RESUMO
Cells perceive their microenvironment through chemical and physical cues. However, how the mechanical signals are interpreted during embryonic tissue deformation to result in specific cell behaviors is largely unknown. The Yap/Taz family of transcriptional co-activators has emerged as an important regulator of tissue growth and regeneration, responding to physical cues from the extracellular matrix, and to cell shape and actomyosin cytoskeletal changes. In this study, we demonstrate the role of Yap/Taz-TEAD activity as a sensor of mechanical signals in the regulation of the progenitor behavior of boundary cells during zebrafish hindbrain compartmentalization. Monitoring of in vivo Yap/Taz activity during hindbrain segmentation indicated that boundary cells responded to mechanical cues in a cell-autonomous manner through Yap/Taz-TEAD activity. Cell-lineage analysis revealed that Yap/Taz-TEAD boundary cells decreased their proliferative activity when Yap/Taz-TEAD activity ceased, which preceded changes in their cell fate from proliferating progenitors to differentiated neurons. Functional experiments demonstrated the pivotal role of Yap/Taz-TEAD signaling in maintaining progenitor features in the hindbrain boundary cell population.
Assuntos
Divisão Celular/genética , Proteínas de Ligação a DNA/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/fisiologia , Proteínas Nucleares/fisiologia , Rombencéfalo/citologia , Rombencéfalo/embriologia , Células-Tronco/fisiologia , Transativadores/fisiologia , Fatores de Transcrição/fisiologia , Proteínas de Peixe-Zebra/fisiologia , Animais , Animais Geneticamente Modificados , Padronização Corporal/genética , Diferenciação Celular/genética , Movimento Celular/genética , Proteínas de Ligação a DNA/genética , Embrião não Mamífero , Peptídeos e Proteínas de Sinalização Intracelular/genética , Fenômenos Mecânicos , Mecanotransdução Celular/genética , Mecanotransdução Celular/fisiologia , Neurogênese/genética , Proteínas Nucleares/genética , Organogênese/genética , Rombencéfalo/metabolismo , Transdução de Sinais/genética , Células-Tronco/citologia , Fatores de Transcrição de Domínio TEA , Transativadores/genética , Fatores de Transcrição/genética , Proteínas com Motivo de Ligação a PDZ com Coativador Transcricional , Proteínas de Sinalização YAP , Peixe-Zebra/embriologia , Peixe-Zebra/genética , Proteínas de Peixe-Zebra/genéticaRESUMO
Developmental programs often rely on parallel morphogenetic mechanisms that guarantee precise tissue architecture. While redundancy constitutes an obvious selective advantage, little is known on how novel morphogenetic mechanisms emerge during evolution. In zebrafish, rhombomeric boundaries behave as an elastic barrier, preventing cell intermingling between adjacent compartments. Here, we identify the fundamental role of the small-GTPase Rac3b in actomyosin cable assembly at hindbrain boundaries. We show that the novel rac3b/rfng/sgca regulatory cluster, which is specifically expressed at the boundaries, emerged in the Ostariophysi superorder by chromosomal rearrangement that generated new cis-regulatory interactions. By combining 4C-seq, ATAC-seq, transgenesis, and CRISPR-induced deletions, we characterized this regulatory domain, identifying hindbrain boundary-specific cis-regulatory elements. Our results suggest that the capacity of boundaries to act as an elastic mesh for segregating rhombomeric cells evolved by cooption of critical genes to a novel regulatory block, refining the mechanisms for hindbrain segmentation.
Assuntos
Actomiosina/fisiologia , Regulação da Expressão Gênica no Desenvolvimento , Rombencéfalo/embriologia , Sarcoglicanas/fisiologia , Proteínas de Peixe-Zebra/fisiologia , Peixe-Zebra/embriologia , Proteínas rac de Ligação ao GTP/fisiologia , Animais , Padronização Corporal/genética , Sistemas CRISPR-Cas , Movimento Celular , Characidae/genética , Characidae/fisiologia , Cromatina/genética , Cromatina/ultraestrutura , Evolução Molecular , Peixes/classificação , Peixes/genética , Morfogênese , Mutagênese Sítio-Dirigida , Neurogênese , Filogenia , Sarcoglicanas/genética , Especificidade da Espécie , Peixe-Zebra/genética , Proteínas de Peixe-Zebra/genética , Proteínas rac de Ligação ao GTP/genéticaRESUMO
Establishing topographical maps of the external world is an important but still poorly understood feature of the vertebrate sensory system. To study the selective innervation of hindbrain regions by sensory afferents in the zebrafish embryo, we mapped the fine-grained topographical representation of sensory projections at the central level by specific photoconversion of sensory neurons. Sensory ganglia located anteriorly project more medially than do ganglia located posteriorly, and this relates to the order of sensory ganglion differentiation. By single-plane illumination microscopy (SPIM) in vivo imaging, we show that (1) the sequence of arrival of cranial ganglion inputs predicts the topography of central projections, and (2) delaminated neuroblasts differentiate in close contact with the neural tube, and they never loose contact with the neural ectoderm. Afferent entrance points are established by plasma membrane interactions between primary differentiated peripheral sensory neurons and neural tube border cells with the cooperation of neural crest cells. These first contacts remain during ensuing morphological growth to establish pioneer axons. Neural crest cells and repulsive slit1/robo2 signals then guide axons from later-differentiating neurons toward the neural tube. Thus, this study proposes a new model by which the topographical representation of cranial sensory ganglia is established by entrance order, with the entry points determined by cell contact between the sensory ganglion cell bodies and the hindbrain.