International Journal of Aquaculture, 2025, Vol.15, No.4, 184-196 http://www.aquapublisher.com/index.php/ija 189 Figure 2 Tracing of Dmrt1-expressing cells during MT-feeding-induced sex reversal. The black arrows show the high magnification of the picture. Scale bars, 25 μm. Dmrt1 is detected in goniae cells around the efferent dust (black arrowheads) of MT-feeding fish at 12 dat (A). Dmrt1 is detected in a few of spermatogonia scattered in the gonads (black arrowheads) at 24 dat (B), and then they appear in gathered spermatogonia (black arrowheads) at 36 dat and 96 dat (C, D) of the MT-feeding fish. ED: efferent dust; BV: blood vessel; SG: spermatogonia; ST: spermatid (Adopted from Wang et al., 2018) 4.2 Dynamic changes in DNA methylation and histone modification in gender transition Epigenetic regulation is another key aspect of gender determination and transition mechanisms. DNA methylation is one of the most common epigenetic markers, and can enable or silence gene expression for a long time by affecting the methylation state of the promoter region of the gene. In fish gender studies, DNA methylation is often negatively correlated with the expression of gender-related genes. In grouper, the latest study analyzed the methylation status of the aromatase cyp19a1a promoter region of female fish and sexually reversing male fish, and found that the cyp19a1a promoter in female fish ovaries had a low methylation level (large number of CpG sites were not methylated), while in the semen tissue was highly methylated (Peng et al., 2020). As females switch to males, the methylation degree of cyp19a1a promoter gradually increases, consistent with its reduced gene expression. Especially during the sexual reversal induced by artificial MT, after removal of MT, a partial reversal of male cyp19a1a promoter methylation status was restored and reactivated expression, causing certain signs of female reversal in gonad tissue. This result shows that DNA methylation not only participates in the reprogramming of gene expression during grouper gender reversal, but its changes may be reversible under certain conditions, thus conferring certain plasticity to the gender. In Japanese crucian carp, which induced gender reversal in temperature, studies have observed that the promoter region of genes related to schizophrenia is activated with the increase of histone H3K27 demethylation (activation marker), while the ovarian gene obtains H3K27 trimethylation (repression marker) and is silenced (Li et al., 2016). This suggests that during the gender transition of grouper, the histone modification status at key loci will also undergo corresponding changes. 4.3 Research on the association between epigenetic markers and gender plasticity The high gender plasticity of hermaphrodite fish is based on the fact that their gene expression programs can be reset, and reprogramming of epigenetic markers is considered one of the main ways to achieve this. In mammals, gender is often irreversible once it is decided, which is partly because key genes and chromatin regions involving gender are locked by stable epigenetic modifications, forming a "oneway street". However, in fish such as grouper, there is still considerable reversibility after gender determination, and their ovaries can be transformed into sperm.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==