Edward S. Tobias

Recurrent rearrangements of chromosome 1q21.1 and variable pediatric phenotypes

BACKGROUND Duplications and deletions in the human genome can cause disease or predispose persons to disease. Advances in technologies to detect these changes allow for the routine identification of submicroscopic imbalances in large numbers of patients. METHODS We tested for the presence of microdeletions and microduplications at a specific region of chromosome 1q21.1 in two groups of patients with unexplained mental retardation, autism, or congenital anomalies and in unaffected persons. RESULTS We identified 25 persons with a recurrent 1.35-Mb deletion within 1q21.1 from screening 5218 patients. The microdeletions had arisen de novo in eight patients, were inherited from a mildly affected parent in three patients, were inherited from an apparently unaffected parent in six patients, and were of unknown inheritance in eight patients. The deletion was absent in a series of 4737 control persons (P=1.1x10(-7)). We found considerable variability in the level of phenotypic expression of the microdeletion; phenotypes included mild-to-moderate mental retardation, microcephaly, cardiac abnormalities, and cataracts. The reciprocal duplication was enriched in nine children with mental retardation or autism spectrum disorder and other variable features (P=0.02). We identified three deletions and three duplications of the 1q21.1 region in an independent sample of 788 patients with mental retardation and congenital anomalies. CONCLUSIONS We have identified recurrent molecular lesions that elude syndromic classification and whose disease manifestations must be considered in a broader context of development as opposed to being assigned to a specific disease. Clinical diagnosis in patients with these lesions may be most readily achieved on the basis of genotype rather than phenotype.

Mutation update for the CSB/ERCC6 and CSA/ERCC8 genes involved in Cockayne syndrome

Cockayne syndrome is an autosomal recessive multisystem disorder characterized principally by neurological and sensory impairment, cachectic dwarfism, and photosensitivity. This rare disease is linked to mutations in the CSB/ERCC6 and CSA/ERCC8 genes encoding proteins involved in the transcription‐coupled DNA repair pathway. The clinical spectrum of Cockayne syndrome encompasses a wide range of severity from severe prenatal forms to mild and late‐onset presentations. We have reviewed the 45 published mutations in CSA and CSB to date and we report 43 new mutations in these genes together with the corresponding clinical data. Among the 84 reported kindreds, 52 (62%) have mutations in the CSB gene. Many types of mutations are scattered along the whole coding sequence of both genes, but clusters of missense mutations can be recognized and highlight the role of particular motifs in the proteins. Genotype–phenotype correlation hypotheses are considered with regard to these new molecular and clinical data. Additional cases of molecular prenatal diagnosis are reported and the strategy for prenatal testing is discussed. Two web‐based locus‐specific databases have been created to list all identified variants and to allow the inclusion of future reports (www.umd.be/CSA/ and www.umd.be/CSB/). Hum Mutat 31:113–126, 2010.

The TES gene at 7q31,1 is methylated in tumours and encodes a novel growth-suppressing LIM domain protein

Many studies suggest that a multi-tissue tumour suppressor gene is located at human chromosome 7q31.1. We have cloned and characterized a novel gene at this locus. The TES gene lies within the minimal region of overlap of several LOH studies and appears to possess the properties of a tumour suppressor. TES is widely expressed and is predicted to encode a protein of 421 amino acids, with three C-terminal LIM domains. Mutation analysis of the coding TES exons in 21 human tumour-derived cell lines revealed the presence of a frameshift mutation in one allele in the breast cancer cell line ZR-75. Methylation of the CpG island at the 5′ end of TES appears to be a remarkably frequent finding, occurring in seven out of 10 ovarian carcinomas and in each of the 30 tumour-derived cell lines tested. Moreover, forced expression of TES in HeLa or OVCAR5 cells, resulted in a profound reduction in growth potential, as determined by the colony formation assay. We believe that TES is a tumour suppressor gene that is inactivated primarily by transcriptional silencing resulting from CpG island methylation.

Towards earlier diagnosis of 22q11 deletions

Over a 7 year period, 551 patients were investigated for the presence of a chromosome 22q11 deletion by fluorescence in situ hybridisation. Analysis of the presenting features of the 67 individuals with this chromosome deletion permitted us to devise guidelines to facilitate early diagnosis.

Cerebro-oculo-facio-skeletal syndrome: three additional cases with CSB mutations, new diagnostic criteria and an approach to investigation

Background: The cerebro-oculo-facio-skeletal syndrome (COFS syndrome) is an autosomal recessive disorder which was initially described in a specific aboriginal population from Manitoba. In recent years, COFS syndrome has been linked in this original population to a defective DNA repair pathway and to a homozygous mutation in the major gene underlying Cockayne syndrome (CSB). However, most reports of suspected COFS syndrome outside this population have not been confirmed at the molecular level, leading to considerable heterogeneity within the syndrome and confusing overlaps between COFS syndrome and other eye and brain disorders. Objective: To refine the delineation of the syndrome on genetically proven COFS cases. Methods: We report the exhaustive clinical, cellular and molecular data of three unrelated COFS patients with mutations in the CSB gene. Results: All three patients present the cardinal features of COFS syndrome including extreme microcephaly, congenital cataracts, facial dysmorphism and arthrogryposis. They also exhibit a predominantly postnatal growth failure, a severe psychomotor retardation, with axial hypotonia and peripheral hypertonia and neonatal feeding difficulties. Fibroblasts from the patients show the same DNA repair defect which can be complemented by transfection of the CSB wild-type cDNA. Five new mutations in the CSB gene have been identified in these patients. Conclusions: Our data indicate that COFS syndrome represents the most severe end of the Cockayne spectrum. New diagnostic criteria for COFS syndrome are proposed, based on our findings and on the few genetically proven COFS cases from the literature.

An outcome audit at the epilepsy clinic: results from 1000 consecutive referrals

The clinical details, specialist investigation, pharmacological treatment and outcome in 1000 consecutive patients referred to the epilepsy clinic at the Western Infirmary in Glasgow were reviewed. Data were collected by detailed proforma at initial referral and from the clinical notes at audit. 524 (52%) of the patients were 30 years of age or younger. 527 (53%) were sent to the clinic by their general practitioner with the majority of the remainder being referred by another hospital consultant. 240 (24%) came from outwith greater Glasgow. In 253 (25%) patients a possible predisposing factor was identified, usually a major head injury or alcohol abuse. Sixty (6%) patients suffered from additional mental handicap. Focal spike and wave activity was identified in 26% of electroencephalograms. One or more abnormality was found in 33% of the 356 patients who underwent computerized tomographic brain scanning. In 13 (11%) of these, a tumour was demonstrated. On referral, 65% of patients were being treated with antiepileptic drugs; 58% were on monotherapy and 42% took more than one anticonvulsant. The figure at audit was 77% treated, with a higher proportion (68%) than at referral receiving monotherapy (P < 0.005). Sedative anticonvulsants, such as phenobarbitone and primidone, were withdrawn in 29% of cases. 50% of the 519 patients, for whom seizure frequency data were available for the years before referral and audit, were seizure-free and seizure numbers had been reduced by 50% or more in a further 23%. A poorer response to treatment was associated with mental handicap (P < 0.05), birth injury (P < 0.01), and partial or secondary generalized seizures (P < 0.005).

Molecular Analysis of Pheochromocytoma after Maternal Transmission of SDHD Mutation Elucidates Mechanism of Parent-of-Origin Effect

CONTEXT Pheochromocytoma/paraganglioma occurs almost exclusively after paternal transmission of succinate dehydrogenase D (SDHD) mutations. This parent-of-origin effect has not been fully explained but is accompanied by obligate loss of the maternal copy of chromosome 11. Loss of wild-type SDHD and an additional imprinted gene (hypothesized to be H19) appears necessary for tumor formation. Two previous reports suggested tumor formation after maternal transmission of SDHD mutation, but histological and molecular characterization was unavailable. OBJECTIVE We report the first kindred in which histologically confirmed pheochromocytoma/paraganglioma occurred after maternal transmission of an SDHD mutation and investigate the molecular mechanism of tumor formation. DESIGN The design of the investigation was the study of a three-generation family with SDHD c.242C>T (p.Pro81Leu) mutation. RESULTS The index patient had a histologically confirmed pheochromocytoma and an identical SDHD germline mutation (p.Pro81Leu) to her mother (who had a glomus jugulare tumor) and paraganglioma tissue from her maternal grandfather. Tumor DNA from the index patient revealed loss of heterozygosity (LOH) at 11q23, causing loss of the wild-type paternal SDHD allele and LOH affecting maternal 11p15, including H19. These two regions of LOH were separated by a region exhibiting clearly retained heterozygosity, including SDHAF2, a recently reported paraganglioma susceptibility gene. CONCLUSIONS Tumor formation can occur after maternal transmission of SDHD, a finding with important clinical implications for SDHD families. Tumor formation in SDHD mutation requires the loss of both the wild-type SDHD allele and maternal 11p15, leading to the predominant but now not exclusive pattern of disease inheritance after paternal SDHD transmission.

A Study of the Clinical and Radiological Features in a Cohort of 93 Patients with a COL2A1 Mutation Causing Spondyloepiphyseal Dysplasia Congenita or a Related Phenotype

Type 2 collagen disorders encompass a diverse group of skeletal dysplasias that are commonly associated with orthopedic, ocular, and hearing problems. However, the frequency of many clinical features has never been determined. We retrospectively investigated the clinical, radiological, and genotypic data in a group of 93 patients with molecularly confirmed SEDC or a related disorder. The majority of the patients (80/93) had short stature, with radiological features of SEDC (n = 64), others having SEMD (n = 5), Kniest dysplasia (n = 7), spondyloperipheral dysplasia (n = 2), or Torrance‐like dysplasia (n = 2). The remaining 13 patients had normal stature with mild SED, Stickler‐like syndrome or multiple epiphyseal dysplasia. Over 50% of the patients had undergone orthopedic surgery, usually for scoliosis, femoral osteotomy or hip replacement. Odontoid hypoplasia was present in 56% (95% CI 38–74) and a correlation between odontoid hypoplasia and short stature was observed. Atlanto‐axial instability, was observed in 5 of the 18 patients (28%, 95% CI 10–54) in whom flexion‐extension films of the cervical spine were available; however, it was rarely accompanied by myelopathy. Myopia was found in 45% (95% CI 35–56), and retinal detachment had occurred in 12% (95% CI 6–21; median age 14 years; youngest age 3.5 years). Thirty‐two patients complained of hearing loss (37%, 95% CI 27–48) of whom 17 required hearing aids. The ophthalmological features and possibly also hearing loss are often relatively frequent and severe in patients with splicing mutations. Based on clinical findings, age at onset and genotype–phenotype correlations in this cohort, we propose guidelines for the management and follow‐up in this group of disorders.

Absence of learning difficulties in a hyperactive boy with a terminal Xp deletion encompassing the MRX49 locus

Editor—The genetic counselling of a pregnant woman who carries an Xp chromosomal deletion is far from straightforward. While the precise locations of the CDPX1 (arylsulphatase E), steroid sulphatase ( STS ), and Kallman ( KAL1 ) genes are known and FISH probes are available for these well characterised genes, the positions of putative mental retardation genes in this region have not yet been determined. Clinical and molecular studies undertaken over the past 10 years on patients with distal Xp deletions imply, however, that the putative X linked mental retardation (XLMR) gene, MRX49 , lies distal to GS1 and STS but proximal to DXS31 and CDPX1 (fig1).1-4 Figure 1 (a) Case 6, (b) case 8, (c) case 9, (d) case 4, (e) case 12, and (f) case 13 of Ballabio et al,1 (g)-(j) cases BA16, BA20, BA139, and BA75 of Schaefer et al,3 (k) boy with IQ of 46, short stature, generalised ichthyosis, hypogonadotrophic hypogonadism, nystagmus, and photophobia,2 (l) boy with aggressive and hyperactive behaviour, myoclonic epilepsy, developmental delay, and no speech aged 4 years 8 months,4 (m) monozygous male twins with X linked ichthyosis, learning difficulties (LD), and epilepsy,10 (n) our patient, with short stature, Binder syndrome, and ichthyosis (consistent with the loss of the SHOX, CDPX1, and STS genes, respectively) but no significant learning difficulties. The presence (+) or absence (-) of LD is indicated for each case. A broken line indicates the chromosomal region within …

COL2A1-related skeletal dysplasias with predominant metaphyseal involvement

Skeletal dysplasias induced by mutations in the collagen 2 gene (the so‐called “type 2 collagenopathies”) form a wide spectrum in severity and are distinguished by subtle clinical and radiographic differential signs. The unifying features are predominant involvement of the vertebral bodies and the epiphyses of the long bones (“spondylo‐epiphyseal” pattern). A mild degree of metaphyseal dysplasia can be seen in the so‐called Strudwick variant of spondyloepimetaphyseal dysplasia and is generally mild or absent in other forms.