Reproduction Abstracts

Peroxisomes are cell organelles with important functions in the metabolism of lipids and reactive oxygen species. In germ cells, they have only recently been described by our groups. Their role for spermatogenesis has not been characterized in detail yet. We have established a mouse model with a conditional knockout of Pex13 in pre-meiotic germ cells to analyse the functions of peroxisomes for development and differentiation of male germ cells. The peroxisomal membrane protein Pex13 is part of the translocation machinery required for import of peroxisomal matrix proteins into the organelle. The inactivation of Pex13 leads to a biogenesis defect of peroxisomes with loss of all metabolic functions. Based on the Cre-lox technique, floxed Pex13 mice were crossed with transgenic mice expressing cre recombinase under control of the Stra8 promoter for inactivation of Pex13 in pre-meiotic germ cells. Histological analysis of knockout mice revealed a severe disturbance in germ cell differentiation with generation of multinucleated giant cells and post-meiotic arrest of spermatogenesis. Depending on their differentiation state, the multinucleated cells were TUNEL-positive. As a result of the peroxisomal dysfunction in germ cells we found a significant accumulation of lipid droplets within the germinal epithelium. On the ultrastructural level we could observe acrosome formation in multinucleated spermatids. However, several nuclei frequently shared one acrosome.