Identification of a novel mutation in EXT2 in a fourth‐generation Korean family with multiple osteochondromas and overview of mutation spectrum

Multiple osteochondromas (MOs) or hereditary multiple exostoses is a rare autosomal‐dominant disease characterized by growths of MOs, which are benign cartilage‐capped bone tumors that grow away from the growth plates. Almost 90% of MOs have a molecular explanation and 10% are unexplained. MOs are genetically heterogeneous with two causal genes on 8q24.11 (EXT1) and 11p12 (EXT2), with a higher frequency in EXT1. MO is a very rare genetic disorder, and the genotype–phenotype of MO with EXT2 mutation has not been well investigated in Korea. We present the clinical radiographic and molecular analysis of a four‐generation Korean family with 11 MO‐affected members (seven males and four females). The affected members from the third generation available for molecular analysis and their detailed medical histories showed moderate‐to‐severe phenotypes (clinical classes II–III), including bony deformities and limb misalignment with pain requiring surgical correction. The x‐rays showed MOs in multiple sites. A novel EXT2 frameshift mutation (c.590delC, p.P197Qfs*73) was revealed by targeted exome sequencing in the affected members of this family. In this article, we not only expand the phenotypic–genotypic spectrum of MOs but also highlight the phenotypic heterogeneity in a family with the same mutation. In addition, we compiled the mutation spectrum of EXT2 from a literature review and identified that exon 2 of EXT2 is a mutation hot spot. Early medical attention with diagnosis of MO through careful examination of the clinical manifestations and genetic analysis can provide the opportunity to establish coordinated multispecialty management of the patient.     

Multiple schwannomas,multiple nevi,and multiple vaginal leiomyomas: A new dominant syndrome

We report on a family of seven affected with a new syndrome of multiple deep schwannomas, multiple nevi (both intradermal and compound types), and multiple leiomyomas of the vagina. Inheritance is dominant, whether autosomal or X-linked cannot be determined at this time. The nevi, which are congenital, appear to be a marker for the syndrome. Both the schwannomas and leiomyomas do not manifest until adulthood. Am. J. Med. Genet. 78:76–81, 1998. © 1998 Wiley-Liss, Inc.     

Maternal - offspring HLA-DRB1 compatibility in multiple sclerosis

Major histocompatibility complex (MHC) compatibility has been reported to facilitate the long-term tolerance of fetal or maternally derived stem cells exchanged during pregnancy. Furthermore, such compatibility has been suggested to play a role in fetal viability. An increase in maternal - fetal human leukocyte antigen (HLA) compatibility for class II DR alleles has previously been observed in the autoimmune disease scleroderma. Here, we examined the hypothesis that increased maternal - fetal MHC class II DR compatibility was associated with multiple sclerosis (MS) risk. HLA-DRB1 typing was performed in 2170 affected individuals and 2894 unaffected relatives from 1006 families with MS in at least two members. We found no evidence for increased HLA compatibility between affected individuals and their mothers, compared with unaffected individuals and their mothers, nor compared with affected individuals and their fathers. We also observed no excess of homozygosity of mothers compared with fathers of individuals with MS. In families in which the father shared exactly one allele with the mother, we found no excess in transmission of this allele to affected or unaffected offspring. These findings do not support a role for an excess maternal - fetal HLA-DRB1 compatibility in MS susceptibility.     

Diagnosis and management of the phenotypic spectrum of twins with Beckwith‐Wiedemann syndrome

Beckwith‐Wiedemann syndrome (BWS) is an overgrowth disorder with a heterogeneous phenotypic spectrum. There is an increased prevalence of monozygotic twinning in BWS. Given the epigenetic nature and phenotypic spectrum that defines BWS, twins are often discordant for clinical features, and clinicians are faced with the challenge of diagnosing and managing these twins. We present a cohort of multiple pregnancies in which one or more child from each pregnancy was diagnosed with BWS. We conducted a chart review of monochorionic and dichorionic gestations. Clinical scores for monochorionic twins demonstrated phenotypic discordance between the proband and twin. Based on linear regression analysis, a higher clinical score in the proband correlated with larger phenotypic discordance between twin siblings. Despite phenotypic discordance, however, we observed a consistent additive clinical score for a pregnancy (proband's plus twin's scores from a pregnancy). This idea of a finite degree of affectedness for a pregnancy implies a finite number of epigenetically affected cells. This further corroborates the idea that timing of monozygotic monochorionic twinning correlates with the disruption of establishment and/or maintenance of imprinting. The difference in clinical score between a proband and their twin may be due to diffused mosaicism, whereby there is an asymmetric distribution of affected cells among the multiple fetuses in a monozygotic monochorionic pregnancy, leading to a spectrum of variably affected phenotypes. Based on these findings, we recommend an algorithm for a conservative approach to clinically evaluate all children in a monozygotic multiple gestation affected by BWS.     

A large family with multiple epiphyseal dysplasia linked to COL9A2 gene

We describe a large family, including 54 affected individuals, with multiple epiphyseal dysplasia (MED) with involvement of the peripheral joints only. In this family, a mutation in the COL9A2 gene was detected. Every affected person has involvement of the knee joints. Other involved joints are the elbow, ankle, wrist, hand, and feet joints. Involvement of the shoulder or hip joints is never seen after adolescence. The height of the affected individuals is short to normal; spinal involvement is never seen. The penetrance of the gene is complete. However, the expression of the gene is highly variable. Am. J. Med. Genet. 77:234–240, 1998. © 1998 Wiley-Liss, Inc.     

Mutations of the NOG gene in individuals with proximal symphalangism and multiple synostosis syndrome

Proximal symphalangism is an autosomal-dominant disorder with ankylosis of the proximal interphalangeal joints, carpal and tarsal bone fusion, and conductive deafness. These symptoms are shared by another disorder of joint morphogenesis, multiple synostoses syndrome. Recently, it was reported that both disorders were caused by heterozygous mutations of the human noggin gene (NOG). To date, seven mutations of NOG have been identified from unrelated families affected with joint morphogenesis. To characterize the molecular lesions of proximal symphalangism, we performed analyses of NOG in three Japanese individuals with proximal symphalangism. We found three novel mutations: g.551G>A (C184Y) in a sporadic case of symphalangism, g.386T>A (L129X) in a familial case of symphalangism, and a g.58delC (frameshift) in a family with multiple synostosis syndrome. Characteristic genotype-phenotype correlations have not been recognized from the mutations in the NOG gene.     

Power of the affected-sib-pair method to detect disease susceptibility loci of small effect: An application to multiple sclerosis

The distribution of marker locus identity-by-descent scores in affected sib pairs provides a powerful tool for detecting the presence of a linked non-Mendelian disease susceptibility locus. This basic approach is here extended to include a trio of sibs. A special type of sib trio consisting of two affected and one unaffected sib is investigated. It is shown that compared to affected-sib-pairs, trios with the above configuration are less efficient in detecting the presence of a linked disease susceptibility locus. When the generalized two-allele single locus model is fitted to sib pairs affected with multiple sclerosis, an estimate of the recombination fraction of 0.21 between the putative disease susceptibility locus and the HLA complex is obtained. However, this transmission model is deemed inadequate since a recombination fraction this large is inconsistent with the variety of HLA associations observed at the population level.     

Determination of the real effect of genes identified in GWAS: the example of IL2RA in multiple sclerosis

Genome-wide association studies (GWAS), although efficient to detect genes involved in complex diseases, are not designed to measure the real effect of the genes. This is illustrated here by the example of IL2RA in multiple sclerosis (MS). Association between IL2RA and MS is clearly established, although the functional variation is still unknown: the effect of IL2RA might be better described by several SNPs than by a single one. This study investigates whether a pair of SNPs better explains the observed linkage and association data than a single SNP. In total, 522 trio families and 244 affected sib-pairs were typed for 26 IL2RA SNPs. For each SNP and pairs of SNPs, the phased genotypes of patients and controls were compared to determine the SNP set offering the best risk discrimination. Consistency between the genotype risks provided by the retained set and the identical by descent allele sharing in affected sib-pairs was assessed. After controlling for multiple testing, the set of SNPs rs2256774 and rs3118470, provides the best discrimination between the case and control genotype distributions (P-corrected=0.009). The relative risk between the least and most at-risk genotypes is 3.54 with a 95% confidence interval of [2.14-5.94]. Furthermore, the linkage information provided by the allele sharing between affected sibs is consistent with the retained set (P=0.80) but rejects the SNP reported in the literature (P=0.006). Establishing a valid modeling of a disease gene is essential to test its potential interaction with other genes and to reconstruct the pathophysiological pathways.     

An omnibus test for family-based association studies with multiple SNPs and multiple phenotypes

We propose an omnibus family-based association test (MFBAT) that can be applied to multiple markers and multiple phenotypes and that has only one degree of freedom. The proposed test statistic extends current FBAT methodology to incorporate multiple markers as well as multiple phenotypes. Using simulation studies, power estimates for the proposed methodology are compared with the standard methodologies. On the basis of these simulations, we find that MFBAT substantially outperforms other methods, including haplotypic approaches and doing multiple tests with single single-nucleotide polymorphisms (SNPs) and single phenotypes. The practical relevance of the approach is illustrated by an application to asthma in which SNP/phenotype combinations are identified and reach overall significance that would not have been identified using other approaches. This methodology is directly applicable to cases in which there are multiple SNPs, such as candidate gene studies, cases in which there are multiple phenotypes, such as expression data, and cases in which there are multiple phenotypes and genotypes, such as genome-wide association studies that incorporate expression profiles as phenotypes. This program is available in the PBAT analysis package.     

Joint Analysis of Multiple Traits in Rare Variant Association Studies

The joint analysis of multiple traits has recently become popular since it can increase statistical power to detect genetic variants and there is increasing evidence showing that pleiotropy is a widespread phenomenon in complex diseases. Currently, the majority of existing methods for the joint analysis of multiple traits test association between one common variant and multiple traits. However, the variant‐by‐variant methods for common variant association studies may not be optimal for rare variant association studies due to the allelic heterogeneity as well as the extreme rarity of individual variants. Current statistical methods for rare variant association studies are for one single trait only. In this paper, we propose an adaptive weighting reverse regression (AWRR) method to test association between multiple traits and rare variants in a genomic region. AWRR is robust to the directions of effects of causal variants and is also robust to the directions of association of traits. Using extensive simulation studies, we compare the performance of AWRR with canonical correlation analysis (CCA), Single‐TOW, and the weighted sum reverse regression (WSRR). Our results show that, in all of the simulation scenarios, AWRR is consistently more powerful than CCA. In most scenarios, AWRR is more powerful than Single‐TOW and WSRR.     

Prenatal diagnosis of distal arthrogryposis

We report the prenatal diagnosis of distal arthrogryposis type I by ultrasound at 18 wk gestation in a family with two other affected members (mother and sister of the fetus). The pregnancy was followed with serial ultrasounds, and the diagnosis was confirmed after birth. The clinical findings in all affected family members are described. A literature survey of prenatally diagnosed cases of multiple joint contractures is presented. These include cases with many different diagnoses. This is the first report of the prenatal diagnosis of distal arthrogryposis type I. It helps to illustrate the variability and prenatal natural history of the condition and the subtlety of the prenatal ultrasound findings.     

Incomplete penetrance and expressivity skewing in hereditary multiple exostoses

Hereditary multiple exostosis (EXT) is an autosomal dominant skeletal disorder characterized by the formation of cartilage-capped prominences developing from the juxta-epiphyseal regions of the long bones and causing orthopedic deformities and occasionally sarcomatous degeneration. Reviewing a large cohort of 175 EXT patients referred to us over the last 40 years (1955–1995), we found 109 familial forms (62%) and 66 isolated cases (38%). The disease is consistently diagnosed before the age of 12 years and the risk of malignancy, although increased, is quite modest in our series (0.57%). The observation of seven unaffected individuals (six females, one male) with a family history and affected offspring supports the incomplete penetrance of the disease. Moreover, the observation of an unequal sex-ratio with a preponderance of males among probands in this series (103: 72, p < 0.02) and in all series reported to date (198: 133, p < 0.001) gives support to the variable penetrance of EXT genes among sexes. Whether this incomplete penetrance is associated with one of the disease genes recently identified in EXT is currently under investigation.     

Natural history study of hereditary multiple exostoses

Hereditary multiple exostosis (EXT) is an autosomal dominant disorder in which the clinical hallmark is the growth of bony protuberances from long bones and which can cause a variety of orthopedic deformities. This study sought to further delineate the natural history of EXT. In addition, since previous studies have suggested that there are deviations from Mendelelian expectations in EXT, including incomplete penetrance and a skewed sex ratio, we attempted to confirm or refute these suggestions. Both portions of the study were carried out through retrospective review of 43 affected probands and 137 of their affected relatives. Data are presented concerning frequency and severity of complications of EXT including short stature, sequelae of exostoses, occurrence of malignant degeneration of exostoses, and problems in pregnancy and delivery of affected females. Only 2.8% of the total affected population had experienced exostosis-related malignancy, an estimate which is considerably less than earlier reports would suggest. Penetrance was 100%. There was an excess of males within the entire affected population (104:76) and within identified probands (28:15). However, the male to female ratio was unskewed in nuclear families (probands, affected sibs, and parents). The excess of males appears to be related to males having more severe and more frequent complications of EXT than having any primary genetic origin. © 1995 Wiley-Liss, Inc.     

Compact miniature microelectrode-telemetry system

A multiple semi-microelectrode assembly and a pretuned miniature FM transmitter for recording unit and slow wave potentials are described. This compact system makes it possible to record unit and slow-wave potentials from the same brain locus over long periods of time in freely behaving animals. The procedure for constructing the ten wire electrode is described in detail. Used in conjunction with the transmitter, broadcast distance is at least 30 ft and locomotor activity of rats and rabbits is not affected by the light weight assembly. The fidelity of transmitted single unit potentials compares favorably with and is more noise-free than any currently available direct-wire procedure.     

From micro‐ to macro‐structures in multiple sclerosis: what is the added value of diffusion imaging

Diffusion imaging has been instrumental in understanding damage to the central nervous system as a result of its sensitivity to microstructural changes. Clinical applications of diffusion imaging have grown exponentially over the past couple of decades in many neurological and neurodegenerative diseases, such as multiple sclerosis (MS). For several reasons, MS has been extensively researched using advanced neuroimaging techniques, which makes it an ‘example disease’ to illustrate the potential of diffusion imaging for clinical applications. In addition, MS pathology is characterized by several key processes competing with each other, such as inflammation, demyelination, remyelination, gliosis and axonal loss, enabling the specificity of diffusion to be challenged. In this review, we describe how diffusion imaging can be exploited to investigate micro‐, meso‐ and macro‐scale properties of the brain structure and discuss how they are affected by different pathological substrates. Conclusions from the literature are that larger studies are needed to confirm the exciting results from initial investigations before current trends in diffusion imaging can be translated to the neurology clinic. Also, for a comprehensive understanding of pathological processes, it is essential to take a multiple‐level approach, in which information at the micro‐, meso‐ and macroscopic scales is fully integrated.     

The epidemiology of multiple births.

On the basis of MEDLINE and manual searches, we examined the main papers in the English literature regarding risk factors for spontaneous (i.e. not related to fertility drug use) multiple births. The constant frequency of monozygotic (MZ) pregnancies over time and in different geographical areas suggests that the determination of MZ twins is largely unchanged over time, and that a genetic mechanism may have a role. In contrast, temporal and geographical trends observed in dizygotic (DZ) pregnancies suggest that environmental factors play a role in determining this condition. At present, maternal age and hereditary components are the best-defined determinants for spontaneous multiple births.     

Synaptic pathology in the cerebellar dentate nucleus in chronic multiple sclerosis

In multiple sclerosis, cerebellar symptoms are associated with clinical impairment and an increased likelihood of progressive course. Cortical atrophy and synaptic dysfunction play a prominent role in cerebellar pathology and although the dentate nucleus is a predilection site for lesion development, structural synaptic changes in this region remain largely unexplored. Moreover, the mechanisms leading to synaptic dysfunction have not yet been investigated at an ultrastructural level in multiple sclerosis. Here, we report on synaptic changes of dentate nuclei in post‐mortem cerebella of 16 multiple sclerosis patients and eight controls at the histological level as well as an electron microscopy evaluation of afferent synapses of the cerebellar dentate and pontine nuclei of one multiple sclerosis patient and one control. We found a significant reduction of afferent dentate synapses in multiple sclerosis, irrespective of the presence of demyelination, and a close relationship between glial processes and dentate synapses. Ultrastructurally, we show autophagosomes containing degradation products of synaptic vesicles within dendrites, residual bodies within intact‐appearing axons and free postsynaptic densities opposed to astrocytic appendages. Our study demonstrates loss of dentate afferent synapses and provides, for the first time, ultrastructural evidence pointing towards neuron‐autonomous and neuroglia‐mediated mechanisms of synaptic degradation in chronic multiple sclerosis.     

Novel mutations in the EXT1 gene in two consanguineous families affected with multiple hereditary exostoses (familial osteochondromatosis)

Multiple hereditary exostoses (HME) is an autosomal dominant developmental disorder exhibiting multiple osteocartilaginous bone tumors that generally arise near the ends of growing long bones. Here, we report two large consanguineous families from Pakistan, who display the typical features of HME. Affected individuals also show a previously unreported feature--bilateral overriding of single toes. Analysis using microsatellite markers for each of the known EXT loci, EXT1, EXT2, and EXT3 showed linkage to EXT1. In the first family, mutation analysis of the EXT1 gene revealed that affected individuals were heterozygous for an in-frame G-to-C transversion at the conserved splice donor site in intron 1. This mutation is predicted to disrupt splicing of the first intron and produce a frameshift that leads to a premature termination codon. In the second family, an insertion of an A in exon 8 is predicted to produce a frameshift at codon 555 followed by a premature termination, a further 10 codons downstream. In both families, an increased number of affected male subjects were observed. In affected females in family 2, phenotypic variability and incomplete penetrance were noted.     

多发性硬化的免疫研究进展

多发性硬化(MS)是中枢神经系统(CNS)自身免疫性疾病的代表.本文对多发性硬化的免疫发病机制和免疫干预治疗的研究进展作一概述.     

In search of cerebrospinal fluid biomarkers of fatigue in multiple sclerosis: A proteomics study

Fatigue in multiple sclerosis is a very common and cumbersome symptom, but its aetiology is poorly understood. Proteomics is increasingly implemented in multiple sclerosis research, but has not yet been used to study the neurobiological basis of fatigue in multiple sclerosis. To identify potential cerebrospinal fluid biomarkers of fatigue in multiple sclerosis, we collected cerebrospinal fluid of 20 patients with multiple sclerosis with fatigue (MS+), 20 patients with multiple sclerosis without fatigue (MS?), and 20 control subjects without multiple sclerosis and without fatigue (HC). We used a shotgun proteomics approach and label‐free quantitative proteomics to analyse the protein content in cerebrospinal fluid. Selected proteins with differential abundance were further validated by immunoblotting. Out of 591 detected cerebrospinal fluid proteins, the abundance of nine proteins differed between the three groups, and seven additional proteins differed between MS+ and MS? patients. Using immunoblot or slot‐blot techniques, we confirmed decreased levels of protein kinase C‐binding protein NELL2, neural cell adhesion molecule L1‐like protein, and reelin in MS+ patients. In conclusion, cerebrospinal fluid proteomics may provide insight into the neurobiological basis of fatigue in multiple sclerosis. The proteins identified to be decreased in MS+ are involved in synaptic plasticity and energy homeostasis, and thus appear as plausible biomarkers of this common symptom.