Diversity of mouse lipoxygenases: identification of a subfamily of epidermal isozymes exhibiting a differentiation-dependent mRNA expression pattern.

By using reverse transcription-polymerase chain reaction technology (RT-PCR) and Northern blot analysis, the tissue-specific mRNA expression patterns of seven mouse lipoxygenases (LOX)--including 5S-, 8S-, three isoforms of 12S-, 12R-LOX, and a LOX of an as-of-yet unknown specificity, epidermis-type LOX-3 (e-LOX-3)--were investigated in NMRI mice. Among the various tissues tested epidermis and forestomach were found to express the broadest spectrum of LOX. With the exception of 5S- and platelet-type 12S-LOX (p12S-LOX) the remaining LOX showed a preference to exclusive expression in stratifying epithelia of the mouse, in particular the integumental epidermis. The expression of the individual LOX in mouse epidermis was found to depend on the state of terminal differentiation of the keratinocytes. mRNA of epidermis-type 12S-LOX (e12S-LOX) was detected in all layers of neonatal and adult NMRI mouse skin, whereas expression of p12S-LOX, 12R-LOX, and e-LOX-3 was restricted to suprabasal epidermal layers of neonatal and adult mice. 8S-LOX mRNA showed a body-site-dependent expression in that it was detected in stratifying epithelia of footsole and forestomach but not in back skin epidermis. In the latter, 8S-LOX mRNA was strongly induced upon treatment with phorbol esters. With the exception of e12S-LOX and p12S-LOX, the isozymes that are preferentially expressed in stratifying epithelia are structurally related and may be grouped together into a distinct subgroup of epidermis-type LOX.