Laminin expression in human fetal female and male gonads during first and second trimester. (A-C) Longitudinal sight of W9 (A, A’) and transversal sight of W10.5 (B, B’) old female gonad showed a distinctive expression pattern of laminin (green). (C, C’) Laminin (green) detected in the BM surrounding the developing seminiferous tubes in male gonad of first trimester (W10). (D-F) Laminin (green) expression in the BM of ovarian cords in female gonads (D, D’, E, E’) and in the BM of seminiferous tubes in male gonads (F, F’). Germ cells (red) were identified by the early marker OCT4 (nuclear) and late marker VASA (cytoplasmatic). The same secondary antibody was used to detect OCT4 and VASA, because the two proteins localize to different cellular compartments (nucleus and cytoplasm, respectively) and their expression can therefore be clearly distinguished. Red arrows point to the BM of the OSE, yellow arrows point to the BM of the primordial follicles, green arrows show the BM of the seminiferous tubes, and white arrows to the BM of blood vessels, and white asterisks marked individual germ cells expressing laminin. Note that occasional autofluorescent red blood cells are visible as red/orange cells inside blood vessels. Scalebars are 100 μm.