Mind and brain in Rett disorder

Analysis of the parental origin of de novo MECP2 mutations and X chromosome inactivation in 24 sporadic patients with Rett syndrome in China

Rett syndrome is an X-linked neurodevelopmental disorder that predominantly affects females. It is caused by mutations in methyl-CpG-binding protein 2 gene. Due to the sex-limited expression, it has been suggested that de novo X-linked mutations may exclusively occur in male germ cells and thus only females are affected. In this study, the authors have analyzed the parental origin of mutations and the X-chromosome inactivation status in 24 sporadic patients with identified methyl-CpG-binding protein 2 gene mutations. The results showed that 22 of 24 patients have a paternal origin. Only 2 patients have a maternal origin. Except for 2 cases which were homozygotic at the androgen receptor gene locus, of the remaining 22 cases, 16 cases have a random X-chromosome inactivation pattern; the other 6 cases have a skewed X-chromosome inactivation and they favor expression of the wild allele. The relationship between X-chromosome inactivation and phenotype may need more cases to explore.

Autism spectrum disorders in genetic syndromes: implications for diagnosis, intervention and understanding the wider autism spectrum disorder population

BACKGROUND

An emerging literature on behavioural phenotypes has highlighted apparent associations between autism spectrum disorders (ASDs) or ASD-related phenomenology and a number of different genetically determined syndromes.

METHOD

A systematic review of the current literature regarding the association with ASD and ASD characteristics was conducted in the following syndrome groups: Fragile X, Rett, Tuberous Sclerosis Complex, Down, Angelman, CHARGE and Phenylketonuria. Specific consideration was given to the role of intellectual disability in assessing the association between ASD and these syndrome groups.

RESULTS

The review highlights that while formal diagnostic assessments may indicate an association between ASD and specific syndrome groups, detailed investigation has revealed subtle but qualitative differences in the presentation of ASD-like phenomenology in particular syndrome groups. The degree of ID of the individual clearly has a role to play with regard to the development and presentation of ASD-like characteristics, and caution should be taken when assessing ASD symptomatology in genetically determined syndromes associated with severe ID. However, degree of ID cannot solely account for the heightened prevalence of ASD characteristics in some specific syndrome groups.

CONCLUSIONS

There is a need for caution in interpreting the significance of superficial similarities between ASD and the behavioural phenotypes of certain genetically determined syndromes. However, recognition of ASD-like characteristics (even where a true diagnosis of ASD may not be relevant) in individuals with genetic syndromes is crucial in ensuring that individuals receive appropriate behavioural management and educational placement. Further research in this field requires fine-grained investigation of behavioural phenomenology within individual syndrome groups.

MECP2 mutations in Serbian Rett syndrome patients

BACKGROUND

Rett syndrome is a severe neurodevelopmental X-linked dominant disorder affecting 1/15,000 girls worldwide. Eight years ago, the MECP2 gene was associated with the devastating clinical features observed in Rett syndrome patients.

OBJECTIVES

To investigate the spectrum and the frequency of MECP2 mutations in Serbian Rett syndrome patients.

PATIENTS AND METHODS

We screened the MECP2 coding region by conventional mutational screening (single-strand conformation polymorphism/sequencing) in 24 patients of Serbian origin and in their 41 unaffected family members. In search for gene dosage alterations in seemingly mutation-negative girls, we developed a new, specific quantitative PCR method.

RESULTS

Nineteen patients (79%) carried MECP2 mutations, five of which were novel (one nonsense mutation, one duplication and three deletions). Fourteen previously described disease-causing sequence changes and one polymorphism were also detected. Detailed case reports are given for the carriers of the novel mutations. Large MECP2 rearrangements cause Rett syndrome in a significant number of girls without 'classic' mutations in this gene. Therefore, we developed a specific quantitative PCR method, covering MECP2 exons 3 and 4, which previously has not been used for screening. No dosage alterations of the two exons were found in the four tested mutation-negative girls.

CONCLUSIONS

This is the first genetic study of Rett syndrome in Serbian patients describing the MECP2 mutational and phenotypic spectrum in this population. Detailed clinical descriptions of this ethnically homogeneous patient population add to our knowledge of genotype/phenotype correlations in this severe condition.

People with MECP2 mutation-positive Rett disorder who converse

BACKGROUND

People with useful speech after regression constitute a distinct group of those with mutation-positive Rett disorder, 6% (20/331) reported among mutation-positive people in the British Survey. We aimed to determine the physical, mental and genetic characteristics of this group and to gain insight into their experience of Rett syndrome.

METHODS

Clinical and molecular data for people with Rett, aged 10 or more years at follow-up (the study group, n = 13), with the ability to converse and a MECP2 mutation are presented. They were compared with an age-matched control group (n = 110), who could not converse and had a pathogenic MECP2 mutation.

RESULTS

The study group differed significantly from the control group with regard to their disease severity (P < 0.001); feeding difficulty scores (P < 0.001); health scores (P < 0.001); epilepsy (P < 0.001); head circumference (P < 0.004); age at onset of the regression period (P < 0.001) (six in the study group did not regress) and mutation frequency (C-terminal deletions P = 0.014, R133C P < 0.006). The results indicate that favourable skewing of X-inactivation is only present in a small proportion of mild cases. Speech was fragmented with a soft, breathless quality, and all but two had obviously irregular breathing. One person with an R168X mutation preferred signing to speech. All enjoyed interpersonal contact, showing affection and preferring people to objects, clearly distinguishing the condition from autism. Most were habitually anxious. Music was a source of pleasure and relaxation also providing a valuable educational asset. Even in these most able cases, understanding was severely restricted in most and little initiative was shown.

CONCLUSIONS

While the Rett profile is present in these people they are commonly not classic, and the presence of speech, good head growth and lack of regression may lead to missed diagnoses. A strong association was demonstrated between this milder form of the disease and R133C and C-terminal deletions.

Rett syndrome from a family perspective: The Swedish Rett Center survey

The aim of this study was to make a description of the early development in individuals with the diagnosis Rett syndrome using parents' information. Information received from 125 cases of Rett syndrome in Sweden in 1997 provided us with families' description of early development in gross motor function, fine motor function and communication/social interplay. Best abilities before regression were presented, 62% lost their best abilities, 22% kept them and 5% kept them with deterioration. Seventy-three percent learnt to walk, 20% stopped walking and 2% retrained walking. Concerning feeding, 69% learnt to feed themselves, 57% lost this ability, 7% retrained the ability and 5% learnt to feed after regression. Sixty-four percent were one year or younger when there was a deviation in development. Sixty answers reported the girl was late in developing functions while 35 reported sudden loss of reached abilities. Seventy-four percent developed a scoliosis and 83% reported other deformities; of these, deformities in feet were the most common. Postural control was poor since all but 15 girls/women learnt in different directions when sitting. Transitional movements were difficult to perform. In 80% of cases, the families were those who suspected early that something was wrong in the child's development. Because of this it is essential that medical staff is aware of the different ways RS develops in order to give families early appropriate support and a plan for intervention. Since there is not only loss of function in this group but also kept abilities, retrained abilities and abilities achieved after regression, more research has to be focused on management and treatment to help persons with Rett syndrome keep and develop abilities according to their individual resources.

Management of young children with Rett disorder in the controlled multi-sensory (Snoezelen) environment

Rett syndrome is a neurological disorder resulting from an X-linked dominant mutation. It is characterized by a variety of physical and perceptual disabilities, resulting in a need for constant therapy programs to be administered on a regular basis throughout the client's life. As the child with Rett disorder (RD) is entering the more obvious, hectic phase of this syndrome (stage II), signs of extreme agitation and discomfort are usually exhibited. This behavior is suspected to reflect damaging chaotic processes accruing in the brain at that time. Experts advise that calming techniques might be helpful for children with Rett during this period. This may be our earliest opportunity to change the course of the disorder. Now that our knowledge of RD has increased and children are being diagnosed at a substantially earlier age, new intervention methods should be introduced for parents and therapists. This may ensure more suitable treatment. The multi-sensory environment may provide a soothing haven, which appeals to the child with RD. This article provides a short review of RD typical phenotype and suggests suitable activities that could take place in the multi-sensory environment with this population at the early stages of appearance of the Rett disorder.

Gross rearrangements of the MECP2 gene are found in both classical and atypical Rett syndrome patients

MECP2 mutations are identifiable in approximately 80% of classic Rett syndrome (RTT), but less frequently in atypical RTT. We recruited 110 patients who fulfilled the diagnostic criteria for Rett syndrome and were referred to Cardiff for molecular analysis, but in whom an MECP2 mutation was not identifiable. Dosage analysis of MECP2 was carried out using multiplex ligation dependent probe amplification or quantitative fluorescent PCR. Large deletions were identified in 37.8% (14/37) of classic and 7.5% (4/53) of atypical RTT patients. Most large deletions contained a breakpoint in the deletion prone region of exon 4. The clinical phenotype was ascertained in all 18 of the deleted cases and in four further cases with large deletions identified in Goettingen. Five patients with large deletions had additional congenital anomalies, which was significantly more than in RTT patients with other MECP2 mutations (2/193; p<0.0001). Quantitative analysis should be included in molecular diagnostic strategies in both classic and atypical RTT.

Nurse recognition of early deviation in development in home videos of infants with Rett disorder

BACKGROUND

In the genetic Rett disorder (RD), infants make some progress then suffer a dramatic developmental regression, usually before 2 years of age. Home videos, taken before the problems are recognized, offer an objective source for detecting early signs.

METHODS

Thirty-six health visitors and midwives were invited to view brief examples from home videos of a cohort of 14 infants with RD and 11 control infants with normal development in the first year of life, and to indicate, by pressing a button, points in the recordings which aroused their suspicion of developmental deviation. They were then invited to comment on their selection. The participants were blind as to whether any individual example showed an infant with normal development or one with some form of developmental disturbance.

RESULTS

From the first month of life and throughout the first year, infants with RD received more button presses than controls (46%, 361 out of 778 viewings) in comparison with the control group (12%, 67 of 558). The consistent nature of the health professionals' comments made possible their categorization under four headings: appearance, posture, movement and contact. In the first month of life, the hand postures of infants with RD received particular comment from midwives (23 out of 37 comments overall on posture).

CONCLUSIONS

The present study strongly suggests the presence of early signs of developmental deviation in infants with RD, although, in most cases, formal developmental screening procedures have failed to detect these before the ages of 12 or 18 months.

[Rett syndrome]

This article is focus on the currently knowledge about Rett syndrome, based on the more recent information in the international literature on genetic and epidemiological aspects of this condition, as well as on its clinical and laboratory diagnosis, neuropathology, electrophysiology. and clinical outcome (epilepsy, respiratory disorders, autonomic disturbances and nutritional aspects). Although it has been known as a female condition, nowadays it is described the possibility of affected males with a different phenotype.

Annotation: Rett syndrome: recent progress and implications for research and clinical practice

BACKGROUND

Rett syndrome was first described 40 years ago as a profoundly disabling condition in girls.

METHOD

Over the last 20 years' national surveys, neuropathological and neurophysiological research have steadily improved understanding of its character and natural history.

RESULTS

In the last two years identification of the causative mutations in the gene methyl CpG binding protein 2 (Xq28) has led to a sudden expansion in knowledge about the underlying developmental disorder, with important implications for clinical practice and new opportunities to develop more effective intervention.

CONCLUSIONS

It is now clear that the disorder occurs in males and females and that there is a wide range in severity.