Topographie molekularer Faktoren der Keimzellentwicklung während der frühembryonalen Entwicklung des Kaninchens

Abstract

Key factors known to be involved in the foundation of the mammalian germ cell lineage have been described in the mouse only. To find mechanisms applicable to all mammals we analysed the temporal and spatial expression patterns of the transcriptional repressor PRDM1 (also known as BLIMP1) and of the signalling molecules BMP2 and BMP4 in finely staged perigastrulation rabbit embryos using whole-mount in situ hybridisation and high-resolution light microscopy of semithin sections. Similar to mouse, PRDM1 expression begins in the hypoblast at stage 1 and emerges in presumptive primordial germ cell (PGC) precursors localised in the posterior epiblast at stage 2. Following the onset of gastrulation PRDM1 is found in the mesoderm at positions resembling those identified by PGC specific antibodies. The bone morphogenetic proteins BMP2 and BMP4 are expressed in annular expression domains at the boundary of the embryonic disc, which - in contrast to mouse data, belong to intraembryonic tissue-layers. While BMP2 starts to be expressed at stage 1 in the hypoblast, BMP4 expression commences diffusely at stage 2 and from stage 3 onwards it is expressed peripherally in the hypoblast and epiblast showing the strongest expression in the mesoderm at the posterior pole of the embryo. These expression patterns suggest that function and chronology of factors involved in germ cell differentiation are similar in mouse and rabbit, whereas specific topographical patterns seen in the rabbit might be due to the divergent extraembryonic morphologies seen amongst mammalian embryos at perigastrulation stages.