Analysis of transcripts in gilthead seabream sperm and zebrafish testicular cells: mRNA profile as a predictor of gamete quality

The possibility of using mRNA profile as a predictor of fertilization ability could be of great importance in aquaculture. Studies in mammals and other species have shown that mRNA profile may be used for gamete quality molecular diagnosis. Zebrafish is a well established model and the genetic tools available for this species make it the perfect biological model to carry out this type of study. The expression of eleven genes, potentially relevant in mature spermatozoa, was evaluated in testicular cells from good and bad zebrafish breeders. Our results showed that there were differences in the transcript abundance of the studied genes. Five of the eleven studied transcripts (bdnf, lhcgr, lepa, bik, dmrt1, fshb and hsd17b4) were present in lower quantity in bad zebrafish breeders whereas two were more abundant (bik and hsd17b4). Moreover, we observed a different mRNA pattern profile in seabream spermatozoa depending on their motility. In both cases (zebrafish testicular cells and gilthead seabream spermatozoa) bdnf and kita transcripts were more abundant in good breeders or high quality samples. Although cryopreservation has been reported to decrease transcript levels in spermatozoa from other species, the protocol employed in this study for gilthead seabream sperm cryopreservation does not affect mRNA levels. This is a relevant observation since it is known that alterations in spermatozoa transcripts could have a serious effect on fertilization or even on the offspring.