Molecular screening for proximal 15q abnormalities in a mentally retarded population

Clinical aspects of a large group of adults with Angelman syndrome

Descriptions of the clinical features of Angelman syndrome (AS) have mainly been focused on children. Here, we describe the evolution of the clinical phenotypes of AS in adulthood, using clinical data from 95 individuals (mean age 31.6 years, median 29.0 years, range 18-83 years), with genetically confirmed AS. Data was collected through physical examination and inspection of medical records, combined with questionnaires and interviews. Adults with AS experience substantial debilitating health problems. Constipation, reflux, visual problems, scoliosis, behavioral and sleeping problems occurred frequently and require appropriate attention. Epilepsy was reported in 57% of adults, negatively affecting the level of functioning. Non-convulsive status epilepticus was not observed in the adults, however some individuals developed prolonged episodes of rhythmic shaking while awake. A decline in mobility was noted in the majority of adults. A minority of adults with AS showed microcephaly. Taken together, this first phenotypic study of adults with AS to include in person interviews with care-givers and physical examination of patients, including the eldest adult reported to date, provides important insight in the development of the syndrome into adulthood. This knowledge is required to improve care for adult individuals with AS and to evaluate future therapies for this group.

Role of Genetics in the Etiology of Autistic Spectrum Disorder: Towards a Hierarchical Diagnostic Strategy

Progress in epidemiological, molecular and clinical genetics with the development of new techniques has improved knowledge on genetic syndromes associated with autism spectrum disorder (ASD). The objective of this article is to show the diversity of genetic disorders associated with ASD (based on an extensive review of single-gene disorders, copy number variants, and other chromosomal disorders), and consequently to propose a hierarchical diagnostic strategy with a stepwise evaluation, helping general practitioners/pediatricians and child psychiatrists to collaborate with geneticists and neuropediatricians, in order to search for genetic disorders associated with ASD. The first step is a clinical investigation involving: (i) a child psychiatric and psychological evaluation confirming autism diagnosis from different observational sources and assessing autism severity; (ii) a neuropediatric evaluation examining neurological symptoms and developmental milestones; and (iii) a genetic evaluation searching for dysmorphic features and malformations. The second step involves laboratory and if necessary neuroimaging and EEG studies oriented by clinical results based on clinical genetic and neuropediatric examinations. The identification of genetic disorders associated with ASD has practical implications for diagnostic strategies, early detection or prevention of co-morbidity, specific treatment and follow up, and genetic counseling.

Reframing autism as a behavioral syndrome and not a specific mental disorder: Implications of genetic and phenotypic heterogeneity

Clinical and molecular genetics have advanced current knowledge on genetic disorders associated with autism. A review of diverse genetic disorders associated with autism is presented and for the first time discussed extensively with regard to possible common underlying mechanisms leading to a similar cognitive-behavioral phenotype of autism. The possible role of interactions between genetic and environmental factors, including epigenetic mechanisms, is in particular examined. Finally, the pertinence of distinguishing non-syndromic autism (isolated autism) from syndromic autism (autism associated with genetic disorders) will be reconsidered. Given the high genetic and etiological heterogeneity of autism, autism can be viewed as a behavioral syndrome related to known genetic disorders (syndromic autism) or currently unknown disorders (apparent non-syndromic autism), rather than a specific categorical mental disorder. It highlights the need to study autism phenotype and developmental trajectory through a multidimensional, non-categorical approach with multivariate analyses within autism spectrum disorder but also across mental disorders, and to conduct systematically clinical genetic examination searching for genetic disorders in all individuals (children but also adults) with autism.

Angelman syndrome

Angelman syndrome combines severe mental retardation, epilepsy, ataxia, speech impairment, and unique behavior with happy demeanor, laughing, short attention span, hyperactivity, and sleep disturbance. Occurrence has been calculated at 1:20000 to 1:12000 constituting about 6% of all children with severe mental retardation and epilepsy. The physical "prototype" includes microcephaly with flat neck, fair skin and hair, wide-spaced teeth, and open mouth with tongue protrusion. Epilepsy is characterized by atypical absences, erratic myoclonus, and occasional tonic-clonic seizures. EEG demonstrates high-amplitude 2-3Hz delta activity with spike and slow-wave discharges and sleep-activated generalized epileptiform discharges. Sodium valproate, benzodiazepines, and priacetam are frequently used and effective. Development is generally slow, the majority attaining independent walking in the first 2.5-6 years. Vocabulary is limited to a few single words with superior speech and object apprehension. The condition is due to a lack of expression of the UBE3A gene on chromosome 15q. Maternal deletions of 15q11-13 produce the most pronounced phenotype (65-70% of probands), uniparental disomy and imprinting center mutations (10%), and UBE3A point mutations (11%) produce milder phenotypes.

Repetitive and ritualistic behaviour in children with Prader-Willi syndrome and children with autism

BACKGROUND

Recent research has shown that the range of repetitive behaviour seen in individuals with Prader-Willi syndrome (PWS) extends beyond food-related behaviour.

METHODS

The presence and intensity of repetitive, rigid and routinized behaviour in children with PWS was compared with that seen in children with another neurodevelopmental condition in which repetitive behaviour is common: children with autism. Parents completed the Childhood Routines Inventory (CRI).

RESULTS

Contrary to our predictions, controlling for developmental level, children with PWS and children with autism showed similar levels of repetitive and ritualistic behaviour overall and on the two CRI factors measuring 'just right' and 'repetitive' behaviour. Indeed, the majority of the sample of parents of children with PWS endorsed most items on the CRI. However there was some specificity at the level of individual items with parents of children with PWS more frequently endorsing an item on 'collecting and storing objects' and parents of children with autism more frequently endorsing 'lining up objects', 'has a strong preference for certain foods' and 'seems aware of detail at home'.

CONCLUSIONS

These findings confirm the range of repetitive behaviours that form part of the behavioural phenotype of PWS, including insistence on sameness and 'just right' behaviours, and uncover a surprising overlap with those seen in children with autism. Clinical management for children with PWS should include advice and education regarding management of repetitive and rigid behaviour. Future research should investigate whether the repetitive behaviours that form part of the behavioural phenotype of both PWS and autism are associated with a common neuropsychological, neurotransmitter or genetic origin.

Prevalence of Angelman syndrome and Prader–Willi syndrome in Estonian children: Sister syndromes not equally represented

In 2000-2004, we performed a focused search for individuals with Angelman syndrome (AS) and Prader-Willi syndrome (PWS) aiming to establish the prevalence data for the individuals born between 1984 and 2004 in Estonia. All persons with probable AS or PWS (n = 184) were studied using the DNA methylation test. Individuals with abnormal methylation were all further tested by chromosomal and FISH analysis, and if necessary for uniparental disomy and UBE3A gene mutation. Nineteen cases with abnormal methylation test result were identified. Seven of them had AS, including six (85.7%) due to 15q11-13 deletion and one paternal UPD15. Twelve subjects had PWS: 4 (33%) 15q11-13 deletions, 6 (50%) maternal UPD15, 1 unbalanced chromosome 14;15 translocation resulting in a chromosome 15pter-q13 deletion, and 1 Robertsonian 15q;15q translocation. The minimum livebirth prevalence in 1984-2004 for AS was 1:52,181 (95% CI 1:25,326-1:1,29,785) and for PWS 1:30,439 (95% CI 1:17,425-1:58,908). The livebirth prevalence of AS and PWS increased within this period, but the change was statistically significant only for PWS (P = 0.032), from expected 1:88,495 (95% CI 1:24,390-1:3,22,580) to expected 1:12,547 (95% CI 1:540-1:29,154). Six individuals with AS and 11 with PWS were alive on the prevalence day (January 1, 2005), indicating the point prevalence proportion of 1:56,112 (95% CI 1:25,780-1:1,52,899) and 1:30,606 (95% CI 1:17,105-1:61,311), respectively. Our results showing the birth prevalence of AS 1.7 times less than PWS challenge the opinion that both syndromes are equally represented, and are in line with the view that mutations in sperm and oocytes occur at different frequencies.

Neurological aspects of the Angelman syndrome

Angelman syndrome (AS) has emerged as an important neurogenetic syndrome due to its relatively high prevalence and easier confirmation of the diagnosis by improved genetic testing. In infancy, nonspecific clinical features of AS pose diagnostic challenges to the neurologist and these include any combination of microcephaly, seizure disorder, global developmental delay or an ataxic/hypotonic cerebral palsy-like picture. In later childhood, however, absent speech, excessively happy behavior, ataxia and jerky movements usually present as a recognizable clinical syndrome. Brain MRI shows nonspecific or normal findings but occasionally the characteristic EEG patterns alone can lead to the correct diagnosis. The physical, clinical and behavioral aspects appear to be attributable to localized CNS dysfunction of the ubiquitin ligase gene, UBE3A, located at 15q11.2. In certain brain regions, UBE3A normally has mono-allelic expression from the maternally derived chromosome 15. Several distinct genetic mechanisms can inactivate or disrupt the maternally derived UBE3A: chromosome microdeletions, paternal uniparental disomy, imprinting defects and intragenic UBE3A mutations. Those with the deletion type of AS are the most prevalent (about 70% of cases) and appear to have a more severe clinical phenotype. The unique epileptic patterns and distinct behavioral features may be related to multiple actions of UBE3A, possibly occurring during, as well as after, the time of neuronal development.

Specific Genetic Disorders and Autism: Clinical Contribution Towards their Identification

Autism is a heterogeneous disorder that can reveal a specific genetic disease. This paper describes several genetic diseases consistently associated with autism (fragile X, tuberous sclerosis, Angelman syndrome, duplication of 15q11-q13, Down syndrome, San Filippo syndrome, MECP2 related disorders, phenylketonuria, Smith-Magenis syndrome, 22q13 deletion, adenylosuccinate lyase deficiency, Cohen syndrome, and Smith-Lemli-Opitz syndrome) and proposes a consensual and economic diagnostic strategy to help practitioners to identify them. A rigorous initial clinical screening is presented to avoid unnecessary laboratory and imaging studies. Regarding psychiatric nosography, the concept of "syndromal autism"--autism associated with other clinical signs should be promoted because it may help to distinguish patients who warrant a multidisciplinary approach and further investigation.

Chromosome 15q11-13 abnormalities and other medical conditions in individuals with autism spectrum disorders

OBJECTIVES

The frequency of abnormalities of 15q11-q13 and other possibly causal medical disorders including karyotypic abnormalities was investigated in an unselected series of children who were referred to one of two autism assessment centres.

METHODS

Two hundred and twenty-one cases were assessed using the Autism Diagnostic Interview and Observation Schedule and, where appropriate, standardized tests of intelligence and language abilities. Medical histories and notes were reviewed, and molecular and cytogenetic investigations used to detect chromosomal abnormalities.

RESULTS

One hundred and eighty-one cases were diagnosed according to International Classification of Diseases - version 10 criteria as having an autism spectrum disorder (autistic-like Pervasive Developmental Disorder) and 40 cases as having other disorders. Twenty-one (11.6%) of the children with autism spectrum disorders had a possibly causal condition compared with six (15%) of the children with other diagnoses. One child with an autism spectrum disorder had a paternally inherited familial duplication of 15q11-13. The pattern of genotype-phenotype correlation within the family indicated that this form of abnormality might carry a risk for developmental difficulties, although the risk did not appear to be specific for autism spectrum disorders.

CONCLUSION

The overall rate of possibly causal medical and cytogenetic conditions in children with autism spectrum disorders was low and no different from the rate of disorder in children with other developmental/neuropsychiatric disorders that attended the same clinics. Further research is required to determine whether paternal duplication of 15q11-13 gives rise to adverse developmental outcomes.

A rational approach to the child with mental retardation for the paediatrician

Mental Retardation (MR) is a problem encountered in almost all paediatric clinical settings. The assessment of a child with MR is a common diagnostic and management dilemma for paediatricians. The field of MR research is currently in a state of flux regarding not just our understanding of the condition, but also in the language and the processes we use in naming, defining and describing MR. This article will provide a better understanding and a rational approach toward MR. Prevalence rates for MR are variable in the literature and may be attributable to the variation in major classification systems and the diversity in study operation definitions and methodologies. Etiologies of MR are diverse and include many different influences. MR most often presents during infancy or preschool years as developmental delay. There is no universally accepted approach to the etiological work-up of mental retardation. The number of medical conditions associated with MR that are completely treatable by medical means remains small. The paediatrician plays a key role establishing short and long term treatment goals, as well as providing support to families who have children with MR.

Angelman syndrome methylation screening of 15q11-q13 in institutionalized individuals with severe mental retardation

Among several genetic diseases that comprise mental retardation, Angelman syndrome (AS) has been extensively recognized and investigated. In the general population, the syndrome occurs in about 1 in 20,000 live births and its prevalence in severely mentally retarded individuals is 1.4%. These figures, however, may be an underestimate, because of the variable phenotype of AS. The main objective of this work was to investigate AS patients among a group of mentally retarded subjects, using the methylation pattern of the SNRPN gene, as determined by Southern blotting molecular analysis. The molecular investigation of 75 institutionalized individuals with severe to profound mental retardation resulted in the detection of 1 case with an abnormal methylation pattern of the SNRPN gene, corresponding to AS. The patient's phenotype was classified as atypical, without outbursts of inappropriate laughter or a happy disposition; the patient would not have been diagnosed in the usual screens for AS, which only select patients who demonstrate the typical clinical findings characteristic of the disease.

Behavioral phenotypes of genetic syndromes: a reference guide for psychiatrists

OBJECTIVE

To review the literature on behavioral phenotypes of genetic syndromes, displaying the data as a reference guide for everyday practice.

METHOD

A computerized search was performed for articles published in the past 10 years, and selected papers were surveyed.

RESULTS

The behavioral phenotypes of 11 major genetic syndromes were reviewed including the following topics: genetic etiology, genetic counseling, physical features, medical problems, cognitive and behavioral profile, and psychopathology. The speculated correlation between the identified gene and the pathophysiology of the cognitive and behavioral features is discussed.

CONCLUSIONS

Updated knowledge of behavioral phenotypes will help psychiatrists identify these conditions, refer the patient and his/her family for genetic diagnosis and counseling, make specific treatment recommendations, and contribute to research and syndrome delineation.

Hypermethylation of the DAP-Kinase CpG Island Is a Common Alteration in B-Cell Malignancies

Death-associated protein kinase (DAP-Kinase) is a novel serine/threonine kinase whose expression is required for γ interferon-induced apoptosis. A previous study suggested that DAP-Kinase expression may be lost epigenetically in cancer cell lines, because treatment of several nonexpressing cell lines with 5-aza-2′-deoxycytidine resulted in the expression of DAP-Kinase. Using methylation-specific polymerase chain reaction (MSP), we examined the DAP-Kinase CpG island for hypermethylation in cancer. Normal lymphocytes and lymphoblastoid cell lines are unmethylated in the 5′ CpG island of DAP-Kinase. However, in primary tumor samples, all Burkitt’s lymphomas and 84% of the B-cell non-Hodgkin’s lymphomas were hypermethylated in the DAP-Kinase CpG island. In contrast, none of the T-cell non-Hodgkin’s lymphoma samples and 15% or less of leukemia samples examined had hypermethylated DAP-Kinase alleles. U937, an unmethylated, DAP-Kinase–expressing leukemia cell line, was treated with γ interferon and underwent apoptosis; however, Raji, a fully methylated, DAP-Kinase nonexpressing Burkitt’s lymphoma cell line, only did so when treated with 5-aza-2′-deoxycytidine followed by γ interferon. Our findings in cell lines and primary tumors suggest that hypermethylation of the DAP-Kinase gene and loss of γ interferon-mediated apoptosis may be important in the development of B-cell malignancies and may provide a promising biomarker for B-cell–lineage lymphomas.

Hypermethylation of the DAP-Kinase CpG Island Is a Common Alteration in B-Cell Malignancies

Death-associated protein kinase (DAP-Kinase) is a novel serine/threonine kinase whose expression is required for γ interferon-induced apoptosis. A previous study suggested that DAP-Kinase expression may be lost epigenetically in cancer cell lines, because treatment of several nonexpressing cell lines with 5-aza-2′-deoxycytidine resulted in the expression of DAP-Kinase. Using methylation-specific polymerase chain reaction (MSP), we examined the DAP-Kinase CpG island for hypermethylation in cancer. Normal lymphocytes and lymphoblastoid cell lines are unmethylated in the 5′ CpG island of DAP-Kinase. However, in primary tumor samples, all Burkitt’s lymphomas and 84% of the B-cell non-Hodgkin’s lymphomas were hypermethylated in the DAP-Kinase CpG island. In contrast, none of the T-cell non-Hodgkin’s lymphoma samples and 15% or less of leukemia samples examined had hypermethylated DAP-Kinase alleles. U937, an unmethylated, DAP-Kinase–expressing leukemia cell line, was treated with γ interferon and underwent apoptosis; however, Raji, a fully methylated, DAP-Kinase nonexpressing Burkitt’s lymphoma cell line, only did so when treated with 5-aza-2′-deoxycytidine followed by γ interferon. Our findings in cell lines and primary tumors suggest that hypermethylation of the DAP-Kinase gene and loss of γ interferon-mediated apoptosis may be important in the development of B-cell malignancies and may provide a promising biomarker for B-cell–lineage lymphomas.

Prader-Willi and Angelman syndromes: update on genetic mechanisms and diagnostic complexities

Significant advances have been made in determining the genetic basis of the Prader-Willi and Angelman syndromes; disorders in which genomic imprinting is abnormal. These advances will be instrumental in unravelling the pathogenesis that underlies these neurobehavioural disorders.