The mammalian core Hippo signaling components include Ste20 family kinases Mst1 (604965) and Mst2 (605030), which are homologous to Drosophila Hippo. To determine whether Hippo signaling controls mammalian heart size, Heallen et al. (2011) inactivated Hippo pathway components (e.g., SAV) in the developing mouse heart. Hippo-deficient embryos had overgrown hearts with elevated cardiomyocyte proliferation. Gene expression profiling and chromatin immunoprecipitation revealed that Hippo signaling negatively regulates a subset of Wnt (see 606359) target genes. Genetic interaction studies indicated that beta-catenin (116806) heterozygosity suppressed the Hippo cardiomyocyte overgrowth phenotype. Furthermore, the Hippo effector Yap (606608) interacts with beta-catenin on Sox2 (184429) and Snai2 (602150) genes.
NCBI Summary:
WW domain-containing proteins are found in all eukaryotes and play an important role in the regulation of a wide variety of cellular functions such as protein degradation, transcription, and RNA splicing. This gene encodes a protein with two WW domains, a SARAH domain, and a coiled-coil region and is ubiquitously expressed in adult tissues. This protein binds to MST1 (mammalian sterile 20-like kinase 1) and promotes MST1-induced apoptosis. It has also been shown to bind to HAX1 (hematopoietic cell-specific protein 1 (HS1)-associated protein X-1) and to attenuate the anti-apoptotic effects of HAX1. Studies in human and mouse suggest this gene acts as a tumor suppressor. [provided by RefSeq, Aug 2012]
General function
Intracellular signaling cascade, Enzyme
Comment
Hippo pathway deficiency reverses systolic heart failure after infarction. Leach JP et al. (2017) Mammalian organs vary widely in regenerative capacity. Poorly regenerative organs, such as the heart are particularly vulnerable to organ failure. Once established, heart failure commonly results in mortality. The Hippo pathway, a kinase cascade that prevents adult cardiomyocyte proliferation and regeneration, is upregulated in human heart failure. Here we show that deletion of the Hippo pathway component Salvador (Salv) in mouse hearts with established ischaemic heart failure after myocardial infarction induces a reparative genetic program with increased scar border vascularity, reduced fibrosis, and recovery of pumping function compared with controls. Using translating ribosomal affinity purification, we isolate cardiomyocyte-specific translating messenger RNA. Hippo-deficient cardiomyocytes have increased expression of proliferative genes and stress response genes, such as the mitochondrial quality control gene, Park2. Genetic studies indicate that Park2 is essential for heart repair, suggesting a requirement for mitochondrial quality control in regenerating myocardium. Gene therapy with a virus encoding Salv short hairpin RNA improves heart function when delivered at the time of infarct or after ischaemic heart failure following myocardial infarction was established. Our findings indicate that the failing heart has a previously unrecognized reparative capacity involving more than cardiomyocyte renewal.//////////////////
Hippo signaling disruption and Akt stimulation of ovarian follicles for infertility treatment. Kawamura K 2013 et al.
Primary ovarian insufficiency (POI) and polycystic ovarian syndrome are ovarian diseases causing infertility. Although there is no effective treatment for POI, therapies for polycystic ovarian syndrome include ovarian wedge resection or laser drilling to induce follicle growth. Underlying mechanisms for these disruptive procedures are unclear. Here, we explored the role of the conserved Hippo signaling pathway that serves to maintain optimal size across organs and species. We found that fragmentation of murine ovaries promoted actin polymerization and disrupted ovarian Hippo signaling, leading to increased expression of downstream growth factors, promotion of follicle growth, and the generation of mature oocytes. In addition to elucidating mechanisms underlying follicle growth elicited by ovarian damage, we further demonstrated additive follicle growth when ovarian fragmentation was combined with Akt stimulator treatments. We then extended results to treatment of infertility in POI patients via disruption of Hippo signaling by fragmenting ovaries followed by Akt stimulator treatment and autografting. We successfully promoted follicle growth, retrieved mature oocytes, and performed in vitro fertilization. Following embryo transfer, a healthy baby was delivered. The ovarian fragmentation-in vitro activation approach is not only valuable for treating infertility of POI patients but could also be useful for middle-aged infertile women, cancer patients undergoing sterilizing treatments, and other conditions of diminished ovarian reserve.
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The Hippo/MST Pathway Member SAV1 Plays a Suppressive Role in Development of the Prehierarchical Follicles in Hen Ovary. Lyu Z et al. (2016) The Hippo/MST signaling pathway is a critical player in controlling cell proliferation, self-renewal, differentiation, and apoptosis of most tissues and organs in diverse species. Previous studies have shown that Salvador homolog 1 (SAV1), a scaffolding protein which functions in the signaling system is expressed in mammalian ovaries and play a vital role in governing the follicle development. But the exact biological effects of chicken SAV1 in prehierarchical follicle development remain poorly understood. In the present study, we demonstrated that the SAV1 protein is predominantly expressed in the oocytes and undifferentiated granulosa cells in the various sized prehierarchical follicles of hen ovary, and the endogenous expression level of SAV1 mRNA appears down-regulated from the primordial follicles to the largest preovulatory follicles (F2-F1) by immunohistochemistry and real-time RT-PCR, respectively. Moreover, we found the intracellular SAV1 physically interacts with each of the pathway members, including STK4/MST1, STK3/MST2, LATS1 and MOB2 using western blotting. And SAV1 significantly promotes the phosphorylation of LATS1 induced by the kinase of STK4 or STK3 in vitro. Furthermore, SAV1 knockdown by small interfering RNA (siRNA) significantly increased proliferation of granulosa cells from the prehierarchical follicles (6-8 mm in diameter) by BrdU-incorporation assay, in which the expression levels of GDF9, StAR and FSHR mRNA was notably enhanced. Meanwhile, these findings were consolidated by the data of SAV1 overexpression. Taken together, the present results revealed that SAV1 can inhibit proliferation of the granulosa cells whereby the expression levels of GDF9, StAR and FSHR mRNA were negatively regulated. Accordingly, SAV1, as a member of the hippo/MST signaling pathway plays a suppressive role in ovarian follicle development by promoting phosphorylation and activity of the downstream LATS1, may consequently lead to prevention of the follicle selection during ovary development.//////////////////
Goes up during luteinization in a DNA microarray.