Protogenin in Mouse Embryo. Protogenin was detected in immersion fixed frozen sections of mouse embryo (E9.5) using Sheep Anti-Human Protogenin Antigen Affinity-purified Polyclonal Antibody (Catalog # AF6795) at 10 µg/mL overnight at 4 °C. Tissue was stained using the NorthernLights™ 493-conjugated Anti-Sheep IgG Secondary Antibody (green; Catalog # NL012) and counterstained with DAPI (blue). Specific staining was localized to nuclei in the neural tube. View our protocol for Fluorescent IHC Staining of Frozen Tissue Sections.