Lysyl oxidase and P-ATPase-7A expression during embryonic development in the rat

Lysyl oxidase activity is critical for the assembly and cross-linking of ex tracellular matrix proteins, such as collagen and elastin, Moreover, lysyl oxidase activity is sensitive to changes in copper status and genetic pertu rbations in copper transport, e.g., mutations in the P-type ATPase gene, AT P7A, associated with cellular copper transport. Lysyl oxidase may also serv e as a vehicle for copper transport from extracellular matrix cells. Herein , we demonstrate that sufficient lysyl oxidase functional activity is prese nt in the rat embryo at gestation day (GD) 9 to be detected in conventional enzyme assays. Estimation of embryonic lysyl oxidase functional activity, however, required partial purification in order to remove inhibitors. From GD 9 to GD 15, lysyl oxidase activity was relatively constant when expresse d per unit of protein or DNA, In contrast, the steady-state levels of lysyl oxidase and ATP7A mRNA, measured by RT-PCR and expressed relative to total RNA and cyclophilin mRNA, increased approximately fourfold from GD 9 to 15 . The pattern of temporal expression for ATP7A was consistent with its poss ible role in copper delivery to lysyl oxidase. (C) 2000 Academic Press.