EXPRESSION AND ALTERNATIVE SPLICING OF THE NEURAL CELL-ADHESION MOLECULE NCAM IN HUMAN GRANULOSA-CELLS DURING LUTEINIZATION

Freshly aspirated human granulosa cells from pre-ovulatory follicles a nd granulosa cells luteinized in culture possess the neural cell adhes ion molecule (NCAM) of approximate molecular mass of 140,000 and NCAM mRNA as confirmed by S1-nuclease protection assays and RT-PCR. Moreove r, in the process of luteinization the NCAM isoform pattern is modifie d. Isoforms containing an insert of 10 amino acids (termed VASE) in th e extracellular domain of NCAM were supplemented by alternatively spli ced isoforms without this insert. NCAM immunoreactivity, at light and electron microscope levels, was associated with the cell membrane of m ost granulosa cells which formed clusters. During time in culture an i ncreasing subpopulation of granulosa cells, devoid of NCAM immunoreact ivity, spread out and formed monolayers. This differential expression and the alternative splicing of NCAM during luteinization of granulosa cells raise the possibility that NCAM could be involved in folliculog enesis and the formation of the corpus luteum in the human.