RESUMO
Species-specific symmetry-breaking events at the left-right organizer (LRO) drive an evolutionarily-conserved cascade of gene expression in the lateral plate mesoderm that is required for the asymmetric positioning of organs within the body cavity. The mechanisms underlying the transfer of the left and right laterality information from the LRO to the lateral plate mesoderm are poorly understood. Here, we investigate the role of Claudin-10, a tight junction protein, in facilitating the transfer of left-right identity from the LRO to the lateral plate mesoderm. Claudin-10 is asymmetrically expressed on the right side of the chick LRO, Hensen's node. Gain- and loss-of-function studies demonstrated that right-sided expression of Claudin-10 is essential for normal rightward heart tube looping, the first morphological asymmetry during organogenesis. Manipulation of Claudin-10 expression did not perturb asymmetric gene expression at Hensen's node, but did disrupt asymmetric gene expression in the lateral plate mesoderm. Bilateral expression of Claudin-10 at Hensen's node prevented expression of Nodal, Lefty-2 and Pitx2c in the left lateral plate mesoderm, while morpholino knockdown of Claudin-10 inhibited expression of Snail1 in the right lateral plate mesoderm. We also determined that amino acids that are predicted to affect ion selectivity and protein interactions that bridge Claudin-10 to the actin cytoskeleton were essential for its left-right patterning function. Collectively, our data demonstrate a novel role for Claudin-10 during the transmission of laterality information from Hensen's node to both the left and right sides of the embryo and demonstrate that tight junctions have a critical role during the relay of left-right patterning cues from Hensen's node to the lateral plate mesoderm.
Assuntos
Padronização Corporal/genética , Claudinas/metabolismo , Mesoderma/metabolismo , Organizadores Embrionários/metabolismo , Junções Íntimas/metabolismo , Citoesqueleto de Actina/metabolismo , Animais , Embrião de Galinha , Claudinas/biossíntese , Claudinas/genética , Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Técnicas de Silenciamento de Genes , Coração/embriologia , Fatores de Determinação Direita-Esquerda/biossíntese , Morfolinos/genética , Proteína Nodal/biossíntese , Organogênese/genética , Transdução de Sinais/genética , Fatores de Transcrição da Família Snail , Fatores de Transcrição/biossíntese , Proteínas de Peixe-Zebra/biossínteseRESUMO
Recent advances in stem cell biology and tissue engineering have laid the groundwork for building complex tissues in a dish. We propose that these technologies are ready for a new challenge: recapitulating cardiac morphogenesis in vitro. In development, the heart transforms from a simple linear tube to a four-chambered organ through a complex process called looping. Here, we re-examine heart tube looping through the lens of an engineer and argue that the linear heart tube is an advantageous starting point for tissue engineering. We summarize the structures, signaling pathways, and stresses in the looping heart, and evaluate approaches that could be used to build a linear heart tube and guide it through the process of looping.