Yaf2 Inhibits Caspase 8-mediated Apoptosis and Regulates Cell Survival during Zebrafish Embryogenesis

Abstract

Rybp (DEDAF) is a member of the Rybp/Yaf2 protein family and has been shown to encode pro-apoptotic functions and to be essential for mouse embryogenesis. The related Yaf2 protein has not been studied extensively at the cellular or organismal levels. Here we describe zebrafish yaf2 (zyaf2) and show that it is widely expressed during early embryogenesis, with subsequent enrichment of transcripts in the anterior head region. Depletion of zYaf2 during embryogenesis using specific morpholinos activates a wide-spread program of apoptosis and causes developmental arrest before the one somite stage. Partial depletion of Yaf2, achieved by injecting lower dosages of morpholino, circumvents the early arrest but leads to CNS degeneration associated with excessive apoptosis. These phenotypes can be rescued by co-injection of human YAF2 mRNA with the morpholinos or by treatment with a pan-caspase inhibitor or a caspase 8-specific inhibitor. Finally, the observed activation of caspase 8 in the morphants is in accord with the ability of Yaf2 to inhibit caspase 8-mediated apoptosis in cultured cells. Our findings implicate Yaf2 as a survival factor during early zebrafish development and organogenesis. This may suggest that Yaf2 and Rybp can encode opposing functions in the regulation of apoptosis.

RYBP Represses Endogenous Retroviruses and Preimplantation- and Germ Line-Specific Genes in Mouse Embryonic Stem Cells

“…The subset of these targets encoding developmental regulators with promoters enriched in H2A-monoubiquitylated nucleosomes is particularly insensitive to RYBP deficiency. We show that this is not due to compensation by its paralog Yaf2, an observation in line with previous reports showing distinctive functions for the two paralogs (48,52). Moreover, in RYBP-mutant ES cells, these promoters remain associated with PRC1 subunits.…”

Control of Programmed Cell Death During Zebrafish Embryonic Development

“…Furthermore, Caspase 8 was found to be a downstream effector of the Yaf2 apoptosis regulator, a zinc finger-containing protein shown to interact with the DED domain of Caspase 8 and to inhibit apoptosis. Injection of zebrafish embryos with yaf2 targeting morpholino did not affect gastrulation but compromised somitogenesis, which could be rescued by inhibiting Caspase 8 [12].…”

Rybp interacts with Hippi and enhances Hippi-mediated apoptosis

“…Whole cell lysates were prepared 48 h post-transfection and immunoprecipitated with 4 ll of Flag antibody (Sigma) as described in [23]. Cells were lysed in PG buffer (50 mM Tris pH 7.5, 150 mM NaCl, 0.5% NP40, 1 mM DTT, and 5 mM EDTA) with protease inhibitors (1 mM PMSF, 10 lg/ml aprotinin, and 10 lg/ml leupeptin).…”

“…Whole cell lysates were made from an aliquot of the transfected cells, and Western blotting was performed to ensure construct expression of the introduced constructs. The Acridine Orange/Ethidium Bromide morphological apoptosis assays were performed as described in [23] and [24].…”