Comparative in situ hybridization histochemistry of APLP2, PCSK9, and sortilin mRNA expression. Comparative in situ hybridization localization of APLP2, PCSK9, and sortilin mRNA in cryostat sagittal sections of whole body postnatal mouse at post-partum day 10 (P10) mice (left panel, magnification ×2.4) and in the liver of adult mice (right panel, magnification ×4). A, x-ray film autoradiography showing widespread APLP2 expression pattern with high mRNA concentration in the eye retina and lens, brain, cerebellum, brown fat, liver, spleen, skin, small intestine, colon, and kidney. B, tissue-specific PCSK9 expression pattern with moderate to high level mRNA concentration in the eye retina inner nuclear layer, brain olfactory tract and cerebellum, spleen, liver, small intestine, and colon. C, tissue-specific sortilin expression pattern with moderate to high level mRNA concentration in the eye retina and lens, brain, cerebellum, skin, kidney medulla, colon, and small intestine. Abbreviations: BF, brown fat; BM, bone marrow; Br, brain; Cb, cerebellum; Co, colon; Ki, kidney; LG, lacrimal gland; Le, eye lens; Li, liver; Lu, lung; Mo, molars; OT, olfactory tract; Re, retina; SIn, small intestine; Sk, skin; Spl, spleen; St, stomach; Str, brain striatum; Th, thymus. *, indicates nonspecific staining of the aorta.