Debora Rapaport

Serum creatine-kinase (CK) and pyruvate-kinase (PK) activities in Duchenne (DMD) as compared with Becker (BMD) muscular dystrophy

Serum creatine-kinase (CK) activities were determined in 536 patients affected with X-linked muscular dystrophy (456 with Duchenne or DMD and 80 with Becker or BMD) and serum pyruvate-kinase (PK) in 360 among them (309 DMD and 51 BMD). The aim of this investigation was to assess the variability and rate of decrease in serum activity in DMD as compared with BMD as a function of age and in DMD as a function of Vignos scale as well. In DMD, maximum CK and PK activities were found around 1-6 years old and the average rate of decline according to age was estimated as 0.18 per year and 0.27-0.29 for both enzymes as a function of Vignos scale (assessed in 291 cases). For BMD, maximum serum enzyme levels were found around 10-15 years old and the rate of decline of serum activity per year was 0.06 for CK and 0.07 for PK. If maximum levels of serum enzyme reflect active muscle degeneration and the rate of decline per year to progressive loss of muscle mass (responsible for the release of muscle enzymes to the blood stream) our observations suggest: (a) active muscle degeneration occurs, on average, 5 years later in the group of outliers and 10 years later in BMD as compared with severe DMD; (b) the rate in which muscle mass is lost is significantly greater in DMD than in BMD and therefore serum enzyme determinations may represent an important test for evaluation of therapeutic trials; (c) serum enzymes determination may represent an important preliminary test to discriminate in a proportion of young patients if they will develop a severe or milder phenotype.

Immunofluorescence dystrophin study in Duchenne dystrophy through the concomitant use of two antibodies directed against the carboxy-terminal and the amino-terminal region of the protein.

Dystrophin immunohistochemical studies in muscle from Duchenne patients (DMD) have shown a population of fibers with partial labelling. In order to determine whether this is related to a cross reaction or to the presence of dystrophin. 22 DMD patients were studied immunohistochemically, through the concomitant use of antibodies from the N-terminal and the C-terminal regions of the protein. In 2, the reaction was negative while in 2 others 17 and 25% of fibers were positive with both antibodies. In the remainder, a population of partially stained fibers was seen: 11 were positive with both antibodies and in 7 only with the N-terminal one. Apparently, there is no correlation between the proportion of positive fibers and clinical progression, or the presence and pattern of DNA deletions in the central part of the gene. These observations led us to suggest that some truncated protein, intermediate synthesis or degradation products of dystrophin are present in muscle from Duchenne patients.

Dystrophin immunostaining in muscles from patients with different types of muscular dystrophy : a Brazilian study

The localization of the protein dystrophin was studied using the immunofluorescence method, in muscle biopsies from 74 patients affected by different types of muscular dystrophy and 4 normal controls. In 15 patients with limb-girdle muscular dystrophy (LGMD) the pattern was indistinguishable from normal. Among 42 Duchenne patients (DMD), 3 were totally negative and 39 showed a variable proportion (4-30%) of partially labelled fibers. With one exception 17 Becker dystrophy patients (BMD), showed a positive sarcolemmal reaction. A diffuse reaction inside the fibers, which was not observed in normal controls, was seen in the majority of DMD and also in some of the BMD patients. Based on these observations it is suggested that in DMD, a small quantity of protein is still present or there is a cross-reaction with other proteins which share some homology with dystrophin. The present results suggest that it is possible to make a differential diagnosis between DMD and BMD through dystrophin immunohistochemistry. However, to distinguish between patients with BMD and LGMD phenotypes, or DMD and outliers, complementary immunoblot studies and quantitative determination of dystrophin are necessary.

A deletion including the brain promoter of the Duchenne muscular dystrophy gene is not associated with mental retardation

A total of 161 unrelated Duchenne (DMD) and Becker muscular dystrophy (BMD) patients were screened for deletions in the brain promoter region of the dystrophin gene. Southern blot analysis using a probe for the brain promoter detected a deletion in this region in only one of the DMD families, in a patient with normal intelligence. This deletion also included the promoter of the muscle-type dystrophin and the exons encoding the actin-binding and part of the spectrin-like domains. Our data suggest that deletions in the brain promoter region are rare in DMD and are compatible with normal intelligence.

Dystrophin immunofluorescence pattern in manifesting and asymptomatic carriers of Duchenne's and Becker muscular dystrophies of different ages☆

In order to investigate if the same apparent decrease in dystrophin negative fibers with aging observed in mouse mdx female heterozygotes also occurs in carriers of the DMD and BMD gene, we have studied the muscle of 29 DMD carriers (19 adults and 10 young daughters of obligate carriers, including 3 manifesting carriers) and 5 adult asymptomatic heterozygotes for Becker dystrophy (BMD). All young DMD possible carriers and 11 of 24 adult DMB/BMD heterozygotes had increased serum enzymes activities. A population of dystrophin negative fibers, more evident with the use of the C-terminal antibody, was seen in the three manifesting and in a 9-yr-old possible DMD carrier. In the remaining females, a positive immunohistochemical pattern of dystrophin, which did not differ from normal controls, was observed. Our results suggest that: (1) the increased population of dystrophin negative fibers reported in young mdx female heterozygotes was not seen in young DMD carriers, aged 6-17 yr; and (2) abnormalities in dystrophin immunostaining are not easily observed and are more frequent in manifesting carriers, when the muscle is grossly altered.

Exclusion of the gene responsible for facioscapulohumeral muscular dystrophy (FSH) at 6q23-q27

Facioscapulohumeral muscular dystrophy (FSH) is an autosomal dominant condition with variable expressivity and age dependent penetrance. Linkage studies still did not exclude regions 11, 2q, 6q, 7p, 8p, 10q, 12p and 14p as possible locations for the FSH gene. In the present study we have analysed 80 individuals (36 patients and 44 normals) belonging to 8 unrelated Brazilian families with 3 probes located on the long arm of chromosome 6:MHB(6q22-q23), ESR(6q24-q27) and TCP1(6q25-q27). Results of linkage analysis suggest that the gene responsible for FSH muscular dystrophy is not in the region 6q23-q27.

The duchenne muscular dystrophy gene: A giant gene with multiple products

The DMD gene is the largest known gene to date (~2500 Kbp). The product of the gene in muscle is a 427 kDa protein, dystrophin. Dystrophin is also expressed in the nervous system, where it is regulated by three promoters. Smaller products of the gene are Dp71, Dp116, Dp140 and Dp260. The main DMD gene product in non-muscle cells is a 70.8 kDa protein, Dp71, consisting of the C-terminal region of dystrophin. Dp71 is the main DMD gene product in the brain, and is the first product of the gene expressed during mouse development. Experiments with transgenic mdx mice that express in the muscle Dp71 instead of dystrophin, showed that Dp71 restored the level of dystrophin associated proteins, but did not alleviate muscle damage. It is, therefore, suggested that the function of Dp71 is different from that of dystrophin. Gene inactivation techniques are being used to investigate the biological function of Dp71. The possible involvement of Dp71 in embryogenesis and in brain function will be discussed. BIS7

Estimate of the intrafamilial correlation for serum creatine kinase and pyruvate kinase in females at risk for Duchenne and Becker muscular dystrophies.

In order to verify the possibility of nonrandom X-inactivation in females heterozygous for Duchenne (DMD) and Becker (BMD) muscular dystrophies, intrafamilial correlations and the heritabilities for serum creatine kinase (CK) and pyruvate kinase (PK) were estimated in a large sample of females belonging to families with affected patients. The results of the present investigation suggest that the apparent intrafamilial correlations for serum CK reported in previous studies in DMD families are not related with the presence of the DMD/BMD gene. Our data do not seem to support the hypothesis of a gene leading to a preferential inactivation of the X-chromosome in females at risk for the dystrophin gene.