Filiform Verrucous Sarcoidosis of the Face: A Warty Report.

Sarcoidosis is a multisystem inflammatory condition of unknown etiology. Variability in the cutaneous features of sarcoidosis is profound, and its protean manifestations affirm the condition's designation as one of dermatology's "great mimics." Cutaneous phenotypes of sarcoidosis include but are by no means limited to ichthyosiform, alopecic, erythrodermic, angiolupoid, and verrucous variants. Verrucous sarcoidosis is an exceedingly rare manifestation, and previous reports of this phenotype are limited to 15 cases. Most cases in the extant literature presented on the extremities, with clinical features mimicking that of a common wart, or as verrucous crateriform nodules, ulcers, or cutaneous horns. Only 4 previous reports of facial verrucous sarcoidosis exist in the literature, and to our knowledge, no prior cases have demonstrated filiform lesion morphology. Here we present a case of filiform verrucous sarcoidosis in an otherwise healthy, middle-aged African American man, devoid of internal organ involvement and limited to the face, histopathologically confirmed by the presence of characteristic granulomata devoid of lymphocytic infiltrates.

Hetero-trans-ß-glucanase, an enzyme unique to Equisetum plants, functionalizes cellulose.

Cell walls are metabolically active components of plant cells. They contain diverse enzymes, including transglycanases (endotransglycosylases), enzymes that 'cut and paste' certain structural polysaccharide molecules and thus potentially remodel the wall during growth and development. Known transglycanase activities modify several cell-wall polysaccharides (xyloglucan, mannans, mixed-linkage ß-glucan and xylans); however, no transglycanases were known to act on cellulose, the principal polysaccharide of biomass. We now report the discovery and characterization of hetero-trans-ß-glucanase (HTG), a transglycanase that targets cellulose, in horsetails (Equisetum spp., an early-diverging genus of monilophytes). HTG is also remarkable in predominantly catalysing hetero-transglycosylation: its preferred donor substrates (cellulose or mixed-linkage ß-glucan) differ qualitatively from its acceptor substrate (xyloglucan). HTG thus generates stable cellulose-xyloglucan and mixed-linkage ß-glucan-xyloglucan covalent bonds, and may therefore strengthen ageing Equisetum tissues by inter-linking different structural polysaccharides of the cell wall. 3D modelling suggests that only three key amino acid substitutions (Trp → Pro, Gly → Ser and Arg → Leu) are responsible for the evolution of HTG's unique specificity from the better-known xyloglucan-acting homo-transglycanases (xyloglucan endotransglucosylase/hydrolases; XTH). Among land plants, HTG appears to be confined to Equisetum, but its target polysaccharides are widespread, potentially offering opportunities for enhancing crop mechanical properties, such as wind resistance. In addition, by linking cellulose to xyloglucan fragments previously tagged with compounds such as dyes or indicators, HTG may be useful biotechnologically for manufacturing stably functionalized celluloses, thereby potentially offering a commercially valuable 'green' technology for industrially manipulating biomass.

Hetero-trans-ß-Glucanase Produces Cellulose-Xyloglucan Covalent Bonds in the Cell Walls of Structural Plant Tissues and Is Stimulated by Expansin.

Current cell-wall models assume no covalent bonding between cellulose and hemicelluloses such as xyloglucan or mixed-linkage ß-d-glucan (MLG). However, Equisetum hetero-trans-ß-glucanase (HTG) grafts cellulose onto xyloglucan oligosaccharides (XGOs) - and, we now show, xyloglucan polysaccharide - in vitro, thus exhibiting CXE (cellulose:xyloglucan endotransglucosylase) activity. In addition, HTG also catalyzes MLG-to-XGO bonding (MXE activity). In this study, we explored the CXE action of HTG in native plant cell walls and tested whether expansin exposes cellulose to HTG by disrupting hydrogen bonds. To quantify and visualize CXE and MXE action, we assayed the sequential release of HTG products from cell walls pre-labeled with substrate mimics. We demonstrated covalent cellulose-xyloglucan bonding in plant cell walls and showed that CXE and MXE action was up to 15% and 60% of total transglucanase action, respectively, and peaked in aging, strengthening tissues: CXE in xylem and cells bordering intercellular canals and MXE in sclerenchyma. Recombinant bacterial expansin (EXLX1) strongly augmented CXE activity in vitro. CXE and MXE action in living Equisetum structural tissues potentially strengthens stems, while expansin might augment the HTG-catalyzed CXE reaction, thereby allowing efficient CXE action in muro. Our methods will enable surveys for comparable reactions throughout the plant kingdom. Furthermore, engineering similar hetero-polymer formation into angiosperm crop plants may improve certain agronomic traits such as lodging tolerance.