MEIOC is expressed throughout most of meiotic prophase I in the male and female germline.

(A) Immunohistochemistry for MEIOC (brown) in adult testis, with hematoxylin counterstaining to enable identification of germ cell types by nuclear morphology [57]. Low magnification image shows MEIOC staining in the majority of meiotic cell populations. Background staining was also observed in mature sperm in center of the tubule. High magnification images show that MEIOC was detected in meiotic germ cells at preleptotene (pL), leptotene (L), zygotene (Z), and pachytene (P) stages; it was not detected in meiotic germ cells at diplotene (D) stage, in cells undergoing meiotic metaphase (MI), or in postmeiotic round spermatids (rs). Low magnification scale bar = 100 μm, high magnification scale bar = 10 μm. (B) Immunohistochemistry for STRA8 (brown) in adult testis, counterstained with hematoxylin. In contrast to MEIOC, STRA8 expression is limited to germ cells initiating meiosis (preleptotene and leptotene stages) as well as differentiating spermatogonia. Scale bar = 100 μm. (C) Immunofluorescence staining for MEIOC in ovary at E13.5, E14.5, E16.5, E18.5, P0, P2, P15, and adult (>8 weeks). Mouse Vasa Homolog (MVH) costaining identifies germ cells [58]. Nuclei stained by DAPI. MEIOC is detected in germ cells at all stages. From E13.5 to E18.5, corresponding to premeiotic to late pachytene stages, MEIOC is detected predominantly in cytoplasm. Towards the end of this period, MEIOC is detected in nucleus (arrowheads), and continues to be expressed in nuclei of germ cells at postnatal timepoints. Scale bar = 10 μm.