Molecular and clinical study of 61 Angelman syndrome patients (original) (raw)

Molecular Mechanism of Angelman Syndrome in Two Large Families Involves an Imprinting Mutation

The American Journal of Human Genetics, 1999

Patients with Angelman syndrome (AS) and Prader-Willi syndrome with mutations in the imprinting process have biparental inheritance but uniparental DNA methylation and gene expression throughout band 15q11-q13. In several of these patients, microdeletions upstream of the SNRPN gene have been identified, defining an imprinting center (IC) that has been hypothesized to control the imprint switch process in the female and male germlines. We have now identified two large families (AS-O and AS-F) segregating an AS imprinting mutation, including one family originally described in the first genetic linkage of AS to 15q11-q13. This demonstrates that this original linkage is for the 15q11-q13 IC. Affected patients in the AS families have either a 5.5-or a 15-kb microdeletion, one of which narrowed the shortest region of deletion overlap to 1.15 kb in all eight cases. This small region defines a component of the IC involved in AS (ie., the paternal-to-maternal switch element). The presence of an inherited imprinting mutation in multiple unaffected members of these two families, who are at risk for transmitting the mutation to affected children or children of their daughters, raises important genetic counseling issues.

Phenotypic variability in Angelman syndrome - report of two cases

2008

Angelman syndrome is a genetic condition, characterized by severe mental retardation, ataxic gait, severe speech delay, dysmorphic features, abnormal behaviours, movement disorder. It is caused by a variety of genetic mechanisms which all interfere with expression of the UBE3A gene on chromosome 15q11-13. In this paper, we present two cases of Angelman syndrome, one of them with classical phenotype, and the other with a Rett syndrome – like phenotype. In both patients, the molecular cytogenetic investigation confirmed the interstitial deletion within critical region 15q11-13.

The elusive Angelman syndrome critical region

Journal of Medical Genetics, 1997

DNA mapping studies in two families provide further information on the Angelman syndrome critical region, which has recently been defined by the gene UBE3A.

Angelman Syndrome: A Case Report

Objective Angelman syndrome (AS) is a neurodevelopmental disorder presented by jerky movement, speech delay and cognitive disability epilepsy as well as dysmorphic features. It occurs due to an expression deletion in 15q11-q13 chromosome. In this article, we present an eight yr boy referred to Pediatrics Neurologic Clinic Mashhad, Iran for speech delay. He had abnormal behavior ataxia unusual laughing facial expression intellectual disability and mandibular prognathism. Metabolic screening tests and brain MRI were normal. Genetic analysis was pathognomonic for AS.

Phenotype–genotype correlation in 20 deletion and 20 non-deletion Angelman syndrome patients

European Journal of Human Genetics, 1999

Angelman syndrome (AS) is a neurodevelopmental disorder caused by the absence of a maternal contribution to chromosome 15q11-q13. There are four classes of AS according to molecular or cytogenetic status: maternal microdeletion of 15q11-q13 (approximately 70% of AS patients); uniparental disomy (UPD); defects in a putative imprinting centre (IM); the fourth includes 20-30% of AS individuals with biparental inheritance and a normal pattern of allelic methylation in 15q11-q13. Mutations of UBE3A have recently been identified as causing AS in the latter group. Few studies have investigated the phenotypic differences between these classes. We compared 20 non-deletion to 20 age-matched deletion patients and found significant phenotypic differences between the two groups. The more severe phenotype in the deletion group may suggest a contiguous gene syndrome.

Genetic counseling in Angelman syndrome: The challenges of multiple causes

American Journal of Medical Genetics, 1998

The causal heterogeneity of Angelman syndrome (AS) makes providing information regarding recurrence risk both important and challenging, and may have a dramatic impact on reproductive decision-making for the nuclear and extended family. Most cases of AS result from typical large de novo deletions of 15q11-q13, and are expected to have a low (<1%) risk of recurrence. AS due to paternal uniparental disomy (UPD), which occurs in the absence of a parental translocation, is likewise expected to have a <1% risk of recurrence. Parental transmission of a structurally or functionally unbalanced chromosome complement can lead to 15q11-q13 deletions or to UPD and will result in case-specific recurrence risks. In instances where there is no identifiable large deletion or UPD, the risk for recurrence may be as high as 50% as the result of either a maternally inherited imprinting center (IC) mutation or a ubiquitin-protein ligase (UBE3A) gene mutation. Individuals with AS who have none of the above abnormalities comprise a significant proportion of cases, and some may be at a 50% recurrence risk. Misdiagnoses, as well, can be represented in this group. In light of the many conditions which are clinically similar to AS, it is essential to address the possibility of diagnostic uncertainty and potential misdiagnosis prior to the provision of genetic counseling. Summaries of the different causal classes of AS as an algorithm for determination of recurrence risks are presented. Am.