Transcript levels of the soluble sperm factor protein phospholipase C zeta 1
(PLCζ1) increase through induced spermatogenesis in European eel
M.
Morini, D.S. Peñaranda, M.C. Vílchez, V. Gallego, R.
Nourizadeh-Lillabadi, J.F. Asturiano, F.-A. Weltzien, L. Pérez
Activation at fertilization of the vertebrate egg is
triggered by Ca2+ waves. Recent studies suggest the phospholipase C
zeta (PLCζ), a sperm-specific protein, triggers egg activation by an
IP3-mediated Ca2+ release and allow Ca2+ waves at
fertilization.
In the present study we cloned, characterized, and
phylogenetically positioned the European eel PLCζ (PLCζ1). It is 1521bp long,
with 10 exons encoding an open reading frame of 506 amino acids. The amino acid
sequence contains an EF-hand domain, X and Y catalytic domains, and a
carboxy-terminal C2 domain, all typical of other PLCζ orthologous. The sequence
is truncated not only at the N-terminus of the EF-hand domain, as in all
teleost PLCζ, but also in the C-terminal region of the X-domain and in a large
part of the N-terminal X/Y linker region.
The tissue distribution was studied, and the gene
expression was determined in testis during induced sexual maturation at three
different thermal regimes. Also, brain and pituitary expression were studied
through sex maturation at constant temperature. plcζ1 was expressed in brain of male and female, in testis but not in ovaries. By first time in vertebrates,
it is reported plcζ1 expression in
the pituitary gland. Testis plcζ1 expression
increased through spermatogenesis under all the
thermal regimes, but being significantly elevated at
lower temperatures. It was very low when testis contained only
spermatogonia or spermatocytes, while maximum
expression was found during spermiogenesis. These results support the
hypothesis for an eel sperm-specific PLCζ1 inducing egg activation, similarly
to mammals and some teleosts, but different from some other teleost species,
which express this protein in ovaries, but not in testes.
