El
Dr. José Miguel Cerdá Reverter (del Instituto de Acuicultura de Torre de la
Sal, CSIC) actuó como Presidente del Tribunal, el Dr. Ibon Cancio (de la Universidad
del País Vasco/Euskal Herriko
Unibertsitatea) fue el Secretario, y la Dra. Salima Aroua (de la Université du Havre, Francia) fue el
tercer miembro del mismo.
Al acabar el acto de defensa, el Tribunal le concedió
la máxima calificación, Sobresaliente Cum
Laude. Enhorabuena Dra. Morini!
El documento final es un compendio de 4
artículos:
● Temperature modulates the testis steroidogenesis in European eel
Peñaranda et al., 2016. Comparative
Biochemistry and Physiology Part A: Molecular & Integrative Physiology
● Expression of nuclear and membrane estrogen receptors in the European
eel throughout spermatogenesis
Morini et al., en revisión en Comparative
Biochemistry and Physiology Part A: Molecular & Integrative Physiology
● Nuclear and membrane progestin receptors in the European eel:
characterization and expression in vivo through spermatogenesis
Morini et al., en revisión
en PloS ONE
● Transcript levels of the soluble sperm
factor protein phospholipase C zeta 1 (PLCζ1)
increase through induced spermatogenesis in European eel
Morini et al., 2015. Comparative Biochemistry and Physiology Part A: Molecular &
Integrative Physiology
con una introducción y una discusión general. El pdf con el texto completo esta disponible on-line en: .
Resumen
The European eel (Anguilla
anguilla, L., 1758) population is in dramatic decline, so much so that this
species has been listed as “Critically Endangered” on the Red List of
Threatened Species, by the International Union for Conservation of Nature
(IUCN). The European eel has a complex life cycle, with sexual maturation
blocked in the absence of the reproductive oceanic migration, and an inability
to mature in captivity without the administration of hormonal treatments. Even
though experimental maturation induces gamete production of both sexes, the
fertilization results in infertile eggs, unviable embryos and larvae, which die
within a few days of hatching. Therefore, understanding the eel reproductive
physiology during maturation is very important if we want to recover the wild
eel population. Furthermore, due to its phylogenetic position, representative
of a basal group of teleosts, the Elopomorphs, the Anguilla species may provide
insights into ancestral regulatory physiology processes of reproduction in
teleosts, the largest group of vertebrates.
In this thesis, characterization, phylogeny and
synteny analyses have given us new insight into the evolutionary history of the
reproductive process in vertebrates. The European eel possesses five membrane
(mPRs) and two nuclear (nPR or pgrs) progestin receptors. Eel mPRs clustered in
two major monophyletic groups. Phylogeny analysis of vertebrate nPRs and PLCζ1 (sperm specific protein) places both eel PLCζ1 and nPR sequences at the base of the teleost clade, which is
consistent with the basal position of elopomorphs in the phylogeny of teleosts.
To further resolve the origin of the duplicated eel nPRs, synteny analyses of
the nPR neighboring genes in several vertebrate genomes were performed.
Phylogeny and synteny analyses allowed us to propose the hypothesis that eel
duplicated nPRs originated from the 3R.
In order to gain a better understanding of the role of the genes
implicated in eel reproduction, analyses of their regulation during
experimental maturation were carried out. The change in salinity induced
parallel increases in E2 plasma and nuclear estrogen receptor expression
levels, revealing a stimulatory effect of salinity on the E2 signalling pathway
along the BPG axis, leading to a control of spermatogonial stem cell renewal.
Brain and pituitary estrogen receptors may then mediate the stimulation of
androgens and steroidogenic enzymes linked to androgen synthesis. Androgen synthesis
is not dependent on temperature, but further maturation requires higher
temperatures to induce a change in the steroidogenic pathway towards estrogen
and progestin synthesis. This is consistent with our studies on estrogen and
progestin receptors. In the testis, progestin seems to regulate meiosis through
membrane and nuclear progestin receptors, and final sperm maturation seems to
be controlled by both estrogen and progestin through the estrogen and progestin
membrane receptors. Finally, eel sperm-specific PLCζ1 seems to have an
important function in spermatozoa by inducing egg activation and temperature
may play a role in its regulation, especially during the process of
spermiogenesis.
This thesis attempts to evaluate the physiological function of the genes
involved in eel reproduction during spermatogenesis, and demonstrates that
salinity and temperature play crucial roles in the sexual maturation of the
male European eel.
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