The incidence of hypoplasia of the corpus callosum in patients with dup (X)(q28) involving MECP2 is associated with the location of distal breakpoints

MECP2-related disorders while gene-based therapies are on the horizon

The emergence of new genetic tools has led to the discovery of the genetic bases of many intellectual and developmental disabilities. This creates exciting opportunities for research and treatment development, and a few genetic disorders (e.g., spinal muscular atrophy) have recently been treated with gene-based therapies. MECP2 is found on the X chromosome and regulates the transcription of thousands of genes. Loss of MECP2 gene product leads to Rett Syndrome, a disease found primarily in females, and is characterized by developmental regression, motor dysfunction, midline hand stereotypies, autonomic nervous system dysfunction, epilepsy, scoliosis, and autistic-like behavior. Duplication of MECP2 causes MECP2 Duplication Syndrome (MDS). MDS is found mostly in males and presents with developmental delay, hypotonia, autistic features, refractory epilepsy, and recurrent respiratory infections. While these two disorders share several characteristics, their differences (e.g., affected sex, age of onset, genotype/phenotype correlations) are important to distinguish in the light of gene-based therapy because they require opposite solutions. This review explores the clinical features of both disorders and highlights these important clinical differences.

Duplication within two regions distal to MECP2: clinical similarity with MECP2 duplication syndrome

BACKGROUND

X-linked methyl-CpG-binding protein 2 (MECP2) duplication syndrome is prevalent in approximately 1% of X-linked intellectual disabilities. Accumulating evidence has suggested that MECP2 is the causative gene of MECP2 duplication syndrome. We report a case of a 17-year-old boy with a 1.2 Mb duplication distal to MECP2 on chromosome Xq28. Although this region does not contain MECP2, the clinical features and course of the boy are remarkably similar to those observed in MECP2 duplication syndrome. Recently, case reports have described duplication in the region distal to, and not containing, MECP2. These regions have been classified as the K/L-mediated Xq28 duplication region and int22h1/int22h2-mediated Xq28 duplication region. The case reports also described signs similar to those of MECP2 duplication syndrome. To the best of our knowledge, ours is the first case to include these two regions.

CASE PRESENTATION

The boy presented with a mild to moderate regressive intellectual disability and progressive neurological disorder. He developed epilepsy at the age of 6 years and underwent a bilateral equinus foot surgery at 14 years of age because of the increasing spasticity in lower extremities since the age of 11. Intracranial findings showed hypoplasia of the corpus callosum, cerebellum, and brain stem; linear hyperintensity in the deep white matter; and decreased white matter capacity. During his childhood, he suffered from recurrent infection. However, genital problems, skin abnormalities and gastrointestinal manifestations (gastroesophageal reflux) were not observed.

CONCLUSIONS

Cases in which duplication was observed in the region of Xq28 that does not include MECP2 also showed symptoms similar to those of MECP2 duplication syndrome. We compared four pathologies: MECP2 duplication syndrome with minimal regions, duplication within the two distal regions without MECP2, and our case including both regions. Our results suggest that MECP2 alone may not explain all symptoms of duplication in the distal part of Xq28.

IRAK1 Duplication in MECP2 Duplication Syndrome Does Not Increase Canonical NF-κB-Induced Inflammation

PURPOSE

Besides their developmental and neurological phenotype, most patients with MECP2/IRAK1 duplication syndrome present with recurrent and severe infections, accompanied by strong inflammation. Respiratory infections are the most common cause of death. Standardized pneumological diagnostics, targeted anti-infectious treatment, and knowledge of the underlying pathomechanism that triggers strong inflammation are unmet clinical needs. We investigated the influence of IRAK1 overexpression on the canonical NF-κB signaling as a possible cause for excessive inflammation in these patients.

METHODS

NF-κB signaling was examined by measuring the production of proinflammatory cytokines and evaluating the IRAK1 phosphorylation and degradation as well as the IκBα degradation upon stimulation with IL-1β and TLR agonists in SV40-immortalized fibroblasts, PBMCs, and whole blood of 9 patients with MECP2/IRAK1 duplication syndrome, respectively.

RESULTS

Both, MECP2/IRAK1-duplicated patients and healthy controls, showed similar production of IL-6 and IL-8 upon activation with IL-1β and TLR2/6 agonists in immortalized fibroblasts. In PBMCs and whole blood, both patients and controls had a similar response of cytokine production after stimulation with IL-1β and TLR4/2/6 agonists. Patients and controls had equivalent patterns of IRAK1 phosphorylation and degradation as well as IκBα degradation upon stimulation with IL-1β.

CONCLUSION

Patients with MECP2/IRAK1 duplication syndrome do not show increased canonical NF-κB signaling in immortalized fibroblasts, PBMCs, and whole blood. Therefore, we assume that these patients do not benefit from a therapeutic suppression of this pathway.

Pain in Rett syndrome: a pilot study and a single case study on the assessment of pain and the construction of a suitable measuring scale

Background

Rett Syndrome (RTT) is a severe, neurodevelopmental disorder mainly caused by mutations in the MECP2 gene, affecting around 1 in 10,000 female births. Severe physical, language, and social impairments impose a wide range of limitations in the quality of life of the patients with RTT. Comorbidities of patients with RTT are varied and cause a lot of pain, but communicating this suffering is difficult for these patients due to their problems, such as apraxia that does not allow them to express pain in a timely manner, and their difficulties with expressive language that also do not permit them to communicate. Two studies, a pilot study and a single case study, investigate the manifestation of pain of patients with RTT and propose a suitable scale to measure it.

Aims of this study

The first aim was to describe pain situations of RTT by collecting information by parents; the second aim was to test and compare existing questionnaires for non-communicating disorders on pain such as Pain assessment in advanced demenzia (PAINAD), the Critical care pain observation tool (CPOT) and the Non-communicating Children’s Pain Checklist-Revised (NCCPC-R) to assess which of them is best related to the pain behavior of patients with RTT. The third aim was to identify the specific verbal and non-verbal behaviors that characterize pain in girls with Rett syndrome, discriminating them from non-pain behaviors.

Method

Nineteen participants, eighteen girls with RTT and one girl with RTT with 27 manifestations of pain were video-recorded both in pain and base-line conditions. Two independent observers codified the 90 video-recording (36 and 54) to describe their behavioral characteristics.

Results

The two studies showed that the most significant pain behaviors expressed by girls with respect to the baseline condition, at the facial level were a wrinkled forehead, wide eyes, grinding, banging teeth, complaining, making sounds, crying and screaming, and the most common manifestations of the body were tremors, forward and backward movement of the torso, tension in the upper limbs, increased movement of the lower limbs and a sprawling movement affecting the whole body.

Conclusion

The results of the two studies helped to create an easy-to-apply scale that healthcare professionals can use to assess pain in patients with Rett’s syndrome. This scale used PAINAD as its basic structure, with some changes in the items related to the behavior of patients with RTT.

A brief history of MECP2 duplication syndrome: 20-years of clinical understanding

MECP2 duplication syndrome (MDS) is a rare, X-linked, neurodevelopmental disorder caused by a duplication of the methyl-CpG-binding protein 2 (MECP2) gene-a gene in which loss-of-function mutations lead to Rett syndrome (RTT). MDS has an estimated live birth prevalence in males of 1/150,000. The key features of MDS include intellectual disability, developmental delay, hypotonia, seizures, recurrent respiratory infections, gastrointestinal problems, behavioural features of autism and dysmorphic features-although these comorbidities are not yet understood with sufficient granularity. This review has covered the past two decades of MDS case studies and series since the discovery of the disorder in 1999. After comprehensively reviewing the reported characteristics, this review has identified areas of limited knowledge that we recommend may be addressed by better phenotyping this disorder through an international data collection. This endeavour would also serve to delineate the clinical overlap between MDS and RTT.

MECP2-Related Disorders in Males

Methyl CpG binding protein 2 (MECP2) is located at Xq28 and is a multifunctional gene with ubiquitous expression. Loss-of-function mutations in MECP2 are associated with Rett syndrome (RTT), which is a well-characterized disorder that affects mainly females. In boys, however, mutations in MECP2 can generate a wide spectrum of clinical presentations that range from mild intellectual impairment to severe neonatal encephalopathy and premature death. Thus, males can be more difficult to classify and diagnose than classical RTT females. In addition, there are some variants of unknown significance in MECP2, which further complicate the diagnosis of these children. Conversely, the entire duplication of the MECP2 gene is related to MECP2 duplication syndrome (MDS). Unlike in RTT, in MDS, males are predominantly affected. Usually, the duplication is inherited from an apparently asymptomatic carrier mother. Both syndromes share some characteristics, but also differ in some aspects regarding the clinical picture and evolution. In the following review, we present a thorough description of the different types of MECP2 variants and alterations that can be found in males, and explore several genotype-phenotype correlations, although there is still a lot to understand.

Intellectual disability and epilepsy due to the K/L-mediated Xq28 duplication: Further evidence of a distinct, dosage-dependent phenotype

Copy number variants of the X-chromosome are a common cause of X-linked intellectual disability in males. Duplication of the Xq28 band has been known for over a decade to be the cause of the Lubs X-linked Mental Retardation Syndrome (OMIM 300620) in males and this duplication has been narrowed to a critical region containing only the genes MECP2 and IRAK1. In 2009, four families with a distal duplication of Xq28 not including MECP2 and mediated by low-copy repeats (LCRs) designated "K" and "L" were reported with intellectual disability and epilepsy. Duplication of a second more distal region has been described as the cause of the Int22h-1/Int22h-2 Mediated Xq28 Duplication Syndrome, characterized by intellectual disability, psychiatric problems, and recurrent infections. We report two additional families possessing the K/L-mediated Xq28 duplication with affected males having intellectual disability and epilepsy similar to the previously reported phenotype. To our knowledge, this is the second cohort of individuals to be reported with this duplication and therefore supports K/L-mediated Xq28 duplications as a distinct syndrome.

[MECP2 duplication syndrome: a clinical analysis of three cases and literature review]

MECP2 duplication syndrome (MDS) is a rare pediatric disease and mainly manifests as delayed motor development, language loss or delay, recurrent infection, severe intellectual disability, epilepsy, autistic symptoms, and early infantile hypotonia. In this article, the three children with this disease were all boys. Cases 1 and 2 had delayed motor development, and language loss or delay as initial manifestations, and case 3 had recurrent infection as initial manifestation. Physical examination showed hypotonia and negative pathological signs in each case. Case 1 had tonic-clonic seizures and electroencephalography showed focal seizures, for which he was given oxcarbazepine, levetiracetam, and clonazepam as the antiepileptic treatment to control seizures. Case 3 experienced one absence seizure and three head-nodding seizures with normal electroencephalographic findings during these seizures, and therefore, he was not given antiepileptic treatment. In each case, recurrent infection was improved with the increase in age, but there were no significant improvements in language or intelligence. Array-based comparative genomic hybridization (aCGH) showed MECP2 duplication in X chromosome in each case, and so they were diagnosed with MDS. MDS should be considered for children with delayed development complicated by recurrent infection and epileptic seizures, and early aCGH helps with the diagnosis of this disease.

Expansion of the phenotypic spectrum in three families of methyl CpG-binding protein 2 duplication syndrome

The methyl CpG-binding protein 2 duplication syndrome (OMIM #300260) is characterized by hypotonia, developmental delay, spasticity, seizures, and recurrent infections. It is fully penetrant in males and the females can have varied manifestations because of skewed X-inactivation. The size of the duplication can range from 0.2 Mb to over 100 Mb. Around 150 cases have been reported in the literature so far. Here, we report the unusual findings in three cases such as hepatomegaly, ataxia and females with mild intellectual disability that further expand the phenotypic spectrum of this disorder. This paper also stresses the need to perform microarray and/or multiplex ligation probe amplification in all cases of nonspecific intellectual disability.

Two girls with a de novo Xq rearrangement of paternal origin: t(X;9)(q24;q12) or rea(X)dup q

OBJECTIVE

We report on two rare Xq rearrangements, namely a t(X;9)(q24;q12) found in a mildly-affected girl (Patient 1) and a rea(X)dup q concomitant with a rob(14;21)mat in a Down syndrome girl (Patient 2).

CASE REPORT

Both rearrangements were characterized by banding techniques [Giemsa (G), constitutive heterochromatin (C), and bromodeoxyuridine (BrdU) pulse], fluorescence in situ hybridization (FISH) assays, human androgen receptor (HUMAR) assays, and microarray analyses. Patient 1 had a t(X;9)(q24;q12)dn. Patient 2 had a de novo rea(X)(qter→q23 or q24::p11.2→qter) concomitant with an unbalanced rob(14;21)mat. X-Inactivation studies in metaphases and DNA revealed a fully skewed inactivation: the normal homolog was silenced in Patient 1 and the rea(X) in Patient 2. Both rearranged X chromosomes were of paternal descent. Microarray analyses revealed no imbalances in Patient 1 whereas loss of Xp (∼52 Mb) and duplication of Xq (∼44 Mb) and 21q were confirmed in Patient 2.

CONCLUSION

Our observations further document the cytogenetic heterogeneity and predominant paternal origin of certain de novo X-chromosome rearrangements.

Infectious and immunologic phenotype of MECP2 duplication syndrome

MECP2 (methyl CpG binding protein 2) duplication causes syndromic intellectual disability. Patients often suffer from life-threatening infections, suggesting an additional immunodeficiency. We describe for the first time the detailed infectious and immunological phenotype of MECP2 duplication syndrome. 17/27 analyzed patients suffered from pneumonia, 5/27 from at least one episode of sepsis. Encapsulated bacteria (S.pneumoniae, H.influenzae) were frequently isolated. T-cell immunity showed no gross abnormalities in 14/14 patients and IFNy-secretion upon ConA-stimulation was not decreased in 6/7 patients. In 6/21 patients IgG₂-deficiency was detected – in 4/21 patients accompanied by IgA-deficiency, 10/21 patients showed low antibody titers against pneumococci. Supra-normal IgG₁-levels were detected in 11/21 patients and supra-normal IgG₃-levels were seen in 8/21 patients – in 6 of the patients as combined elevation of IgG₁ and IgG₃. Three of the four patients with IgA/IgG₂-deficiency developed multiple severe infections. Upon infections pronounced acute-phase responses were common: 7/10 patients showed CRP values above 200 mg/l. Our data for the first time show systematically that increased susceptibility to infections in MECP2 duplication syndrome is associated with IgA/IgG₂-deficiency, low antibody titers against pneumococci and elevated acute-phase responses. So patients with MECP2 duplication syndrome and low IgA/IgG₂ may benefit from prophylactic substitution of sIgA and IgG.

Clinical impacts of genomic copy number gains at Xq28

Duplications of the Xq28 region are the most frequent chromosomal aberrations observed in patients with intellectual disability (ID), especially in males. These duplications occur by variable mechanisms, including interstitial duplications mediated by segmental duplications in this region and terminal duplications (functional disomy) derived from translocation with other chromosomes. The most commonly duplicated region includes methyl CpG-binding protein 2 gene (MECP2), which has a minimal duplicated size of 0.2 Mb. Patients with MECP2 duplications show severe ID, intractable seizures and recurrent infections. Duplications in the telomeric neighboring regions, which include GDP dissociation inhibitor 1 gene (GDI1) and ras-associated protein RAB39B gene (RAB39B), are independently associated with ID, and many segmental duplications located in this region could mediate these frequently observed interstitial duplications. In addition, large duplications, including MECP2 and GDI1, induce hypoplasia of the corpus callosum. Abnormalities observed in the white matter, revealed by brain magnetic resonance imaging, are a common finding in patients with MECP2 duplications. As primary sequence analysis cannot be used to determine the region responsible for chromosomal duplication syndrome, finding this region relies on the collection of genotype-phenotype data from patients.