Prenatal ultrasonographic diagnosis of a recurrent case of Johanson-Blizzard syndrome

We report on ultrasonographic prenatal diagnosis of a recurrent case of Johanson-Blizzard syndrome. The pregnancy was terminated at 21 weeks'. This observation highlights the great variability of the expression of this syndrome, including in the same family, and the necessity of collaborating with an experienced geneticist in all antenatal diagnosis of any complex of abnormalities.     

X-linked dominant inherited diseases with lethality in hemizygous males

Summary X-linked dominant inheritance with lethality in hemizygous males is a rare mode of inheritance. The three best-known disorders which seem to be inherited in this way, are incontinentia pigmenti (IP) Bloch-Sulzberger, oral-facial-digital I (OFD I) syndrome, and focal dermal hypoplasia (FDH syndrome, Goltz syndrome). It is the purpose of this article to give a review of the clinical and genetic aspects of the abovementioned diseases and to add those disorders in which this mode of inheritance is discussed. These disorders are: X-linked chondrodysplasia punctata (CP), cervico-oculo-acusticus syndrome (Wildervanck syndrome, COA), congenital cataract with microcornea or slight microphthalmia, muscular dystrophy-hemizygous lethal, partial lipodystrophy with lipatrophic diabetes and hyperlipidemia, Aicardi syndrome, coxo-auricular syndrome, and Johanson-Blizzard syndrome. OTC defiency is included in the study, although there is no lethality in utero, only in the neonatal period.A critical evaluation of the current literature is carried out.     

SWI/SNF complex in disorder: SWItching from malignancies to intellectual disability

Heterozygous germline mutations in components of switch/sucrose nonfermenting (SWI/SNF) chromatin remodeling complexes were recently identified in patients with non-syndromic intellectual disability, Coffin-Siris syndrome and Nicolaides-Baraitser syndrome. The common denominator of the phenotype of these patients is severe intellectual disability and speech delay. Somatic and germline mutations in SWI/SNF components were previously implicated in tumor development. This raises the question whether patients with intellectual disability caused by SWI/SNF mutations in the germline are exposed to an increased risk of developing cancer. Here we compare the mutational spectrum of SWI/SNF components in intellectual disability syndromes and cancer, and discuss the implications of the results of this comparison for the patients.     

SWI/SNF complex in disorder

Heterozygous germline mutations in components of switch/sucrose nonfermenting (SWI/SNF) chromatin remodeling complexes were recently identified in patients with non-syndromic intellectual disability, Coffin-Siris syndrome and Nicolaides-Baraitser syndrome. The common denominator of the phenotype of these patients is severe intellectual disability and speech delay. Somatic and germline mutations in SWI/SNF components were previously implicated in tumor development. This raises the question whether patients with intellectual disability caused by SWI/SNF mutations in the germline are exposed to an increased risk of developing cancer. Here we compare the mutational spectrum of SWI/SNF components in intellectual disability syndromes and cancer, and discuss the implications of the results of this comparison for the patients.     

Johanson-Blizzard syndrome. a new case with autopsy findings.

Here we present a new case of Johanson-Blizzard Syndrome. Clinical features consistent with the diagnosis of Johanson-Blizzard Syndrome in a term neonate are described: intra-uterine growth retardation, aplasia of the nasal alae, midline scalp defect, total situs inversus, imperforate anus, malrotation of the small intestine, pancreatic insufficiency, deafness, and lethal congenital heart defects with dextrocardia. These features were confirmed by findings at autopsy. Parents were consanguineous. We compare these clinical features and findings at autopsy with previous cases reported in the literature.     

Editor's preface

Smith-Lemli-Opitz syndrome, a syndrome of multiple malformations and mental retardation that for years was relegated to the atlases of genetic esoterica, was recently found to be a relatively common inborn error of metabolism. The underlying defect is absent or deficient activity of 7-dehydrocholesterol- delta 7-reductase, the enzyme catalysing the final step of cholesterol synthesis. The discovery of the biochemical defect causing Smith-Lemli-Opitz syndrome has resulted in the development of a diagnostic test and a potentially beneficial treatment (dietary cholesterol supplementation). Infants and young children with the syndrome have shown marked improvement in growth, behaviour and general health after receiving cholesterol therapy; older children and adults have shown some improvement in development and intellectual functioning. Despite the excitement these developments have elicited among geneticists and biochemists, this syndrome remains relatively unknown to many primary care physicians. Increased awareness of Smith-Lemli-Opitz syndrome is needed to identify affected patients so that they and their families can benefit from appropriate treatment and genetic counselling.     

Hypomorphic temperature-sensitive alleles of NSDHL cause CK syndrome

CK syndrome (CKS) is an X-linked recessive intellectual disability syndrome characterized by dysmorphism, cortical brain malformations, and an asthenic build. Through an X chromosome single-nucleotide variant scan in the first reported family, we identified linkage to a 5 Mb region on Xq28. Sequencing of this region detected a segregating 3 bp deletion (c.696_698del [p.Lys232del]) in exon 7 of NAD(P) dependent steroid dehydrogenase-like (NSDHL), a gene that encodes an enzyme in the cholesterol biosynthesis pathway. We also found that males with intellectual disability in another reported family with an NSDHL mutation (c.1098 dup [p.Arg367SerfsX33]) have CKS. These two mutations, which alter protein folding, show temperature-sensitive protein stability and complementation in Erg26-deficient yeast. As described for the allelic disorder CHILD syndrome, cells and cerebrospinal fluid from CKS patients have increased methyl sterol levels. We hypothesize that methyl sterol accumulation, not only cholesterol deficiency, causes CKS, given that cerebrospinal fluid cholesterol, plasma cholesterol, and plasma 24S-hydroxycholesterol levels are normal in males with CKS. In summary, CKS expands the spectrum of cholesterol-related disorders and insight into the role of cholesterol in human development.     

Dissecting the genotype in syndromic intellectual disability using whole exome sequencing in addition to genome-wide copy number analysis

When a known microimbalance affecting multiple genes is detected in a patient with syndromic intellectual disability, it is usually presumed causative for all observed features. Whole exome sequencing (WES) allows questioning this assumption. In this study of three families with children affected by unexplained syndromic intellectual disability, genome-wide copy number and subsequent analyses revealed a de novo maternal 1.1 Mb microdeletion in the 14q32 imprinted region causing a paternal UPD(14)-like phenotype, and two inherited 22q11.21 microduplications of 2.5 or 2.8 Mb. In patient 1 carrying the 14q32 microdeletion, tall stature and renal malformation were unexplained by paternal UPD(14), and there was no altered DLK1 expression or unexpected methylation status. By WES and filtering with a mining tool, a novel FBN1 missense variant was found in patient 1 and his mother, who both showed clinical features of Marfan syndrome by thorough anthropometric assessment, and a novel EYA1 missense variant as a probable cause of the renal malformation in the patient. In patient 2 with the 22q11.21 microduplication syndrome, skin hypo- and hyperpigmentation and two malignancies were only partially explained. By WES, compound heterozygous BLM stop founder mutations were detected causing Bloom syndrome. In male patient 3 carrying a 22q11.21 microduplication inherited from his unaffected father, WES identified a novel missense variant in the OPHN1 X-linked intellectual disability gene inherited from the unaffected mother as a possible additional cause for developmental delay. Thus, WES seems warranted in patients carrying microdeletions or microduplications, who have unexplained clinical features or microimbalances inherited from an unaffected parent.     

Cholinergic Senescence in the Ts65Dn Mouse Model for Down Syndrome

Neurochemical Research - Down syndrome (DS) induces a variable phenotype including intellectual disabilities and early development of Alzheimer’s disease (AD). Moreover, individuals with DS...     

Exploring the behavioral and cognitive phenotype of KBG syndrome

KBG syndrome is a neurodevelopmental disorder, caused by dominant mutations in ANKRD11, that is characterized by developmental delay/intellectual disability, mild craniofacial dysmorphisms, and short stature. Behavior and cognition have hardly been studied, but anecdotal evidence suggests higher frequencies of ADHD‐symptoms and social‐emotional impairments. In this study, the behavioral and cognitive profile of KBG syndrome will be investigated in order to examine if and how cognitive deficits contribute to behavioral difficulties. A total of 18 patients with KBG syndrome and a control group consisting of 17 patients with other genetic disorders with comparable intelligence levels, completed neuropsychological assessment. Age‐appropriate tasks were selected, covering overall intelligence, attention, memory, executive functioning, social cognition and visuoconstruction. Results were compared using Cohen's d effect sizes. As to behavior, fewer difficulties in social functioning and slightly more attentional problems, hyperactivity, oppositional defiant behavior and conduct problems were found in the KBG syndrome group. Regarding cognitive functioning, inspection of the observed differences shows that patients with KBG syndrome showed lower scores on sustained attention, cognitive flexibility, and visuoconstruction. In contrast, the KBG syndrome group demonstrated higher scores on visual memory, social cognition and emotion recognition. The cognitive profile of KBG syndrome in this sample indicates problems in attention and executive functioning that may underlie the behavior profile which primarily comprises impulsive behavior. Contrary to expectations based on previous (case) reports, no deficits were found in social cognitive functioning. These findings are important for counseling purposes, for tailored education planning, and for the development of personalized intervention.     

Siblings with opposite chromosome constitutions,dup(2q)/del(7q) and del(2q)/dup(7q)

Chromosome 7q36 microdeletion syndrome is a rare genomic disorder characterized by underdevelopment of the brain, microcephaly, anomalies of the sex organs, and language problems. Developmental delay, intellectual disability, autistic spectrum disorders, BDMR syndrome, and unusual facial morphology are the key features of the chromosome 2q37 microdeletion syndrome. A genetic screening for two brothers with global developmental delay using high-resolution chromosomal analysis and subtelomeric multiplex ligation-dependent probe amplification revealed subtelomeric rearrangements on the same sites of 2q37.2 and 7q35, with reversed deletion and duplication. Both of them showed dysmorphic facial features, severe disability of physical and intellectual development, and abnormal genitalia with differential abnormalities in their phenotypes. The family did not have abnormal genetic phenotypes. According to the genetic analysis of their parents, adjacent-1 segregation from their mother's was suggested as a mechanism of their gene mutation. By comparing the phenotypes of our patients with previous reports on similar patients, we tried to obtain the information of related genes and their chromosomal locations.     

Assessment of objectively measured physical activity levels in individuals with intellectual disabilities with and without Down's syndrome

Objective

To investigate, using accelerometers, the levels of physical activity being undertaken by individuals with intellectual disabilities with and without Down''s syndrome.

Methods

One hundred and fifty two individuals with intellectual disabilities aged 12–70 years from East and South-East England. Physical activity levels in counts per minute (counts/min), steps per day (steps/day), and minutes of sedentary, light, moderate, vigorous, and moderate to vigorous physical activity (MVPA) measured with a uni-axial accelerometer (Actigraph GT1M) for seven days.

Results

No individuals with intellectual disabilities met current physical activity recommendations. Males were more active than females. There was a trend for physical activity to decline and sedentary behaviour to increase with age, and for those with more severe levels of intellectual disability to be more sedentary and less physically active, however any relationship was not significant when adjusted for confounding variables. Participants with Down''s syndrome engaged in significantly less physical activity than those with intellectual disabilities without Down''s syndrome and levels of activity declined significantly with age.

Conclusions

Individuals with intellectual disabilities, especially those with Down''s syndrome may be at risk of developing diseases associated with physical inactivity. There is a need for well-designed, accessible, preventive health promotion strategies and interventions designed to raise the levels of physical activity for individuals with intellectual disabilities. We propose that there are physiological reasons why individuals with Down''s syndrome have particularly low levels of physical activity that also decline markedly with age.     

Autism and Intellectual Disability-Associated KIRREL3 Interacts with Neuronal Proteins MAP1B and MYO16 with Potential Roles in Neurodevelopment

Cell-adhesion molecules of the immunoglobulin superfamily play critical roles in brain development, as well as in maintaining synaptic plasticity, the dysfunction of which is known to cause cognitive impairment. Recently dysfunction of KIRREL3, a synaptic molecule of the immunoglobulin superfamily, has been implicated in several neurodevelopmental conditions including intellectual disability, autism spectrum disorder, and in the neurocognitive delay associated with Jacobsen syndrome. However, the molecular mechanisms of its physiological actions remain largely unknown. Using a yeast two-hybrid screen, we found that the KIRREL3 extracellular domain interacts with brain expressed proteins MAP1B and MYO16 and its intracellular domain can potentially interact with ATP1B1, UFC1, and SHMT2. The interactions were confirmed by co-immunoprecipitation and colocalization analyses of proteins expressed in human embryonic kidney cells, mouse neuronal cells, and rat primary neuronal cells. Furthermore, we show KIRREL3 colocalization with the marker for the Golgi apparatus and synaptic vesicles. Previously, we have shown that KIRREL3 interacts with the X-linked intellectual disability associated synaptic scaffolding protein CASK through its cytoplasmic domain. In addition, we found a genomic deletion encompassing MAP1B in one patient with intellectual disability, microcephaly and seizures and deletions encompassing MYO16 in two unrelated patients with intellectual disability, autism and microcephaly. MAP1B has been previously implicated in synaptogenesis and is involved in the development of the actin-based membrane skeleton. MYO16 is expressed in hippocampal neurons and also indirectly affects actin cytoskeleton through its interaction with WAVE1 complex. We speculate KIRREL3 interacting proteins are potential candidates for intellectual disability and autism spectrum disorder. Moreover, our findings provide further insight into understanding the molecular mechanisms underlying the physiological action of KIRREL3 and its role in neurodevelopment.     

Revealing the Complexity of a Monogenic Disease: Rett Syndrome Exome Sequencing

Rett syndrome (OMIM#312750) is a monogenic disorder that may manifest as a large variety of phenotypes ranging from very severe to mild disease. Since there is a weak correlation between the mutation type in the Xq28 disease-gene MECP2/X-inactivation status and phenotypic variability, we used this disease as a model to unveil the complex nature of a monogenic disorder. Whole exome sequencing was used to analyze the functional portion of the genome of two pairs of sisters with Rett syndrome. Although each pair of sisters had the same MECP2 (OMIM*300005) mutation and balanced X-inactivation, one individual from each pair could not speak or walk, and had a profound intellectual deficit (classical Rett syndrome), while the other individual could speak and walk, and had a moderate intellectual disability (Zappella variant). In addition to the MECP2 mutation, each patient has a group of variants predicted to impair protein function. The classical Rett girls, but not their milder affected sisters, have an enrichment of variants in genes related to oxidative stress, muscle impairment and intellectual disability and/or autism. On the other hand, a subgroup of variants related to modulation of immune system, exclusive to the Zappella Rett patients are driving toward a milder phenotype. We demonstrate that genome analysis has the potential to identify genetic modifiers of Rett syndrome, providing insight into disease pathophysiology. Combinations of mutations that affect speaking, walking and intellectual capabilities may represent targets for new therapeutic approaches. Most importantly, we demonstrated that monogenic diseases may be more complex than previously thought.     

DSCR1 interacts with FMRP and is required for spine morphogenesis and local protein synthesis

Most common genetic factors known to cause intellectual disability are Down syndrome and Fragile X syndrome. However, the underlying cellular and molecular mechanisms of intellectual disability remain unclear. Recently, dendritic spine dysmorphogenesis and impaired local protein synthesis are posited to contribute to the cellular mechanisms of intellectual disability. Here, we show that Down syndrome critical region1 (DSCR1) interacts with Fragile X mental retardation protein (FMRP) and regulates both dendritic spine morphogenesis and local protein synthesis. Interestingly, decreasing the level of FMRP restores the DSCR1-induced changes in dendritic spine morphology. Our results imply that DSCR1 is a novel regulator of FMRP and that Fragile X syndrome and Down syndrome may share disturbances in common pathways that regulate dendritic spine morphology and local protein synthesis.     

Sensory impairment in mental retardation: a potential role for NGF

Sensory impairment is defined as the inability to interpret outside stimuli such as visual, auditory, verbal, sense of touch, taste or smell or feelings of pain. This leads to absence of sensation and neuronal coordination. The impairment may be caused by ageing and other physiological changes, accident or injuries or can be found in some cases of mental retardation (MR) also referred to as intellectual disability. Known cases of MR involving inability to accurately interpret an outside source or stimuli are: Fragile-X syndrome; Tuberous sclerosis complex (TSC) with associated autism spectrum disorder (ASD); Rett syndrome; Autism and ASD with or without MR; Chromosome 22q13.3 deletion syndrome; familial dysautonomia, Prader-Willi's syndrome, Williams syndrome. In this review we will discuss in particular form of ASD and altered sensory sensitivity. The role of NGF in causing pronociceptive activity and its role in peripheral sensitisation is discussed under the light of its involvement in forms of MR where loss of pain perception is a main feature due to mutations to NGF receptors or NGF genes during development. Other forms of MR with altered sensory impairment will be considered as well as additional potential mechanisms involved.     

Fragile X and X-linked intellectual disability: four decades of discovery

X-Linked intellectual disability (XLID) accounts for 5%-10% of intellectual disability in males. Over 150 syndromes, the most common of which is the fragile X syndrome, have been described. A large number of families with nonsyndromal XLID, 95 of which have been regionally mapped, have been described as well. Mutations in 102 X-linked genes have been associated with 81 of these XLID syndromes and with 35 of the regionally mapped families with nonsyndromal XLID. Identification of these genes has enabled considerable reclassification and better understanding of the biological basis of XLID. At the same time, it has improved the clinical diagnosis of XLID and allowed for carrier detection and prevention strategies through gamete donation, prenatal diagnosis, and genetic counseling. Progress in delineating XLID has far outpaced the efforts to understand the genetic basis for autosomal intellectual disability. In large measure, this has been because of the relative ease of identifying families with XLID and finding the responsible mutations, as well as the determined and interactive efforts of a small group of researchers worldwide.     

Maternal meiosis II nondisjunction in a case of 47,XXY testicular feminization

Summary An 11-year-old patient with incomplete testicular feminization and a 47,XXY karyotype is described. The patient had female external genitalia, clitoromegaly, and some features of Klinefelter's syndrome, including speech delay and delayed intellectual development. DNA analysis using X chromosomal DNA sequences suggests that the supernumerary X chromosome in the patient resulted from maternal nondisjunction during meiosis II. The M II error thereby provides the basis for homozygosity of a mutation in the androgen receptor locus.     

A new X-linked dysplasia gigantism syndrome: Identical with the Simpson dysplasia syndrome?

Summary Thirteen male newborns of a family spanning five generations revealed a syndrome consisting in elevated birth weight and length, a disproportionately large head with coarse, distinctive facies, short neck, slight obesity, and broad, short hands and feet. The affected who reached adulthood attained heights of about 2 m; their unusual facial and general appearance and the clumsiness of all their motions, remarkable during infancy and childhood, had become somewhat less conspicuous. In all but one affected individual, intellectual development was normal. In two index cases neither clinical nor laboratory evaluations revealed a basic defect. X-linked recessive inheritance is most probable.     

Warburg micro syndrome in two children from a highly inbred Turkish family

Warburg Micro syndrome (WMS) was first reported by Warburg in 1993. The cardinal features are microcephaly, microphthalmia, congenital cataract and intellectual disability. We report on two children from a highly inbred family with microcephaly, congenital cataract, optic atrophy, hypotonia and severe psychomotor retardation. This phenotype is similar to other reported rare entities and especially to the family reported by Warburg. Four other children in the same family may also have been affected. In this report, the symptoms and features of our cases are compared with the Warburg Micro syndrome patients in literature.