RESUMEN
Wnt dependency and Lgr5 expression define multiple mammalian epithelial stem cell types. Under defined growth factor conditions, such adult stem cells (ASCs) grow as 3D organoids that recapitulate essential features of the pertinent epithelium. Here, we establish long-term expanding venom gland organoids from several snake species. The newly assembled transcriptome of the Cape coral snake reveals that organoids express high levels of toxin transcripts. Single-cell RNA sequencing of both organoids and primary tissue identifies distinct venom-expressing cell types as well as proliferative cells expressing homologs of known mammalian stem cell markers. A hard-wired regional heterogeneity in the expression of individual venom components is maintained in organoid cultures. Harvested venom peptides reflect crude venom composition and display biological activity. This study extends organoid technology to reptilian tissues and describes an experimentally tractable model system representing the snake venom gland.
Asunto(s)
Técnicas de Cultivo de Célula/métodos , Organoides/crecimiento & desarrollo , Venenos de Serpiente/metabolismo , Células Madre Adultas/metabolismo , Animales , Serpientes de Coral/metabolismo , Perfilación de la Expresión Génica/métodos , Organoides/metabolismo , Glándulas Salivales/metabolismo , Venenos de Serpiente/genética , Serpientes/genética , Serpientes/crecimiento & desarrollo , Células Madre/metabolismo , Toxinas Biológicas/genética , Transcriptoma/genéticaRESUMEN
Natural Somatostatin-14 is a small cyclic neuropeptide hormone with broad inhibitory effects on endocrine secretions. Here we show that natural Somatostatin-14 spontaneously self-assembles in water and in 150 mM NaCl into liquid crystalline nanofibrils, which follow characteristic structural features of amyloid fibrils. These non-covalent highly stable structures are based on the Somatostatin native backbone conformation and are formed under non-denaturing conditions. Our results support the hypothesis that self-assembly into amyloid fibrils is a generic property of the polypeptide chain under appropriate conditions. Given recent advances on the mechanisms of biological storage and sorting modes of peptide/protein hormones into secretory granules, we propose that Somatostatin-14 fibrillation could be relevant to the regulated secretion pathway of this neuropeptide hormone. Such a hypothesis is consistent with the emerging concept of the existence of non-disease related but functional amyloids.
Asunto(s)
Somatostatina/química , Amiloide/química , Cromatografía Líquida de Alta Presión/métodos , Rojo Congo/farmacología , Cristalización , Técnica de Fractura por Congelación , Hormonas/química , Hormonas/metabolismo , Humanos , Concentración de Iones de Hidrógeno , Cristales Líquidos , Microscopía , Microscopía Electrónica de Transmisión , Conformación Molecular , Nanopartículas/química , Hormonas Peptídicas/metabolismoRESUMEN
Nuclear envelope (NE) formation during cell division in multicellular organisms is a central yet poorly understood biological process. We report that the conserved nucleoporin Nup155 has an essential function in NE formation in Caenorhabditis elegans embryos and in Xenopus laevis egg extracts. In vivo depletion of Nup155 led to failure of nuclear lamina formation and defects in chromosome segregation at anaphase. Nup155 depletion inhibited accumulation of nucleoporins at the nuclear periphery, including those recruited to chromatin early in NE formation. Electron microscopy analysis revealed that Nup155 is also required for the formation of a continuous nuclear membrane in vivo and in vitro. Time-course experiments indicated that Nup155 is recruited to chromatin at the time of NE sealing, suggesting that nuclear pore complex assembly has to progress to a relatively late stage before NE membrane assembly occurs.