Discordant phenotypes in first cousins withUBE3Aframeshift mutation

Clinical Characteristics Suggestive of a Genetic Cause in Cerebral Palsy: A Systematic Review

BACKGROUND

Cerebral palsy (CP) is a clinical diagnosis and was long categorized as an acquired disorder, but more and more genetic etiologies are being identified. This review aims to identify the clinical characteristics that are associated with genetic CP to aid clinicians in selecting candidates for genetic testing.

METHODS

The PubMed database was systematically searched to identify genes associated with CP. The clinical characteristics accompanying these genetic forms of CP were compared with published data of large CP populations resulting in the identification of potential indicators of genetic CP.

RESULLTS

Of 1930 articles retrieved, 134 were included. In these, 55 CP genes (described in two or more cases, n = 272) and 79 candidate genes (described in only one case) were reported. The most frequently CP-associated genes were PLP1 (21 cases), ARG1 (17 cases), and CTNNB1 (13 cases). Dyskinesia and the absence of spasticity were identified as strong potential indicators of genetic CP. Presence of intellectual disability, no preterm birth, and no unilateral distribution of symptoms were classified as moderate genetic indicators.

CONCLUSIONS

Genetic causes of CP are increasingly identified. The clinical characteristics associated with genetic CP can aid clinicians regarding to which individual with CP to offer genetic testing. The identified potential genetic indicators need to be validated in large CP cohorts but can provide the first step toward a diagnostic algorithm for genetic CP.

Novel UBE3A pathogenic variant in a large Georgian family produces non-convulsive status epilepticus responsive to ketogenic diet

PURPOSE

To report the effect of the ketogenic diet (KD) on non-convulsive status epilepticus (NCSE) due to Angelman syndrome (AS) in two members of a large Georgian family affected by a novel frameshift variant in the UBE3A gene (NM_000462.3).

METHODS

We evaluated two members of this family who were affected with clinical and EEG features of AS. Clinical history with special emphasis on development, seizure type, frequency, and treatment was reviewed. Routine and long-term video EEG monitoring were conducted, particularly during NCSE. A non-fasting inpatient KD protocol was implemented using blended food orally with full administration of 4:1 (fat to non-fat) ratio. Urine ketone bodies (KBs), measured with urine ketone acetone strips readings, reached 150 mg/dL in both patients.

RESULTS

Patients had characteristic signs of AS and presented with epilepsy between the age of 2-4 years. As methylation tests were negative, next generation sequencing disclosed a c.2365del variant. For both, NCSE was revealed by cognitive deterioration and did not respond to anti-seizure medication. As recommended, IV pyridoxine, benzodiazepines, and valproic acid were administered, but without success. For both patients, NCSE resolved on the second-third day of KD initiation, before the appearance of ketonuria and resulting in improved communication, mood and sleep.

CONCLUSION

KD is safe and effective for the treatment of NCSE due to AS. Resolution before the appearance of ketone bodies points to a possible mechanism of action of KD.

Mutation Update for UBE3A variants in Angelman syndrome

Angelman syndrome is a neurodevelopmental disorder caused by a deficiency of the imprinted and maternally expressed UBE3A gene. Although de novo genetic and epigenetic imprinting defects of UBE3A genomic locus account for majority of Angelman diagnoses, approximately 10% of individuals affected with Angelman syndrome are a result of UBE3A loss-of-function mutations occurring on the expressed maternal chromosome. The variants described in this manuscript represent the analysis of 2,515 patients referred for UBE3A gene sequencing at our institution, along with a comprehensive review of the UBE3A mutation literature. Of these, 267 (10.62%) patients had a report issued for detection of a UBE3A gene nucleotide variant, which in many cases involved family studies resulting in reclassification of variants of unknown clinical significance (VUS). Overall, 111 (4.41%) probands had a nucleotide change classified as pathogenic or strongly favored to be pathogenic, 29 (1.15%) had a VUS, and 126 (5.0%) had a nucleotide change classified as benign or strongly favored to be benign. All variants and their clinical interpretations are submitted to NCBI ClinVar, a freely accessible human variation and phenotype database.

1031-1034delTAAC (Leu125Stop): a novel familial UBE3A mutation causing Angelman syndrome in two siblings showing distinct phenotypes

Background

More than 50 mutations in the UBE3A gene (E6-AP ubiquitin protein ligase gene) have been found in Angelman syndrome patients with no deletion, no uniparental disomy, and no imprinting defect.

Case Presentation

We here describe a novel UBE3A frameshift mutation in two siblings who have inherited it from their asymptomatic mother. Despite carrying the same UBE3A mutation, the proband shows a more severe phenotype whereas his sister shows a milder phenotype presenting the typical AS features.

Conclusions

We hypothesized that the mutation Leu125Stop causes both severe and milder phenotypes. Potential mechanisms include: i) maybe the proband has an additional problem (genetic or environmental) besides the UBE3A mutation; ii) since the two siblings have different fathers, the UBE3A mutation is interacting with a different genetic variant in the proband that, by itself, does not cause problems but in combination with the UBE3A mutation causes the severe phenotype; iii) this UBE3A mutation alone can cause either typical AS or the severe clinical picture seen in the proband.

A novel UBE3A truncating mutation in large Tunisian Angelman syndrome pedigree

We identified in a large Tunisian pedigree a novel UBE3A frameshift mutation in exon 16 coding region, and we expect that the resulting UBE3A truncated protein in our patients is non-functional since the mutation implies the catalytic region of the enzyme. The family includes 14 affected patients born from four sisters. This mutation was found in all surviving affected individuals and their mothers pointing out the importance of genetic counseling possibility in Angelman syndrome (AS). All patients had severe mental retardation with epilepsy and microcephaly. Minor clinical expression variation was observed among the investigated patients. The severity of clinical expression is related to the detected molecular variation: deletion of 15 bp and insertion of 7 bp. These results are concordant with the gene expression observed in previously reported individuals with AS and truncated UBE3A protein.

Abnormal myelination in Angelman syndrome

Patients with Angelman syndrome (OMIM # 105830) are generally thought to have normal brain imaging studies except for occasional minor cerebral atrophy. We report 9 patients with genetically proven Angelman syndrome, who were examined by magnetic resonance imaging (MRI) between the ages of 7.5 months and 5 years. MRI in the 5 patients examined during infancy revealed myelination delay and a deficit of white matter. Retarded and/or abnormal myelination in Angelman syndrome seems to be a common finding that may be diagnostically misleading. This is particularly important in the evaluation of infants with possible Angelman syndrome, who present with nonspecific clinical features and have not yet developed the characteristic behavioural, language, and movement abnormalities.

The overlapping spectrum of rett and angelman syndromes: a clinical review

Rett and Angelman syndromes comprise part of the spectrum of neurologic disorders associated with autism. Their clinical presentations overlap, with both presenting in later infancy with global developmental delays, severe speech and communication impairments, progressive microcephaly, seizures, autistic behaviors, and characteristic albeit different movement disorders and stereotypic hand movements. Although other features can help differentiate these disorders, significant phenotypic overlap and variation in severity sometimes cloud the underlying diagnosis. Rett syndrome is caused by a mutation in the MECP2 gene located on Xq28, whereas Angelman syndrome results from the loss of UBE3A function on chromosomal region 15q11-q13 related to a variety of molecular genetic mechanisms. Recent advances have uncovered interactions between these and other genes that affect the function and structure of neurons in the brain. The reversal of symptoms of Rett syndrome in a mature mouse model suggests the possibility for treatment of these and perhaps other autism-related disorders in the future.

Strategies for preimplantation genetic diagnosis of Angelman syndrome caused by mutations in the UBE3A gene

Angelman syndrome (AS) is a neurodevelopmental disorder associated with the loss of maternal gene expression in chromosome region 15q11-q13. AS is caused by a wide variety of genetic mechanisms, including mutations in the UBE3A gene that have been identified in 10-15% of patients; when the mother is heterozygous for the causative mutation, the risk of recurrence in subsequent pregnancies is 50%. The present authors have developed a preimplantation genetic diagnosis (PGD) assay for a family displaying a 10 bp deletion in exon 9 of the UBE3A gene, which was shared by two affected children and their phenotypically normal mother. A duplex polymerase chain reaction protocol was established, allowing the efficient amplification of the mutation together with an informative microsatellite marker (D15S122) located in intron 1 of the UBE3A gene. As most of UBE3A mutations identified so far are unique to one family, the present authors have also developed an indirect single cell protocol based upon the co-amplification of two microsatellite markers located within (D15S122) and close to the UBE3A gene (D15S1506). This strategy may be applied to all informative families requesting PGD for Angelman syndrome associated with mutations in the UBE3A gene.