Collagen VII maintains proteostasis in dermal fibroblasts by scaffolding TANGO1 cargo.

Lack of type VII collagen (C7) disrupts cellular proteostasis yet the mechanism remains undescribed. By studying the relationship between C7 and the extracellular matrix (ECM)-associated proteins thrombospondin-1 (TSP1), type XII collagen (C12) and tissue transglutaminase (TGM2) in primary human dermal fibroblasts from multiple donors with or without the genetic disease recessive dystrophic epidermolysis bullosa (RDEB) (n=31), we demonstrate that secretion of each of these proteins is increased in the presence of C7. In dermal fibroblasts isolated from patients with RDEB, where C7 is absent or defective, association with the COPII outer coat protein SEC31 and ultimately secretion of each of these ECM-associated proteins is reduced and intracellular levels are increased. In RDEB fibroblasts, overall collagen secretion (as determined by the levels of hydroxyproline in the media) is unchanged while traffic from the ER to Golgi of TSP1, C12 and TGM2 occurs in a type I collagen (C1) dependent manner. In normal fibroblasts association of TSP1, C12 and TGM2 with the ER exit site transmembrane protein Transport ANd Golgi Organization-1 (TANGO1) as determined by proximity ligation assays, requires C7. In the absence of wild-type C7, or when ECM-associated proteins are overexpressed, C1 proximity and intracellular levels increase resulting in elevated cellular stress responses and elevated TGFß signaling. Collectively, these data demonstrate a role for C7 in loading COPII vesicle cargo and provides a mechanism for disrupted proteostasis, elevated cellular stress and increased TGFß signaling in patients with RDEB. Furthermore, our data point to a threshold of cargo loading that can be exceeded with increased protein levels leading to pathological outcomes in otherwise normal cells.

Ancestral patterns of recessive dystrophic epidermolysis bullosa mutations in Hispanic populations suggest sephardic ancestry.

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare genodermatosis caused by mutations in the gene coding for type VII collagen (COL7A1). More than 800 different pathogenic mutations in COL7A1 have been described to date; however, the ancestral origins of many of these mutations have not been precisely identified. In this study, 32 RDEB patient samples from the Southwestern United States, Mexico, Chile, and Colombia carrying common mutations in the COL7A1 gene were investigated to determine the origins of these mutations and the extent to which shared ancestry contributes to disease prevalence. The results demonstrate both shared European and American origins of RDEB mutations in distinct populations in the Americas and suggest the influence of Sephardic ancestry in at least some RDEB mutations of European origins. Knowledge of ancestry and relatedness among RDEB patient populations will be crucial for the development of future clinical trials and the advancement of novel therapeutics.

Novel IL31RA gene mutation and ancestral OSMR mutant allele in familial primary cutaneous amyloidosis.

Primary cutaneous amyloidosis (PCA) is an itchy skin disorder associated with amyloid deposits in the superficial dermis. The disease is relatively common in Southeast Asia and South America. Autosomal dominant PCA has been mapped earlier to 5p13.1-q11.2 and two pathogenic missense mutations in the OSMR gene, which encodes the interleukin-6 family cytokine receptor oncostatin M receptor beta (OSMRbeta), were reported. Here, we investigated 29 Taiwanese pedigrees with PCA and found that 10 had heterozygous missense mutations in OSMR: p.D647V (one family), p.P694L (six families), and p.K697T (three families). The mutation p.P694L was associated with the same haplotype in five of six families and also detected in two sporadic cases of PCA. Of the other 19 pedigrees that lacked OSMR pathology, 8 mapped to the same locus on chromosome 5, which also contains the genes for 3 other interleukin-6 family cytokine receptors, including interleukin-31 receptor A (IL31RA), which can form a heterodimeric receptor with OSMRbeta through interleukin-31 signaling. In one family, we identified a point mutation in the IL31RA gene, c.1562C>T that results in a missense mutation, p.S521F, which is also sited within a fibronectin type III-like repeat domain as observed in the OSMR mutations. PCA is a genetically heterogeneous disorder but our study shows that it can be caused by mutations in two biologically associated cytokine receptor genes located on chromosome 5. The identification of OSMR and IL31RA gene pathology provides an explanation of the high prevalence of PCA in Taiwan as well as new insight into disease pathophysiology.

Familial primary localized cutaneous amyloidosis in Brazil.

BACKGROUND: Macular and lichen amyloidosis are clinical variants of primary localized cutaneous amyloidosis (PLCA). Most cases are sporadic, but approximately 10% of cases may be familial. To our knowledge, the clinicopathologic and molecular features of such pedigrees, however, have not been studied in detail. OBSERVATIONS: We assessed 2 Brazilian families with either lichen-type (family 1 had 14 affected subjects) or macular-type (family 2 had 7 affected subjects) PLCA. Typically, in both pedigrees, the onset of symptoms was around puberty, and pruritus usually began on the lower legs. Findings from lesional skin biopsy samples from both families showed thioflavin T-positive material in the papillary dermis, which was more prominent in the lichen phenotype in family 1. Spontaneous improvement occurred in 3 subjects (from both families) after age 25 years. All affected individuals in family 1 had a heterozygous missense mutation in the OSMR gene (p.I691T), but no pathogenic mutation in OSMR was found in family 2. CONCLUSIONS: Familial PLCA shows autosomal dominant inheritance, but there is clinical and genetic heterogeneity and variable clinical penetrance. Demonstration of mutations in the OSMR gene provides new insight into mechanisms of itch and apoptosis in human skin.

Oncostatin M receptor-beta mutations underlie familial primary localized cutaneous amyloidosis.

Familial primary localized cutaneous amyloidosis (FPLCA) is an autosomal-dominant disorder associated with chronic skin itching and deposition of epidermal keratin filament-associated amyloid material in the dermis. FPLCA has been mapped to 5p13.1-q11.2, and by candidate gene analysis, we identified missense mutations in the OSMR gene, encoding oncostatin M-specific receptor beta (OSMRbeta), in three families. OSMRbeta is a component of the oncostatin M (OSM) type II receptor and the interleukin (IL)-31 receptor, and cultured FPLCA keratinocytes showed reduced activation of Jak/STAT, MAPK, and PI3K/Akt pathways after OSM or IL-31 cytokine stimulation. The pathogenic amino acid substitutions are located within the extracellular fibronectin type III-like (FNIII) domains, regions critical for receptor dimerization and function. OSM and IL-31 signaling have been implicated in keratinocyte cell proliferation, differentiation, apoptosis, and inflammation, but our OSMR data in individuals with FPLCA represent the first human germline mutations in this cytokine receptor complex and provide new insight into mechanisms of skin itching.

Advances in understanding the genetic basis of inherited single gene skin barrier disorders: new clues to key genes that may be involved in the pathogenesis of atopic dermatitis

Increasing knowledge of genomic DNA sequences and genetic databases has led to the characterization of the molecular basis of several inherited skin disorders. In this review we summarize some of the major recent discoveries that have been made in defining the pathogenic mutations that cause inherited disorders of the skin barrier leading to skin scaling or increased transepidermal water loss in either rare disorders (NethertonÆs syndrome or harlequin ichthyosis) or more common genodermatoses (ichthyosis vulgaris). These molecular breakthroughs have led to more accurate diagnoses, better genetic counselling and, where appropriate, the feasibility of DNA-based prenatal diagnosis, as well as the possibility of developing newer forms of treatment, including gene or protein therapy. Identifying the molecular basis of these conditions, especially ichthyosis vulgaris, has also provided dramatic new insight into the genetic abnormalities in the common disorder, atopic dermatitis. Thus research on the relatively rare single gene inherited skin disorders not only has benefits for patients and their families with these uncommon conditions but also has the potential to yield fresh and significant new information about very common skin diseases.

O maior conhecimento sobre as de sequências genômicas de DNA e as bases de dados genéticas levou à caracterização da base molecular de várias doenças hereditárias de pele. Nesta revisão resumimos algumas das descobertas recentes mais importantes quanto à definição das mutações patogênicas que causam as doenças hereditárias da barreira cutânea, levando a descamação ou aumento da perda hídrica transepidérmica, seja em doenças raras, (síndrome de Netherton ou ictiose em Arlequim) ou genodermatoses mais comuns (ictiose vulgar). Estas descobertas moleculares têm conduzido a diagnósticos mais acurados, melhor aconselhamento genético e, quando apropriado, à possibilidade de diagnóstico pré-natal baseado em DNA, assim como desenvolvimento de novas formas de tratamento, incluindo terapia gênica ou proteica. A identificação da base molecular destas doenças, especialmente ictiose vulgar, também propiciou importante entendimento das anormalidades genéticas de doença comum, a dermatite atópica. Assim, as pesquisas em doenças hereditárias monogênicas de pele relativamente raras não apenas trazem benefícios para os pacientes e familiares, mas também têm o potencial de trazer informações novas e significativas sobre doenças de pele muito comuns.

[2470insG, represents the commonest mutation in Mexican patients with dystrophic bullous epidermolysis. A study of 21 families]. / Las epidermolisis bullosas distróficas en México: 2470insG representa la mutación mas común en 21 familias.

BACKGROUND: Type VII collagen gene (COL 7 Al) mutations are the cause of dystrophic epidermolysis bullosa (DEB), but most mutations are specific to individual families and there is limited data on the nature of COL 7 Al mutations in certain ethnic populations. OBJECTIVE: To determine the molecular basis of DEB in Mexican patients and describe the most frequent mutation among this ethnic population. METHODS: Most subjects were approached at FUNDACION DEBRA MEXICO AC. Molecular analysis was performed by polymerase chain reaction (PCR) of genomic DNA using COL 7 A l-specific primers, heteroduplex analysis, and direct nucleotide sequencing. RESULTS: Fifty nine of 67 COL 7 Al possible mutations (88%) were identified; 36 individuals (31 recessive, five dominant) from 21 families. Recessive mutations included six frameshift mutations, four silent glycine substitutions and two splice site mutations. CONCLUSIONS: The present study informs a different kind of mutation observed in our patient population. Only two mutations informed in this study had been described earlier among another ethnic group. The most frequent mutation was 2470insG, affecting 21 (58.3%) out of 36 patients with DEB. These new data will be helpful in facilitating the accurate diagnosis of an DEB subtype, and will add further insight into the pathophysiology of this mechanobullous disease.

Las epidermolisis bullosas distróficas en México: 2470insG representa la mutación mas común en 21 familias / 2470insG, represents the commonest mutation in Mexican patients with dystrophic bullous epidermolysis: a study of 21 families

Antecedentes: Las epidermolisis ampollosas congénitas son enfermedades caracterizadas por ampollas en piel y mucosas al mínimo traumatismo. Son tres tipos: simple, unión y distrófica. Las epidermolisis ampollosas distróficas (EAD) son causadas por mutaciones en el gen COL 7Al que codifica la producción del colágeno tipo VII localizado en las fibrillas de anclaje de la unión dermoepidérmica. Objetivo: Determinar las bases moleculares de las EAD en México. Material y métodos: se analizaron ADN de 21 familias mexicanas con EAD. Se realizó reacción en cadena de la polimerasa, estudios de heteroduplex secuenciación de nucleótidos en ADN de los pacientes. Resultados: Se detectó 59 de 67 mutaciones en 36 pacientes. Se encontraron seis mutaciones de tipo codón de terminación prematuro, substitución de glicina, remoción de intrones de novo y depleción interna. La mutación comúnmente más encontrada fue la 2470insG, en 21 (58.35%) de 36 pacientes. Conclusiones: En pacientes con EAD, la mutación 2470insG es la más frecuente en México. Recomendamos analizar esta mutación a Mexicanos con EAD como primera opción. Estos resultados son útiles para clasificar los subtipos de EAD, dar asesoramiento genético, así como para entender un poco más la fisiopatología de esta enfermedad mecano ampollosa.

BACKGROUND: Type VII collagen gene (COL 7 Al) mutations are the cause of dystrophic epidermolysis bullosa (DEB), but most mutations are specific to individual families and there is limited data on the nature of COL 7 Al mutations in certain ethnic populations. OBJECTIVE: To determine the molecular basis of DEB in Mexican patients and describe the most frequent mutation among this ethnic population. METHODS: Most subjects were approached at FUNDACION DEBRA MEXICO AC. Molecular analysis was performed by polymerase chain reaction (PCR) of genomic DNA using COL 7 A l-specific primers, heteroduplex analysis, and direct nucleotide sequencing. RESULTS: Fifty nine of 67 COL 7 Al possible mutations (88%) were identified; 36 individuals (31 recessive, five dominant) from 21 families. Recessive mutations included six frameshift mutations, four silent glycine substitutions and two splice site mutations. CONCLUSIONS: The present study informs a different kind of mutation observed in our patient population. Only two mutations informed in this study had been described earlier among another ethnic group. The most frequent mutation was 2470insG, affecting 21 (58.3%) out of 36 patients with DEB. These new data will be helpful in facilitating the accurate diagnosis of an DEB subtype, and will add further insight into the pathophysiology of this mechanobullous disease.

Bone metabolism in children with epidermolysis bullosa.

We evaluated bone mineral density, vitamin D status, and biochemical markers of bone turnover in seven children with epidermolysis bullosa (EB). Four had osteopenia (Z score, -1.5) and four 25(OH) vitamin D <34 nmol/L (14 ng/mL), two of which had hyperparathyroidism. Children with severe EB should have evaluation of bone metabolism.