Dystrophin: localization and presumed function

Motor dysfunction of the gut in Duchenne muscular dystrophy: A review

BACKGROUND

Duchenne's muscular dystrophy (DMD) is a severe type of hereditary, neuromuscular disorder caused by a mutation in the dystrophin gene resulting in the absence or production of truncated dystrophin protein. Conventionally, clinical descriptions of the disorder focus principally on striated muscle defects; however, DMD manifestations involving gastrointestinal (GI) smooth muscle have been reported, even if not rigorously studied.

PURPOSE

The objective of the present review is to offer a comprehensive perspective on the existing knowledge concerning GI manifestations in DMD, focusing the attention on evidence in DMD patients and mdx mice. This includes an assessment of symptomatology, etiological pathways, and potential corrective approaches. This paper could provide helpful information about DMD gastrointestinal implications that could serve as a valuable orientation for prospective research endeavors in this field. This manuscript emphasizes the effectiveness of mdx mice, a DMD animal model, in unraveling mechanistic insights and exploring the pathological alterations in the GI tract. The gastrointestinal consequences evident in patients with DMD and the mdx mice models are a significant area of focus for researchers. The exploration of this area in depth could facilitate the development of more efficient therapeutic approaches and improve the well-being of individuals impacted by the condition.

Correlations Between Dark-Adapted Rod Threshold Elevations and ERG Response Deficits in Duchenne Muscular Dystrophy

Purpose

The purpose of this study was to characterize changes in the full-field flash electroretinogram (ERG) in association with psychophysical dark-adapted visual thresholds in patients with genetically characterized Duchenne muscular dystrophy (DMD) either lacking Dp427 (Up 30) or at least Dp260 in addition to Dp427 (Down 30).

Methods

Twenty-one patients with DMD and 27 age-similar controls participated in this study. Dark-adapted (0.01, 3.0, and 10 cd.s/m² flashes) and light-adapted (3.0 cd.s/m² flash) ERGs were recorded following International Society for Clinical Electrophysiology of Vision (ISCEV) standard protocols. Visual detection thresholds to 625-nm (cone function) and 527-nm (rod function) light-emitting diode (LED) flashes (2 degree diameter) were measured during a dark adaptation period after a 1-minute exposure to a bleaching light (3000 cd/m²). Initially, 8 minutes of interleaved 625-nm and 527-nm thresholds were measured. After an additional 5 minutes of dark-adaptation, a second set of threshold measurements to 527-nm stimuli was performed during the subsequent 6 minutes.

Results

Dark-adapted b-wave amplitude was significantly reduced to all strengths of flash and a-wave in response to the strong flash stimulus was delayed (15.6 vs. 14.7 ms, P < 0.05) in patients with Down 30 compared with controls. Dark-adapted cone thresholds did not differ among the groups (−2.0, −1.8, and −1.7 log cd/m² for Down 30, Up 30, and controls, respectively, P = 0.21). In contrast, dark-adapted rod thresholds were elevated (F_(2,36) = 8.537, P = 0.001) in patients with Down 30 (mean = −3.2 ± 1.1 log cd/m²) relative to controls (mean = −4.2 ± 0.3 log cd/m²). Dark-adapted b-wave amplitudes were correlated with dark-adapted rod sensitivity in patients with DMD (Spearman Rho = 0.943, P = 0.005). The changes were much smaller or absent in patients with intact Dp260.

Conclusions

Dp260 is particularly required for normal rod-system function in dark adaptation.

Gigantic Stomach: A Rare Manifestation of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is characterized by degeneration and atrophy of skeletal, cardiac, and smooth muscles after a latent period of apparently normal development and function. The gastrointestinal manifestations start in the second decade of life and are mainly due to atrophy of smooth muscle layers. Refractory gastroparesis and chronic constipation can lead to severe gastric and small bowel dilatation, which can be life threatening. Here, we present a case of a 21-year-old male with a gigantic stomach secondary to DMD resolved with conservative management and no surgical intervention.

Supplementation action with ascorbic acid in the morphology of the muscular layer and reactive acetylcholinesterase neurons of ileum of mdx mice

The Duchenne Muscular Dystrophy (DMD) is a genetic disorder characterized by the absence of dystrophin protein, causing severe myopathy from increases of oxidative stress. Injuries of intestinal muscle can compromise the myenteric plexus. This study aimed to evaluate the disorders occurred in the muscular layer and in the acetylcholinesterase myenteric neurons (ACHE-r) of ileum of mdx mice, and the effects of supplementation with ascorbic acid (AA) in both components. 30 male mice C57BL/10, and 30 male mice C57BL/10Mdx were separated according to the age and treatment (n=10/group): 30-days-old control group (C30); 30-days-old dystrophic group (D30); 60-days-old control group (C60); 60-days-old dystrophic group (D60); 60-days-old control group supplemented with AA (CS60); and 60-days-old dystrophic group supplemented with AA (DS60). The animals were euthanized and the ileum was collected and processed. Semi-serial sections were stained by Masson's trichrome, and acetylcholinesterase histochemical technique in whole-mounts preparations to identify the myenteric neurons. The muscular layer thickness and the area of smooth muscle of ileum were lower in dystrophic groups, especially in D30 group. The DS60 group showed the muscular layer thickness similar to C60. The density of ACHE-r neurons of myenteric plexus of ileum was lower in D30 animals; however, it was similar in animals of 60-days-old without treatment (C60 and D60) and, higher in DS60. The cell body profile area of ACHE-r neurons was similar in C30-D30 and C60-D60; however, it was higher in DS60. DMD caused damage to the ileum's musculature and myenteric plexus, and the AA prevented the ACHE-r neuronal loss.

In vivo dynamics of skeletal muscle Dystrophin in zebrafish embryos revealed by improved FRAP analysis

Dystrophin forms an essential link between sarcolemma and cytoskeleton, perturbation of which causes muscular dystrophy. We analysed Dystrophin binding dynamics in vivo for the first time. Within maturing fibres of host zebrafish embryos, our analysis reveals a pool of diffusible Dystrophin and complexes bound at the fibre membrane. Combining modelling, an improved FRAP methodology and direct semi-quantitative analysis of bleaching suggests the existence of two membrane-bound Dystrophin populations with widely differing bound lifetimes: a stable, tightly bound pool, and a dynamic bound pool with high turnover rate that exchanges with the cytoplasmic pool. The three populations were found consistently in human and zebrafish Dystrophins overexpressed in wild-type or dmd(ta222a/ta222a) zebrafish embryos, which lack Dystrophin, and in Gt(dmd-Citrine)(ct90a) that express endogenously-driven tagged zebrafish Dystrophin. These results lead to a new model for Dystrophin membrane association in developing muscle, and highlight our methodology as a valuable strategy for in vivo analysis of complex protein dynamics.

Regeneration of soft tissues is promoted by MMP1 treatment after digit amputation in mice

The ratio of matrix metalloproteinases (MMPs) to the tissue inhibitors of metalloproteinases (TIMPs) in wounded tissues strictly control the protease activity of MMPs, and therefore regulate the progress of wound closure, tissue regeneration and scar formation. Some amphibians (i.e. axolotl/newt) demonstrate complete regeneration of missing or wounded digits and even limbs; MMPs play a critical role during amphibian regeneration. Conversely, mammalian wound healing re-establishes tissue integrity, but at the expense of scar tissue formation. The differences between amphibian regeneration and mammalian wound healing can be attributed to the greater ratio of MMPs to TIMPs in amphibian tissue. Previous studies have demonstrated the ability of MMP1 to effectively promote skeletal muscle regeneration by favoring extracellular matrix (ECM) remodeling to enhance cell proliferation and migration. In this study, MMP1 was administered to the digits amputated at the mid-second phalanx of adult mice to observe its effect on digit regeneration. Results indicated that the regeneration of soft tissue and the rate of wound closure were significantly improved by MMP1 administration, but the elongation of the skeletal tissue was insignificantly affected. During digit regeneration, more mutipotent progenitor cells, capillary vasculature and neuromuscular-related tissues were observed in MMP1 treated tissues; moreover, there was less fibrotic tissue formed in treated digits. In summary, MMP1 was found to be effective in promoting wound healing in amputated digits of adult mice.

Morphological changes in the trigemino-rubral pathway in dystrophic (mdx) mice

The lack of dystrophin that causes Duchenne muscle disease affects not only the muscles but also the central nervous system. Dystrophin-deficient mdx mice present changes in several brain fiber systems. We compared the projections from the trigeminal sensory nuclear complex to the red nucleus in control and mdx mice using retrograde tracers. Injection of 200 nL 2% fluorogold into the red nucleus caused labeling in the mesencephalic trigeminal nucleus, the principal sensory nucleus and the oral, interpolar, and caudal subnuclei of the spinal trigeminal nucleus in both control and mdx mice. Injection of latex microbeads labeled with rhodamine and fluorescein gave results similar to those seen with fluorogold. The number of labeled neurons in the trigeminal sensory nuclear complex was significantly reduced in mdx mice. In the oral subnucleus of the spinal trigeminal nucleus this reduction was 50%. These results indicate that the trigemino-rubral pathway is reduced in dystrophin-deficient mice.

Structural basis of voiding dysfunction in megacystis microcolon intestinal hypoperistalsis syndrome

PURPOSE

Megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) is a rare, congenital and usually fatal condition of unknown etiology. It is characterized by abdominal distension caused by a distended, non-obstructed urinary bladder and intestinal hypoperistalsis with functional intestinal obstruction. Previous studies reported vacuolar degenerative changes in the smooth muscle cells of bowel and bladder suggesting that MMIHS may be due to a visceral myopathy. The aim of this study was to examine the expression of contractile, cytoskeletal and extracellular matrix proteins in the detrusor muscle of MMIHS patients.

MATERIAL AND METHODS

Bladder specimens were obtained from six MMIHS patients. Normal bladder specimens were obtained during partial cystectomy and served as controls. Single fluorescence immunohistochemistry for alpha-smooth muscle actin (SMA), desmin, dystrophin, vinculin and collagen types I and III was carried out. Specific connective tissue stains (trichrome Masson, van Gieson) and electron microscopical investigations were also performed.

RESULTS

Trichrome Masson and van Gieson staining demonstrated markedly increased dense connective tissue between the layers of the detrusor muscle in MMIHS compared to controls. Collagen type I immunoreactivity was markedly increased and SMA, desmin and dystrophin immunoreactivity was markedly reduced in the bladder muscle of MMIHS compared to controls. Electron microscopy revealed vacuolar degenerative changes in smooth muscle cells and an abundance of connective tissue between these cells.

CONCLUSION

These data suggest that the detrusor muscle in MMIHS is strikingly abnormal and is the likely cause of voiding dysfunction.

Smooth muscle-specific dystrophin expression improves aberrant vasoregulation in mdx mice

Duchenne muscular dystrophy (DMD) is a fatal X-linked muscle-wasting disease caused by mutations of the gene encoding the cytoskeletal protein dystrophin. Therapeutic options for DMD are limited because the pathogenetic mechanism by which dystrophin deficiency produces the clinical phenotype remains obscure. Recent reports of abnormal alpha-adrenergic vasoregulation in the exercising muscles of DMD patients and in the mdx mouse, an animal model of DMD, prompted us to hypothesize that the dystrophin-deficient smooth muscle contributes to the vascular and dystrophic phenotypes of DMD. To test this, we generated transgenic mdx mice that express dystrophin only in smooth muscle (SMTg/mdx). We found that alpha-adrenergic vasoconstriction was markedly attenuated in the contracting hindlimbs of C57BL/10 wild-type mice, an effect that was mediated by nitric oxide (NO) and was severely impaired in the mdx mice. SMTg/mdx mice showed an intermediate phenotype, with partial restoration of the NO-dependent modulation of alpha-adrenergic vasoconstriction in active muscle. In addition, the elevated serum creatine kinase levels observed in mdx mice were significantly reduced in SMTg/mdx mice. This is the first report of a functional role of dystrophin in vascular smooth muscle.

Impaired primary hemostasis with normal platelet function in Duchenne muscular dystrophy during highly-invasive spinal surgery

A defective, normal or enhanced hemostasis has been reported in Duchenne muscular dystrophy (DMD). A retrospective analysis of intra-and postoperative (up to 36 h) estimated blood losses was performed in 156 patients undergoing spinal surgery for: DMD (n = 31), idiopathic scoliosis (IS) (n = 70), poliomyelitis (n = 10), cerebral palsy (CP) (n = 28), spinal muscular atrophy (SMA) (n = 17). Platelet aggregation and bleeding times were also investigated in DMD patients. Immunohistochemistry for dystrophin was performed in platelets, megakaryocytes and blood vessels of normal tissues. DMD patients showed significantly higher intraoperative estimated blood losses (DMD: 3495+/-890 ml; IS: 2269+/-804 ml; poliomyelitis: 2582+/-1252 ml; CP: 2071+/-683 ml; SMA: 2464+/-806 ml; P < 0.05), while postoperative blood losses were similar among different groups. Higher estimated blood losses in DMD were independent of the duration of surgery, body weight, gender, age, vertebral levels or preoperative Cobb angle. DMD children had significantly prolonged bleeding times, but retained normal platelet function. From control samples dystrophin was expressed in vascular smooth muscle cells, but not in platelets. DMD appears to be characterized by immediate bleeding during highly-invasive surgery and increased bleeding time without platelet abnormalities. Considering dystrophin expression in normal vascular smooth muscle cells, these results altogether suggest a selective defect of primary hemostasis in DMD, likely to be due to impaired vessel reactivity.

Altered cytoskeleton in smooth muscle of aganglionic bowel

CONTEXT

Intestinal motility is under the control of smooth muscle cells, enteric plexus, and hormonal factors. In Hirschsprung disease (HD), the aganglionic colon remains spastic or tonically enhanced and unable to relax. The smooth muscle cell's cytoskeleton consists of proteins or structures whose primary function is to link or connect protein filaments to each other or to the anchoring sites. Dystrophin is a subsarcolemmal protein with a double adhesion property, one between the membrane elements and the contractile filaments of the cytoskeleton and the other between the cytoskeletal proteins and the extracellular matrix. Desmin and vinculin are functionally related proteins that are present in the membrane-associated dense bodies in the sarcolemma of the smooth muscle cells.

OBJECTIVE

To examine the distribution of the cytoskeletal proteins in the smooth muscle of the aganglionic bowel.

DESIGN

Bowel specimens from ganglionic and aganglionic sections of the colon were collected at the time of pull-through surgery from 8 patients with HD. Colon specimens collected from 4 patients at the time of bladder augmentation acted as controls. Anti-dystrophin, anti-desmin, and anti-vinculin antibodies were used for fluorescein immunostaining using confocal laser scanning microscopy.

RESULTS

Moderate to strong dystrophin immunoreactivity was observed at the periphery of smooth muscle fibers in normal bowel and ganglionic bowel from patients with HD, whereas dystrophin immunoreactivity was either absent or weak in the smooth muscle of aganglionic colon. Moderate to strong cytoplasmic immunostaining for vinculin and desmin was seen in the smooth muscle of normal bowel and ganglionic bowel from patients with HD, whereas vinculin and desmin staining in the aganglionic colon was absent or weak.

CONCLUSION

This study demonstrates that the cytoskeletal proteins are abundant in the smooth muscle of normal bowel, but are absent or markedly reduced in the aganglionic bowel of HD. As cytoskeletal proteins are required for the coordinated contraction of muscle cells, their absence may be responsible for the motility dysfunction in the aganglionic segment.

Administration of chinese herbal medicines facilitates the locomotor activity in dystrophin-deficient mice

The purpose of this study was to access the effects of chinese herbal medicines on Duchenne muscular dystrophy (DMD). We use dystrophin-deficient mice (mdx), an animal model of DMD, to evaluate the effect of chinese herbal medicines on locomotor activity. The consumption of water for each mouse was controlled during the three-month experimental session. Each mouse was allowed to drink 3 ml water with or without herbal medicines daily for three months. The estimated intake of chinese herbal medicine in adult mdx mouse with 30 g weight is 100 mg/kg per day, close to a dose used in human. The locomotor activity of the mdx mice was measured every month. Monitoring the locomotor activity of mdx mice after three-month administration of chinese herbal medicines, the results showed that liu-wei-di-huang-wan (LDW) and san-lin-pai-tsu-san (SPS) can facilitate locomotor activity with the parameters of horizontal activity, total distance, number of movements, movement time, vertical activity, number of vertical movements, vertical movement time, stereotypy, number of stereotyped movements, and stereotyped movement time. These results suggest that either LDW or SPS can act as a potent herbal medicine for the pharmacological treatment of DMD patients.

Cardiovascular autonomic control in Becker muscular dystrophy

Although autonomic symptoms are not prominent in dystrophinopathies, a reduced vagal activity and an enhanced sympathetic tone have been found in Duchenne muscular dystrophy. Twenty patients with Becker muscular dystrophy (BMD) were investigated by a battery of six cardiovascular autonomic tests (beat-to-beat variability during quiet breathing and deep breathing, heart rate responses to Valsalva maneuver and standing, blood pressure responses to standing and sustained handgrip) and power spectral analysis (PSA) of heart rate variability. Although 11 patients revealed abnormal findings at some cardiovascular tests, none of them had a definite autonomic damage, as indicated by two or more abnormal tests. The mean results of the single tests did not differ from normal controls, except for the beat-to-beat variability during quiet breathing, which was significantly higher in BMD (p<0.05). Such finding was confirmed by a significantly higher total variance (p<0.05), indicating an increased parasympathetic activity. Spectral components were not significantly different from normal controls. PSA values were not influenced by age, functional ability score or presence of heart abnormalities. Our data suggest that autonomic involvement does not represent a major finding in BMD.

Dynamic restoration of dystrophin to dystrophin-deficient myotubes

Dystrophin domains are observed in myoblast transplantation experiments and in muscle fibers after somatic reversion in human Duchenne and mdx mouse muscular dystrophy. However, the formation and evolution of dystrophin-positive domains are not well established. Using a muscle satellite cell coculture system, we examined the dynamic restoration of dystrophin expression in dystrophin-deficient myotubes. The dystrophin-positive domains around source nuclei were clearly identified in hybrid myotubes. The occurrence of dystrophin domains was higher in myotubes differentiated from cocultures with a low concentration of normal wild-type satellite cells in relation to dystrophin-deficient satellite cells. At higher seeding ratios, the domain feature of dystrophin expression was more transitory and decreased as myotubes differentiated over time in culture. The average domain size initially increased with the addition of new nuclei by fusion early after differentiation of cocultures. However, separating dystrophin-positive domains according to their number of dystrophin-expressing contributory nuclei showed that diffusion of dystrophin contributed to domain elongation, even in early myotubes and later without fusion of additional nuclei. Diffusion occurred for all domains of one to six wild-type nuclei, and the diffusion rate was higher in domains with larger numbers of nuclei. This dynamic domain feature of dystrophin expression was also related to restoring the organization of dystrophin-associated proteins and acetylcholine receptors to hybrid myotubes. Factors regulating domain formation and diffusion therefore are important considerations in the design of strategies for both myoblast transplantation and gene therapy of Duchenne muscular dystrophy.

Characteristics of skeletal muscle in mdx mutant mice

We review the extensive research conducted on the mdx mouse since 1987, when demonstration of the absence of dystrophin in mdx muscle led to X-chromosome-linked muscular dystrophy (mdx) being considered as a homolog of Duchenne muscular dystrophy. Certain results are contradictory. We consider most aspects of mdx skeletal muscle: (i) the distribution and roles of dystrophin, utrophin, and associated proteins; (ii) morphological characteristics of the skeletal muscle and hypotheses put forward to explain the regeneration characteristic of the mdx mouse; (iii) special features of the diaphragm; (iv) changes in basic fibroblast growth factor, ion flux, innervation, cytoskeleton, adhesive proteins, mastocytes, and metabolism; and (v) different lines of therapeutic research.

Effects of dystrophin isoforms on signal transduction through neural retina: genotype-phenotype analysis of duchenne muscular dystrophy mouse mutants

Duchenne and Becker muscular dystrophy patients have mutations in the dystrophin gene. Most show reduced b-wave amplitudes in the dark-adapted electroretinogram (ERG). We studied normal C57BL/6J mice and five X-linked muscular dystrophy strains with different dystrophin mutations to determine whether the location of the mutation within the gene affects the mouse ERG and to correlate such effects with dystrophin isoform expression. Amplitudes and implicit times were measured for a-waves, b-waves, and digitally filtered oscillatory potentials. mdx and mdxCv5 mice, with mutations near the amino terminus and lacking expression of Dp427, had ERGs similar to those of C57BL/6J mice. mdxCv2 and mdxCv4 mice, with mutations in the center of dystrophin and who do not express isoforms Dp427, Dp260, or Dp140 (mdxCv4), had increased b-wave and oscillatory potential implicit times. mdxCv3 mice, with a mutation near the carboxy terminus resulting in deficiency of all dystrophin isoforms, had increased b-wave and oscillatory potential implicit times and reduced scotopic b-wave amplitudes. Fitting the a-wave data to a transduction activation phase mathematical model showed normal responses for all phenotypes, suggesting that the b-wave delays are due to defects beyond the rod outer segment, most likely at the rod to on-bipolar cell synapse. The variation in the ERG phenotype with the position of the dystrophin gene mutation suggests that there are different contributions by each isoform to retinal electrophysiology. Although Dp427 and Dp140 isoforms do not appear to be important contributors to the ERG, lack of Dp260 and possibly Dp71 isoforms is associated with an abnormal ERG.

Differences in both inositol 1,4,5-trisphosphate mass and inositol 1,4,5-trisphosphate receptors between normal and dystrophic skeletal muscle cell lines

Human normal (RCMH) and Duchenne muscular dystrophy (RCDMD) cell lines, as well as newly developed normal and dystrophic murine cell lines, were used for the study of both changes in inositol 1,4,5-trisphosphate (IP3) mass and IP3 binding to receptors. Basal levels of IP3 were increased two- to threefold in dystrophic human and murine cell lines compared to normal cell lines. Potassium depolarization induced a time-dependent IP3 rise in normal human cells and cells of the myogenic mouse cell line (129CB3), which returned to their basal levels after 60 s. However, in the human dystrophic cell line (RCDMD), IP3 levels remained high up to 200 s after potassium depolarization. Expression of IP3 receptors was studied measuring specific binding of 3H-IP3 in the murine cell lines (normal 129CB3 and dystrophic mdx XLT 4-2). All the cell lines bind 3H-IP3 with relatively high affinity (Kd: between 40 and 100 nmol/L). IP3 receptors are concentrated in the nuclear fraction, and their density is significantly higher in dystrophic cells compared to normal. These findings together with high basal levels of IP3 mass suggest a possible role for this system in the deficiency of intracellular calcium regulation in Duchenne muscular dystrophy.

Electroretinogram in Duchenne/Becker muscular dystrophy

The authors studied all cases with dystrophinopathy consecutively reviewed between May 1995 and December 1996 by means of electroretinography (ERG), which was recorded using skin eyelid electrodes and with standard flash stimulation. This methodology can detect the functional abnormalities associated with dystrophinopathies. The most valuable parameter is the ratio of B-wave amplitude to A-wave amplitude (B/A amplitude ratio), which was greater than 2 in all normal control patients (n = 10) and nondystrophinopathic muscular dystrophy (MD) patients (n = 2). It was less than 2 in 100% (n = 16) of Duchenne muscular dystrophy (DMD) patients (mean ratio 0.73; range 0.4-1.26). It was less than 2 in 71% (n = 7) of Becker muscular dystrophy (BMD) patients (mean ratio 1.12; range 0.88-1.37), and less than 2 in 50% (n = 4) of definitive DMD carriers. Twenty-nine percent of BMD, 50% of DMD carriers, and the only case with asymptomatic dystrophinopathy had normal ratios (greater than 2). The differences between the mean ratios of control, DMD, and BMD groups were statistically significant, all of them with P < 0.001. ERG abnormalities of dystrophinopathies were associated with the more severe muscular phenotype but not with the presence or location of gene deletion. ERG is an easy and simple technique that is useful in cases of suspected dystrophinopathy with a nonconclusive molecular study. It is less useful in patients who are DMD carriers.

2.1 kb 5'-flanking region of the brain type dystrophin gene directs the expression of lacZ in the cerebral cortex, but not in the hippocampus

Duchenne muscular dystrophy is a muscle-wasting disease accompanied by a variable, but often significant degree of mental retardation, possibly due to the absence of dystrophin. However, the function of brain type dystrophin remains insufficiently clear. With this background, in order to study the cell-specific regulation of brain type dystrophin expression in mice, we generated transgenic mice carrying the 2.1 kb 5'-fragment of the mouse brain type dystrophin gene, fused to the coding region of the bacterial lacZ gene. Three transgenic mice lines showed lacZ expression in the cerebral cortex. However, lacZ expression was not detected in the CA region of the hippocampus. These results suggest that the 2.1 kb 5'-fragment of the mouse brain type dystrophin gene contains the regulatory element required for its expression in the cerebral cortex, but not in the hippocampus.

Extra-muscle involvement in dystrophinopathies: an electroretinography and evoked potential study

Dystrophin is present in various tissues other than skeletal and cardiac muscles, including the central nervous system (CNS) and the outer plexiform layer of the retina. Therefore lack of dystrophin might be related to mental retardation or to changes in electrophysiological tests exploring retina and CNS. We performed electroretinography, VEPs, BAEPs, SEPs and MEPs in 18 patients with Duchenne muscular dystrophy (DMD), 18 with Becker muscular dystrophy (BMD) and 12 obligate carriers. We observed a marked reduction of the b-wave amplitude in the scotopic ERG, mainly in DMD patients. Oscillatory potentials were altered in all groups, even in carriers, suggesting that dystrophin may be also involved in retinal circulation. VEPs changes confirmed the role of dystrophin in visual function. The other evoked potentials were altered only in a small percentage of subjects but changes of different tests did not overlap in individual subjects. Neurophysiological abnormalities did not correlate with type, site and size of alteration in the dystrophin gene.

Architectural changes of the cortico-spinal system in the dystrophin defective mdx mouse

The mutant mdx mice which lack the protein dystrophin are an animal model of Duchenne muscular dystrophy. We studied the organization of the cortico-spinal (CS) system in mdx mice using the horseradish peroxidase retrograde tracing technique. Tracer injections were placed in the cervical spinal cord of mutant and control mice. The tangential and radial distribution of CS labeled neurons were similar in mdx and normal mice. Conversely, the absolute number and the cell packing density of labeled CS neurons were considerably lower in mdx than in controls. In mdx, the average size of CS cells was smaller while the perikaryal sizes displayed a normal distribution. In addition, CS neurons of mdx appeared round-shaped compared to the pyramidal cells labeled in control animals. The structural modifications described here should prompt a reconsideration of the involvement of central nervous system in the dystrophin deficient mdx mice.

Desmin-related neuromuscular disorders

Desmin, the intermediate filament protein of skeletal muscle fibers, cardiac myocytes, and certain smooth muscle cells, is a member of the cytoskeleton linking Z-bands with the plasmalemma and the nucleus. The pathology of desmin in human neuromuscular disorders is always marked by increased amounts, diffusely or focally. Desmin is highly expressed in immature muscle fibers, both during fetal life and regeneration as well as in certain congenital myopathies, together with vimentin. Desmin is also enriched in neonatal myotonic dystrophy and small fibers in infantile spinal muscular atrophy. Focal accretion of desmin may be twofold, in conjunction with certain inclusion bodies, cytoplasmic and spheroid bodies, and in a more patchy fashion, granulofilamentous material. Both lesions have been found in certain families, affected by a myopathy and/or cardiomyopathy. Other proteins, e.g., dystrophin, vimentin, actin, ubiquitin, and alpha-B crystallin, may also be overexpressed. Desmin pathology may be genetically regulated or may merely reflect profoundly impaired metabolism of several proteins within myofibers.

Analysis of peristaltic reflex in young mdx dystrophic mice

Experiments have been carried out in isolated distal colon of young normal and mdx dystrophic mice, the animal homologous of Duchenne muscular dystrophy. Intraluminal pressure, longitudinal displacement, ejected fluid volume and changes in morphology during peristaltic events were recorded. In both male and female normal animals, pressure waves were observed to be generally regular in shape, amplitude (14.19 +/- 2.45 (SD) cm H2O), frequency (54.00 +/- 10.78 h-1) and duration (31.12 +/- 3.47 s). The propulsive activity resulted in orthograde transport of intraluminal content. Mdx mice exhibited great changes in relation to sex, since clear and more marked dysfunctions were recorded in female mice. In male mdx animals, an increase of intraluminal pressure (22%) and ejected fluid volume (38%) were recorded. In females, a remarkable significant (P < 0.001) increase (78%) of intraluminal pressure was observed. Simultaneous anterograde and retrograde propulsive activity also occurred. Localized annular constrictions in proximal, central and distal portions of colonic segment were observed. The implications of the results are discussed in terms of injury of myogenic and nervous pathways controlling mdx colonic smooth muscle.

Duchenne muscular dystrophy: negative electroretinograms and normal dark adaptation. Reappraisal of assignment of X linked incomplete congenital stationary night blindness

Aland Island eye disease (AIED) and X linked congenital stationary night blindness (CSNB) have been mapped to Xp11.3. Patients have been described with deletions of the Duchenne muscular dystrophy (DMD) gene who also had a negative electroretinogram (ERG) similar to that seen in patients with CSNB and AIED. This seems to confirm that some cases of AIED and CSNB map to Xp21. We examined 16 boys with DMD/BMD (Becker muscular dystrophy) of whom 10 had negative ERGs, eight of them having deletions downstream from exon 44. Normal dark adaptation thresholds were observed in all patients and there were no anomalous visual functions. Hence, CSNB cannot be assigned to Xp21 and negative ERG in DMD/BMD is not associated with eye disease. Six boys with DMD/BMD had normal ERGs. We speculate that a retinal or glial dystrophin may be truncated or absent in the boys with negative ERGs.

Dystrophin expression in skin biopsy immunohistochemical. Localisation of striated muscle type dystrophin

Dystrophin is normally localized in smooth muscle fibers of various organs in experimental animals, and it has been shown to be defective in the smooth muscle fibers of the mdx mouse, including the myoepithelial cell layer of the sweat glands. We investigated dystrophin localization, using three antisera raised against different domains of skeletal muscle type of dystrophin, in the smooth muscle structures of the skin, using immunohistochemical methods with monoclonal antibodies against dystrophin, in 24 patients with various neuromuscular diseases, and in a normal control. Skin biopsy showed a strong dystrophin reaction in the arrector pili muscles and in the myoepithelial cells of the sweat glands of patients with congenital muscular dystrophy, polymyositis, distal myopathy, putative Duchenne muscular dystrophy carriers, myoglobinuria, neurogenic atrophy and in a normal control. A faint positive dystrophin reaction was seen in four patients with Becker muscular dystrophy, whereas it was absent in 3 patients with Duchenne muscular dystrophy. As our data suggest that immunohistochemical dystrophin expression in smooth muscle structures of the skin is similar to that observed in striated muscle, skin biopsy may represent an alternative way to ascertain dystrophin deficiency.

Ion channels in a skeletal muscle cell line from a Duchenne muscular dystrophy patient

A cell line (RCDMD), derived from a muscle biopsy taken from a 7-year-old patient with Duchenne muscular dystrophy (DMD), was established in vitro using conditioned media from the UCHT1 thyroid cell line as described elsewhere (Biochim Biophys Acta 1992; 1134:247-255). Unlike other cell lines established by the same procedure, RCDMD cells were highly refractory to transformation and the resulting cell line grew slowly with a doubling time of approximately 72 h. Further, cells continue to grow after more than 20 doublings and 15 passages. Some of the characteristics of the cell line include lack of reaction with antidystrophin antibodies and the presence of receptors for the dihydropyridine PN200-110 (Kd) = 0.3 +/- 0.05 nmol/L and Bmax = 1.06 +/- 0.03 pmol/mg protein) and for alpha-bungarotoxin (Kd = 1.02 +/- 0.17 nmol/L and Bmax = 4.2 +/- 0.37 pmol/mg protein). Patch clamped cells in the voltage clamp configuration lack ion currents when growing in complete medium with high serum, but they can be induced to differentiate by serum deprivation and addition of hormones and trace elements. After 5 days in differentiating medium, noninactivating, delayed rectifier potassium currents are seen. At day 12, A-type, inactivating potassium currents as well as transient inward currents are seen. In conditions in which sodium and potassium currents are absent, a very fast activating and fast inactivating calcium current was evident. The cell line offers the possibility of studying cellular mechanisms in the pathophysiology of DMD.

Immunohistochemical detection of neural cell adhesion molecule and laminin in X-linked dystrophic dogs and mdx mice

Although dystrophin deficiency is known to be the genetic and biochemical defect causing Duchenne muscular dystrophy (DMD), much remains unknown about the underlying factors affecting clinical and pathological expression of the disease. Two animal forms of muscular dystrophy resembling DMD have been described. Neural cell adhesion molecule (NCAM) and laminin expression were examined in the proliferation-competent mdx mouse and non-regenerative "golden retriever muscular dystrophy dog" (GRMD). The results showed that (1) NCAM expression was greater in dystrophic dogs and mice than in age-matched normal animals, (2) myoblast-specific NCAM was greater in mdx mice than in dystrophic dogs, and (3) laminin strongly labelled mdx and GRMD myofibre membranes but was also sometimes found in individual interstitial cells of mdx muscle. Expression of these proteins may partly determine the clinicopathological expression of dystrophin deficiency.

Does muscular dystrophy affect metabolic rate? A study in mdx mice

In this study metabolic consequences of muscular dystrophy were investigated using the mdx mouse model. Measurements were performed on C57BL/10SNJ (control) and dystrophic (mdx) mice of ages 4-6 weeks (young) and 1 year (adult), i.e. at times when muscle degeneration and regeneration are known to be high (young) and low (adult). Whole body metabolic rate (MR) was measured indirectly under usual living conditions by recording O2 consumption and CO2 production over 24 h. Physical activity of mice was measured simultaneously. Oxygen consumption of soleus (SOL) and extensor digitorum longus (EDL) muscles of control and mdx mice was recorded in vitro, using polarographic O2 electrodes. MR in young mdx was significantly decreased compared to young control, but no differences were found in adults. Also, food consumption and physical activity of mdx were decreased significantly compared to control in young but not in adult mice. There was no difference in resting oxygen consumption of muscles from young mdx and control mice, but oxygen consumption of EDL from adult mdx was less than control. Results suggest that muscular dystrophy results in decreased rate of energy metabolism mainly as a consequence of decreased physical activity. The extensive muscular degeneration and regeneration characteristic of muscular dystrophy therefore do not appear to lead to an increase in whole body metabolism.

Single channel properties of synaptic acetylcholine receptors in dystrophic fibers

Neuromuscular transmission in dystrophic mice has been extensively studied through analysis of nerve-evoked endplate potentials. In the present study, single channel ACh-induced activity recorded from endplates of fast twitch muscle fibers from mdx and dy dystrophic mice, was compared with activity recorded from wild-type fiber endplates to ascertain whether expression of these phenotypes leads to changes in ACh receptor properties and synaptic transmission. An 89 pS class of ACh-induced events predominated in recordings from wild-type and both strains of dystrophic mice. The mean open times for this class of events was well described by two exponential components, one with a voltage-independent time constant of approximately 0.3 ms and the other with a time constant of 2-5 ms which increased e-fold with approximately 120 mV of hyperpolarization. The expression of the mdx or the dy phenotype was not associated with significant differences in the conductance, distribution of open durations, or the voltage-dependence of the mean open time for this class of ACh-induced events.

The distribution of dystrophin in the murine central nervous system: an immunocytochemical study

A mild non-progressive cognitive defect is a feature of the fatal X-linked disease, Duchenne muscular dystrophy. Recent studies have identified the genetic defect and the resulting loss of the protein dystrophin, and shown that dystrophin messenger RNA and protein are present in normal brain tissue. We have performed western immunoblotting and fluorescence immunocytochemistry using a sensitive antibody made against a large fragment of the dystrophin molecule to study the regional, cellular and subcellular distribution of dystrophin in the mammalian brain. The brains of B10 (control) and mdx (dystrophin deficient null mutant) mouse brain were compared on a point-by-point basis to verify that only dystrophin and not autosomal dystrophin related protein or cross-reacting proteins were being identified. In addition three murine neurologic mutants, nervous, lurcher, and weaver, were studied to refine the localization of dystrophin. In western immunoblots, dystrophin is present in all regions of the brain and in greatest abundance in the cerebellum. Dystrophin, as demonstrated in immunofluorescence, is present in neurons, but not in glia or myelin, and forms punctate foci associated with the plasma membrane of perikarya and dendrites, but not axons. While dystrophin is abundant in cerebral cortical neurons and cerebellar Purkinje cells, it is absent from most subcortical neurons, the granule cells of fascia dentata, and cerebellar neurons other than Purkinje cells. The absence of dystrophin in the cerebellum of the Purkinje cell deficient mutants nervous and lurcher, and its presence in the granule cell deficient mutant weaver indicate that dystrophin is a component of Purkinje cells rather than closely apposed afferents to those cells. The distribution and localization of dystrophin suggests a role in organizing the plasma membrane, possibly as an anchor of the postsynaptic apparatus, a possible basis for the cognitive defect in Duchenne dystrophy.

An alternative dystrophin transcript specific to peripheral nerve

Transcription of the 2.5 megabase dystrophin gene gives rise to multiple isoforms. We describe a 5.2 kilobase transcript, expressed specifically in peripheral nerve, that initiates at a previously unrecognized exon located approximately 850 basepairs upstream of dystrophin exon 56. The likely product of this transcript (Dp116) is detected by C-terminal dystrophin antibodies exclusively in peripheral nerve and cultured Schwann cells. Dp116 is located along the Schwann cell membrane but is not present in the compact myelin lamellae or in axons. Dp116 lacks actin-binding and spectrin-like rod domains, arguing that it functions differently in the Schwann cell than does the major dystrophin transcript in muscle.

Developmental studies of dystrophin-positive fibers in mdx, and DRP localization

Dystrophin positive fibers (DPFs) were observed in about 1% of the total muscle fibers in 1-year-old mice. Some of these fibers were found to have positive staining with all six antibodies, while others showed a negative reaction with specific antibodies. These results suggest that the most likely mechanism giving rise to these DPFs is a second site mutation which prepares in-frame deletion. A study of the frequency of DPF during development showed single and scattered DPFs in younger mice, which gradually increased in number and began to form small groups with age. DRP was observed constantly on the neuromuscular junctions in both control and mdx muscle, and surface membrane of immature muscle fibers such as regenerating fibers in mdx and newborn muscle during 2 weeks of age in control and mdx.

Diseases and disorders of muscle

Muscle may suffer from a number of diseases or disorders, some being fatal to humans and animals. Their management or treatment depends on correct diagnosis. Although no single method may be used to identify all diseases, recognition depends on the following diagnostic procedures: (1) history and clinical examination, (2) blood biochemistry, (3) electromyography, (4) muscle biopsy, (5) nuclear magnetic resonance, (6) measurement of muscle cross-sectional area, (7) tests of muscle function, (8) provocation tests, and (9) studies on protein turnover. One or all of these procedures may prove helpful in diagnosis, but even then identification of the disorder may not be possible. Nevertheless, each of these procedures can provide useful information. Among the most common diseases in muscle are the muscular dystrophies, in which the newly identified muscle protein dystrophin is either absent or present at less than normal amounts in both Duchenne and Becker's muscular dystrophy. Although the identification of dystrophin represents a major breakthrough, treatment has not progressed to the experimental stage. Other major diseases of muscle include the inflammatory myopathies and neuropathies. Atrophy and hypertrophy of muscle and the relationship of aging, exercise, and fatigue all add to our understanding of the behavior of normal and abnormal muscle. Some other interesting related diseases and disorders of muscle include myasthenia gravis, muscular dysgenesis, and myclonus. Disorders of energy metabolism include those caused by abnormal glycolysis (Von Gierke's, Pompe's, Cori-Forbes, Andersen's, McArdle's, Hers', and Tauri's diseases) and by the acquired diseases of glycolysis (disorders of mitochondrial oxidation). Still other diseases associated with abnormal energy metabolism include lipid-related disorders (carnitine and carnitine palmitoyl-transferase deficiencies) and myotonic syndromes (myotonia congenita, paramyotonia congenita, hypokalemic and hyperkalemic periodic paralysis, and malignant hyperexia). Diseases of the connective tissues discussed include those of nutritional origin (scurvy, lathyrism, starvation, and protein deficiency), the genetic diseases (dermatosparaxis, Ehlers-Danlos syndrome, osteogenesis imperfecta, Marfan syndrome, homocystinuria, alcaptonuria, epidermolysis bullosa, rheumatoid arthritis in humans, polyarthritis in swine, Aleutian disease of mink, and the several types of systemic lupus erythematosus) and the acquired diseases of connective tissues (abnormal calcification, systemic sclerosis, interstitial lung disease, hepatic fibrosis, and carcinomas of the connective tissues). Several of the diseases of connective tissues may prove to be useful models for determining the relationship of collagen to meat tenderness and its other physical properties. Several other promising models for studying the nutrition-related disorders and the quality-related characteristics of meat are also reviewed.

Dystrophin-like immunoreactivity in monkey and human brain areas involved in learning and motor functions

Two antidystrophin antibodies against different fragments of dystrophin were used to detect this polypeptide in monkey and human brains. Dystrophin was revealed by immunoperoxidase amplified with the biotin/avidin system and by immunoblotting. A dystrophin-like immunoreactivity was uniformly expressed in several brain regions implicated in learning and motor functions. Dystrophin function is not clear but our results raise the possibility that this protein may be involved in the cognitive impairment observed in several Duchenne muscular dystrophy (DMD) patients.

Dystrophin and a dystrophin-related protein in intrafusal muscle fibers, and neuromuscular and myotendinous junctions

To determine whether or not and how dystrophin exists in neuromuscular junctions (NMJs) and myotendinous junctions (MTJs), we studied the mid-belly and peripheral portions of control and mdx muscles, immunohistochemically and immunoelectrophoretically, using six kinds of polyclonal antibodies, and an antibody against a dystrophin-related protein (DRP). In controls these regions and the polar region of intrafusal muscle fibers showed a rather clearer immunohistochemical dystrophin reaction than those of extrafusal muscle fibers with all antibodies used. In the muscles of mdx mice NMJs only showed a positive dystrophin reaction with the c-terminal antibody, that is, no reaction with the other five antibodies, and MTJs in mdx showed a positive reaction with the c-terminal antibody and a faint to negative reaction with the other five antibodies. In biopsied human muscles NMJs and MTJs also showed a clear reaction with all ten antibodies, i.e., six polyclonal and four monoclonal ones. Although an immunohistochemical DRP reaction was clearly seen at NMJs, only a faint or no reaction was seen on MTJs and on intrafusal muscle fibers in both mouse and human materials. Western blot analysis of control mouse muscle for dystrophin showed a clearer band for the peripheral portion, which contains many MTJs, than for the mid-belly portion. These data suggest that dystrophin really exists on MTJs, and that dystrophin and DRP exist on NMJs in mouse and human muscles.

Dystrophin isoforms and/or cross-reactive proteins on neurons and glial cells in control and mdx central nervous systems

We studied the central nervous system (CNS) of control mice in comparison with that of mdx mice, immunohistochemically and immunoelectrophoretically, using 5 kinds of polyclonal antibodies against dystrophin (DMDP-II, 60-kDa, 30-kDa, P-20 and DMDP-IV) to determine whether or not and, if so, how dystrophin exists in the central nervous system. A positive dystrophin reaction was seen on the neurons and glial cells in both control and mdx tissue, without any immunohistochemical difference. In control mice, Western blot analysis showed two relatively clear bands corresponding to 400-kDa, with all 4 antibodies used (60-kDa, 30-kDa, P-20 and DMDP-IV), and 280-kDa, with 3 of them, the exception being 30-kDa, and 2 other faint bands corresponding to larger M(r) than 400-kDa, with 3 of them, the exception being P-20, respectively. In the mdx CNS, the 400-kDa band was absent, the other 3 bands being seen. The results suggest that dystrophin really exists in the control CNS, and some dystrophin isoforms or cross-reactive proteins exist on the neurons and glial cells in mdx as well as control mice. The localization of dystrophin in CNS also suggests its physiological function in the conduction system rather than a mechanical one, and a defect of it in CNS is a possible cause of the mental retardation in Duchenne muscular dystrophy.

Localization of dystrophin in the Purkinje cells of normal mice

A monoclonal antibody that reacts with a mid rod fragment of dystrophin was used to localize this protein in the central nervous system (CNS). Due to a low abundance of dystrophin in the CNS, an immunoperoxidase reaction amplified with a biotin-avidin system was used. All Purkinje cells in normal mice were dystrophin positive while the mdx mouse cerebellum was completely devoid of reaction. Dystrophin staining was present in the soma and dendrites of Purkinje cells but not in their axons. This uniform dystrophin labelling in the normal mouse Purkinje cells indicates that this protein is not only localized in synaptic contact regions of the CNS.

Congenital myopathy associated with abnormal accumulation of desmin and dystrophin

We studied a 5-yr-old boy clinically presenting congenital myopathy. Muscle biopsy showed sarcoplasmic accumulation of desmin filaments leading to diagnosis of desmin storage myopathy. An immunohistochemical study of other cytoskeletal proteins (actin, alpha-actinin, vimentin and dystrophin) was performed. Desmin positive areas reacted strongly with anti-mid-rod and C-terminus dystrophin antibodies. Probed with the same antibodies by Western blot, desmin and dystrophin showed normal molecular size but densitometric analysis demonstrated a parallel increase of both proteins. Our results indicate that intrasarcoplasmic desmin storage is associated with an abnormal accumulation of dystrophin. Since no other cytoskeletal proteins are accumulated this finding seems to be specific and suggests a possible structural and functional association between these two proteins in striated muscle.

Becker muscular dystrophy patient with a large intragenic dystrophin deletion: implications for functional minigenes and gene therapy

The genetic defects responsible for the allelic disorders of BMD and the more severe DMD have been shown to be mutations within the dystrophin gene, which encodes a 14 kb transcript. We describe here a BMD patient who belongs to a small class of subjects with large in frame deletions of the dystrophin gene that remove apparently dispensable coding sequence, thereby producing functional truncated dystrophin. The in vitro reconstruction of these deletion derivatives of full length dystrophin transcripts should enable higher efficiency transfection of human muscle or murine germline cells using retroviral based vectors, compared with the full length transcript. This capability offers a means of examining retroviral mediated transfer as a potential therapeutic strategy in severely affected DMD patients.

Recent advances in dystrophin research

Evidence suggesting that dystrophin is a component of the membrane cytoskeleton of excitable cells continues to accumulate. Whereas the specific mechanisms leading to muscle pathology in Duchenne muscular dystrophy are still being debated it is apparent that the progressive weakness that occurs in this disease is the result of a chronic process that is initiated by dystrophin deficiency.

Experimental serotonin myopathy as an animal model of muscle degeneration and regeneration in muscular dystrophy

Degenerating and regenerating muscle fibers, in serotonin-induced myopathy (SM) of rats, were investigated histochemically, immunohistochemically and electron microscopically with polyclonal antibodies against dystrophin, type IV collagen and laminin. The myopathy produced was characterized by grouping of degenerating and regenerating muscle fibers, and degeneration of capillary endothelial cells. Dystrophin disappeared in an early stage of muscle degeneration and reappeared in an early stage of regeneration. On the other hand, type IV collagen and laminin were well preserved throughout the degeneration and regeneration processes, even on the shrunk and wrinkled basement membrane of empty muscle fibers after phagocytosis. Muscle fiber regeneration was completed within each tube of the preserved basement membrane through the fusion of myoblasts derived from satellite cells of single necrotic fibers, myotubes already being visible on the 1st or 2nd day of regeneration on light microscopy. These small regenerating myotubes did not fuse with each other at all. The findings in the present experimental SM study are compatible with those in Duchenne muscular dystrophy, especially at the preclinical stage.

Dystrophin and disease

Recent advances concerning the genetic and biochemical basis of Duchenne and Becker muscular dystrophies have resulted in a good understanding of the etiology of these common dystrophies. An important secondary consequence of the genetic and biochemical research has been the generation of gene-based and protein-based diagnostic tools which enable a 'molecular diagnosis' for patients and their families. This review summarizes our current understanding of the genetics, biochemistry, and pathophysiology of Duchenne dystrophy, and gives an overview of the molecular diagnostic tools and their applications. Recent correlations of clinical, genetic and biochemical data have indicated that dystrophinopathies can present with a wide range of neuromuscular symptoms, and that neither male sex nor proximal weakness are diagnostic prerequisites for consideration of an underlying dystrophin abnormality.

Nerve growth factor receptor immunoreactivity on the tunica adventitia of intramuscular blood vessels in childhood muscular dystrophies

Muscle tissues from cases of childhood neuromuscular disorders were examined immunohistochemically and immunoelectrophoretically using a monoclonal antibody against the human nerve growth factor receptor (NGFR). Strong NGFR immunoreactivity on the tunica adventitia of blood vessels and proliferating peripheral nerve endings in biopsied muscle specimens from muscular dystrophy patients was observed, but it was almost completely absent in specimens from non-diagnostic controls and cases of other neuromuscular disorders. This suggests a process in the sympathetic nervous system involving blood vessels in muscular dystrophies. Immunoblot analysis failed to show a band corresponding to 70-75 kd, the reported molecular size of the NGFR, but showed a clear band corresponding to 25 kd in muscular dystrophy patients, which is assumed to be a detached amino-terminal domain of the NGFR.

Dystrophin in control and mdx retina

To determine whether or not dystrophin really exists in the outer plexiform layer (OPL) of the retina, we studied control and mdx mice, using four kinds of polyclonal antibodies (DMDP-II, 60 kd, 30 kd and DMDP-IV) against dystrophin. Although control OPL showed a positive immunohistochemical reaction with all four antibodies, mdx OPL showed a positive reaction with DMDP-II and DMDP-IV, a negative reaction with 60 kd and 30 kd antibodies. Immunoblot analysis showed the positive band compatible with the immunohistochemical reaction.

Vascular alterations in Fukuyama type congenital muscular dystrophy

Blood vessels in muscle biopsy specimens from 6 Fukuyama type congenital muscular dystrophy (FCMD) patients were examined by electron microscopy and compared with ones in non-diagnostic biopsy specimens from age-matched controls and patients with childhood neuromuscular disorders. The most striking feature was the blister-like swelling of vascular endothelial cells in the biopsied muscle specimens from 5 of the 6 patients with FCMD. Morphometric analysis of capillaries in biopsied muscles showed the extremely greater capillary, endothelial and pericyte areas in the FCMD patients than in controls. These phenomena are quite similar to those found in Duchenne muscular dystrophy (DMD) at the preclinical stage and suggest an as yet undetermined process in blood vessels in FCMD as well as DMD. An immunohistochemical study involving dystrophin antibodies showed positive staining in FCMD.