Discovery of a connective tissue dysplasia in the Martin-Bell syndrome

Effects of Soy Protein Isolate on Fragile X Phenotypes in Mice

Obesity is a pediatric epidemic that is more prevalent in children with developmental disabilities. We hypothesize that soy protein-based diets increase weight gain and alter neurobehavioral outcomes. Our objective herein was to test matched casein- and soy protein-based purified ingredient diets in a mouse model of fragile X syndrome, Fmr1KO mice. The experimental methods included assessment of growth; 24-7 activity levels; motor coordination; learning and memory; blood-based amino acid, phytoestrogen and glucose levels; and organ weights. The primary outcome measure was body weight. We find increased body weight in male Fmr1KO from postnatal day 6 (P6) to P224, male wild type (WT) from P32-P39, female Fmr1KO from P6-P18 and P168-P224, and female Fmr1HET from P9-P18 as a function of soy. Activity at the beginning of the light and dark cycles increased in female Fmr1HET and Fmr1KO mice fed soy. We did not find significant differences in rotarod or passive avoidance behavior as a function of genotype or diet. Several blood-based amino acids and phytoestrogens were significantly altered in response to soy. Liver weight was increased in WT and adipose tissue in Fmr1KO mice fed soy. Activity levels at the beginning of the light cycle and testes weight were greater in Fmr1KO versus WT males irrespective of diet. DEXA analysis at 8-months-old indicated increased fat mass and total body area in Fmr1KO females and lean mass and bone mineral density in Fmr1KO males fed soy. Overall, dietary consumption of soy protein isolate by C57BL/6J mice caused increased growth, which could be attributed to increased lean mass in males and fat mass in females. There were sex-specific differences with more pronounced effects in Fmr1KO versus WT and in males versus females.

The RNA-binding fragile-X mental retardation protein and its role beyond the brain

It is well-established that variations of a CGG repeat expansion in the gene FMR1, which encodes the fragile-X mental retardation protein (FMRP), cause the neurocognitive disorder, fragile-X syndrome (FXS). However, multiple observations suggest a general and complex regulatory role of FMRP in processes outside the brain: (1) FMRP is ubiquitously expressed in the body, suggesting it functions in multiple organ systems; (2) patients with FXS can exhibit a physical phenotype that is consistent with an underlying abnormality in connective tissue; (3) different CGG repeat expansion lengths in FMR1 result in different clinical outcomes due to different pathogenic mechanisms; (4) the function of FMRP as an RNA-binding protein suggests it has a general regulatory role. This review details the complex nature of FMRP and the different CGG repeat expansion lengths and the evidence supporting the essential role of the protein in a variety of biological and pathological processes.

A family with two cases of melanocytic tumors and fragile X syndrome

Fragile X syndrome (FXS), a leading cause of inherited intellectual disability, most commonly results from an expansion of the CGG trinucleotide repeat in the fragile X mental retardation 1 (FMR1) gene to more than 200 copies (full mutation). The FXS phenotype differs by sex and is associated with intellectual and cognitive impairment, characteristic physical features, epilepsy, and/or behavioral challenges including autism spectrum disorder. In this patient population, tumors involving blood cells, digestive organs, the central nervous system, and testes have been described, but melanocytic tumors have not been reported. Here, we describe two maternal cousins with FXS, one of whom has melanoma and the other has atypical nevus syndrome. We discuss possible mechanisms leading to this unusual or possibly coincidental association and the difficulties in the optimal treatment of FXS patients.

Event-related potential alterations in fragile X syndrome

Fragile X Syndrome (FXS) is the most common form of X-linked intellectual disability (ID), associated with a wide range of cognitive and behavioral impairments. FXS is caused by a trinucleotide repeat expansion in the FMR1 gene located on the X-chromosome. FMR1 is expected to prevent the expression of the "fragile X mental retardation protein (FMRP)", which results in altered structural and functional development of the synapse, including a loss of synaptic plasticity. This review aims to unveil the contribution of electrophysiological signal studies for the understanding of the information processing impairments in FXS patients. We discuss relevant event-related potential (ERP) studies conducted with full mutation FXS patients and clinical populations sharing symptoms with FXS in a developmental perspective. Specific deviances found in FXS ERP profiles are described. Alterations are reported in N1, P2, Mismatch Negativity (MMN), N2, and P3 components in FXS compared to healthy controls. Particularly, deviances in N1 and P2 amplitude seem to be specific to FXS. The presented results suggest a cascade of impaired information processes that are in line with symptoms and anatomical findings in FXS.

Fragile X syndrome and epilepsy

Fragile X syndrome (FXS) is one of the most prevalent mental retardations. It is mainly caused by the loss of fragile X mental retardation protein (FMRP). FMRP is an RNA binding protein and can regulate the translation of its binding RNA, thus regulate several signaling pathways. Many FXS patients show high susceptibility to epilepsy. Epilepsy is a chronic neurological disorder which is characterized by the recurrent appearance of spontaneous seizures due to neuronal hyperactivity in the brain. Both the abnormal activation of several signaling pathway and morphological abnormality that are caused by the loss of FMRP can lead to a high susceptibility to epilepsy. Combining with the research progresses on both FXS and epilepsy, we outlined the possible mechanisms of high susceptibility to epilepsy in FXS and tried to give a prospect on the future research on the mechanism of epilepsy that happened in other mental retardations.

Cancer incidence among persons with fragile X syndrome in Finland: a population-based study

BACKGROUND

Fragile X syndrome is a common inheritable cause of intellectual disability (ID) and is characterised by a large number of CGG repeats at the gene FMR1 located on the X-chromosome. It has been reported that this genetic mechanism may protect against malignant transformations.

METHODS

We extracted from the Finnish registry on persons with ID a cohort of 302 persons with a fragile X diagnosis during 1982-1986. Follow-up for cancer incidence was performed in the Finnish Cancer Registry until the end of the year 2005.

RESULTS

There were 11 reported cancers during the mean follow-up of 21.4 years per person. The expected number of cancers based on the average Finnish population was 13.8 and no statistically significant protective effect was detected [standardised incidence ratios (SIR) 0.80, confidence interval (CI) 95% 0.40-1.4]. An increased risk for lip cancer was found (SIR 23, CI 95% 2.8-85).

CONCLUSIONS

Confirmation of hypotheses about the mechanisms linking FXS and cancer needs further research.

Chromosomal microarray analysis (CMA) detects a large X chromosome deletion including FMR1, FMR2, and IDS in a female patient with mental retardation

Chromosomal microarray analysis (CMA) by array-based comparative genomic hybridization (CGH) is a new clinical test for the detection of well-characterized genomic disorders caused by chromosomal deletions and duplications that result in gene copy number variation (CNV). This powerful assay detects an abnormality in approximately 7-9% of patients with various clinical phenotypes, including mental retardation. We report here on the results found in a 6-year-old girl with mildly dysmorphic facies, obesity, and marked developmental delay. CMA was requested and showed a heterozygous loss in copy number with clones derived from the genomic region cytogenetically defined as Xq27.3-Xq28. This loss was not cytogenetically visible but was seen on FISH analysis with clones from the region. Further studies confirmed a loss of one copy each of the FMR1, FMR2, and IDS genes (which are mutated in Fragile X syndrome, FRAXE syndrome, and Hunter syndrome, respectively). Skewed X-inactivation has been previously reported in girls with deletions in this region and can lead to a combined Fragile X/Hunter syndrome phenotype in affected females. X-inactivation and iduronate 2-sulfatase (IDS) enzyme activity were therefore examined. X-inactivation was found to be random in the child's peripheral leukocytes, and IDS enzyme activity was approximately half of the normal value. This case demonstrates the utility of CMA both for detecting a submicroscopic chromosomal deletion and for suggesting further testing that could possibly lead to therapeutic options for patients with developmental delay.

Phenotypic variation and FMRP levels in fragile X

Data on the relationships between cognitive and physical phenotypes, and a deficit of fragile X mental retardation 1 (FMR1) gene-specific protein product, FMRP, are presented and discussed in context with earlier findings. The previously unpublished results obtained, using standard procedures of regression and correlations, showed highly significant associations in males between FMRP levels and the Wechsler summary and subtest scores and in females between these levels and the full-scale intelligence quotient (FSIQ), verbal and performance IQ, and some Wechsler subtest scores. The published results based on data from 144 extended families with fragile X, recruited from Australia and the United States within a collaborative NIH-supported project, were obtained using robust modification of maximum likelihood in pedigrees. The results indicated that processing speed, short-term memory, and the ability to control attention, especially in the context of regulating goal-directed behavior, may be primarily affected by the FMRP depletion. The effect of this depletion on physical phenotype was also demonstrated, especially on body and head height and extensibility of finger joints. It is recommended that further studies should rely on more accurate measures of FMRP levels, and use of larger samples, to overcome extensive variability in the data.

Relationship of deficits of FMR1 gene specific protein with physical phenotype of fragile X males and females in pedigrees: a new perspective

The effect of deficit of the FMR1-gene product (FMRP) on physical phenotype was investigated using a robust modification of the maximum likelihood estimators for pedigree data. The approach is a powerful method of examining genotype-phenotype relationships because it adjusts for intra-familial variation, and the robust modification allows violation of distributional assumptions in the data to be overcome by objectively down-weighting unusual observations. The data on 19 age- or height-adjusted physical measures including head, trunk and limb measures and height and weight from 110 extended fragile X families (including 185 fragile X males and females and 120 normal relatives) were related to the FMRP levels assessed in peripheral blood lymphocytes. A significant interaction between FMRP and age was also included in the models for some measures. The results have demonstrated a linear effect of progressively reducing levels of FMRP on the values of a majority of physical measures considered in the study. The most evident effect of FMRP deficit in sexes combined was in decreasing body height and limb length, and in increasing head height and the degree of connective tissue involvement (measured by the middle finger extension angle). Heritability estimated from the complex FMRP models showed the highest values for height and limb length, and the lowest for weight, finger extension angle and some facial measures. On the basis of the present data, a possible mechanism by which the FMRP deficit impacts physical phenotype is discussed.

A decade of molecular studies of fragile X syndrome

Fragile X syndrome is one of the most common forms of inherited mental retardation. In most cases the disease is caused by the methylation-induced transcriptional silencing of the fragile X mental retardation 1 (FMR1) gene that occurs as a result of the expansion of a CGG repeat in the gene's 5'UTR and leads to the loss of protein product fragile X mental retardation protein (FMRP). FMRP is an RNA binding protein that associates with translating polyribosomes as part of a large messenger ribonucleoprotein (mRNP) and modulates the translation of its RNA ligands. Pathological studies from the brains of patients and from Fmr1 knockout mice show abnormal dendritic spines implicating FMRP in synapse formation and function. Evidence from both in vitro and in vivo neuronal studies indicates that FMRP is located at the synapse and the loss of FMRP alters synaptic plasticity. As synaptic plasticity has been implicated in learning and memory, analysis of synapse abnormalities in patients and Fmr1 knockout mice should prove useful in studying the pathogenesis of fragile X syndrome and understanding learning and cognition in general. If an appreciable portion of the total variance (in IQ) is due to sex linked genes, it is of more importance that a boy should have a clever mother than a clever father. Hogben 1932 (quoted in Lehrke 1974)

Aspects of skeletal development in fragile X syndrome fetuses

The purpose of the present investigation was to describe the skeletal development in prenatal fragile X syndrome. We studied fetuses (4 males, 2 females), with gestational ages (GA) 12-14 weeks, from 5 unrelated, different, known carrier mothers. Because of trauma to the fetus during abortion, different parts of the 6 fetuses were available for investigation. The vertebral column and the facial skeleton of all the fetuses were examined, the feet and hands of 5 fetuses, and the cranial base of 3 fetuses. The tissue remnants were examined radiographically and histochemically, and the results compared with previously published normal findings. Radiographic findings included normal ossification sequence, except for 1 fetus where there was an abnormal sequence in the first finger; normal morphology of ossification centres; and nasal bones were absent in the 5 fetuses and present in 1 (14 weeks of gestation). The histological study suggests presence of an acid mucopolysaccharide malfunction in the supporting tissue, because the normal cartilage resorption and orthochromatic cartilage reactions do not appear during the initial enchondral ossification. In addition, the apoptosis of ectodermally derived cells (notochord and palatal epithelial layers) appears delayed or abnormal. The sella turcica was malformed in the 2 fetuses investigated for sella turcica morphology.

Fragile X syndrome in two siblings with major congenital malformations

We report on 2 brothers with both fragile X and VACTERL-H syndrome. The first sibling, age 5, had bilateral cleft lip and palate, ventricular septal defect, and a hypoplastic thumb. The second sibling, age 2 1/2, had a trachesophageal fistula, esophageal atresia, and vertebral abnormality. High-resolution chromosome analysis showed a 46, XY chromosome constitution in both siblings. By PCR and Southern blot analysis, the siblings were found to have large triplet repeat expansions in the fragile X gene (FMR 1) and both had methylation mosaicism. Enzyme kinetic studies of iduronate sulfatase demonstrated a two-fold increase in activity in the first sib as compared to the second. Possible mechanisms through which the fragile X mutation can cause down-regulation of adjacent loci are discussed.

Fragile X (Martin-Bell) syndrome

Fragile X syndrome is a common condition resulting from a cytogenetic abnormality in the X chromosome. Mental retardation, characteristic facies, and large testes are some of the most important characteristics of the condition. The relatively high incidence of the syndrome--approximately one per thousand--the high incidence of cardiac anomalies in these individuals, the oral and facial features associated with the condition, and the paucity of reported cases in the dental literature make it particularly interesting to dentistry. Here we report the case of a 12-year-old male, including the cytogenetic and cephalometric analyses, presenting with some of the classic features and some features not commonly reported.

What is associated with the fragile X syndrome?

In addition to mental retardation (MR), fragile X[fra(X)] syndrome has been associated with a variety of other disorders. Despite earlier reports, it has been shown that MR fra(X) males are at no greater risk for autism than is any MR male. Therefore, studies in which fra(X) has been associated with behavioral, developmental, and psychopathological disabilities were examined to determine whether fra(X) individuals were at an increased risk for these dysfunctions as well. Psychiatric disorders among fra(X) individuals were found not to occur more frequently than in other individuals with cognitive deficits. It was also observed that hyperactivity and attention deficit disorder among MR fra(X) individuals do not occur more frequently than in other MR individuals. Pooled results from studies of cognitive profiles used to characterize fra(X) phenotypes also indicated that there are no consistent patterns in either males or females. Plausible explanations for a variable phenotype include allelic heterogeneity and pleitropy.

Mortality in the fragile X syndrome: preliminary data

Mortality was studied among 348 males and 433 females who had or who carried the gene for the fragile X syndrome. The average age of death was about 12 years lower than in the general population for both men and women but this was likely a bias of ascertainment. The commonest causes of death were cardiovascular, cerebrovascular and malignant disease similar to those in the general population. No evidence for any specific disease susceptibility was found in this preliminary study.

The fragile-X syndrome. On the way to a behavioural phenotype

The fragile-X syndrome accounts for up to 10% of individuals with mental handicap, and 50% of cases of X-linked mental retardation. Knowledge of the genetic basis of mental functioning, psychopathology, and neuropsychology is being furthered by this recently recognised condition. The disorder has considerable significance for psychiatrists, particularly, but by no means exclusively, those working in the field of mental handicap and with children. This review outlines the slow clarification of this complex and important behavioural phenotype and the implications of these advances for identification, diagnosis, genetic counselling and a wide range of management interventions.

Association of the Robin sequence with the fragile X syndrome

We report on 4 individuals with the fragile X [fra(X)] syndrome and the Robin sequence (or elements of that sequence). To our knowledge, this association has been described in only one other boy. However, males with the fra(X) syndrome have been reported to have an increased incidence of cleft palate. We recommend that children with a cleft palate or the Robin sequence be assessed for developmental delays and a family history of mental retardation. The fra(X) syndrome may be one of the genetic causes of the Robin sequence and, when indicated, children with the sequence should be tested for fra(X).

Fragile X syndrome

Fragile X syndrome is one of the most intriguing genetic conditions now being studied. As the most common inherited form of mental retardation, it has an incidence of approximately 1 in 1000 male infants and boys. Because the cytogenetic diagnosis has only recently been available, many affected boys and female carriers have not yet been identified. This article reviews the characteristic, clinical features of fragile X syndrome and discusses treatment and intervention.

Aortic hypoplasia and cardiac valvular abnormalities in a boy with fragile X syndrome

An 18-year-old mentally retarded male with the Martin-Bell syndrome was fragile X positive. He died suddenly with viral pneumonia and myocarditis. At autopsy, generalized tubular hypoplasia of the aorta and a mild coarctation were discovered. The base of the mitral and tricuspid valves showed striking aberrations in elastin distribution and structure by light microscopy. Local collagen alterations were also noted. Comparable changes were seen in the skin elastin as well as a severe depletion of acid mucopolysaccharides. These changes suggest a structural disruption underlying the clinical connective tissue problems in some patients with the fragile X syndrome.

The predictive value of dermatoglyphic anomalies in the diagnosis of fra(X)-positive Martin-Bell syndrome (MBS)

In a representative group of 160 institutionalized mentally retarded males without Down syndrome, prospective dermatoglyphic-cytogenetic studies were performed in order to assess the utility of the dermatoglyphic index system of Rodewald [1986] for an efficient ascertainment of patients with Martin-Bell syndrome (MBS). A negative (abnormal) score was found in 32 men (20 +/- 3%), 14 of whom (predictive value: 44 +/- 9%) were fra(X)-positive. This prevalence of 14/160 = 9 +/- 2% patients with fra(X)-positive MBS indicates that in our study most, if not all, MBS patients have been detected by the simple pre-screening of dermatoglyphics. In the MBS patients, there was no correlation between the dermatoglyphic scores and percentage of fra(X)-positive cells.

Anthropometry in Martin-Bell syndrome

Thirty anthropometric measurements were analyzed in 147 adults with Martin-Bell syndrome (MBS) (56 men and 91 women) and in a random sample of 108 normal women and 111 men. Results of the univariate comparison of the age, height, or weight-adjusted variables between MBS and normal individuals of either sex indicated that a decrease in stature, in upper limb length, and in upper face height, and an increase in jaw length, chest circumference, and waist width occurred in both affected men and in heterozygous women. While the increase in ear height and breadth and in hypermobility of finger joints and decrease in palm width and bigonial diameter occurred only in affected men, increased bispinal and bitrochanteric diameters, upper arm circumference, and palm and wrist widths were characteristic deviations in heterozygous women. Multivariate analysis in the form of principal components showed some differences in the pattern of interrelationships in individual measures between MBS and normal individuals. In particular, and in contrast with both normal groups, height and weight tended to load on separate components (as did head and midfacial measures) in MBS individuals. A discriminant function based on all body measurements included in this study resulted in almost complete separation of discriminant scores of normal from those of MBS men and in good separation of the scores from normal and heterozygous women. Classification rates based on these functions were from 95% in men to 85% in women. These already high classification rates may be further improved mainly by enlarging the samples and including some other category of traits such as dermatoglyphic measurements.

Fragile X syndrome

The fragile X syndrome is the most common inherited form of mental retardation known. Its phenotype includes large or prominent ears, macroorchidism, and characteristic behavioral problems. It has attracted the interest of cytogeneticists and molecular biologists because of its characteristic fragile site on the X chromosome. It has puzzled geneticists because of its unusual inheritance pattern involving nonpenetrant males. This syndrome has also spearheaded an appreciation of cytogenetic abnormalities in the etiology of all degrees of developmental delay.

Phenotypic variation in male-transmitted fragile X: genetic inferences

Three families with confirmed and one family with suspected male transmission of the fragile X are presented, with psychological and physical assessment of all available members. The psychological tests used were the Peabody Picture Vocabulary test and Block Design which measured verbal and non-verbal abilities, respectively. Physical status was assessed by recording dysmorphic features and by anthropometric measurements. This study demonstrated that there are appreciable differences in mental and physical status within sibships of daughters of male carriers, as well as recognizable physical alterations and intellectual impairment in the transmitting males. These findings contradict the concept that there are two distinct categories of fragile X carriers: phenotypically normal as opposed to affected. They suggest instead that the defect may be graded and emphasize the importance of intellectual deficits and physical alterations in defining the fragile X phenotype, both in low-penetrant males and female heterozygotes.

Recently recognized chromosomal defects of clinical importance

We review those conditions which have recently been recognized to be associated with small, sometimes difficult to detect, chromosomal abnormalities. These include the Prader-Willi syndrome and X-linked mental retardation.

Aortic root dilatation and mitral valve prolapse in the fragile X syndrome

Forty patients with fragile X [fra(X)] or Martin-Bell syndrome, confirmed by chromosome analysis, underwent full cardiac evaluation including physical examination, chest film, electrocardiography (ECG), and M-mode and 2-dimensional echocardiography. Thirty-four males and six females were studied. Although all patients were asymptomatic, seven males were found to have mild aortic root dilatation. All seven also had evidence of mitral valve prolapse. Twenty-two (55%) of the study patients had mitral valve prolapse with either a click or murmur heard on physical examination and confirmation by M-mode echocardiography. The frequency of mitral valve prolapse was the same in males and females, but 80% of males older than 18 years had mitral valve prolapse. These findings support the hypothesis of a connective tissue dysplasia in the fra(X) syndrome.

Neurofibromatosis and fragile-X syndrome in the same patient

We report on an 11 1/2-year-old boy with neurofibromatosis and the fragile-X syndrome. Clinical manifestation of neurofibromatosis include multiple cafe-au-lait spots, axillary freckles, congenital glaucoma, relative macrocephaly, radiologic findings of overtubulation of the long bones, and precocious puberty. The fragile-X syndrome manifests itself as mental retardation with behavior problems, macro-orchidism, and specific cytogenetic findings. The boy has normal serum hormone levels, but a greatly elevated FSH on a first morning void, which contains the nocturnally secreted gonadotropins. This seems to be the first reported occurrence of the fragile-X syndrome with another inherited disease.