Congenital muscular dystrophy and epidermolysis bullosa simplex

Plectin in the Central Nervous System and a Putative Role in Brain Astrocytes

Plectin, a high-molecular-mass cytolinker, is abundantly expressed in the central nervous system (CNS). Currently, a limited amount of data about plectin in the CNS prevents us from seeing the complete picture of how plectin affects the functioning of the CNS as a whole. Yet, by analogy to its role in other tissues, it is anticipated that, in the CNS, plectin also functions as the key cytoskeleton interlinking molecule. Thus, it is likely involved in signalling processes, thereby affecting numerous fundamental functions in the brain and spinal cord. Versatile direct and indirect interactions of plectin with cytoskeletal filaments and enzymes in the cells of the CNS in normal physiological and in pathologic conditions remain to be fully addressed. Several pathologies of the CNS related to plectin have been discovered in patients with plectinopathies. However, in view of plectin as an integrator of a cohesive mesh of cellular proteins, it is important that the role of plectin is also considered in other CNS pathologies. This review summarizes the current knowledge of plectin in the CNS, focusing on plectin isoforms that have been detected in the CNS, along with its expression profile and distribution alongside diverse cytoskeleton filaments in CNS cell types. Considering that the bidirectional communication between neurons and glial cells, especially astrocytes, is crucial for proper functioning of the CNS, we place particular emphasis on the known roles of plectin in neurons, and we propose possible roles of plectin in astrocytes.

Epidermolysis bullosa simplex associated with muscular dystrophy and cardiac involvement

We report a new clinical variant of epidermolysis bullosa simplex with muscular dystrophy (EBS-MD) that was associated with cardiac involvement. A 33-year-old patient had atrial fibrillation, pericardial effusion, and hypokinetic left ventricular cardiac walls. The muscle biopsy material revealed diffuse endomysial fibrosis and small atrophic muscle fibers with rounded contours. A positive desmin expression with abnormal localization in the subsarcolemmal groups was observed. We concluded that patients with EBS-MD should be investigated carefully when there are associated cardiac findings.

Congenital muscular dystrophy, myasthenic symptoms and epidermolysis bullosa simplex (EBS) associated with mutations in the PLEC1 gene encoding plectin

Mutations in the PLEC1 gene encoding plectin have been reported in neonatal epidermolysis bullosa simplex with muscular dystrophy of later-onset (EBS-MD). A neuromuscular transmission defect has been reported in one previous patient. We report a boy presenting from birth with features of a congenital muscular dystrophy and late-onset myasthenic symptoms. Repetitive nerve stimulation showed significant decrement, and strength improved with pyridostigmine. Subtle blistering noticed only retrospectively prompted further genetic testing, revealing recessive PLEC1 mutations. We conclude that PLEC1 should be considered in the differential diagnosis of congenital muscular dystrophies and myasthenic syndromes, even in the absence of prominent skin involvement.

Identification of the cytolinker protein plectin in neuronal cells - expression of a rodless isoform in neurons of the rat superior cervical ganglion

Plectin, a large (> 500 kDa) dumbbell-shaped cytolinker protein plays an important role in the organization of the cytoskeletal network and the maintenance of cell integrity in a wide variety of tissues and cell types. Earlier experiments revealed the presence of plectin in the central nervous system, whereas the expression in the peripheral nervous system remained unclear. Our results obtained with reverse transcriptase-PCR (RT-PCR) provide evidence that plectin is expressed in structures of the rat peripheral nervous system. In addition to well-characterized plectin transcripts we were able to reveal novel splicing variants affecting the region coding for the central rod domain. Previous studies report a high, but tissue-specific variability of the N-terminal domain of plectin due to alternatively spliced first coding exons and the optionally spliced small exons 2 alpha and 3 alpha. We demonstrate for the first time, using single-cell RT-PCR and immunocytochemistry, that plectin is expressed in neurons of the rat superior cervical ganglion (SCG). Plectin transcripts of single SCG neurons, starting with exon 1c as the first coding exon, contain the optionally spliced exon 2 alpha but lack exon 31. These data therefore suggest that plectin is expressed in rat SCG neurons as a rodless isoform with the molecular mass of 390 kDa.

Plectin regulates the organization of glial fibrillary acidic protein in Alexander disease

Alexander disease (AxD) is a rare but fatal neurological disorder caused by mutations in the astrocyte-specific intermediate filament protein glial fibrillary acidic protein (GFAP). Histologically, AxD is characterized by cytoplasmic inclusion bodies called Rosenthal fibers (RFs), which contain GFAP, small heat shock proteins, and other undefined components. Here, we describe the expression of the cytoskeletal linker protein plectin in the AxD brain. RFs displayed positive immunostaining for plectin and GFAP, both of which were increased in the AxD brain. Co-localization, co-immunoprecipitation, and in vitro overlay analyses demonstrated direct interaction of plectin and GFAP. GFAP with the most common AxD mutation, R239C (RC GFAP), mainly formed abnormal aggregates in human primary astrocytes and murine plectin-deficient fibroblasts. Transient transfection of full-length plectin cDNA converted these aggregates to thin filaments, which exhibited diffuse cytoplasmic distribution. Compared to wild-type GFAP expression, RC GFAP expression lowered plectin levels in astrocytoma-derived stable transfectants and plectin-positive fibroblasts. A much higher proportion of total GFAP was found in the Triton X-insoluble fraction of plectin-deficient fibroblasts than in wild-type fibroblasts. Taken together, our results suggest that insufficient amounts of plectin, due to RC GFAP expression, promote GFAP aggregation and RF formation in AxD.

Plectin deficient epidermolysis bullosa simplex with 27-year-history of muscular dystrophy

BACKGROUND

Epidermolysis bullosa simplex associated with muscular dystrophy is caused by plectin deficiency.

OBJECTIVE

To report clinical, immunohistochemical, ultrastructural and molecular features of a 52-year-old Japanese patient affected with this disease, whose muscular disease had been followed-up for 27 years.

METHODS

We performed histopathological study, immunofluorescence, electron microscopic study and mutation detection analysis for plectin.

RESULTS

The patient developed blisters and erosions followed by nail deformity on the traumatized regions from birth. The skin lesions were continuously developed to date. The histopathological study showed subepidermal blister. Electron microscopic study showed blister formation inside the basal cells at the level just above the attachment plaque of hemidesmosome. Immunofluorescence showed complete loss of staining to plectin. The mutation analysis using protein truncation test and DNA sequencing revealed a C-to-T transition at nucleotide position 7006 of the plectin cDNA sequence, which lead a novel homozygous nonsense mutation (R2319X).

CONCLUSION

From the above results, the diagnosis of epidermolysis bullosa simplex associated with muscular dystrophy was made. Slight muscular dystrophy was noticed at the age of 25 years. The muscular dystrophy gradually progressed and she could not walk at the age of 46 years. However, she can still breathe and swallow by herself. This is the patient of this disease with the longest follow-up, and may indicate the slow progress of muscular condition of this disease.

Skin lesions in the neonate

Neonatal skin provides physical protection and assists in fluid balance,immunosurveillance, and thermoregulation; thus, playing a vital role in the newborn's transition from an aqueous to an air-dominant environment. Worried parents often seek medical attention from their child's physician regarding skin lesions. Thus,a working knowledge of both normal and abnormal cutaneous lesions of the neonate is required to properly address these issues. In this article, the authors briefly discuss transient benign lesions,pustular and vesicular infections, "birthmarks" (vascular and pigmentary lesions), common congenital abnormalities, select blistering disorders, and various other skin conditions.

Cultured keratinocytes from plectin/HD1-deficient epidermolysis bullosa simplex showed altered ability of adhesion to the matrix

Epidermolysis bullosa simplex associated with late onset of muscular dystrophy has been found to show defective expression of plectin, an intracytoplasmic protein in hemidesmosomes. In this report, we examined ability of cell-to-matrix attachment of cultured keratinocytes derived from a case with this disease by various cell biological methods, and compared it to that of normal keratinocytes. In cell adhesion assay, the patient keratinocytes showed more prominent short-time cell adhesion than normal keratinocytes. In contrast, the patient keratinocytes could be detached much easier than normal keratinocytes in cell detachment assay by treatment with dispase. In phagokinetic track assay, no apparent difference of cell migration was observed between the patient and normal keratinocytes. These results indicate that plectin-deficiency may up-regulate short-term cell contact and reduce stable cell-matrix adhesion at the epidermal basement membrane zone.

Mutation reports: epidermolysis bullosa simplex associated with severe mucous membrane involvement and novel mutations in the plectin gene

We report a novel case of epidermolysis bullosa simplex with severe mucous membrane involvement and mutations in the plectin gene (PLEC1). The patient suffered from extensive blistering of the skin and oral and laryngeal mucous membranes. Electron microscopy of a lesional skin biopsy showed cleft formation within the basal cell layer of the epidermis. Antigen mapping displayed entirely negative staining for plectin, a large (>500 kDa) multifunctional adhesion protein present in hemidesmosomes of the basal keratinocytes. Mutation analysis revealed compound heterozygous, previously undisclosed nonsense mutations, Q1713X and R2351X, of paternal and maternal origin, respectively, within exon 32 of PLEC1. Based on earlier reports, plectin deficiency is associated with late onset muscular dystrophy in patients with epidermolysis bullosa. No signs of muscle weakness have been observed during the 4 y follow-up of our patient. This case illustrates the fact that molecular pathological analyses have prognostic implications in identification and evaluation of patients who appear to be at risk for development of muscular dystrophy later in life.

Partial dominance of a keratin 14 mutation in epidermolysis bullosa simplex--increased severity of disease in a homozygote

Epidermolysis bullosa simplex is a disease in which keratin gene mutations cause the production of defective intermediate filaments, which leads in turn to epidermal basal cell fragility and blistering. The inheritance in nearly all kindreds is autosomal dominant, most kindreds have missense mutations, and the encoded proteins appear to exert a dominant negative function. One previously reported patient with generalized blistering had a fully dominant mutation of keratin 5; in that kindred a homozygote was affected no more severely than the heterozygotes. By contrast we report here a keratin 14 mutation that causes blistering limited to the hands and feet in heterozygotes, but homozygotes have more severe, widespread blistering of the skin and mucous membranes. Thus keratin gene mutations may be not only fully recessive or fully dominant but also partially dominant as well.

A homozygous nonsense mutation in the PLEC1 gene in patients with epidermolysis bullosa simplex with muscular dystrophy

Plectin is a widely expressed cytomatrix component involved in the attachment of the cytoskeleton to the plasma membrane. We have recently reported that the skin and muscles of three patients affected by epidermolysis bullosa simplex with muscular dystrophy (MD-EBS), a genetic disorder characterized by skin blistering associated with muscle involvement, are not reactive with antibodies specific to plectin. We demonstrated that in the skin, lack of plectin leads to failure of keratin filaments to connect to the plasma membrane via the hemidesmosomes, whereas in the muscle the deficient expression of the molecule correlates with an aberrant localization of desmin in the muscle fibers. In this study we demonstrate that in a MD-EBS kindred with two affected members, the disease results from a homozygous nonsense mutation in the plectin (PLEC1) gene leading to a premature stop codon (CGA to TGA) and decay of the aberrant plectin messenger RNA. The segregation of the mutated allele implicates the mutation in the pathology of the disorder. These results confirm the critical role of plectin in providing cell resistance to mechanical stresses both in the skin and the muscle.

Plectin and human genetic disorders of the skin and muscle. The paradigm of epidermolysis bullosa with muscular dystrophy

Recent progress in understanding the molecular organization of the cutaneous basement membrane zone (BMZ) has revealed an intricate network of structural proteins necessary for stable association of the epidermis to the underlying dermis. Molecular genetics of the cutaneous BMZ has also revealed that defects in as many as nine distinct genes within the dermal-epidermal junction which result in different forms of epidermolysis bullosa (EB), a group of heritable mechano-bullous disorders. We have recently demonstrated that a variant of EB associated with late-onset development of muscular dystrophy (EB-MD, MIM no. 226670) results from mutations in the gene encoding plectin (PLEC1), a cytoskeleton associated attachment protein present in the hemidesmosomal inner plaque and the sarcolemma of the muscle. Consequently, mutations in this multi-functional gene/protein system can result in phenotypic manifestations of EB-MD both in the skin and the muscle. In this overview, we will summarize the domain organization of plectin and the structure of the corresponding gene (PLEC1), as well as the genetic basis of EB-MD in families studied thus far. Elucidation of the molecular basis of this subtype of EB adds to our understanding of the structural and functional complexity of the cutaneous BMZ.

Loss of plectin causes epidermolysis bullosa with muscular dystrophy: cDNA cloning and genomic organization

Plectin is a widely expressed high molecular weight protein that is involved in cytoskeleton-membrane attachment in epithelial cells, muscle, and other tissues. The human autosomal recessive disorder epidermolysis bullosa with muscular dystrophy (MD-EBS) shows epidermal blister formation at the level of the hemidesmosome and is associated with a myopathy of unknown etiology. Here, plectin was found to be absent in skin and cultured keratinocytes from an MD-EBS patient by immunofluorescence and immunoprecipitation, suggesting that plectin is a candidate gene/protein system for MD-EBS mutation. The 14800-bp human plectin cDNA was cloned and sequenced. The predicted 518-kD polypeptide has homology to the actin-binding domain of the dystrophin family at the amino terminus, a central rod domain, and homology to the intermediate filament-associated protein desmoplakin at the carboxyl terminus. The corresponding human gene (PLEC1), consisting of 33 exons spanning >26 kb of genomic DNA was cloned, sequenced, and mapped to chromosomal band 8q24. Homozygosity by descent was observed in the consanguineous MD-EBS family with intragenic plectin polymorphisms. Direct sequencing of PCR-amplified plectin cDNA from the patient's keratinocytes revealed a homozygous 8-bp deletion in exon 32 causing a frameshift and a premature termination codon 42 bp downstream. The clinically unaffected parents of the proband were found to be heterozygous carriers of the mutation. These results establish the molecular basis of MD-EBS in this family and clearly demonstrate the important structural role for plectin in cytoskeleton-membrane adherence in both skin and muscle.

Management of patients with epidermolysis bullosa

Epidermolysis bullosa is a group of systemic disorders whose management requires familiarity with its many extracutaneous complications. These include gastrointestinal, ophthalmologic, laryngeal, dental, and hematologic problems. This article reviews wound care and management of systemic complications seen in patients with epidermolysis bullosa.

Molecular complexity of the cutaneous basement membrane zone. Revelations from the paradigms of epidermolysis bullosa

Spectacular success has recently been made towards elucidation of the molecular basis of various forms of epidermolysis bullosa (EB), a group of heritable blistering skin diseases. The information derived from these studies has already had a profound impact in terms of precise diagnosis and classification, early prenatal prediction of the phenotype and genetic counseling in families at risk for recurrence. This review highlights recent progress made in defining the molecular basis of junctional and dystrophic forms of EB and the genotype/phenotype relationships established from these studies. Extensive molecular studies, such as the ones captured in this review, form a foundation for the rational design of gene therapies to counteract these conditions in the future.

Anesthetic management in epidermolysis bullosa: review of 129 anesthetic episodes in 32 patients

BACKGROUND

Anesthetic and monitoring instrumentations such as endotracheal intubation may cause skin and mucosal damage with potentially serious consequences in patients with epidermolysis bullosa (EB).

OBJECTIVE

This study defines the risks of skin and mucosal damage from anesthetic and monitoring techniques in patients with EB and formulates management guidelines.

METHODS

We retrospectively analyzed the outcome of 129 anesthetic episodes in 32 patients with various types of EB.

RESULTS

Serious complications did not occur in any patient with EB from the use of endotracheal intubation, face mask, nerve blocks, local anesthetics, and intravenous or intramuscular anesthetic agents.

CONCLUSION

With appropriate precautions, patients with EB can undergo standard anesthetic techniques with only minor and infrequent complications.