic loci as well as aneuploidies of chromosomes X, Y, and 21. Moderate to large effect sizes on global and regional brain morphometry are observed across all genomic loci, which is in line with levels of symptom severity reported for these variants. This is in stark contrast with the much milder neuroimaging effects observed in idiopathic psychiatric disorders. Data also suggest that CNVs have independent effects on global versus regional measures as well as on cortical surface versus thickness. Findings highlight a broad diversity of regional morphometry patterns across genomic loci. This heterogeneity of brain patterns provides insight into the weak effects reported in magnetic resonance imaging studies of cognitive dimension and psychiatric conditions. Neuroimaging studies across many more variants will be required to understand links between gene function and brain morphometry.

22q11.2 deletion syndrome and schizophrenia

22q11.2 deletion is a common microdeletion that causes an array of developmental defects including 22q11.2 deletion syndrome (22q11DS) or DiGeorge syndrome and velocardiofacial syndrome. About 30% of patients with 22q11.2 deletion develop schizophrenia. Mice with deletion of the ortholog region in mouse chromosome 16qA13 exhibit schizophrenia-like abnormal behaviors. It is suggested that the genes deleted in 22q11DS are involved in the pathogenesis of schizophrenia. Among these genes, COMT, ZDHHC8, DGCR8, and PRODH have been identified as schizophrenia susceptibility genes. And DGCR2 is also found to be associated with schizophrenia. In this review, we focused on these five genes and reviewed their functions in the brain and the potential pathophysiological mechanisms in schizophrenia, which will give us a deeper understanding of the pathology of schizophrenia.

The Prevalence of Apraxia Characteristics in Patients with Velocardiofacial Syndrome as Compared with Other Cleft Populations

Objective:

The purpose of this study was to assess the oral-motor function of children with a history of cleft lip and palate, cleft palate only, velocardiofacial syndrome, and children with normal oral structures to determine if children with velocardiofacial syndrome have more apraxia characteristics than the other populations have.

Design:

The Apraxia Profile (Hickman, 1997) was administered to all participants in a prospective study.

Setting:

The investigation was conducted at Cincinnati Children's Hospital Medical Center.

Participants:

In this study, 10 children with cleft lip and palate, 10 with cleft palate only, 7 with velocardiofacial syndrome, and 47 with normal structures were tested.

Results:

This study revealed that when compared with children with normal structures, children with cleft lip and palate did not demonstrate significant apraxia characteristics, children with cleft palate only demonstrated some apraxia characteristics, and children with velocardiofacial syndrome demonstrated the most apraxia characteristics.

Conclusions:

There appears to be a high prevalence of apraxia characteristics in the speech of patients with velocardiofacial syndrome. This information has implications for the type of treatment recommended. Further investigation is warranted with a larger patient population and a focus on the association of abnormal brain structure with apraxia in this population.

Differences in speech and language abilities between children with 22q11.2 deletion syndrome and children with phenotypic features of 22q11.2 deletion syndrome but without microdeletion

BACKGROUND

22q11.2DS is the most common microdeletion syndrome in humans, usually associated with speech and language delay (SLD). Approximately 75% of children with 22q11.2 microdeletion have congenital heart malformations (CHM) which after infant open-heart surgery might lead to SLD.

AIMS

The purpose of this study was to determine whether factors associated with microdeletion contribute to SLD in children with 22q11.2DS.

METHODS AND PROCEDURES

We compared speech and language abilities of two groups of school-aged children: those with 22q11.2 microdeletion (E1) and those with the phenotype resembling 22q11.2DS but without the microdeletion (E2). An age-matched group of typically developing children was also tested.

OUTCOMES AND RESULTS

The obtained results revealed that children from group E1 have lower level of speech and language abilities compared to children from group E2 and control group. Additionally, mild to moderate SLD was detected in children from group E2 compared to children from the control group.

CONCLUSIONS AND IMPLICATIONS

The obtained results imply that both CHM after infant open-heart surgery and other factors associated with 22q11.2 microdeletion, contribute to SLD in patients with 22q11.2 microdeletion. Based on this, we could postulate that there is/are some potential candidate gene(s), located in the 22q11.2 region, whose function could be important for speech and language development.

Acute Dystonia in a Patient with 22q11.2 Deletion Syndrome

The 22q11.2 deletion syndrome (di George syndrome) is one of the most prevalent genetic disorders. The clinical features of the syndrome are distinct facial appearance, velopharyngeal insufficiency, conotruncal heart disease, parathyroid and immune dysfunction; however, little is known about possible neurodegenerative diseases. We describe the case of an 18-year old patient suffering from 22q11.2 deletion syndrome. Since adolescence, he presented with behavioral disorders, recommended treatment with 2 mg aloperidin and he presented cervical dystonia and emergence of torticollis and trunk dystonia. Antipsychotic medications either accelerate or reveal dystonic symptoms.

The 22q11.2 deletion syndrome as a window into complex neuropsychiatric disorders over the lifespan

Evidence is rapidly accumulating that rare, recurrent copy number variants represent large effect risk factors for neuropsychiatric disorders. 22q11.2 deletion syndrome (22q11DS) (velocardiofacial syndrome or DiGeorge syndrome) is the most common known contiguous gene deletion syndrome and is associated with diverse neuropsychiatric disorders across the life span. One of the most intriguing aspects of the syndrome is the variability in clinical and cognitive presentation: children with 22q11DS have high prevalence of autism spectrum, attention deficit, and anxiety disorders, as well as psychotic-like features, and up to 30% of adolescents and adults develop schizophrenia-like psychosis. Recently, cases of early-onset Parkinson's disease in adults have been reported, collectively suggesting a role for disrupted dopaminergic neurotransmission in the observed neuropsychiatric phenotypes. There is also some evidence that 22q11DS-associated autism spectrum disorder and schizophrenia represent two unrelated phenotypic manifestations, consistent with a neuropsychiatric pleiotropy model. This genetic lesion thus provides a unique model for the discovery of specific genomic risk and (potentially) protective factors for neuropsychiatric disease. Here, we provide an overview of neuropsychiatric findings to date, which highlight the value of this syndrome in mapping the developmental trajectory of dimensional phenotypes that traverse multiple diagnostic categories. Potential sources of genetic variability that may contribute to the disorder's heterogeneous presentation are reviewed. Because of its known genetic etiology, animal models can readily be developed that recapitulate specific aspects of the syndrome. Future research directions involve translational models and potential for drug screenable targets in the context of this human model system.

Evaluation of PRDM9 variation as a risk factor for recurrent genomic disorders and chromosomal non-disjunction

Recent studies have identified PRDM9, a zinc finger (ZF) protein, as a key regulator of meiotic recombination. As both recurrent genomic disorders and chromosomal non-disjunction are known to be associated with specific unusual patterns of recombination, we hypothesized a possible link between PRDM9 ZF variation and susceptibility to microdeletion syndromes and/or trisomy. We sequenced the PRDM9 ZF domain in 271 parents of patients with de novo microdeletions of known parental origin (velocardiofacial syndrome, the 17q21.31 microdeletion syndrome, Prader-Willi/Angelman syndrome and Williams-Beuren syndrome), and in 61 parents of individuals with a supernumerary X chromosome. We compared PRDM9 ZF genotype frequencies between parents in whose germ line the de novo rearrangement occurred and their spouses. We observed a significantly increased frequency (p = 0.006) of PRDM9 variants in parents who transmitted de novo 7q11.23 deletions to their offspring. These data suggest that certain PRDM9 alleles may be associated with an increased susceptibility to recurrent 7q11.23 microdeletions that cause Williams-Beuren syndrome. However, as the majority of parents who transmitted a de novo microdeletion/supernumerary X chromosome to their offspring have the common AA genotype, we conclude that none of the rearrangements we have studied are dependent on specific non-A PRDM9 alleles.

Dysregulation of DGCR6 and DGCR6L: psychopathological outcomes in chromosome 22q11.2 deletion syndrome

Chromosome 22q11.2 deletion syndrome (22q11DS) is the most common microdeletion syndrome in humans. It is typified by highly variable symptoms, which might be explained by epigenetic regulation of genes in the interval. Using computational algorithms, our laboratory previously predicted that DiGeorge critical region 6 (DGCR6), which lies within the deletion interval, is imprinted in humans. Expression and epigenetic regulation of this gene have not, however, been examined in 22q11DS subjects. The purpose of this study was to determine if the expression levels of DGCR6 and its duplicate copy DGCR6L in 22q11DS subjects are associated with the parent-of-origin of the deletion and childhood psychopathologies. Our investigation showed no evidence of parent-of-origin-related differences in expression of both DGCR6 and DGCR6L. However, we found that the variability in DGCR6 expression was significantly greater in 22q11DS children than in age and gender-matched control individuals. Children with 22q11DS who had anxiety disorders had significantly lower DGCR6 expression, especially in subjects with the deletion on the maternal chromosome, despite the lack of imprinting. Our findings indicate that epigenetic mechanisms other than imprinting contribute to the dysregulation of these genes and the associated childhood psychopathologies observed in individuals with 22q11DS. Further studies are now needed to test the usefulness of DGCR6 and DGCR6L expression and alterations in the epigenome at these loci in predicting childhood anxiety and associated adult-onset pathologies in 22q11DS subjects.

Three phases of DiGeorge/22q11 deletion syndrome pathogenesis during brain development: patterning, proliferation, and mitochondrial functions of 22q11 genes

DiGeorge, or 22q11 deletion syndrome (22q11DS), the most common survivable human genetic deletion disorder, is caused by deletion of a minimum of 32 contiguous genes on human chromosome 22, and presumably results from diminished dosage of one, some, or all of these genes--particularly during development. Nevertheless, the normal functions of 22q11 genes in the embryo or neonate, and their contribution to developmental pathogenesis that must underlie 22q11DS are not well understood. Our data suggests that a substantial number of 22q11 genes act specifically and in concert to mediate early morphogenetic interactions and subsequent cellular differentiation at phenotypically compromised sites--the limbs, heart, face and forebrain. When dosage of a broad set of these genes is diminished, early morphogenesis is altered, and initial 22q11DS phenotypes are established. Thereafter, functionally similar subsets of 22q11 genes--especially those that influence the cell cycle or mitochondrial function--remain expressed, particularly in the developing cerebral cortex, to regulate neurogenesis and synaptic development. When dosage of these genes is diminished, numbers, placement and connectivity of neurons and circuits essential for normal behavior may be disrupted. Such disruptions likely contribute to vulnerability for schizophrenia, autism, or attention deficit/hyperactivity disorder seen in most 22q11DS patients.

Bridging the gene-behavior divide through neuroimaging deletion syndromes: Velocardiofacial (22q11.2 Deletion) and Williams (7q11.23 Deletion) syndromes

Investigating the relationship between genes and the neural substrates of complex human behavior promises to provide essential insight into the pathophysiology of mental disorders. One approach to this inquiry is through neuroimaging of individuals with microdeletion syndromes that manifest in specific neuropsychiatric phenotypes. Both Velocardiofacial syndrome (VCFS) and Williams syndrome (WS) involve haploinsufficiency of a relatively small set of identified genes on the one hand and association with distinct, clinically relevant behavioral and cognitive profiles on the other hand. In VCFS, there is a deletion in chromosomal region 22q11.2 and a resultant predilection toward psychosis, poor arithmetic proficiency, and low performance intelligence quotients. In WS, there is a deletion in chromosomal region 7q11.23 and a resultant predilection toward hypersociability, non-social anxiety, impaired visuospatial construction, and often intellectual impairment. Structural and functional neuroimaging studies have begun not only to map these well-defined genetic alterations to systems-level brain abnormalities, but also to identify relationships between neural phenotypes and particular genes within the critical deletion regions. Though neuroimaging of both VCFS and WS presents specific, formidable methodological challenges, including comparison subject selection and accounting for neuroanatomical and vascular anomalies in patients, and many questions remain, the literature to date on these syndromes, reviewed herein, constitutes a fruitful "bottom-up" approach to defining gene-brain relationships.

Meta-analysis of magnetic resonance imaging studies in chromosome 22q11.2 deletion syndrome (velocardiofacial syndrome)

OBJECTIVES

22q11.2 deletion syndrome (22q11.2DS), also known as velocardiofacial syndrome (VCFS) or DiGeorge Syndrome, is a genetic disorder due to a micro deletion on chromosome 22q11.2. VCFS is associated with abnormalities in brain structure and with an increased risk of psychiatric disorders, particularly schizophrenia. The aim of this review was to statistically summarize the structural imaging literature on VCFS which due to the relatively rarity of the disorder tends to consider small sample sizes.

METHOD

A systematic review and meta-analysis of region of interest (ROI) studies comparing VCFS with healthy controls was carried out. Significant heterogeneity was explored using meta-regression.

RESULTS

Subjects with VCFS were characterised by global brain volumetric reduction including several cortical regions, cerebellum and hippocampus. The area of the corpus callosum was increased.

CONCLUSIONS

Many regions extensively studied in schizophrenia were not covered in the existing VCFS literature. However, the studies considered support volumetric abnormalities which may help explain why VCFS is associated with a greatly increased risk of psychosis and other psychiatric disorders.

Psychiatric disorders and intellectual functioning throughout development in velocardiofacial (22q11.2 deletion) syndrome

OBJECTIVE

Velocardiofacial syndrome (VCFS) is associated with cognitive deficits and high rates of schizophrenia and other neuropsychiatric disorders. We report the data from two large cohorts of individuals with VCFS from Israel and Western Europe to characterize the neuropsychiatric phenotype from childhood to adulthood in a large sample.

METHOD

Individuals with VCFS (n = 172) aged 5 to 54 years were evaluated with structured clinical interviews for psychiatric disorders and age-appropriate versions of the Wechsler intelligence tests.

RESULTS

The frequency of psychiatric disorders was high and remarkably similar between samples. Psychotic disorders and depression were uncommon during childhood but increased in rates during adulthood (depressive disorders: 40.7% in young adults [aged 18-24 years]; psychotic disorders: 32.1% in adults [age >24 years]). Cognitive scores were inversely associated with age in subjects with VCFS, including patients without psychosis. Specifically, Verbal IQ (VIQ) scores negatively correlated with age, and the subjects with VCFS and psychotic disorders had significantly lower VIQ scores than nonpsychotic VCFS subjects.

CONCLUSIONS

Neuropsychiatric deficits in individuals with VCFS seem to follow a developmental pattern. The VIQ scores are negatively associated with age and rates of mood, and psychotic disorders increase dramatically during young adulthood. The data presented here support careful monitoring of psychiatric symptoms during adolescence and young adulthood in VCFS. Prospective longitudinal studies are needed to examine the nature of age-related cognitive changes and their association with psychiatric morbidity in VCFS.

Copy number variations and risk for schizophrenia in 22q11.2 deletion syndrome

22q11.2 Deletion Syndrome (22q11.2DS) is a common microdeletion syndrome with congenital and late-onset features. Testing for the genomic content of copy number variations (CNVs) may help elucidate the 22q11.2 deletion mechanism and the variable clinical expression of the syndrome including the high (25%) risk for schizophrenia. We used genome-wide microarrays to assess CNV content and the parental origin of 22q11.2 deletions in a cohort of 100 adults with 22q11.2DS (44 with schizophrenia) and controls. 22q11.2DS subjects with schizophrenia failed to exhibit de novo CNVs or any excess of novel inherited CNVs outside the 22q11.2 region. There were no significant effects of parental origin of the 22q11.2 deletion, deletion length, parental age or family history on expression of schizophrenia. There was no evidence for a general increase of de novo CNVs in 22q11.2DS. A novel finding was the relative paucity of males with de novo 22q11.2 deletions of paternal origin (P = 0.019). The Y chromosome may play a mediating role in the mechanism of 22q11.2 deletion events during spermatogenesis, resulting in the previously observed excess of maternal de novo 22q11.2 deletions. Hemizygosity of the 22q11.2 region appears to be the major CNV-related risk factor for schizophrenia in 22q11.2DS. The results reinforce the need for further efforts to identify specific molecular mechanisms underlying this expression and to identify the 1% of patients with schizophrenia who carry 22q11.2 deletions.

Quetiapine facilitates oligodendrocyte development and prevents mice from myelin breakdown and behavioral changes

Recent neuroimaging and postmortem studies have reported abnormalities in white matter of schizophrenic brains, suggesting the involvement of oligodendrocytes in the etiopathology of schizophrenia. This view is being supported by gene microarray studies showing the downregulation of genes related to oligodendrocyte function and myelination in schizophrenic brain compared to control subjects. However, there is currently little information available on the response of oligodendrocytes to antipsychotic drugs (APDs), which could be invaluable for corroborating the oligodendrocyte hypothesis. In this study we found: (1) quetiapine (QUE, an atypical APD) treatment in conjunction with addition of growth factors increased the proliferation of neural progenitors isolated from the cerebral cortex of embryonic rats; (2) QUE directed the differentiation of neural progenitors to oligodendrocyte lineage through extracellular signal-related kinases; (3) addition of QUE increased the synthesis of myelin basic protein and facilitated myelination in rat embryonic cortical aggregate cultures; (4) chronic administration of QUE to C57BL/6 mice prevented cortical demyelination and concomitant spatial working memory impairment induced by cuprizone, a neurotoxin. These findings suggest a new neural mechanism of antipsychotic action of QUE, and help to establish a role for oligodendrocytes in the etiopathology and treatment of schizophrenia.

Association between a common haplotype in the COMT gene region and psychiatric disorders in individuals with 22q11.2DS

The 22q11.2 deletion syndrome (22q11.2DS) is the most common hemizygous deletion syndrome in humans. In addition to a wide range of physical abnormalities 22q11.2DS subjects show high prevalence of several psychiatric disorders. In our previous study we showed that the low-activity allele (158Met) of the COMT gene is a risk factor for attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD) in 22q11.2DS individuals. In the present study we have genotyped fifty-five 22q11.2DS individuals and 95 of their parents for eight SNPs in and around the COMT gene. A haplotype composed of three SNPs [rs2097603; rs4680 (158Val/Met); rs165599] representing the major linkage disequilibrium blocks in COMT and previously implicated in functional variation, was found to be associated with ADHD and OCD in 22q11.2DS individuals. A common risk haplotype (G-A-A) was significantly associated with both ADHD (OR 3.13, chi2=4.38, p=0.036) and OCD (OR 4.00, chi2=6.41, p=0.011) in 22q11.2DS individuals. Interestingly, the same haplotype was recently found to be associated with efficient prefrontal performance in the general population. The risk haplotype was not found to be associated with IQ scores in our 22q11.2DS sample. Parental origin of the deletion did not affect the susceptibility to ADHD and OCD in the 22q11.2DS subjects. This study demonstrated the association of a particular COMT haplotype with susceptibility to both ADHD and OCD in 22q11.2DS and supports the hypothesis that COMT gene variations contribute to genetic predisposition to psychiatric disorders in the general population.

A surface-based approach to quantify local cortical gyrification

The high complexity of cortical convolutions in humans is very challenging both for engineers to measure and compare it, and for biologists and physicians to understand it. In this paper, we propose a surface-based method for the quantification of cortical gyrification. Our method uses accurate 3-D cortical reconstruction and computes local measurements of gyrification at thousands of points over the whole cortical surface. The potential of our method to identify and localize precisely gyral abnormalities is illustrated by a clinical study on a group of children affected by 22q11 Deletion Syndrome, compared to control individuals.

From genes to brain: understanding brain development in neurogenetic disorders using neuroimaging techniques

For almost two decades, a considerable amount of work has been devoted to the accurate delineation of normal and abnormal brain development using cerebral MRI. In the broad field of neuroimaging research, specific genetic conditions associated with impaired cognitive performances or with psychiatric symptoms have received increased attention because of their potential for revealing insight on the biologic correlates of behavior. First delineated by volumetric measurements of cerebral lobes or regions of interest, new image processing techniques are currently defining cerebral phenotypes associated with neurogenetic disorders with increasing precision. In this article the authors review the contribution of structural brain imaging in advancing our understanding of the pathogenic processes underlying altered brain development in Down, fragile X, and velocardiofacial (22q11DS) syndromes.

Cognition, psychosocial adjustment and coping in familial cases of velocardiofacial syndrome

Velocardiofacial syndrome (VCFS) is characterized by both physical manifestations and neuropsychiatric disabilities. About 6-28% of cases are familial. The aim of the present study was to compare the clinical characteristics of subjects with familial and nonfamilial VCFS, with a special focus on cognitive and psychiatric disabilities. In addition, the complexities of coping with the disease in families in which both a parent and children are affected were highlighted in case vignettes. Sixteen patients from six families with VCFS were compared to 63 subjects with nonfamilial VCFS for physical parameters, IQ, and rate of major psychiatric disorders. After controlling for the effect of age, IQ was significantly lower in the familial compared to the nonfamilial group of VCFS patients. Rate of psychiatric disorders was similarly high in both groups. The familial group had fewer cardiac and palate anomalies. A significant negative correlation was found between IQ and age. Most of the adults with familial VCFS were neuropsychiatrically disabled. Thus, although familial VCFS seems to be associated with a milder physical phenotype than nonfamilial VCFS, the neuropsychiatric deficits are significant in both types, at all ages.

Analysis of meiotic recombination in 22q11.2, a region that frequently undergoes deletions and duplications

Background

The 22q11.2 deletion syndrome is the most frequent genomic disorder with an estimated frequency of 1/4000 live births. The majority of patients (90%) have the same deletion of 3 Mb (Typically Deleted Region, TDR) that results from aberrant recombination at meiosis between region specific low-copy repeats (LCRs).

Methods

As a first step towards the characterization of recombination rates and breakpoints within the 22q11.2 region we have constructed a high resolution recombination breakpoint map based on pedigree analysis and a population-based historical recombination map based on LD analysis.

Results

Our pedigree map allows the location of recombination breakpoints with a high resolution (potential recombination hotspots), and this approach has led to the identification of 5 breakpoint segments of 50 kb or less (8.6 kb the smallest), that coincide with historical hotspots. It has been suggested that aberrant recombination leading to deletion (and duplication) is caused by low rates of Allelic Homologous Recombination (AHR) within the affected region. However, recombination rate estimates for 22q11.2 region show that neither average recombination rates in the 22q11.2 region or within LCR22-2 (the LCR implicated in most deletions and duplications), are significantly below chromosome 22 averages. Furthermore, LCR22-2, the repeat most frequently implicated in rearrangements, is also the LCR22 with the highest levels of AHR. In addition, we find recombination events in the 22q11.2 region to cluster within families. Within this context, the same chromosome recombines twice in one family; first by AHR and in the next generation by NAHR resulting in an individual affected with the del22q11.2 syndrome.

Conclusion

We show in the context of a first high resolution pedigree map of the 22q11.2 region that NAHR within LCR22 leading to duplications and deletions cannot be explained exclusively under a hypothesis of low AHR rates. In addition, we find that AHR recombination events cluster within families. If normal and aberrant recombination are mechanistically related, the fact that LCR22s undergo frequent AHR and that we find familial differences in recombination rates within the 22q11.2 region would have obvious health-related implications.

Neuropsychological Profile and Neuroimaging in Patients with 22Q11.2 Deletion Syndrome: A Review Keywords:

22q11.2 Deletion Syndrome is associated with cognitive, behavioural, and psychiatric problems and is known to affect brain structure. Recently, 22q11.2 Deletion Syndrome has been proposed as a disease model for a genetic subtype of schizophrenia. In this paper we discuss the currently available literature on neurocognitive functioning and brain anatomy in patients with 22q11.2 Deletion Syndrome, and how this contributes to our understanding of the neurobiology of schizophrenia. Research on cognitive functioning in 22q11.2 Deletion Syndrome patients suggests a specific cognitive profile with impairments on arithmetical, visuo-spatial, and executive tasks and relatively preserved language skills. Prominent findings of neuroimaging studies in 22q11.2 Deletion Syndrome patients are: reduction of overall brain volume, midline defects, structural alterations of cerebellum and frontal lobe, white matter abnormalities, and decreased grey matter volumes in parietal and temporal areas. We describe how brain abnormalities in patients with 22q11.2 Deletion Syndrome may contribute to the understanding of the clinical syndrome including cognitive impairments, psychotic symptoms, and social and communication problems.

No evidence for parental imprinting of mouse 22q11 gene orthologs

Non-Mendelian factors may influence central nervous system (CNS) phenotypes in patients with 22q11 Deletion Syndrome (22q11DS, also known as DiGeorge or Velocardiofacial Syndrome), and similar mechanisms may operate in mice carrying a deletion of one or more 22q11 gene orthologs. Accordingly, we examined the influence of parent of origin on expression of 25 murine 22q11 orthologs in the developing and mature CNS using single nucleotide polymorphism (SNP)-based analysis in interspecific crosses and quantification of mRNA in a murine model of 22q11DS. We found no evidence for absolute genomic imprinting or silencing. All 25 genes are biallelically expressed in the developing and adult brains. Furthermore, if more subtle forms of allelic biasing are present, they are very small in magnitude and most likely beyond the resolution of currently available quantitative approaches. Given the high degree of similarity of human 22q11 and the orthologous region of mmChr16, genomic imprinting most likely cannot explain apparent parent-of-origin effects in 22q11DS.

Parental and chromosomal origins of microdeletion and duplication syndromes involving 7q11.23, 15q11-q13 and 22q11

Non-allelic homologous recombination between chromosome-specific LCRs is the most common mechanism leading to recurrent microdeletions and duplications. To look for locus-specific differences, we have used microsatellites to determine the parental and chromosomal origins of a large series of patients with de novo deletions of chromosome 7q11.23 (Williams syndrome), 15q11-q13 (Angelman syndrome, Prader-Willi syndrome) and 22q11 (Di George syndrome) and duplications of 15q11-q13. Overall the majority of rearrangements were interchromosomal, so arising from unequal meiotic exchange, and there were approximately equal numbers of maternal and paternal deletions. Duplications and deletions of 15q11-q13 appear to be reciprocal products that arise by the same mechanisms. The proportion arising from interchromosomal exchanges varied among deletions with 22q11 the highest and 15q11-q13 the lowest. However, parental and chromosomal origins were not always independent. For 15q11-q13, maternal deletions tended to be interchromosomal while paternal deletions tended to be intrachromosomal; for 22q11 there was a possible excess of maternal cases among intrachromosomal deletions. Several factors are likely to be involved in the formation of recurrent rearrangements and the relative importance of these appear to be locus-specific.

Memory and learning in children with 22q11.2 deletion syndrome: evidence for ventral and dorsal stream disruption?

This study examined memory functioning in children and adolescents with 22q11.2 Deletion Syndrome (DS; velocardiofacial syndrome). An overall verbal better than nonverbal memory pattern was evident on the Test of Memory and Learning (TOMAL), with children with 22q11.2 DS performing significantly below their siblings and children with low average IQ but similar to children with autism on facial memory. Children with 22q11 DS also performed significantly below their siblings on tests of verbal working memory. Children with autism performed significantly poorer than the siblings of children with 22q11.2 DS only on their recall of stories. Delayed recall was significantly poorer in children with 22q11.2 DS and children with autism, compared to sibling controls. Although there were no significant group differences on tests of multiple trial verbal or visual learning, a relative weakness was noted with multiple trial visual learning in children with 22q11.2 DS and their siblings, suggesting that an alternative or interactive factor other than the deletion may account for the relatively better verbal compared to nonverbal memory abilities. Deficits in facial memory in children with both 22q11.2 DS and autism suggest disruptions in ventral temporal pathways such as between fusiform gyrus and parahippocampal/hippocampal regions whereas deficits in verbal working memory in children with 22q11.2 DS implicates dorsolateral prefrontal regions, both intimating aberrant white matter pathways.

22q11.2 deletion syndrome: genetics, neuroanatomy and cognitive/behavioral features keywords

This paper presents a conceptual review of the genetic underpinnings of 22q11.2 Deletion Syndrome. The neuroanatomical, neuropsychological, behavioral, and psychiatric phenotype associated with 22q11.2 Deletion Syndrome is also explored, including variables that are thought to affect symptom expression. The history of the deletion syndrome is described, and future directions for continued research are discussed.

Annotation: velo-cardio-facial syndrome

BACKGROUND

Velo-cardio-facial syndrome (VCFS), the most frequent known interstitial deletion identified in man, is associated with chromosomal microdeletions in the q11 band of chromosome 22. Individuals with VCFS are reported to have a characteristic behavioural phenotype with high rates of behavioural, psychiatric, neuropsychological and linguistic disorders.

METHODS

A selective literature review was undertaken.

RESULTS

Children and adults with VCFS have high rates of behavioural, psychiatric and communication disorders. While VCFS children have high rates of ADHD, anxiety and affective disorders, adults have high rates of psychotic disorders, particularly schizophrenia. In addition, the presence of a chromosome 22q11 deletion is associated with specific neuropsychological and neuroanatomical abnormalities.

CONCLUSIONS

People with VCFS have a characteristic behavioural phenotype with high rates of behavioural, psychiatric, neuropsychological and communication disorders. Early diagnosis and treatment within a multidisciplinary framework is of paramount importance for VCFS individuals as this will have a major effect in determining the long-term outcome in affected individuals. Longitudinal studies of VCFS children are currently under way to identify precursor symptoms and areas of dysfunction which precede the later development of major psychiatric disorder. Identification of such prodromal features in VCFS may have enormous implications for the clinical management of major psychiatric disorder in VCFS and in the wider population.

The neurodevelopmental model of schizophrenia: update 2005

Neurodevelopmental models of schizophrenia that identify longitudinal precursors of illness have been of great heuristic importance focusing most etiologic research over the past two decades. These models have varied considerably with respect to specificity and timing of hypothesized genetic and environmental 'hits', but have largely focused on insults to prenatal brain development. With heritability around 80%, nongenetic factors impairing development must also be part of the model, and any model must also account for the wide range of age of onset. In recent years, longitudinal brain imaging studies of both early and adult (to distinguish from late ie elderly) onset populations indicate that progressive brain changes are more dynamic than previously thought, with gray matter volume loss particularly striking in adolescence and appearing to be an exaggeration of the normal developmental pattern. This supports an extended time period of abnormal neurodevelopment in schizophrenia in addition to earlier 'lesions'. Many subtle cognitive, motor, and behavioral deviations are seen years before illness onset, and these are more prominent in early onset cases. Moreover, schizophrenia susceptibility genes and chromosomal abnormalities, particularly as examined for early onset populations (ie GAD1, 22q11DS), are associated with premorbid neurodevelopmental abnormalities. Several candidate genes for schizophrenia (eg dysbindin) are associated with lower cognitive abilities in both schizophrenic and other pediatric populations more generally. Postmortem human brain and developmental animal studies document multiple and diverse effects of developmental genes (including schizophrenia susceptibility genes), at sequential stages of brain development. These may underlie the broad array of premorbid cognitive and behavioral abnormalities seen in schizophrenia, and neurodevelopmental disorders more generally. Increased specificity for the most relevant environmental risk factors such as exposure to prenatal infection, and their interaction with susceptibility genes and/or action through phase-specific altered gene expression now both strengthen and modify the neurodevelopmental theory of schizophrenia.

Behavior and corpus callosum morphology relationships in velocardiofacial syndrome (22q11.2 deletion syndrome)

Velocardiofacial syndrome (VCFS) is a neurodevelopmental disorder caused by a microdeletion on chromosome 22q11.2 that predisposes affected individuals to learning disabilities and psychiatric conditions. Previous research has indicated that compared with comparison children, children with VCFS have larger corpus callosal areas. Children with VCFS are often diagnosed with comorbid attention deficit hyperactivity disorder (ADHD), and previous research has indicated that children with ADHD often have smaller corpus callosal areas than controls. The present study investigated two hypotheses: children with VCFS would have larger callosal areas than controls, and children with VCFS+ADHD would have smaller callosal areas than children with VCFS. Corpus callosum area was obtained from the mid-sagittal slice and was assessed in children with VCFS (n=60) and age- and gender-matched control participants (n=52). Results indicated that all of the corpus callosum measures were significantly different between the two groups except for the genu. Across all measures, children with VCFS demonstrated a larger corpus callosum area. Within the VCFS sample, children with VCFS+ADHD (n=30) had smaller total callosal, splenium, and genu areas than children with VCFS alone. Although children with VCFS+ADHD had smaller total callosal areas than children with VCFS, relative to control participants, these children had larger total callosal and subregion areas except for the genu. In addition to other anatomic anomalies, corpus callosal abnormalities appear to be another variable to consider when analyzing brain/behavior relations in this population.

Dear old dad

The origin and frequency of spontaneous mutations that occur with age in humans have been a topic of intense discussion. The mechanisms by which spontaneous mutations arise depend on the parental germ line in which a mutation occurs. In general, paternal mutations are more likely than maternal mutations to be base substitutions. This is likely due to the larger number of germ cell divisions in spermatogenesis than in oogenesis. Maternal mutations are more often chromosomal abnormalities. Advanced parental age seems to influence some mutations, although it is not a factor in the creation of others. In this review, we focus on patterns of paternal bias and age dependence of mutations in different genetic disorders, and the various mechanisms by which these mutations arise. We also discuss recent data on age and the frequency of these mutations in the human male germ line and the impact of these data on this field of research.

Functional and structural alterations of the intraparietal sulcus in a developmental dyscalculia of genetic origin

Cognitive theories of numerical representation suggest that understanding of numerical quantities is driven by a magnitude representation associated with the intraparietal sulcus and possibly under genetic control. The aim of this study was to investigate, using fMRI and structural imaging, the interaction between the abnormal development of numerical representation in an X-linked condition, Turner syndrome (TS), and the development of the intraparietal sulcus. fMRI during exact and approximate calculation in TS showed an abnormal modulation of intraparietal activations as a function of number size. Morphological analysis revealed an abnormal length, depth, and sulcal geometry of the right intraparietal sulcus, suggesting an important disorganization of this region in TS. Thus, a genetic form of developmental dyscalculia can be related to both functional and structural anomalies of the right intraparietal sulcus, suggesting a crucial role of this region in the development of arithmetic abilities.

Increased basal ganglia volumes in velo-cardio-facial syndrome (deletion 22q11.2)

BACKGROUND

This study evaluated differences in caudate volumes in subjects with velo-cardio-facial syndrome due to a 22q11.2 (22qDS) deletion. Because psychosis is observed in 30% of adult subjects with 22qDS, this neurogenetic disorder could represent a putative model for a genetically mediated subtype of schizophrenia.

METHODS

Caudate volumes were measured on high-resolution magnetic resonance images in 30 children and adolescents with 22qDS and 30 gender- and age-matched normal comparison subjects.

RESULTS

Caudate head volumes were increased in the 22qDS group independent of neuroleptic medications. Subjects with 22qDS also displayed an abnormal pattern of asymmetry in the anterior caudate, with left side greater than right.

CONCLUSIONS

Alterations in the basal ganglia circuitry have been implicated in learning, cognitive, and behavioral problems in children and therefore could be involved in the expression of the neurobehavioral phenotype expressed by subjects with 22qDS. Abnormal caudate volume is a neurodevelopmental feature shared with schizophrenia, further establishing 22qDS as a potential neurodevelopmental model for this disorder.

22q11 DS: genomic mechanisms and gene function in DiGeorge/velocardiofacial syndrome

22q11 deletion syndrome (22qDS), also known as DiGeorge or velocardiofacial syndrome (DGS/VCFS), is a relatively common genetic anomaly that results in malformations of the heart, face and limbs. In addition, patients with 22qDS are at significant risk for psychiatric disorders as well, with one in four developing schizophrenia, and one in six developing major depressive disorders. Like several other deletion syndromes associated with psychiatric or cognitive problems, it has been difficult to determine which of the specific genes in this genomic region may mediate the syndrome. For example, patients with different genomic deletions within the 22q11 region have been found that have similar phenotypes, even though their deletions do not compromise the same set of genes. In this review, we discuss the individual genes found in the region of 22q11 that is commonly deleted in 22qDS patients, and the potential roles each of these genes may play in the syndrome. Although many of these genes are interesting candidates by themselves, we hypothesize that the full spectrum of anomalies associated with 22qDS may result from the combined result of disruptions to numerous genes within the region that are involved in similar developmental or cellular processes.

Language skills in children with velocardiofacial syndrome (deletion 22q11.2)

OBJECTIVE

To further define the language profile of children with velocardiofacial syndrome (VCFS) and explore the influence of parental origin of the deletion on language.

STUDY DESIGN

Children and adolescents with VCFS (n = 27) were group-matched for sex, age, and IQ with 27 children and adolescents with idiopathic developmental delay. Fifty-four typically developing control subjects were also included in the analyses investigating word association abilities.

RESULTS

Children with VCFS had significantly lower receptive than expressive language skills, a unique finding when compared with IQ-matched control subjects. However, no significant differences in word association were detected. Children with a deletion of paternal origin score significantly higher on receptive language when compared with children with a deletion of maternal origin.

CONCLUSIONS

The Clinical Evaluation of Language Fundamentals-III results suggest that children with VCFS show more severe deficits in receptive than expressive language abilities. Language skills of children with VCFS could be influenced by parental origin of the deletion and thus related to neuroanatomic alterations at the deletion site.

The psychopathological phenotype of velo-cardio-facial syndrome

Velo-cardio-facial syndrome (VCFS) is mostly associated with deletions of chromosome 22q11, and is thought to be characterized by an increased frequency of major psychiatric disorders. Sixteen patients adults with VCFS and psychiatric symptoms were evaluated using a semi-structured investigation of history, symptoms, signs and behaviour. All available data were used in consensus meetings to obtain a classifiable diagnostic category. In contrast to other reports, no categorical diagnosis could be established. Instead, a quite specific psychological, behavioural and psychopathological constellation emerged that should most adequately be denominated as a VCFS-psychiatric syndrome. It is concluded that VCFS is associated with a specific psychopathological syndrome.

Major psychosis and chromosome 22: genetics meets epigenetics

Elucidation of genetic factors in schizophrenia and bipolar disorder remains a challenging task to psychiatric researchers. As a rule, data from genetic linkage and association studies are quite controversial. In this article, we further explore the possibility that in addition to DNA sequences variation, a putative epigenetic dysregulation of brain genes plays an important role in the etiopathogenesis of major psychosis. We provide an epigenetic interpretation of unclear genetic findings specifically pertaining to chromosome 22 in schizophrenia and bipolar disorder. It is suggested that epigenetic strategies, when applied in conjunction with traditional genetic ones, may significantly expedite the uncovering of the molecular causes of major psychosis.

Pubertal neurodevelopment and the emergence of psychotic symptoms

One of the chief epidemiological hallmarks of schizophrenia is its modal age at onset in early adulthood. Clinical onset is preceded by an adolescent period that is usually characterized by increasing adjustment problems. Recent theorizing about the etiology of schizophrenia has focused on postpubertal brain changes that may be involved in triggering the expression of vulnerability for schizophrenia. In this paper, we further examine the normal neurodevelopmental processes that occur in adolescence and the underlying role of hormonal factors in controlling the expression of genes that govern brain maturation. We then consider how postpubertal hormone changes might serve to trigger the expression of vulnerability genes that code for abnormal brain development.

Psychiatric disorders and behavioral problems in children with velocardiofacial syndrome: usefulness as phenotypic indicators of schizophrenia risk

BACKGROUND

Velocardiofacial syndrome (VCFS), a genetic deletion condition with numerous cognitive sequelae, is associated with a high rate of psychiatric disorders in childhood. More recently, VCFS has been identified as a high-risk factor for developing adult onset schizophrenia. However, it has never been demonstrated that the childhood psychiatric disorders found in children with VCFS differ from those found in children with a similar degree of cognitive impairment. Identification of a specific behavioral (psychiatric) phenotype in childhood VCFS offers the potential for elucidating the symptomatic precursors of adult onset schizophrenia.

METHODS

Twenty-eight children with VCFS and 29 age- and cognitively matched control subjects received a standardized assessment of childhood psychiatric disorders and behaviors measured by the Child Behavior Checklist (CBCL). Findings from the two groups were compared.

RESULTS

The rates and types of psychiatric disorder and behavior problems in VCFS and cognitively matched control subjects were very high, but showed no significant differences.

CONCLUSIONS

Psychopathology in children with VCFS may not differ from that found in cognitively matched control subjects. Another explanation is that subtle phenotypic differences in behavior found in VCFS can not be observed using standard symptom inventories. The high rate of psychopathology in children with VCFS is not a useful phenotypic indicator of high risk for adult onset schizophrenia.

Childhood-onset schizophrenia: research update

This review is a research update of recent literature related to childhood-onset schizophrenia (onset of psychotic symptoms by age 12 years). This subgroup of patients has attracted considerable research interest because patients with a childhood onset may represent a more homogeneous patient population in which to search for risk or etiologic factors. We examine data indicating that childhood-onset schizophrenia (COS) shares the same clinical and neurobiologic features as later-onset forms of the disorder. Compared with adults with schizophrenia, however, this subgroup of patients appears to have more severe premorbid neuro-developmental abnormalities, more cytogenetic anomalies, and potentially greater family histories of schizophrenia and associated spectrum disorders. While preliminary, these data indicate that a greater genetic vulnerability may be one of the underpinnings of COS. Future studies of this subgroup may provide important clues as to the genetic basis for schizophrenia and how gene products influence certain features of the disease, such as age of onset and mode of inheritance.