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The c-Jun N-terminal kinases (JNKs) constitute one of the three major types of mitogen-activated protein kinases. Previous studies showed that JNK mediates multiple signaling transduction pathways implicated in cell proliferation, differentiation, inflammation, stress response and apoptosis in mammals. In the present study, we use goldfish as a model system and demonstrate that JNK kinases are necessary to promote embryonic survival and regulate eye development in vertebrates. During goldfish development, JNK1 and JNK2 are expressed at every stage from cleavage to hatching larvae. JNK3 is turned on at the gastrulation stage and then expressed at similar level to that of JNK2. JNK1 activity remains slightly fluctuated during different developmental stages. Inhibition of JNK activity caused massive apoptosis of blastula cells and significant death of goldfish embryos, which are associated with altered expression of the anti-apoptotic regulator, Mcl-1 and the proapoptotic regulator, Bak. These results provide novel information regarding the mechanisms by which JNKs promote embryonic survival. In addition, the embryos that survived inhibition of JNK activity displayed severe phenotype in the eye with clear microphthalmia and lens coloboma. To confirm that the observed phenotype is derived from JNK activity deficiency, we expressed JNK dominant negative mutant (DNM-JNK) in goldfish. Expression of DNM-JNK also caused similar phenotypes with altered expression of pax-6, Sox-2 and β-crystallin. Together, our results demonstrate that JNKs play important roles in promoting survival of vertebrate embryos and regulating development of vertebrate eye.

In response to changes in the external environment cells must initiate a coordinated program of gene expression for them to adapt. IEX-1 (immediate early response gene X-1) is precisely regulated by multiple transcription factors among which p53, NF-kappaB/rel, Sp1 and c-Myc play central roles, to ensure rapid and transient expression of IEX-1 in cells under a variety of stress conditions. Overexpression of IEX-1 renders some cells sensitive to apoptosis and accelerates cell cycle progression, but reduces proliferation of other cells, whereas disruption of IEX-1 expression is associated with decreases in both apoptosis and cell cycle progression. In sharp contrast to in vitro studies, in vivo constitutive expression of IEX-1 prevents activated T cells but not B cells from apoptosis, as shown using IEX-1-transgenic mice that target IEX-1 expression specifically to lymphocytes driven by the Emu enhancer. The animals developed a lupus-like disease and subsequently a high incidence of T cell lymphomas when they aged, due to insufficient apoptosis of T cells. These varied effects of IEX-1 on cell death and cell cycle progression in a cell-context dependent fashion implicate that IEX-1 is involved in more than one signaling pathway, understanding of which will certainly improve our knowledge with respect to cancer biology, cell death and cell cycle regulation.

Our previous studies demonstrated that upon activation, monocytes (Mo) were able to sensitize peripheral blood T (PBT) cells to apoptosis induced by treatment with PMA. However, it is unknown what gene products provide the death signal to the sensitized PBT cells and how activated Mo enable PBT cells to become susceptible to apoptosis. Here, we show that PBT cells, but not Mo, express functional Fas ligand upon treatment with PMA. Moreover, this Mo-dependent T cell apoptosis could be blocked by a Fas-Ig fusion protein, as well as by a nonlytic mAb against Fas molecule. These results strongly suggest involvement of Fas-Fas ligand interaction in the death of PBT cells. Unlike Fas-induced apoptosis, however, Mo-dependent T cell death was completely inhibited by overexpression of the Bcl-2 protein, and PMA alone was sufficient to trigger apoptosis in T cells when Mo were included in culture. Furthermore, anti-CD11a, anti-CD18, or anti-CD45/CD45RA mAbs; could prevent PBT cells from death triggered by PMA plus Mo, suggesting that these Ags participate in the apoptotic process. The participation of CD45RA in the death of PBT cells was further demonstrated by the observation that the J45.01 cell line, a CD45-deficient variant of Jurkat cells, did not undergo apoptosis by this Mo-dependent mechanism. When transfected with cDNA encoding CD45RA, J45.01 cells acquired apoptotic response to PMA stimulation in the presence of Mo to a similar, but lesser, degree than normal Jurkat cells.