Embryonic expression of epithelial membrane protein 1 in early neurons

Epithelial membrane protein 1 (EMP1) is a member of the peripheral myelin p rotein 22 (PMP22) family. This family is best known for the crucial contrib ution of PMP22 to the development and maintenance of the peripheral nervous system (PNS). PMP22 is widely expressed, with highest levels in myelinatin g Schwann cells, and mutations affecting the PMP22 gene lead to PNS-restric ted neuropathies. We have investigated the spatio-temporal distribution of EMP1 and compared it to that of PMP22. We found that EMP1 and PMP22 mRNA ar e most conspicuously expressed in the prenatal mouse brain during neurogene sis. In the developing forebrain, we localized EMP1 mRNA and protein to the first set of neurons that are generated and leave the ventricular zone to form the preplate. Later in development, EMP1 was found in derivatives of t he preplate, the marginal zone and the subplate. Reduced expression was obs erved in the newly generated cortical plate neurons. in other parts of the developing CNS and PNS, EMP1 was also detected in early neurons and along t he initial fiber tracts. Furthermore, EMP1 was highly expressed by immature neurons in embryonal dorsal root ganglia-explant cultures and in neuroecto dermal differentiated P19 cells. While PMP22 functions mainly in Schwann ce ll growth and differentiation the spatio-temporal localization of EMP1 sugg ests a role in neuronal differentiation and neurite outgrowth. (C) 1999 Els evier Science B.V. All rights reserved.