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Immunohistochemical Investigation of the Proliferation Activity in European Roe Deer (Capreolus capreolus) during Embryogenesis after Diapause by Using Ki-67

Abstract

The European roe deer (Capreolus capreolus) is the most common game in Germany with a high reproduction rate. Moreover, the roe deer has a special reproduction strategy, including an embryonic diapause, which is characterized by a reversible arrest of embryo development at the blastocyst stage. The roe deer embryo is in diapause for about five months. However, there is no complete arrest of embryonic growth, but mitotic activity is reduced to a minimal level. Diapause occurs without causing the embryonic death and after reactivation from diapause, the blastocyst elongates rapidly and embryonic growth is as fast as in other mammalian species. This leads to the conclusion, that embryonic cells after diapause exhibit a high proliferation rate. The Ki-67 protein is widely used as a marker for proliferating cells, because it is present in all active stages of cell division, but it is absent in resting cells. Here we describe the distribution of Ki-67 expression in European roe deer embryos during different stages of development by using immunohistochemistry. In general, the Ki-67 protein is expressed during embryogenesis in roe deer. The immunohistochemical staining of 16 Bouinfixed and paraffin-embedded embryos revealed, that the Ki-67 protein was detectable in early post-implantation stages of embryonic development. The distribution pattern and staining intensity of Ki-67 expressing cells varied in different organs of the embryo ranging from clear nuclear signals to no nuclear expression of Ki-67 antigen in active stages of cell division. The Ki-67 antigen was almost ubiquitously expressed in the larger embryos with high abundance in the liver. In contrast there were only weak or no staining signals in different organs of smaller embryos.

Miriam Beyes, Nelia Nause, Martina Bleyer, Franz-Josef Kaup and Stephan Neumann

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