Localization of Apaf1 gene expression in the early
development of the mouse by means of in situ reverse
transcriptase-polymerase chain reaction. Apoptosis in UV-C light irradiated p53 wild-type, apaf-1 and p53
knockout mouse embryonic fibroblasts: Interplay of receptor and
mitochondrial pathway.
Muller M, Berger J, Gersdorff N,
Cecconi F,
Herken R, Quondamatteo F.
Department of Histology,
Apoptosis is an essential ubiquitous process that controls the duration of
the life span of cells, thus playing a crucial role in morphogenetic, histogenetic, and phylogenetic
developmental processes. Apaf1 (apoptosis protease activating factor 1) is
one of the central mediators of the intrinsic apoptotic pathway and a part
of the apoptosome, which activates procaspase-3
and promotes cell death. Gene knockout of Apaf1 in mice leads to late
embryonic lethality with malformations such as the persistence of interdigital webs and hyperplasia of brain and retina.
Therefore, Apaf1 is generally believed to play a crucial role in developmental
apoptosis and have a widespread expression. However, its pattern of
expression in early development remains unknown. To specify whether Apaf1
indeed plays this key role, we investigated the pattern of gene expression
for Apaf1 in mouse embryos on day 7, 9, and 12 of development. Our results
show, that gene expression for Apaf1 first occurs within the embryo between
day 7 and 9 of development, becoming more widespread toward day 12 and then
includes structures, such as yolk sac, mesenchyme,
cartilage, heart anlage, otic
vesicle, peridermis, and anlagen of the spinal
ganglia and vertebral bodies. Our results also show that gene expression
for Apaf1 is not ubiquitous in early mouse development. This finding
indicates that cell death processes are independent of or less dependent on
Apaf1 during this time. Of interest, an active gene expression for Apaf1 is
also present in organ anlagen such as heart or intestine, in which no
obvious phenotype is seen after Apaf1 deletion. This finding suggests a
possible role for Apaf1 in such anlagen as a putative alternative
compensatory pathway, which could be switched on in the case of defects in
the mediators that are normally involved in such organs. Copyright 2005
Wiley-Liss, Inc.
PMID: 16086359 [PubMed - in process]
Tomicic MT, Christmann
M, Kaina
B.
Department of Toxicology,
Mouse embryonic fibroblasts (MEFs) deficient for
the transcription factor p53 are hypersensitive to UV-C light. They also
show a reduced recovery from UV-C induced replication blockage and are
unable to repair UV-C photoproducts. In this study, we utilized wild-type
(wt), Apaf-1 deficient (apaf-1(-/-)) and p53 deficient (p53(-/-))
MEFs in order to elucidate the role of
non-repaired UV-C lesions in apoptotic signalling.
Corresponding with the cellular sensitivity determined by the WST assay, p53(-/-) cells displayed the highest level of apoptosis,
whereas wt cells showed moderate apoptosis after UV-C irradiation. Apaf1(-/-) cells were most resistant. In wt cells
apoptosis was executed both via the mitochondrial and the receptor-mediated
pathway, as shown by Bcl-2 decline, induction of fasR
and activation of c
]