RESUMEN
Fraser syndrome (FS) is a phenotypically variable, autosomal recessive disorder characterized by cryptophthalmus, cutaneous syndactyly, and other malformations resulting from mutations in FRAS1, FREM2, and GRIP1. Transient embryonic epidermal blistering causes the characteristic defects of the disorder. Fras1, Frem1, and Frem2 form the extracellular Fraser complex, which is believed to stabilize the basement membrane. However, several cases of FS could not be attributed to mutations in FRAS1, FREM2, or GRIP1, and FS displays high clinical variability, suggesting that there is an additional genetic, possibly modifying contribution to this disorder. An extracellular matrix protein containing VWA-like domains related to those in matrilins and collagens (AMACO), encoded by the VWA2 gene, has a very similar tissue distribution to the Fraser complex proteins in both mouse and zebrafish. Here, we show that AMACO deposition is lost in Fras1-deficient zebrafish and mice and that Fras1 and AMACO interact directly via their chondroitin sulfate proteoglycan (CSPG) and P2 domains. Knockdown of vwa2, which alone causes no phenotype, enhances the phenotype of hypomorphic Fras1 mutant zebrafish. Together, our data suggest that AMACO represents a member of the Fraser complex.
Asunto(s)
Membrana Basal/metabolismo , Proteínas de la Matriz Extracelular/genética , Proteínas de la Matriz Extracelular/metabolismo , Síndrome de Fraser/metabolismo , Proteínas de Pez Cebra/genética , Proteínas de Pez Cebra/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Animales , Biomarcadores de Tumor , Proteínas de Unión al Calcio , Matriz Extracelular/metabolismo , Femenino , Síndrome de Fraser/genética , Técnicas de Silenciamiento del Gen , Genes Recesivos , Masculino , Ratones , Ratones Noqueados , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Fragmentos de Péptidos/genética , Fragmentos de Péptidos/metabolismo , Fenotipo , Pez CebraRESUMEN
AMACO is a basement membrane associated protein that belongs to the VWA domain-containing protein superfamily. In addition to three VWA domains it contains two EGF-like domains, a cysteine-rich domain and a unique domain. Mouse AMACO has been partially characterized, but its function remains unknown. The zebrafish genome contains a single AMACO ortholog gene on chromosome 12. The domain structure is completely conserved between zebrafish and mouse and the first EGF-like domain, carrying a rare O-glucosylation and O-fucosylation consensus sequence, has the highest identity at the protein level. RT-PCR shows strongest AMACO expression during development, starting at the 5 somite stage. An antibody specific for zebrafish AMACO detected expression mainly in myosepta but also in skin, pronephros, pituitary gland, otic capsule and gills. In situ hybridization revealed that the muscle precursor cells of the somites express the protein that is laid down in the myosepta.