Evidence for heterogeneity in facioscapulohumeral muscular dystrophy (FSHD)

Facioscapulohumeral muscular dystrophy (FSHD) is a slowly progressive primary disease of muscle which is usually inherited as an autosomal dominant disorder. FSHD has been localized to the long arm of chromosome 4, specifically to the 4q3.5-qter region. Initially published linkage studies showed no evidence for heterogeneity in FSHD. In the present study we have examined individuals in seven FSHD families. Two-point lod scores show significant evidence for linkage for D4S163 (lod score 3.04 at recombination fraction .21) and D4S139 (lod score 3.84 at recombination fraction .20). D4S171 also gave a positive score (lod score 2.56 at recombination fraction .24). Significant evidence for heterogeneity was found for each of the three markers. Multipoint linkage analysis in this region resulted in a peak multipoint lod score of 6.47. The multipoint analysis supported the two-point studies with odds of 20:1 showing linkage and heterogeneity over linkage and homogeneity. Five of the seven families gave a posterior probability of > 95% of being of the linked type, while two families appeared unlinked to this region of 4q (P < .01%). Individuals in the two unlinked families met the clinical criteria for the diagnosis of FSHD, including facial weakness, clavicular flattening, scapula winging, proximal muscle weakness, and myopathic changes on muscle biopsies without inflammatory or mitochondrial pathology. This study demonstrates genetic heterogeneity in FSHD and has important implications for both genetic counseling and the elucidation of the etiology of FSHD.     

Facioscapulohumeral muscular dystrophy (FSHD)

Facioscapulohumeral muscular dystrophy (FSHD; MIM 158900) is one of the major forms of muscular dystrophy, and is inherited in an autosomal dominant fashion. In most patients with FSHD, deletion of 3.3 kb tandemly repeated units within the EcoRI fragment, as detected by p13E-11 (D4F104S1) on chromosome 4q35, is associated with the disease (FSHD1A or 4q35-FSHD). Rare (< 5%) 4q35-unlinked FSHD (FSHD1B) is also known, and therefore genetic heterogeneity exists among FSHD. Recent studies based on the distinction of 4q35 EcoRI fragments from those of 10q26 improved the reliability of molecular diagnosis of the disease (> 95% accuracy). However, gene for FSHD1A has not been identified yet. Identification of the FSHD gene and characterization of the gene product are waited on tiptoe with expectation.     

Germline mosaicism in 4q35 facioscapulohumeral muscular dystrophy (FSHD1A) occurring predominantly in oogenesis

The presence of gamma-glutamyl transpeptidase (GGT) in boar spermatozoa and the potential role of the GGT at sperm penetration were examined using in vitro matured porcine oocytes. In the first experiment, GGT of boar spermatozoa was examined using a histochemical stain. GGT was detected in the midpiece and the acrosome regions of boar spermatozoa. In the second experiment, porcine oocytes matured in vitro were injected with approximately 40 pl of 10 mM HEPES solution alone or HEPES containing 0.5 U/ml GGT or 1 mM guanosine-5'-O-(3'-thiotriphosphate) (GTP-gamma-S; G-protein activator). When GGT was injected into oocytes, the incidence of oocytes activated (23.7 +/- 1.4%) was not different (P > 0.05) from HEPES-injected controls (24.9 +/- 1.3%) at 6 h after injection. Injected GTP-gamma-S, however, activated 76.0 +/- 5.3% of oocytes at 6 h after injection, but extrusion of the second polar body was very low (2.8 +/- 4.8%). Total content of glutathione (GSH) and glutathione disulfide (GSSG) did not differ (P > 0.05) between GTP-gamma-S injected oocytes (4.2 +/- 0.7 pmol/oocyte) and noninjected oocytes (4.0 +/- 0.1 pmol/oocyte) at 6 h after injection. However, the total content of GSH and GSSG was lower (P < 0.01) in GGT-injected oocytes (2.1 +/- 0.2 pmol/oocyte) than HEPES-injected oocytes (3.4 +/- 0.2 pmol/oocyte) at 6 h after injection. In the third experiment, in vitro matured porcine oocytes were injected with about 40 pl of 10 mM HEPES solution alone or HEPES containing 0.5 U/ml GGT and then inseminated. At 12 h after insemination, the incidence of male pronuclear formation was significantly lower in oocytes injected with GGT as compared with injected control oocytes. These results demonstrated that (1) GGT was present on the surface of spermatozoa, (2) total oocyte content of GSH and GSSG was decreased by microinjection of GGT but not by that of GTP-gamma-S, and (3) male pronuclear formation was inhibited in GGT-injected oocytes. These results suggest that sperm GGT may be a limiting factor for male pronuclear formation in polyspermic oocytes.     

Cataract and myotonic dystrophy: the role of molecular diagnosis

Myotonic dystrophy (dystrophia myotonica), the commonest and most variable of the muscular dystrophies of adult life, has long been known to be associated with cataract, while slit-lamp examination for specific lens opacities has been one of the principal methods of presymptomatic detection of gene carriers. The recent discovery that the myotonic dystrophy mutation is an unstable DNA sequence, composed of varying numbers of CTG triplet repeats, now allows a specific molecular test for this disorder, as well as explaining the phenomenon of anticipation. A series of case reports is presented to illustrate the important practical applications of this development in relation to ophthalmic aspects of the disorder. Reassessment of the specificity of the ophthalmic changes may be required and it will be important for molecular analysis to be used alongside ophthalmic studies, when determining whether family members carry the mutation for myotonic dystrophy.     

Clinicopathological characteristics and molecular genetics of adhalin deficiency (severe childhood autosomal recessive muscular dystrophy/SCARMD)

Dystrophin is a cytoskeletal protein complexed with a number of cell membrane glycoproteins to from the dystrophin-glycoprotein complex (DGC) in striated muscle. The dystroglycan complex, one of the functional subcomplexes composing the DGC, is a novel type of laminin receptor playing active roles in signal transduction. Another functional subcomplex composing the DGC is the sarcoglycan complex, comprised of alpha-(also called adhalin), beta-, gamma- and delta-sarcoglycans. Recent revelations indicate that genetic defects of either alpha-, beta-, gamma- or delta-sarcoglycan lead to a loss of the entire sarcoglycan complex and result in the phenotype of severe limb-girdle muscular dystrophy (collectively called sarcoglycanopathy). In this review, I discuss the molecular pathogenesis and clinical features sarcoglycanopathy.     

Sequence homology between 4qter and 10qter loci facilitates the instability of subtelomeric KpnI repeat units implicated in facioscapulohumeral muscular dystrophy

An analysis of 13 immunoglobulin A1 (IgA1) protease genes (iga) of strains of Streptococcus pneumoniae, Streptococcus oralis, Streptococcus mitis, and Streptococcus sanguis was carried out to obtain information on the structure, polymorphism, and phylogeny of this specific protease, which enables bacteria to evade functions of the predominant Ig isotype on mucosal surfaces. The analysis included cloning and sequencing of iga genes from S. oralis and S. mitis biovar 1, sequencing of an additional seven iga genes from S. sanguis biovars 1 through 4, and restriction fragment length polymorphism (RFLP) analyses of iga genes of another 10 strains of S. mitis biovar 1 and 6 strains of S. oralis. All 13 genes sequenced had the potential of encoding proteins with molecular masses of approximately 200 kDa containing the sequence motif HEMTH and an E residue 20 amino acids downstream, which are characteristic of Zn metalloproteinases. In addition, all had a typical gram-positive cell wall anchor motif, LPNTG, which, in contrast to such motifs in other known streptococcal and staphylococcal proteins, was located in their N-terminal parts. Repeat structures showing variation in number and sequence were present in all strains and may be of relevance to the immunogenicities of the enzymes. Protease activities in cultures of the streptococcal strains were associated with species of different molecular masses ranging from 130 to 200 kDa, suggesting posttranslational processing possibly as a result of autoproteolysis at post-proline peptide bonds in the N-terminal parts of the molecules. Comparison of deduced amino acid sequences revealed a 94% similarity between S. oralis and S. mitis IgA1 proteases and a 75 to 79% similarity between IgA1 proteases of these species and those of S. pneumoniae and S. sanguis, respectively. Combined with the results of RFLP analyses using different iga gene fragments as probes, the results of nucleotide sequence comparisons provide evidence of horizontal transfer of iga gene sequences among individual strains of S. sanguis as well as among S. mitis and the two species S. pneumoniae and S. oralis. While iga genes of S. sanguis and S. oralis were highly homogeneous, the genes of S. pneumoniae and S. mitis showed extensive polymorphism reflected in different degrees of antigenic diversity.     

The human skeletal muscle adenine nucleotide translocator gene maps to chromosome 4q35 in the region of the facioscapulohumeral muscular dystrophy locus

The large number of sequenced clones of HIV-1 and related viruses made it possible to indicate conserved elements with potential regulatory or structural functions. Such analysis was combined with directed mutagenesis in order to investigate the importance of elements that may influence the initiation of plus-strand DNA synthesis. The main site for plus-strand initiation is a polypurine tract near the 3' end of the viral RNA (the 3' PPT). An exact copy of this PPT is located in the middle of the genome (the internal PPT). Upstream from the internal PPT there is an inverted repeat. Mutants designed to upset the internal PPT (i.e., purine to pyrimidine changes), as well as mutants designed to abolish the potential stem-loop formation (changes around the internal PPT or in the upstream inverted repeat) both resulted in viruses with a reduced ability to replicate. Upsetting the stem-loop formation was, however, less harmful than changing the polypurine nature of the PPT. Changing a conserved T on the 3' side of the PPT to a C did not affect the phenotype.     

Western type cerebro-muscular dystrophy and congenital merosin deficiency muscular dystrophy: two terms for the same disorder

INTRODUCTION: Congenital muscular dystrophies (CMD) are a clinically heterogeneous group of muscular disorders characterized by hypotonia, muscle weakness and early or congenital joint contractures. Electromyography reveals a myopathic pattern, creatine-kinase (CK) may be moderately elevated and muscle biopsy shows pathological changes consistent with a dystrophic process. OBJECTIVE: Report the cases of two brothers with 'Occidental type cerebro-muscular dystrophy' versus 'merosin-deficient CMD'. PATIENTS AND METHODS: Two children, a boy and a girl, of a first consanguineous parents. In the first case, the diagnosis of Occidental type cerebro-muscular dystrophy was made in 1983, at the age of 4 years, according to clinical, biochemical, electromyographic, pathological and neuroradiological data. In the second case, the diagnosis of merosindeficient form of CMD was made with the same criteria and with immunohistochemistry and Western blot techniques in 1997, when she was 6 months old. CONCLUSION: Occidental type cerebro-muscular dystrophy, described 13 years ago by one member of our group, corresponds with merosin-deficient form of CMD.     

Facioscapulohumeral muscular dystrophy: aspects of genetic counselling, acceptance of preclinical diagnosis, and fitness

A questionnaire about the interest in and demand for preclinical diagnosis for facioscapulohumeral muscular dystrophy (FSH) was sent to 46 patients. Most stated that they would have liked to have known their diagnosis earlier in order to seek more efficient help, to avoid strenuous activities, to prepare themselves emotionally, or to choose an appropriate profession. Similar arguments were used to explain their interest in preclinical diagnosis for their children. Most patients also favoured prenatal diagnosis although only two stated they would abort a pregnancy in the case of an affected fetus. Genetic counselling had apparently little influence on family planning. According to this study, FSH does not seem to reduce reproductive performance in our population.     

Assembly of the sarcoglycan complex. Insights for muscular dystrophy

Four unique transmembrane glycoproteins comprise the sarcoglycan complex in striated muscle. The sarcoglycan complex contributes to maintenance of sarcolemma integrity. A shared feature of four types of autosomal recessive limb girdle muscular dystrophy (LGMD) is that mutations in a single sarcoglycan gene result in the loss of all sarcoglycans at the sarcolemma. The mechanism of destabilization is unknown. We report here our findings of sarcoglycan complex biosynthesis in a heterologous cell system. We demonstrate that the sarcoglycans are glycosylated and assemble into a complex that resides in the plasma membrane. Complex assembly was dependent on the simultaneous synthesis of all four sarcoglycans. Mutant sarcoglycans block complex formation and insertion of the sarcoglycans into the plasma membrane. This constitutes the first biochemical evidence to support the idea that the molecular defect in sarcoglycan-deficient LGMD is because of aberrant sarcoglycan complex assembly and trafficking, which leads to the absence of the complex from the sarcolemma.     

Linkage-disequilibrium mapping narrows the Fukuyama-type congenital muscular dystrophy (FCMD) candidate region to <100 kb

Fukuyama-type congenital muscular dystrophy (FCMD), the second most common form of muscular dystrophy in Japan, is an autosomal recessive severe muscular dystrophy associated with brain anomalies. After our initial mapping of the FCMD locus to chromosome 9q31-33, we have further defined the locus within a approximately 5-cM region between D9S127 and D9S2111 and have found linkage disequilibrium between FCMD and D9S306 in this candidate region on 9q31. The high prevalence of FCMD among the Japanese, who are a relatively isolated population, provides an opportunity to utilize linkage-disequilibrium mapping. We developed three new microsatellites, near D9S306, from the FCMD YAC contig, determined their positions on YACs, and performed linkage-disequilibrium mapping with these markers and other newly published loci. The maximum value of p(excess), which represents the strength of linkage disequilibrium, was obtained at D9S2107; and this value showed a relatively steady rise and fall across the region that is likely to contain FCMD. Distances between FCMD and each marker were presumed to be approximately 1 Mb, approximately 350 kb, approximately 140 kb, approximately 20 kb, approximately 280 kb, approximately 450 kb, and approximately 740 kb for D9S306, A107XF9, D9S2105, D9S2107, D9S172, D9S299, and D9S2109, respectively. Haplotype analysis using the three closest markers D9S2105, D9S2107, and D9S172 indicated that most FCMD-bearing chromosomes are derived from a single ancestral founder and suggested that these markers can be used for the diagnosis of sporadic FCMD. Thus, the FCMD gene is most likely to lie within a region of <100 kb containing D9S2107.     

The genomic structure of DCTN1, a candidate gene for limb-girdle muscular dystrophy (LGMD2B)

Dynactin is a required activator for the molecular motor cytoplasmic dynein, and is likely to be essential for normal neuronal development. Previously we mapped the human gene encoding the p150Glued subunit of dynactin to 2p13, in the vicinity of the locus linked to limb-girdle muscular dystrophy (LGMB2B). We now report the genomic organization of DCTN1. We have identified 32 exons in the gene which spans approximately 25 kb. Alternative splicing of several of the exons generates functionally distinct isoforms of the p150Glued polypeptide.     

Role of the extracellular matrix in X-chromosome-linked muscular dystrophy: immunohistochemical study

OBJECTIVE: To study the role of the extracellular matrix in the pathogenesis of the X-linked muscular dystrophy. MATERIAL AND METHODS: Muscle specimens from 8 normal controls with ages ranging from 4 to 14 years of age and those of 14 X-linked muscular dystrophy patients were studied by means of polyclonal antibodies able to recognize extracellular matrix molecules. The findings of each of the controls and patients were evaluated systematically using a semiquantitative morphological method. On the other hand, with the help of an automatic interactive image analyzer, the following structures were measured: a) area occupied by the perimysium; b) area of the endomysium, and c) transverse fibre area. RESULTS: The deposition of the extracellular matrix components of patients with X-linked muscular dystrophy is a selective phenomenon which is mostly related to groups of fibers undergoing necrosis-regeneration. X-linked muscular dystrophy patients have an heterogeneous clinical and pathological picture. At one end of the spectrum there are patients with the most severe phenotype, in which reduction of fiber size, early deposition of connective tissue and distortion of the capillary bed are the most conspicuous pathological changes. At the other end muscle fiber hypertrophy and splitting, lesser connective tissue deposition and a milder clinical course predominate. Selective deposition of extracellular matrix components occurs at each point of the spectrum. The distribution of the extracellular matrix components does not appear to accomplish a substitutive function designed to replace the loss of number or volume of the muscle fibers.     

The pathology of the heart in progressive muscular dystrophy: epimyocardial fibrosis

The gross and microscopic appearance of the hearts from eight patients with Duchenne's progressive muscular dystrophy are described. Seven hearts had gross evidence of myocardial fibrosis, five of these demonstrating distinctive fibrosis of the epimyocardial portion of the free wall of the left ventricle, often with a striking band-like appearance. On the basis of mapping studies of the myocardial fibrosis, a theory regarding the progression of myocardial fibrosis in Duchenne's progressive muscular dystrophy is presented. Correlation of the pathologic anatomy, electrocardiograms, and vectorcardiograms in these patients and the family studies of others suggests that Duchenne's progressive muscular dystrophy represents a generalized cardiomyopathy that has its gravest and most distinctive effect on the epimyocardial portion of the free wall of the left ventricle.     

CT diagnosis and differential diagnosis of renal spaca occupying lesions (author's transl)

In 76 patients with space occupying lesions of the kidneys CT scans were performed. Size, shape and localisation of the kidneys could well be demonstrated by this method. Space occupying lesions were clearly seen, and solid tumors could be differentiated from cysts. However differential diagnosis between either primary renal cell carcinoma and metastases or between malignant and benign mass lesions was not possible. There was no problem in the diagnosis of hydronephrosis where as a differentiation between inflammatory changes and solid masses proved to be difficult. CT scanning seems to be usefull in the diagnosis of renal space occupying lesions. As a non invavise method it should be performed previous to renal angiography, which thereby becomes unnecessary in many cases.