Leydig cells express neural cell adhesion molecules in vivo and in vitro

The neural cell adhesion molecule (NCAM) polypeptides are expressed
by numerous tissues during embryonic development, where they are
involved in cell-cell interactions. In the adult, NCAM expression
is confined to a few cell types, including neurons and
peptide-hormone-producing cells. Here we demonstrate that the
Leydig cells of the adult rat, mouse, and hamster testes express
NCAM as well. Western blotting showed that an NCAM of approximately
120 kDa was present in the adult testes of all three species
investigated. This form was also found in freshly isolated mouse
Leydig cells and in Leydig cells after 2 days in culture. After 4
days in culture, mouse Leydig cells expressed additional NCAM
isoforms of approximately 140 and 180 kDa, indicating changes in
alternative splicing of NCAM primary transcripts. Also, NCAM mRNA
of all isoforms, as detected by S1-nuclease protection assays,
increased with time in culture. The expression of the cell adhesion
molecule NCAM by adult Leydig cells may explain the aggregation of
Leydig cells in clusters in rodent testes, which could be a
prerequisite for functional coordination of groups of Leydig cells.
Furthermore, the presence of this neural and endocrine marker may
indicate a closer relationship between Leydig cells and neural and
peptide-hormone-producing cells than is considered to exist at the
present time.