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1.
Development ; 145(11)2018 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-29769221

RESUMO

Little is known about how the sizes of animal tissues are controlled. A prominent example is somite size, which varies widely both within an individual and across species. Despite intense study of the segmentation clock governing the timing of somite generation, how it relates to somite size is poorly understood. Here, we examine somite scaling and find that somite size at specification scales with the length of the presomitic mesoderm (PSM) despite considerable variation in PSM length across developmental stages and in surgically size-reduced embryos. Measurement of clock period, axis elongation speed and clock gene expression patterns demonstrate that existing models fail to explain scaling. We posit a 'clock and scaled gradient' model, in which somite boundaries are set by a dynamically scaling signaling gradient across the PSM. Our model not only explains existing data, but also makes a unique prediction that we confirm experimentally - the formation of periodic 'echoes' in somite size following perturbation of the size of one somite. Our findings demonstrate that gradient scaling plays a central role in both progression and size control of somitogenesis.


Assuntos
Padronização Corporal/genética , Fase de Clivagem do Zigoto/fisiologia , Morfogênese/genética , Somitos/embriologia , Peixe-Zebra/embriologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/fisiologia , Tamanho Corporal/fisiologia , Fatores de Crescimento de Fibroblastos/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/genética , Modelos Teóricos , Tamanho do Órgão/fisiologia , Proteínas de Peixe-Zebra/fisiologia
2.
J Vis Exp ; (147)2019 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-31107459

RESUMO

In the developmental process, embryos exhibit a remarkable ability to match their body pattern to their body size; their body proportion is maintained even in embryos that are larger or smaller, within certain limits. Although this phenomenon of scaling has attracted attention for over a century, understanding the underlying mechanisms has been limited, owing in part to a lack of quantitative description of developmental dynamics in embryos of varied sizes. To overcome this limitation, we developed a new technique to surgically reduce the size of zebrafish embryos, which have great advantages for in vivo live imaging. We demonstrate that after balanced removal of cells and yolk at the blastula stage in separate steps, embryos can quickly recover under the right conditions and develop into smaller but otherwise normal embryos. Since this technique does not require special equipment, it is easily adaptable, and can be used to study a wide range of scaling problems, including robustness of morphogen mediated patterning.


Assuntos
Cirurgia Geral/métodos , Morfogênese/fisiologia , Peixe-Zebra/embriologia , Animais
3.
Science ; 360(6392): 981-987, 2018 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-29700229

RESUMO

High-throughput mapping of cellular differentiation hierarchies from single-cell data promises to empower systematic interrogations of vertebrate development and disease. Here we applied single-cell RNA sequencing to >92,000 cells from zebrafish embryos during the first day of development. Using a graph-based approach, we mapped a cell-state landscape that describes axis patterning, germ layer formation, and organogenesis. We tested how clonally related cells traverse this landscape by developing a transposon-based barcoding approach (TracerSeq) for reconstructing single-cell lineage histories. Clonally related cells were often restricted by the state landscape, including a case in which two independent lineages converge on similar fates. Cell fates remained restricted to this landscape in embryos lacking the chordin gene. We provide web-based resources for further analysis of the single-cell data.


Assuntos
Evolução Clonal/genética , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Peixe-Zebra/genética , Peixe-Zebra/embriologia , Peixe-Zebra/genética , Animais , Expressão Gênica , Glicoproteínas/genética , Peptídeos e Proteínas de Sinalização Intercelular/genética , Análise de Sequência de RNA/métodos , Análise de Célula Única/métodos
4.
Science ; 360(6386)2018 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-29674564

RESUMO

True physiological imaging of subcellular dynamics requires studying cells within their parent organisms, where all the environmental cues that drive gene expression, and hence the phenotypes that we actually observe, are present. A complete understanding also requires volumetric imaging of the cell and its surroundings at high spatiotemporal resolution, without inducing undue stress on either. We combined lattice light-sheet microscopy with adaptive optics to achieve, across large multicellular volumes, noninvasive aberration-free imaging of subcellular processes, including endocytosis, organelle remodeling during mitosis, and the migration of axons, immune cells, and metastatic cancer cells in vivo. The technology reveals the phenotypic diversity within cells across different organisms and developmental stages and may offer insights into how cells harness their intrinsic variability to adapt to different physiological environments.


Assuntos
Imageamento Tridimensional/métodos , Microscopia/métodos , Animais , Movimento Celular , Endocitose , Olho/ultraestrutura , Humanos , Mitose , Organelas , Análise de Célula Única , Peixe-Zebra
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