Detection and location of amphiregulin and Cripto‐1 expression in the developing postnatal mouse mammary gland

Abstract

Amphiregulin (Ar) and Cripto‐1 (Cr‐1) are growth promoting peptides that share amino acid sequence homology with epidermal growth factor (EGF). The present study examined Ar and Cr‐1 mRNA and protein expression during various stages of C57BL/6 mouse mammary morphogenesis. Reverse transciption‐polymerase chain reaction (RT‐PCR) was used to detect transcripts for Ar and Cr‐1 at all stages of mammary development. Immunocytochemical (ICC) localization demonstrated that in virgin 4‐week to mature 12‐week‐old mouse fourth inguinal mammary gland, Ar and Cr‐1 are expressed in the stromal cells, luminal epithelial cells, and myoepithelial cells of the branching ducts. Ar, and to lesser extent Cr‐1, were also found in the epithelial cap cells and in the luminal epithelial cells of the advancing terminal end bud (TEB) from virgin 4‐week and 6‐week‐old mice. Western blot analysis demonstrated that both Ar (28 and 26 kDa) and Cr‐1 (90, 67, 56, and 21 kDa) proteins are expressed in virgin, 13.5 day midpregnant and in the 14 day lactating mammary gland. In addition, Ar and Cr‐1 are associated with developing alveolar structures as determined by ICC. These results imply that together with EGF and transforming growth factor alpha (TGFα), Ar and Cr‐1 may play salient roles as modifiers in the morphogenesis and differentiation of the mammary gland.