RESUMEN
Remarkable progress has been made in understanding the molecular mechanisms underlying left-right asymmetry in vertebrate animal models but little is known on left-right axis formation in humans. Previously, we identified SESN1 (also known as PA26) as a candidate gene for heterotaxia by positional cloning of the breakpoint regions of a de novo translocation in a heterotaxia patient. In this study, we show by means of a zebrafish sesn1-knockdown model that Sesn1 is required for normal embryonic left-right determination. In this model, developmental defects and expression data of genes implicated in vertebrate left-right asymmetry indicate a role for Sesn1 in mediating Nodal signaling. In the lateral plate mesoderm, Nodal signaling plays a central role in left-right axis formation in vertebrates and is mediated by FoxH1 transcriptional induction. In line with this, we show that Sesn1 physically interacts with FoxH1 or a FoxH1-containing complex. Mutation analysis in a panel of 234 patients with isolated heterotaxia did not reveal mutations, indicating that these are only exceptional causes of human heterotaxia. In this study, we identify SESN1 as an indispensable gene for vertebrate left-right asymmetry and a new player in mediating Nodal signaling.
Asunto(s)
Tipificación del Cuerpo/genética , Regulación del Desarrollo de la Expresión Génica , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Transducción de Señal/genética , Factor de Crecimiento Transformador beta/metabolismo , Proteínas de Pez Cebra/metabolismo , Pez Cebra/embriología , Pez Cebra/genética , Animales , Animales Modificados Genéticamente , Embrión no Mamífero/embriología , Embrión no Mamífero/metabolismo , Factores de Transcripción Forkhead/genética , Factores de Transcripción Forkhead/metabolismo , Expresión Génica , Péptidos y Proteínas de Señalización Intracelular/deficiencia , Péptidos y Proteínas de Señalización Intracelular/genética , Mutación/genética , Proteína Nodal , Unión Proteica , Pez Cebra/metabolismo , Proteínas de Pez Cebra/deficiencia , Proteínas de Pez Cebra/genéticaRESUMEN
Glypican (GPC)-3 inhibits cell proliferation and regulates cell survival during development. This action is demonstrated by GPC3 loss-of-function mutations in humans and mice. Here, we show that the GPC3 core protein is processed by a furinlike convertase. This processing is essential for GPC3 modulating Wnt signaling and cell survival in vitro and for supporting embryonic cell movements in zebrafish. The processed GPC3 core protein is necessary and sufficient for the cell-specific induction of apoptosis, but in vitro effects on canonical and noncanonical Wnt signaling additionally require substitution of the core protein with heparan sulfate. Wnt 5A physically associates only with processed GPC3, and only a form of GPC3 that can be processed by a convertase is able to rescue epiboly and convergence/extension movements in GPC3 morphant embryos. Our data imply that the Simpson-Golabi-Behmel syndrome may in part result from a loss of GPC3 controls on Wnt signaling, and suggest that this function requires the cooperation of both the protein and the heparan sulfate moieties of the proteoglycan.