A) Sumo1 (i), Sumo2 (ii) and Sumo3 (iii) are differentially expressed during spermatogenesis. B) Sae1 (i), Sae2 (ii) and Ube2i (iii) exhibit similar expression patterns in mouse germ cells. C) Pias1 (i), Pias2 (ii), and Pias4 (iv) expression is highest in round spermatids whereas Pias3 (iii) expression is highest in leptotene/ zygotene spermatocytes. Relative quantification of each gene was determined in leptotene/ zygotene (L/Z), prepubertal pachytene (PP) and adult pachytene (P) spermatocytes, as well as in round spermatids (RS) using real-time RT-PCR. Expression was determined in triplicate in each of the three series of germ cells and normalized to 18S expression. For each gene, data are presented as the mean expression in 10 ng of RNA normalized to 18S expression. The p-value obtained for the analysis of variance is given in brackets under each gene name; expression levels in germ cell types not identified by the same letter are considered significantly different. Data reported as mean ± SEM; n= 3 enriched germ cell preparations.