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S C Brown

Publications and source records attributed to S C Brown.

At least 19 recordsLinked to original sources
PubMed2006

A comparative analysis of collagen VI production in muscle, skin and fibroblasts from 14 Ullrich congenital muscular dystrophy patients with dominant and recessive COL6A mutations.

Ullrich congenital muscular dystrophy (UCMD) is caused by recessive and dominant mutations in COL6A genes. We have analysed collagen VI expression in 14 UCMD patients. Sequencing of COL6A genes had identified homozygous and heterozygous mutations in 12 cases. Analysis of collagen VI in fibroblast cultures derived from eight of these patients showed reduced extracellular deposition in all cases and intracellular collagen VI staining in seven cases. This was observed even in cases that showed normal collagen VI labelling in skin biopsies. Collagen VI immunolabelling was reduced in all the available muscle biopsies. When comparisons were possible no correlation was seen between the extent of the reduction in the muscle and fibroblast cultures, the mode of inheritance or the severity of the clinical phenotype. Mutations affecting glycine substitutions in the conserved triple helical domain were common and all resulted in reduced collagen VI. This study expands the spectrum of collagen VI defects and shows that analysis of skin fibroblasts may be a useful technique for the detection of collagen VI abnormalities. In contrast, immunohistochemical analysis of skin biopsies may not always reveal an underlying collagen VI defect.

Adolescent↗
PubMed2006

Phase 1 trial of the antiangiogenic peptide ATN-161 (Ac-PHSCN-NH(2)), a beta integrin antagonist, in patients with solid tumours.

To evaluate the toxicity, pharmacological and biological properties of ATN-161, a five -amino-acid peptide derived from the synergy region of fibronectin, adult patients with advanced solid tumours were enrolled in eight sequential dose cohorts (0.1-16 mg kg(-1)), receiving ATN-161 administered as a 10-min infusion thrice weekly. Pharmacokinetic sampling of blood and urine over 7 h was performed on Day 1. Twenty-six patients received from 1 to 14 4-week cycles of treatment. The total number of cycles administered to all patients was 86, without dose-limiting toxicities. At dose levels above 0.5 mg kg(-1), mean total clearance and volume of distribution showed dose-independent pharmacokinetics (PKs). At 8.0 and 16.0 mg kg(-1), clearance of ATN-161 was reduced, suggesting saturable PKs. Dose escalation was halted at 16 mg kg(-1) when drug exposure (area under the curve) exceeded that associated with efficacy in animal models. There were no objective responses. Six patients received more than four cycles of treatment (>112 days). Three patients received 10 or more cycles (> or =280 days). ATN-161 was well tolerated at all dose levels. Approximately, 1/3 of the patients in the study manifested prolonged stable disease. These findings suggest that ATN-161 should be investigated further as an antiangiogenic and antimetastatic cancer agent alone or with chemotherapy.

Adult↗
PubMed2006

Disease severity in dominant Emery Dreifuss is increased by mutations in both emerin and desmin proteins.

Individuals with the same genetic disorder often show remarkable differences in clinical severity, a finding generally attributed to the genetic background. We identified two patients with genetically proven Emery-Dreifuss muscular dystrophy (EDMD) who followed an unusual course and had uncommon clinicopathological findings. We hypothesized digenic inheritance and looked for additional molecular explanations. Mutations in additional separate genes were identified in both patients. The first patient was a member of a family with molecularly proven X-linked EDMD. However, the clinical features were unusually severe for this condition in the propositus: he presented at 2.5 years with severe proximal weakness and markedly elevated serum creatine kinase. Muscle weakness rapidly progressed, leading to loss of independent ambulation by the age of 12. In addition, the patient developed cardiac conduction system disease requiring pacing at the age of 11 and severe dilated cardiomyopathy in the early teens. Despite pacing, he had several syncopal episodes attributed to ventricular dysrhythmias. As these resemble the cardiac features of patients with the autosomal dominant variant of EDMD, we examined the lamin A/C gene, identifying a de-novo mutation in the propositus. The second patient had a cardioskeletal myopathy, similar to his mother who had died more than 20 years previously. Because of the dominant family history, a laminopathy was suspected and a mutation in exon 11 of the LMNA gene was identified. This mutation, however, was not present in his mother, but instead, surprisingly, was identified in his virtually asymptomatic father. Unusual accumulations of desmin found in the cardiac muscle of the propositus prompted us to examine the desmin gene in this patient, and in so doing, we identified a desmin mutation, in addition to the LMNA mutation in the propositus. These cases suggest that separate mutations in related proteins that are believed to interact, or that represent different parts of a presumed functional pathway, may synergistically contribute to disease severity in autosomal dominant EDMD. Furthermore, digenic inheritance may well contribute to the clinical severity of many other neuromuscular disorders.

Adolescent↗
PubMed2005

Mutated fukutin-related protein (FKRP) localises as wild type in differentiated muscle cells.

The mechanism of disease in forms of congenital and limb girdle muscular dystrophy linked to mutations in the gene encoding for Fukutin-related protein (FKRP) has previously been associated with the mis-localisation of FKRP from the Golgi apparatus. In the present report, we have transfected V5-tagged Fukutin-related protein expression constructs into differentiated C2C12 myotubes and the tibialis anterior of normal mice. The transfection of either wild type (WT) or several mutant constructs (P448L, C318Y, L276I) into myotubes consistently showed clear co-localisation with GM130, a Golgi marker. In contrast, whilst WT and the L276I localised to the Golgi of Cos-7 cells, the P448L and C318Y was mis-localised in the majority of these undifferentiated cells. The injection of the same constructs into the tibialis anterior of mice resulted in similar localisation of both the WT and all the mutants. Immunolabelling of FKRP in the muscle of MDC1C and LGMD2I patients was found to be indistinguishable from normal controls. Overall, these data suggest that retention in the endoplasmic reticulum of FKRP is not the main mechanism of disease but that this may instead relate to a disruption of the functional activity of this putative enzyme with its substrate(s) in the Golgi.

Animals↗
PubMed2005

Extreme variability of skeletal and cardiac muscle involvement in patients with mutations in exon 11 of the lamin A/C gene.

Mutations of the LMNA gene, encoding the nuclear envelope proteins lamins A and C, give rise to Emery-Dreifuss muscular dystrophy and to limb-girdle muscular dystrophy 1B (EDMD and LGMD1B). With one exception, all the reported EDMD and LGMD1B mutations are confined to the first 10 exons of the gene. We report four separate cases, with mutations in the same codon of LMNA exon 11, characterized by remarkable variability of clinical findings, in addition to features not previously reported. One patient had congenital weakness and died in early childhood. In two other patients, severe cardiac problems arose early and, in one of these, cardiac signs preceded by many years the onset of skeletal muscle weakness. The fourth case had a mild and late-onset LGMD1B phenotype. Our cases further expand the clinical spectrum associated with mutations in the LMNA gene and provide new evidence of the role played by the C-terminal domain of lamin A.

Adult↗
PubMed2005

Congenital muscular dystrophy: molecular and cellular aspects.

The congenital muscular dystrophies are a clinically and genetically heterogeneous group of neuromuscular disorders. Each form has a characteristic phenotype, but there is overlap between some entities and their classification is based on a combination of clinical features and the primary or secondary protein defect. Recent studies have identified the genetic basis of a number of congenital muscular dystrophies (11 genes in total) and have recognised a novel pathological mechanism that highlights the importance of the correct posttranslational processing of proteins, in particular alpha-dystroglycan. Diagnosis of these conditions has been aided by the availability of specific antibodies for each protein and a better understanding of the protein changes that accompany each condition. In this review we present the major molecular, clinical and diagnostic aspects of each group of congenital muscular dystrophy with an emphasis in the more recent developments.

Antigens, CD↗
PubMed2005

Nuclear DNA content and chromosome number in some diploid and tetraploid Centaurea (Asteraceae: Cardueae) from the Dalmatia region.

Given the paucity of information about genome size in the genus Centaurea, nuclear DNA content of 15 Centaurea taxa, belonging to four subgenera and six different sections, has been investigated for the first time. The sample concerns 21 populations from the Dalmatia region of Croatia. The 2C DNA content and GC percentage were assessed by flow cytometry and chromosome number was determined using standard methods. Genome size of studied Centaurea ranged from 2C=1.67 to 3.72 pg. These results were in accordance with chromosome number and especially with ploidy level that varies throughout this group; 2C DNA values ranged from 1.67 to 3.43 pg for diploid, and from 3.19 to 3.72 for polyploid taxa. No significant intraspecific variations of DNA amount were found between two subspecies of C. visiani and C. ragusina, nor between two varieties of C. gloriosa. However, some populations of C. glaberrima and C. cuspidata showed a significant difference in DNA amount. Three different basic chromosome numbers were observed in studied species (x=9, 10, and 11). The most frequent basic number was x=9. C. rupestris, C. ragusina ssp. ragusina, and C. r. ssp. lungensis possessed x=10 and C. tuberosa x=11. The species with a basic chromosome number of x=9 had a small genome size and the smallest chromosomes (on average 0.09 to 0.12 pg/chromosome) but frequently present polyploidy. Centaurea ragusina ssp. ragusina and C. r. ssp. lungensis had a mean base composition 41.3% GC.

Centaurea↗
PubMed2005

Evolution of genome size across some cultivated Allium species.

Allium L. (Alliaceae), a genus of major economic importance, exhibits a great diversity in various morphological characters and particularly in life form, with bulbs and rhizomes. Allium species show variation in several cytogenetic characters such as basic chromosome number, ploidy level, and genome size. The purpose of the present investigation was to study the evolution of nuclear DNA amount, GC content, and life form. A phylogenetic approach was used on a sample of 30 Allium species, including major vegetable crops and their wild allies, belonging to the 3 major subgenera Allium, Amerallium, and Rhizirideum and 14 sections. A phylogeny was constructed using internal transcribed spacer (ITS) sequences of 43 accessions representing 30 species, and the nuclear DNA amount and the GC content of 24 Allium species were investigated by flow cytometry. For the first time, the nuclear DNA content of Allium cyaneum and Allium vavilovii was measured, and the GC content of 16 species was measured. We addressed the following questions: (i) Is the variation in nuclear DNA amount and GC content linked to the evolutionary history of these edible Allium species and their wild relatives? (ii) How did life form (rhizome or bulb) evolve in edible Allium? Our results revealed significant interspecific variation in the nuclear DNA amount as well as in the GC content. No correlation was found between the GC content and the nuclear DNA amount. The reconstruction of nuclear DNA amount on the phylogeny showed a tendency towards a decrease in genome size within the genus. The reconstruction of life form history showed that rhizomes evolved in the subgenus Rhizirideum from an ancestral bulbous life form and were subsequently lost at least twice independently in this subgenus.

Allium↗
PubMed2004

Absence of neuronal nitric oxide synthase (nNOS) as a pathological marker for the diagnosis of Becker muscular dystrophy with rod domain deletions.

Immunohistochemistry using antibodies to dystrophin is the pathological basis for the diagnosis of Duchenne and Becker muscular dystrophy (DMD and BMD). While the sarcolemma of DMD muscle is negative, BMD muscle generally shows variable labelling because of the translation of a partially functional dystrophin that is localized to the sarcolemma. In rare cases, however, this labelling is equivocal and similar to that observed in controls making diagnosis difficult. We report here that in such instances immunolabelling with antibodies to the neuronal form of nitric oxide synthase (nNOS) can be useful in suspecting a dystrophinopathy with a mutation in the 'hot-spot' rod domain and help to direct molecular analysis. nNOS localizes to the sarcolemma of mature muscle fibres via several components of the dystrophin-associated protein complex (DAPC) including dystrophin but sarcolemmal nNOS is lost when dystrophin levels are very low or absent because of deletions in critical regions of the rod domain. We report three cases who presented with only mild or no muscle weakness but had elevated serum creatine kinase activity and dystrophin immunolabelling indistinguishable from normal, making a pathological diagnosis difficult. All three cases had a complete absence of sarcolemmal nNOS and were subsequently found to have an in-frame deletion in the common rod domain exons (in these cases 48, 45-51, 47-53) compatible with a BMD. In addition, we observed that nNOS appears to be developmentally regulated with the antibody used and was often absent from the sarcolemma of immature fibres. These findings demonstrate the value of including antibodies to nNOS in routine immunohistochemical studies and that absence of nNOS can be a more sensitive marker than up-regulation of utrophin for diagnosis of BMD. Immaturity of fibres, however, needs to be taken into account, especially in neonates.

Biomarkers↗
PubMed2003

Genome size and base composition of five Pinus species from the Balkan region.

The 2C DNA content and base composition of five Pinus (2 n=24) species and two Pinus subspecies from the Balkan region have been estimated by flow cytometry. P. heldreichii (five populations) and P. peuce (one population) were assessed for the first time, as also were subspecies of P. nigra (three populations-two of subspecies nigra and one of subspecies dalmatica) along with P. sylvestris, and P. mugo from the same region. The 2C DNA values of these Pinus ranged from 42.5 pg to 54.9 pg (41.7-53.8 x 10(9)bp), and the base composition was quite stable (about 39.5% GC). Significant differences were observed between two subspecies of P. nigra and even between two populations of subsp. nigra. The two other species (P. sylvestris and P. mugo) had 2C values of 42.5 pg and 42.8 pg, respectively, while that of P. peuce was 54.9 pg. These genome sizes are in accordance with published values except for P. sylvestris, which was 20% below estimates made by other authors.

Base Composition↗
PubMed2003

FKRP gene mutations cause congenital muscular dystrophy, mental retardation, and cerebellar cysts.

BACKGROUND: Congenital muscular dystrophies (CMD) are autosomal recessive disorders that present within the first 6 months of life with hypotonia and a dystrophic muscle biopsy. CNS involvement is present in some forms. The fukutin-related protein gene (FKRP) is mutated in a severe form of CMD (MDC1C) and a milder limb girdle dystrophy (LGMD2I). Both forms have secondary deficiencies of laminin alpha2 and alpha-dystroglycan immunostaining. Structural brain involvement has not been observed in patients with FKRP gene mutations. METHODS: The authors studied two unrelated patients who had a pattern of muscle involvement identical to MDC1C, mental retardation, and cerebellar cysts on cranial MRI. The FKRP gene was analyzed along with the skeletal muscle expression of laminin alpha2 and alpha-dystroglycan. RESULTS: The muscle biopsy of both patients showed severe dystrophic findings, a reduction in laminin alpha2, and profound depletion of alpha-dystroglycan. Both patients had homozygous FKRP gene mutations not previously reported (C663A [Ser221Arg] and C981A [Pro315Thr]). CONCLUSIONS: Mutations within the FKRP gene can result in CMD associated with mental retardation and cerebellar cysts. This adds structural brain defects to the already wide spectrum of abnormalities caused by FKRP mutations. The severe depletion of alpha-dystroglycan expression suggests that FKRP is involved in the processing of alpha-dystroglycan.

Amino Acid Substitution↗
PubMed2003

Muscle magnetic resonance imaging in patients with congenital muscular dystrophy and Ullrich phenotype.

The aim of this study was to evaluate muscle magnetic resonance imaging findings in patients with congenital muscular dystrophy and Ullrich phenotype. Fifteen children with congenital muscular dystrophy and Ullrich phenotype were included in the study. All patients had collagen VI studies in muscle and, when family structure was informative, linkage studies to the collagen 6 loci. Three of the 15 patients had reduced collagen in muscle. One of the three was from an informative family and linked to one of the collagen 6 loci. Another patient was linked to one of the collagen 6 loci but had normal expression of collagen in muscle. The remaining 11 all had normal collagen expression in muscle. Only two of these 11 were from informative families and linkage to collagen 6 loci was excluded in them. All patients had muscle magnetic resonance imaging of their leg muscles using transverse T1 sequences. With the exception of the two patients in whom linkage to the collagen 6 loci was excluded, the other 13 patients showed the same pattern of selective involvement on magnetic resonance imaging of thigh muscles. This consisted of relative sparing of sartorius, gracilis, adductor longus and rectus. This pattern was also found in the case linked COL6A1/A2 locus but with normal collagen. This finding, and the striking clinical and magnetic resonance imaging concordance between patients with normal and reduced collagen VI in muscle suggest that collagen VI could still be the culprit in several cases with normal collagen expression, or alternatively a primary defect in a protein that closely interacts with collagen VI. Mutation analysis of the collagen 6 genes in cases with normal collagen VI expression is needed to resolve this issue.

Adolescent↗
PubMed2002

Autosomal recessive inheritance of RYR1 mutations in a congenital myopathy with cores.

Central core disease (CCD) is a congenital myopathy due to dominant mutations in the skeletal muscle ryanodine receptor gene (RYR1). The authors report three patients from two consanguineous families with symptoms of a congenital myopathy, cores on muscle biopsy, and confirmed linkage to the RYR1 locus. Molecular genetic studies in one family identified a V4849I homozygous missense mutation in the RYR1 gene. This report suggests a congenital myopathy associated with recessive RYR1 mutations.

Biopsy↗
PubMed2002

Collagen VI involvement in Ullrich syndrome: a clinical, genetic, and immunohistochemical study.

BACKGROUND: Ullrich congenital muscular dystrophy (UCMD) is a form of merosin-positive congenital muscular dystrophy characterized by proximal contractures, distal laxity, rigidity of the spine, and respiratory complications. Recently, a deficiency of collagen VI on muscle and skin biopsy together with recessive mutations in the collagen 6A2 gene were reported in three families with UCMD. However, the clinical spectrum, frequency, and level of heterogeneity of this disorder are not known. SUBJECTS AND METHODS: The authors studied 15 patients (aged 3 to 23.6 years) with a clinical diagnosis of UCMD. Linkage analysis to the three collagen VI genes was performed in all informative families (n = 7), whereas immunohistochemical analysis of collagen VI expression in muscle was performed in the remaining cases. RESULTS: An immunocytochemical reduction of collagen VI was observed in six patients. Three of the six patients belonged to informative families, and haplotype analysis clearly suggested linkage to the COL6A1/2 locus in two cases and to the COL6A3 loci in the third case. In the remaining nine patients, primary collagen VI involvement was excluded based on either the linkage analysis (four families) or considered unlikely based on normal immunolabeling of collagen VI. Age and presentation at onset, the distribution and severity of weakness and contractures, and the frequency of nonambulant patients were similar in the patients with and without collagen VI involvement. Distal laxity, rigidity of the spine, scoliosis, failure to thrive, and early and severe respiratory impairment were found in all patients by the end of the first decade of life, irrespective of their maximum motor functional ability or their collagen status. CONCLUSIONS: These results suggest that collagen VI involvement is relatively common in UCMD (40%); however, the role of this molecule was excluded in a number of cases, suggesting genetic heterogeneity of this condition.

Adolescent↗
PubMed2001

Mutations in the fukutin-related protein gene (FKRP) identify limb girdle muscular dystrophy 2I as a milder allelic variant of congenital muscular dystrophy MDC1C.

The limb girdle and congenital muscular dystrophies (LGMD and CMD) are characterized by skeletal muscle weakness and dystrophic muscle changes. The onset of symptoms in CMD is within the first few months of life, whereas in LGMD they can occur in late childhood, adolescence or adult life. We have recently demonstrated that the fukutin-related protein gene (FKRP) is mutated in a severe form of CMD (MDC1C), characterized by the inability to walk, leg muscle hypertrophy and a secondary deficiency of laminin alpha2 and alpha-dystroglycan. Both MDC1C and LGMD2I map to an identical region on chromosome 19q13.3. To investigate whether these are allelic disorders, we undertook mutation analysis of FKRP in 25 potential LGMD2I families, including some with a severe and early onset phenotype. Mutations were identified in individuals from 17 families. A variable reduction of alpha-dystroglycan expression was observed in the skeletal muscle biopsy of all individuals studied. In addition, several cases showed a deficiency of laminin alpha2 either by immunocytochemistry or western blotting. Unexpectedly, affected individuals from 15 families had an identical C826A (Leu276Ileu) mutation, including five that were homozygous for this change. Linkage analysis identified at least two possible haplotypes in linkage disequilibrium with this mutation. Patients with the C826A change had the clinically less severe LGMD2I phenotype, suggesting that this is a less disruptive FKRP mutation than those found in MDC1C. The spectrum of LGMD2I phenotypes ranged from infants with an early presentation and a Duchenne-like disease course including cardiomyopathy, to milder phenotypes compatible with a favourable long-term outcome.

Adolescent↗
PubMed2001

Mutations in the fukutin-related protein gene (FKRP) cause a form of congenital muscular dystrophy with secondary laminin alpha2 deficiency and abnormal glycosylation of alpha-dystroglycan.

The congenital muscular dystrophies (CMD) are a heterogeneous group of autosomal recessive disorders presenting in infancy with muscle weakness, contractures, and dystrophic changes on skeletal-muscle biopsy. Structural brain defects, with or without mental retardation, are additional features of several CMD syndromes. Approximately 40% of patients with CMD have a primary deficiency (MDC1A) of the laminin alpha2 chain of merosin (laminin-2) due to mutations in the LAMA2 gene. In addition, a secondary deficiency of laminin alpha2 is apparent in some CMD syndromes, including MDC1B, which is mapped to chromosome 1q42, and both muscle-eye-brain disease (MEB) and Fukuyama CMD (FCMD), two forms with severe brain involvement. The FCMD gene encodes a protein of unknown function, fukutin, though sequence analysis predicts it to be a phosphoryl-ligand transferase. Here we identify the gene for a new member of the fukutin protein family (fukutin related protein [FKRP]), mapping to human chromosome 19q13.3. We report the genomic organization of the FKRP gene and its pattern of tissue expression. Mutations in the FKRP gene have been identified in seven families with CMD characterized by disease onset in the first weeks of life and a severe phenotype with inability to walk, muscle hypertrophy, marked elevation of serum creatine kinase, and normal brain structure and function. Affected individuals had a secondary deficiency of laminin alpha2 expression. In addition, they had both a marked decrease in immunostaining of muscle alpha-dystroglycan and a reduction in its molecular weight on western blot analysis. We suggest these abnormalities of alpha-dystroglycan are caused by its defective glycosylation and are integral to the pathology seen in MDC1C.

Adult↗