Testicular involution prior to sex change in gilthead seabream is characterized by a decrease in DMRT1 gene expression and by massive leukocyte infiltration

Abstract

Background: Leukocytes are found within the testis of most, if not all, mammals and are involved in immunological surveillance, physiological regulation and tissue remodelling. The testis of seasonal breeding fish undergoes a regression process. In the present study, the second reproductive cycle (RC) of the protandrous seasonal teleost fish, gilthead seabream, was investigated and the presence of leukocytes analysed. Special attention has been paid to the testicular degenerative process which is particularly active in the last stage of the second RC probably due to the immediacy of the sex change process.

Histological observation of doublesex-mab 3-related transcription factor 1 (DMRT1) localization in the adult testis of three-spot wrasse

“…In contrast, suppression of DMRT1 transcripts in the gonads was observed in estrogen (E2)-treated male embryos of zebrafish (Schulz et al 2007) and tilapia ). In addition, changes were noticed in DMRT1 expression in concordance with the phases of testicular differentiation in several fishes that change their sexes naturally (Alam et al 2008;He et al 2003;Liarte et al 2007). These findings suggest that DMRT1 is involved not only in early testicular differentiation, but also in gonadal sex reversal/change in teleosts.…”

Molecular basis and genetic improvement of economically important traits in aquaculture animals

“…As a group of protogynous hermaphrodite fishes that the gonad development undergoes transition from ovary to intersexual gonad and then to testis, and cells at different stages during oogenesis and spermatogenesis can be synchronously observed in the transitional gonads, groupers have been used as a good model for mining sex determination or sex differentiation-related genes. Xia et al [75] have found that grouper DMRT1 is specifically expressed in spermatogenic cells during female-to-male sex reversal, and the spermatogenic cell-specific and dynamic expression pattern was revealed to be basically similar in several sex reversal fishes including protogynous wrasse (Halichoeres tenuispinis) [76] and rice field eel (Monopterus albus) [77] as well as protandrous black porgy (Acanthopagrus schlegeli) [78,79] and gilthead seabream (Sparus aurata) [80].…”

Immunocytochemical Tools Reveal a New Research Field Between the Boundaries of Immunology and Reproductive Biology in Teleosts

“…During post-spawning the proliferative activity was resumed, although necrotic areas and apoptotic germ cells were also observed (Chaves-Pozo et al, 2005a;Liarte et al, 2007). Interestingly, the last stages of each reproductive cycle (resting and testicular involution, respectively) differed completely.…”

“…Secondly, the infiltration of acidophilic granulocytes depended on the reproductive cycle stage of the specimens and it was strongly regulated by soluble factors produced by the gonad (ChavesPozo et al, 2003(ChavesPozo et al, , 2005a(ChavesPozo et al, , 2005b. Moreover, this migratory influx increased the amount of acidophilic granulocytes in the testis at specific stages (post-spawning and testicular involution) coinciding with a very low proliferative activity of germ cells and with the appearance of necrotic areas and apoptotic germ cells , 2005aLiarte et al, 2007). Interestingly, the ultrastructure of these testicular acidophilic granulocytes at the testicular involution stage strongly suggests their involvement in the renewal process that takes place in the gonad at post-spawning and testicular involution stages .…”

“…Moreover, we have developed some immunocytochemical techniques that allowed us to identify the immune cells in the gonads and to study their main activities and their regulation by different molecules or physiological processes in a teleost species, the gilthead seabream (Sparus aurata L.). The gilthead seabream is a sequential hermaphrodite species that, in the western Mediterranean area, develops as male during the first two reproductive cycles, while from the third reproductive cycle onwards the population divides into males and females (Chaves-Pozo et al, 2005a;Liarte et al, 2007) and due to the morphological arrangement of its bisexual gonad, it´s an interesting model for studying the mechanisms involved in the regulation of the gonads. This chapter deals with the antibodies and the techniques used to set up a novel research line in fish, such as the study of the immune-reproductive interactions which are essential for normal reproductive physiology.…”