Changes of laminin beta 2 chain expression in congenital muscular dystrophy

We studied the distribution of laminin beta 2 chain in the skeletal muscle basement membrane of 16 patients with congenital muscular dystrophy (CMD) by immunohistochemistry. A dramatic reduction in the laminin beta 2 staining was observed in four patients with classical merosin-negative CMD. A moderate reduction of laminin beta 2 labelling was observed in four patients with partial merosin deficiency and two patients with merosin-positive CMD. Two patients with merosin-positive CMD had no apparent changes in the expression of laminin beta 2. In three patients and one fetus diagnosed as Walker-Warburg syndrome (WWS) the laminin beta 2 pattern was similar to normal controls. We conclude that a primary deficiency in the laminin alpha 2 chain may lead to a vast or moderate reduction in the laminin beta 2 chain in the skeletal muscle membrane.     

Variation in surgical trauma and baseline pain intensity: effects on assay sensitivity of an analgesic trial

Humans and mice with deficiency of the alpha2 subunit of the basement membrane protein laminin-2/merosin suffer from merosin-deficient congenital muscular dystrophy (MCMD). We have expressed a human laminin alpha2 chain transgene under the regulation of a muscle-specific creatine kinase promoter in mice with complete or partial deficiency of merosin. The transgene restores the synthesis and localization of merosin in skeletal muscle, and greatly improves muscle morphology and integrity and the health and longevity of the mice. However, the transgenic mice share with the nontransgenic dystrophic mice a progressive lameness of hind legs, suggestive of a nerve defect. These results indicate that the absence of merosin in tissues other than the muscle, such as nervous tissue, is a critical component of MCMD. Future gene therapies of human MCMD, and perhaps of other forms of muscular dystrophy, may require restoration of the defective gene product in multiple tissues.     

Differential heparin sensitivity of alpha-dystroglycan binding to laminins expressed in normal and dy/dy mouse skeletal muscle

The alpha-dystroglycan binding properties of laminins extracted from fully differentiated skeletal muscle were characterized. We observed that the laminins expressed predominantly in normal adult rat or mouse skeletal muscle bound alpha-dystroglycan in a Ca2+-dependent, ionic strength-sensitive, but heparin-insensitive manner as we had observed previously with purified placental merosin (Pall, E. A., Bolton, K. M., and Ervasti, J. M. 1996 J. Biol. Chem. 271, 3817-3821). Rat skeletal muscle laminins partially purified by heparin-agarose affinity chromatography also bound alpha-dystroglycan without sensitivity to heparin. We also confirm previous studies of dystrophic dy/dy mouse skeletal muscle showing that the alpha2 chain of merosin is reduced markedly and that the laminin alpha1 chain is not up-regulated detectably. However, we further observed a quantitative decrease in the expression of laminin beta/gamma chain immunoreactivity in alpha2 chain-deficient dy/dy skeletal muscle and reduced alpha-dystroglycan binding activity in laminin extracts from dy/dy muscle. Most interestingly, the alpha-dystroglycan binding activity of residual laminins expressed in merosin-deficient dy/dy skeletal muscle was inhibited dramatically (69 +/- 19%) by heparin. These results identify a potentially important biochemical difference between the laminins expressed in normal and dy/dy skeletal muscle which may provide a molecular basis for the inability of other laminin variants to compensate fully for the deficiency of merosin in some forms of muscular dystrophy.     

Immunolocalization of several laminin chains in the normal human central and peripheral nervous system

Using specific monoclonal antibodies against different subunits of laminin, we studied the differential distribution pattern of several laminin chains in the central (CNS) and peripheral (PNS) nervous system. Laminin chains alpha 1, beta 1 and gamma 1, were found in the basement membrane (BM) of blood vessels in both CNS and PNS. In contrast, laminin alpha 2 though present in the BM of capillaries in the CNS, was completely absent from PNS capillaries. Laminins alpha 2, beta 1, gamma 1 could be detected in peripheral nerve, in the BM of Schwann cells, which did not contain Laminin alpha 1. The possible importance of laminin alpha 2 for myelination in the PNS as well as in the function of the blood-brain barrier in the CNS, and its potential relevance to the pathology of congenital muscular dystrophy associated with deficiency of this laminin chain, is discussed.     

The frequency of patients with adhalin deficiency in a muscular dystrophy patient population

Immunocytochemical deficiency of alpha-sarcoglycan (adhalin) in the skeletal muscle that is associated with normal dystrophin expression has been called adhalinopathy. However, recent molecular biological and genetic studies revealed that alpha-sarcoglycan is one of four subunits of sarcoglycans (alpha-delta) or sarcoglycan complex. Mutations of any one of the genes of these subunits cause loss of sarcoglycan complex, and therefore they are now called sarcoglycanopathy or limb-girdle muscular dystrophy (LGMD) 2C-2F. The frequency of sarcoglycanopathy is about 5-10% of dystrophin-normal muscular dystrophy. Mutation of alpha-sarcoglycan gene is most frequent (34%) among the four sarcoglycan genes as shown in the tables. However, 38% of the patients with sarcoglycanopathy have no mutation, implying the presence of yet unknown sarcoglycan(s) and/or interacting protein(s) with sarcoglycan complex.     

Progressive muscular dystrophy in alpha-sarcoglycan-deficient mice

Limb-girdle muscular dystrophy type 2D (LGMD 2D) is an autosomal recessive disorder caused by mutations in the alpha-sarcoglycan gene. To determine how alpha-sarcoglycan deficiency leads to muscle fiber degeneration, we generated and analyzed alpha-sarcoglycan- deficient mice. Sgca-null mice developed progressive muscular dystrophy and, in contrast to other animal models for muscular dystrophy, showed ongoing muscle necrosis with age, a hallmark of the human disease. Sgca-null mice also revealed loss of sarcolemmal integrity, elevated serum levels of muscle enzymes, increased muscle masses, and changes in the generation of absolute force. Molecular analysis of Sgca-null mice demonstrated that the absence of alpha-sarcoglycan resulted in the complete loss of the sarcoglycan complex, sarcospan, and a disruption of alpha-dystroglycan association with membranes. In contrast, no change in the expression of epsilon-sarcoglycan (alpha-sarcoglycan homologue) was observed. Recombinant alpha-sarcoglycan adenovirus injection into Sgca-deficient muscles restored the sarcoglycan complex and sarcospan to the membrane. We propose that the sarcoglycan-sarcospan complex is requisite for stable association of alpha-dystroglycan with the sarcolemma. The Sgca-deficient mice will be a valuable model for elucidating the pathogenesis of sarcoglycan deficient limb-girdle muscular dystrophies and for the development of therapeutic strategies for this disease.     

Non-Fukuyama type congenital muscular dystrophy--merosin deficient and positive forms

The classical form of congenital muscular dystrophy (CMD) is now classified into merosin-deficient and -positive forms. The merosin (laminin alpha 2) is one of three subunits of a muscle basement membrane protein, laminin. Patients with the merosin-deficient form have generalized muscle weakness and hypotonia from early infancy as seen in FCMD but with no significant central nervous system involvement. The serum creatine kinase (CK) is markedly elevated. Strikingly all patients examined by a CT/ MRI have diffuse white matter abnormalities mimicking leukodystrophy. The gene has been mapped to chromosome 6q2 in the coding region for merosin. Since the responsible gene and protein have not been identified in the merosin-positive form, this CMD is probably a group of heterogeneous diseases. The overall symptoms are mild, approximately 90% of patients learned to walk alone.     

Genetic epidemiology of muscular dystrophies resulting from sarcoglycan gene mutations

BACKGROUND: The autosomal recessive limb-girdle muscular dystrophies (LGMDs) are a group of genetically heterogeneous muscle diseases characterised by progressive proximal limb muscle weakness. Six different loci have been mapped and pathogenetic mutations in the genes encoding the sarcoglycan complex components (alpha-, beta-, gamma-, and delta-sarcoglycan) have been documented. LGMD patients affected with primary "sarcoglycanopathies" are classified as LGMD2D, 2E, 2C, and 2F, respectively. METHODS: A geographical area in north east Italy (2,319,147 inhabitants) was selected for a genetic epidemiological study on primary sarcoglycanopathies. Within the period 1982 to 1996, all patients living in this region and diagnosed with muscular dystrophy were seen at our centre. Immunohistochemical and immunoblot screening for alpha-sarcoglycan protein deficiency was performed on all muscle biopsies from patients with a progressive muscular dystrophy of unknown aetiology and normal dystrophin. Sarcoglycan mutation analyses were conducted on all patient muscle biopsies shown to have complete or partial absence of alpha-sarcoglycan immunostaining or a decreased quantity of alpha-sarcoglycan protein on immunoblotting. RESULTS: Two hundred and four patient muscle biopsies were screened for alpha-sarcoglycan protein deficiency and 18 biopsies showed a deficiency. Pathogenetic mutations involving one gene for sarcoglycan complex components were identified in 13 patients: alpha-sarcoglycan in seven, beta-sarcoglycan in two, gamma-sarcoglycan in four, and none in the delta-sarcoglycan gene. The overall prevalence of primary sarcoglycanopathies, as of 31 December 1996, was estimated to be 5.6 x 10(-6) inhabitants. CONCLUSION: The prevalence rate estimated in this study is the first to be obtained after biochemical and molecular genetic screening for sarcoglycan defects.     

Preserved merosin M-chain (or laminin-alpha 2) expression in skeletal muscle distinguishes Walker-Warburg syndrome from Fukuyama muscular dystrophy and merosin-deficient congenital muscular dystrophy

The merosin M-chain (or laminin-alpha 2) is one of three subunits of laminin-2 which is highly expressed in striated muscle and peripheral nerve. Complete lack of laminin-alpha 2 expression in skeletal muscle is the hallmark of one form of congenital muscular dystrophy which is characterized by dysmyelination of the central nervous system (CNS), links to chromosome 6q2 and is common among Caucasians. Laminin-alpha 2 expression was also found to be significantly reduced in Fukuyama congenital muscular dystrophy which links to chromosome 9q3. We report consistently preserved laminin-2 expression, including laminin-alpha 2, as detected by immunofluorescence in skeletal muscle from five patients with Walker-Warburg syndrome which is characterized by congenital muscular dystrophy and, in addition, type II lissencephaly or pachygyria, defective CNS myelination, and ocular dysgenesis. These findings show that in spite of partial phenotypic overlap between Fukuyama CMD and Walker-Warburg syndrome the two disorders are nosologically separate disease entities. They also exclude that Walker-Warburg syndrome is allelic to the common form of congenital muscular dystrophy with laminin-alpha 2 deficiency.     

Expression of laminin alpha1, alpha2, alpha4, and alpha5 chains, fibronectin, and tenascin-C in skeletal muscle of dystrophic 129ReJ dy/dy mice

The dy/dy mouse is an animal model for human merosin-negative congenital muscular dystrophy (CMD), which has been reported to have reduced or no expression of the basement membrane protein laminin alpha2. We here investigate various myogenic and nonmyogenic tissues of mature dy/dy and control 129ReJ mice histologically and for laminin alpha2 expression. In addition, expression patterns of laminin alpha1, alpha2, alpha4, and alpha5 chains, the interstitial proteins fibronectin and tenascin-C, and the adhesion molecules VCAM-1, ICAM-1, and alpha4 integrin were characterized in skeletal muscle of 1- and 7-day and mature (>6 weeks old) dy/dy and control 129ReJ mice. The laminin alpha2 chain remained detectable in myogenic tissues of dy/dy mice by immunofluorescence using two different monoclonal antibodies and by Northern blot analysis. However, laminin alpha2 expression was significantly reduced or not detectable in nonmyogenic tissues of dy/dy mice, including skin, lung, kidney, brain, thymus, and eye. Focal lesions were observed in mature skeletal muscle only, characterized by necrotic tissue, isolated VCAM-1- and ICAM-1-positive cells indicative of inflammatory processes, and regenerating muscle fibers surrounded by intense tenascin-C and fibronectin expression. In contrast to studies on human CMD muscle, laminin alpha1 was not detectable in either dy/dy or control skeletal muscle using immunofluorescence or Northern blot analysis. Immunofluorescence localized laminin alpha4 to basement membranes of blood vessels, the endoneurium of the intramuscular nerves, and the neuromuscular junction in skeletal muscle of 1- and 7-day-old dy/dy and control mice. In mature muscle, laminin alpha4 expression shifted to the perineurium of intramuscular nerves in both dy/dy and control mice. Furthermore, strong upregulation of laminin alpha4 in the basement membranes of blood vessels, the perineurium of intramuscular nerves, and of isolated regenerating muscle fibers in the dy/dy mice was apparent. Investigation of 1-day-old animals revealed expression of laminin alpha5 in skeletal muscle fiber basement membranes of dy/dy but not control animals. This difference between dy/dy and control animals was no longer apparent at 7 days after birth, indicating a temporary shift in expression pattern of laminin alpha5 in dy/dy animals. Analysis of the extracellular matrix components of 1- and 7-day-old dy/dy and control skeletal muscle revealed an early onset of the dystrophy, even before histopathological features of the disease were evident. Our data confirm the absence of laminin alpha1 chain in myogenic tissues of both dy/dy and control mice and suggest compensation for reduced laminin alpha2 in dy/dy skeletal muscle by laminin alpha4 and, in early development, also laminin alpha5. These results have significant ramifications in the diagnosis of human merosin-negative CMD.     

Molecular genetics and merosin abnormality in Fukuyama-type congenital muscular dystrophy (FCMD)

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 FCMD to chromosome 9q31-33, we revealed that the gene lies within a region of < 100 kb containing D9S2107(9q31) by linkage-disequilibrium mapping. A-3 kb insertion was found in most FCMD chromosomes with the founder haplotype. On the other hand, a significant reduction in immunostaining of an extracellular matrix, laminin alpha 2 (merosin) has been noted in the FCMD muscle. Others reported basal lamina abnormalities in the FCMD muscle and brain in electron microscopic examination. We here describe recent advances in molecular genetics of FCMD and abnormalities of the basement membranes.     

Presence of laminin alpha5 chain and lack of laminin alpha1 chain during human muscle development and in muscular dystrophies

There is currently a great interest in identifying laminin isoforms expressed in developing and regenerating skeletal muscle. Laminin alpha1 has been reported to localize to human fetal muscle and to be induced in muscular dystrophies based on immunohistochemistry with the monoclonal antibody 4C7, suggested to recognize the human laminin alpha1 chain. Nevertheless, there seems to be no expression of laminin alpha1 protein or mRNA in developing or dystrophic mouse skeletal muscle fibers. To address the discrepancy between the results obtained in developing and dystrophic human and mouse muscle we expressed the E3 domain of human laminin alpha1 chain as a recombinant protein and made antibodies specific for human laminin alpha1 chain (anti-hLN-alpha1G4/G5). We also made antibodies to the human laminin alpha5 chain purified from placenta. In the present report we show that hLN-alpha1G4/G5 antibodies react with a 400-kDa laminin alpha1 chain and that 4C7 reacts with a 380-kDa laminin alpha5 chain. Immunohistochemistry with the hLN-alpha1G4/G5 antibody and 4C7 revealed that the two antibodies stained human kidney, developing and dystrophic muscle in distinct patterns. Our data indicate that the previously reported expression patterns in developing, adult, and dystrophic human muscle tissues with 4C7 should be re-interpreted as an expression of laminin alpha5 chain. Our data are also consistent with earlier work in mouse, indicating that laminin alpha1 is largely an epithelial laminin chain not present in developing or dystrophic muscle fibers.     

Expression of merosin in the thymus and its interaction with thymocytes

Merosin is a 700 kDa multichain protein that has several properties in common with laminin, one of the major extracellular matrix proteins present in basement membranes. Both contain B1 and B2 light chains, but merosin has a distinct M-chain compared with the laminin A-chain. Merosin is present in the basement membrane of placenta, striated muscle, and peripheral nerve. Using the RT-PCR assay, we demonstrate that merosin, but not laminin, is also expressed in the thymus. A partial cDNA sequence of the mouse merosin M-chain was 88% identical to the human M-chain, and the deduced amino acid sequences were 95% identical. 18-24% of adult mouse thymocytes bound to human merosin in vitro. Mg2+, but not Ca2+, was essential for binding. Binding was inhibited by antibodies recognizing VLA alpha 6 or beta 1, suggesting that the VLA-6 integrin is a merosin receptor. An anti-beta 4 integrin subunit mAb failed to inhibit binding, suggesting that the alpha 6 beta 4 integrin was not involved. Thymocytes were fractionated into immature and mature populations based on their expression of the heat stable antigen, recognized by the J11d mAb. Virtually all thymocytes expressed VLA-6, but only immature thymocytes (J11d+) bound to meroson. PMA treatment did not significantly increase the binding of J11d+ thymocytes nor did induce binding in the mature J11d- population. In constrast, both splenic T cells and unseparated lymph node cells showed enhanced binding to merosin after PMA stimulation. The expression of merosin in the thymus and its selective interaction with immature thymocytes suggest that thymocyte-merosin interactions may play a role in T cell development.     

Computerised analysis of fetal behaviour

The beta 1 integrin subunit is identical with the CD29 antigen, which is found at the surface of leukocytes. Integrins are involved in cell-cell and cell-matrix adhesion, mediate neuronal attachment and neurite outgrowth in response to extracellular matrix proteins in cell culture systems. A few analyses of beta 1 integrin subunit have been done on developing and regenerating skeletal muscle in animals; but cell culture systems and animal models differ in some respects from human skeletal muscle in situ. The expression of a beta 1 integrin subunit variant in human skeletal muscle was reported merely by Western blot analysis. Our present study, performed with immunohistochemical procedures, attempts to demonstrate the expression of the beta 1 integrin subunit in developing, normal adult, and diseased human skeletal muscles. The results demonstrated that the beta 1 integrin subunit is expressed in developing, normal adult, regenerating, and denervated human skeletal muscle. In developing muscle, the beta 1 integrin subunit was observed in muscle cells at least from 12 to 16 weeks of gestation. In muscular dystrophy and inflammatory myopathy the beta 1 integrin subunit staining occurs in basophilic muscle fibers. Furthermore, the beta 1 integrin subunit is expressed in mature fast twitch type 2 fibers, and in denervated myocytes in neurogenic muscular atrophy. On serial sections, the beta 1 integrin subunit, N-CAM (neural cell adhesion molecule) and vimentin are expressed in identical muscle fibers. However, in mature fast twitch type 2 fibers the beta 1 integrin subunit is expressed exclusively and in neurogenic muscular atrophy vimentin expression is weak. In conclusion, the beta 1 integrin subunit, in human skeletal muscles, probably plays a role in the growth morphology and innervation of developing, regenerating, and denervated myocytes. Furthermore, the observation that the beta 1 integrin subunit is enriched in mature fast twitch type 2 fibers indicates that the beta 1 integrin subunits may play a role in transducing mechanical forces to extracellular matrix proteins.     

Nitric oxide mediates caerulein-induced suppression of locomotor activity

Congenital muscular dystrophy (CMD) is one of the most frequent dystrophies of childhood, which is commonly characterized by neonatal muscle impairment with or without clinical evidence of central nervous system involvement. Several variants of CMD have been described and the disease has recently been classified into five clinically distinct forms: the two classical CMDs with and without deficit of the laminin M chain (merosin), the Fukuyama CMD described in Japanese patients and recently linked to the chromosome 9q31-33, the clinically more severe Walker-Warburg syndrome and the rare muscle-eye-brain disease described in Finnish patients. The most of these forms have central nervous system involvement. This is usually not seen in the classical merosin positive CMD, but can be very severe in the others. Here we describe a 3-year-old Mediterranean child with clinical and histopathological signs of CMD, normal expression of merosin, severe clinical and radiological evidence of central nervous system involvement without defects of neuronal migration or brain malformations and without ocular anomalies. This report suggests that new forms of CMD and cerebral involvement can still be recognized and confirms the heterogeneity of this group of infantile diseases.     

A functional role for specific spliced variants of the alpha7beta1 integrin in acetylcholine receptor clustering

The clustering of acetylcholine receptors (AChR) on skeletal muscle fibers is an early event in the formation of neuromuscular junctions. Recent studies show that laminin as well as agrin can induce AChR clustering. Since the alpha7beta1 integrin is a major laminin receptor in skeletal muscle, we determined if this integrin participates in laminin and/or agrin-induced AChR clustering. The alternative cytoplasmic domain variants, alpha7A and alpha7B, and the extracellular spliced forms, alpha7X1 and alpha7X2, were studied for their ability to engage in AChR clustering. Immunofluorescence microscopy of C2C12 myofibers shows that the alpha7beta1 integrin colocalizes with laminin-induced AChR clusters and to a much lesser extent with agrin-induced AChR clusters. However, together laminin and agrin promote a synergistic response and all AChR colocalize with the integrin. Laminin also induces the physical association of the integrin and AChR. High concentrations of anti-alpha7 antibodies inhibit colocalization of the integrin with AChR clusters as well as the enhanced response promoted by both laminin and agrin. Engaging the integrin with low concentrations of anti-alpha7 antibody initiates cluster formation in the absence of agrin or laminin. Whereas both the alpha7A and alpha7B cytoplasmic domain variants cluster with AChR, only those isoforms containing the alpha7X2 extracellular domain were active. These results demonstrate that the alpha7beta1 integrin has a physiologic role in laminin-induced AChR clustering, that alternative splicing is integral to this function of the alpha7 chain, and that laminin, agrin, and the alpha7beta1 integrin interact in a common or convergent pathway in the formation of neuromuscular junctions.     

Expression of laminin alpha 1, alpha 5 and beta 2 chains during embryogenesis of the kidney and vasculature

Laminins, found predominantly in basement membranes, are large glycoproteins consisting of different subsets of alpha, beta and gamma chain subunits. To resolve conflicting data in the literature concerning coexpression of alpha 1 and beta 2 chains, expression of alpha 1 chain was studied with two different antisera against the E3 fragment of laminin alpha 1 chain. Expression of the alpha 1 chain was seen in several types of epithelial basement membranes throughout development, but its expression in rat glomerular basement membranes and some other types of epithelial basement membranes occurred only during early stages of development. By contrast, beta 2 chains were detected by immunofluorescence only during advanced stages of glomerulogenesis and vascular development. By Northern and Western blots, beta 2 chains were detected somewhat earlier, but in situ hybridization revealed that beta 2 chain was also confined to vasculature during the earlier stages. It thus seems that, in the tissues studied here, the expression of alpha 1 and beta 2 chains was mutually exclusive. To explore whether the newly described alpha 5 chain is expressed in locations lacking alpha 1 chain, expression of alpha 5 chain was studied by Northern blots and in situ hybridization. The alpha 5 chain was not uniformly expressed in all embryonic epithelial cell types but was present mainly in epithelial sheets which produce very little alpha 1 chain. There also appeared to be a developmental trend, with alpha 1 chain appearing early and alpha 5 later, in maturing epithelial sheets. The alpha 5 chain could be a major alpha chain of the adult glomerular basement membrane.     

Sickle cell adhesion to laminin: potential role for the alpha5 chain

Sickle red blood cell (RBC) adhesion to the endothelium and to exposed, underlying subendothelial proteins is believed to contribute to vascular occlusion in sickle cell disease. Laminin, a major component of the subendothelium, supports significant adhesion of sickle, but not normal RBCs. The purpose of this study was to define the adhesive region for sickle RBCs within a human laminin preparation using a flow adhesion assay designed to mimic physiologic flow through postcapillary venules. Because sickle RBCs did not adhere to the common laminin contaminants entactin or collagen type IV, neither of these proteins are likely to contribute to the observed adhesion to laminin. Known adhesive regions of laminin neither supported nor inhibited sickle RBC adhesion to laminin, suggesting a mechanism of adhesion previously uncharacterized in other laminin adhesion studies. Moreover, sickle RBCs did not adhere to mouse EHS laminin or to human laminin-2 (merosin), eliminating the alpha1, alpha2, beta1, and gamma1 chains as mediators of sickle cell adhesion. The monoclonal antibody 4C7, which binds at or near the G-domain of the laminin alpha5 chain, significantly inhibited sickle RBC adhesion. These results suggest that an adhesive region for sickle RBCs is contained within the laminin alpha5 chain.     

Congenital muscular dystrophy with merosin deficiency: MRI findings in five patients

We present the MRI findings in five patients with congenital muscular dystrophy (CMD) and merosin (laminin alpha2) deficiency, which was total in one and partial in four. In one patient with partial merosin deficiency, MRI was normal. The other four patients had supratentorial white matter abnormalities. In three, T2-weighted images revealed subcortical, deep lobar and periventricular high signal in white matter, while in the other there were only small peritrigonal areas of increased signal. On T1-weighted images, there was slightly low signal. Cortical abnormalities were absent. None of these changes were accompanied by symptoms or signs of central nervous system involvement. White matter abnormalities in a patient with CMD should prompt investigation of merosin.