RESUMO
Obesity is characterized by an expansion of white adipose tissue (WAT) mass, which mainly consists of adipocytes. During the commitment and differentiation of adipocytes, PPARγ functions as a key transcriptional factor for adipogenesis, and is associated with its suppressive coregulator, TAZ. Previous studies have shown the importance of TAZ in adipogenesis using an in vitro model; however, the understanding of its role in adipogenesis in vivo remains limited. Here, we report a unique obese mouse model that is associated with TAZ downregulation, which arose from the overexpression of Yap, a Taz paralog. YAP activation facilitated Hippo signaling feedback, which induced a compensatory reduction in YAP, subsequently neutralizing its functional activity. This feedback also induced TAZ suppression and exclusion from the nucleus. In Yap transgenic mice, TAZ downregulation in adipose stem cells activated PPARγ, leading to their differentiation into mature adipocytes and consequently increased adipose tissue. These results highlight the in vivo necessity of TAZ for adipocyte commitment and differentiation, which could provide insight into anti-obesity therapeutics.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Obesidade/metabolismo , Fosfoproteínas/genética , Fatores de Transcrição/genética , Adipogenia , Animais , Proteínas de Ciclo Celular , Diferenciação Celular , Regulação para Baixo , Camundongos , Camundongos Transgênicos , PPAR gama/fisiologia , Células-Tronco/citologia , Transativadores , Proteínas de Sinalização YAPRESUMO
The internal organs of vertebrates show distinctive left-right asymmetry. Leftward extracellular fluid flow at the node (nodal flow), which is generated by the rotational movement of node cilia, is essential for left-right patterning in the mouse and other vertebrates. However, the identity of the pathways by which nodal flow is interpreted remains controversial as the molecular sensors of this process are unknown. In the current study, we show that the medaka left-right mutant abecobe (abc) is defective for left-right asymmetric expression of southpaw, lefty and charon, but not for nodal flow. We identify the abc gene as pkd1l1, the expression of which is confined to Kupffer's vesicle (KV, an organ equivalent to the node). Pkd1l1 can interact and interdependently colocalize with Pkd2 at the cilia in KV. We further demonstrate that all KV cilia contain Pkd1l1 and Pkd2 and left-right dynein, and that they are motile. These results suggest that Pkd1l1 and Pkd2 form a complex that functions as the nodal flow sensor in the motile cilia of the medaka KV. We propose a new model for the role of cilia in left-right patterning in which the KV cilia have a dual function: to generate nodal flow and to interpret it through Pkd1l1-Pkd2 complexes.
Assuntos
Padronização Corporal/fisiologia , Cílios/metabolismo , Proteínas de Membrana/metabolismo , Proteínas de Membrana/fisiologia , Canais de Cátion TRPP/metabolismo , Canais de Cátion TRPP/fisiologia , Animais , Animais Geneticamente Modificados , Padronização Corporal/genética , Células Cultivadas , Cílios/genética , Cílios/fisiologia , Embrião não Mamífero , Regulação da Expressão Gênica no Desenvolvimento , Humanos , Proteínas de Membrana/genética , Movimento/fisiologia , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo , Complexos Multiproteicos/fisiologia , Oryzias/embriologia , Oryzias/genética , Oryzias/metabolismo , Oryzias/fisiologia , Ligação Proteica/fisiologia , Canais de Cátion TRPP/genética , TransfecçãoRESUMO
Cilia and flagella are highly conserved organelles that have diverse motility and sensory functions. Motility defects in cilia and flagella result in primary ciliary dyskinesia (PCD). We isolated a novel medaka PCD mutant, jaodori (joi). Positional cloning showed that axonemal dynein intermediate chain 2 (dnai2) is responsible for joi. The joi mutation was caused by genomic insertion of the medaka transposon, Tol1. In the joi mutant, cilia in Kupffer's vesicle (KV), an organ functionally equivalent to the mouse node in terms of left-right (LR) specification, are generated but their motility is disrupted, resulting in a LR defect. Ultrastructural analysis revealed severe reduction in the outer dynein arms in KV cilia of joi mutants. We also found the other dnai2 gene in the medaka genome. These two dnai2 genes function either redundantly or distinctly in tissues possessing motile cilia.
Assuntos
Dineínas do Axonema/genética , Cílios/metabolismo , Proteínas de Peixes/genética , Síndrome de Kartagener/genética , Movimento/fisiologia , Mutação/genética , Oryzias/genética , Animais , Dineínas do Axonema/metabolismo , Sequência de Bases , Biomarcadores/metabolismo , Padronização Corporal , Cílios/patologia , Análise Mutacional de DNA , Embrião não Mamífero/anormalidades , Embrião não Mamífero/metabolismo , Embrião não Mamífero/patologia , Regulação da Expressão Gênica no Desenvolvimento , Síndrome de Kartagener/patologia , Dados de Sequência Molecular , Especificidade de Órgãos , Oryzias/embriologia , Fenótipo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reologia , CaudaRESUMO
Ciliary defects lead to various diseases, such as primary ciliary dyskinesia (PCD) and polycystic kidney disease (PKD). We isolated a medaka mutant mii, which exhibits defects in the left-right (LR) polarity of organs, and found that mii encodes dynein axonemal intermediate chain 2a (dnai2a). Ortholog mutations were recently reported to cause PCD in humans. mii mutant embryos exhibited loss of nodal flow in Kupffer's Vesicle (KV), which is equivalent to the mammalian node, and abnormal expression of the left-specific gene. KV cilia in the mii mutant were defective in their outer dynein arms (ODAs), indicating that Dnai2a is required for ODA formation in KV cilia. While the mii mutant retained motility of the renal cilia and failed to show PKD, the loss of dnai2a and another dnai2 ortholog dnai2b led to PKD. These findings demonstrate that Dnai2 proteins control LR polarity and kidney formation through regulation of ciliary motility.
