Neuropeptide signalling shapes feeding and reproductive behaviours in male C. elegans

Sexual dimorphism occurs where different sexes of the same species display differences in characteristics not limited to reproduction. For the nematode Caenorhabditis elegans, in which the complete neuroanatomy has been solved for both hermaphrodites and males, sexually dimorphic features have been observed both in terms of the number of neurons and in synaptic connectivity. In addition, male behaviours, such as food-leaving to prioritise searching for mates, have been attributed to neuropeptides released from sex-shared or sex-specific neurons. In this study, we show that the lury-1 neuropeptide gene shows a sexually dimorphic expression pattern; being expressed in pharyngeal neurons in both sexes but displaying additional expression in tail neurons only in the male. We also show that lury-1 mutant animals show sex differences in feeding behaviours, with pharyngeal pumping elevated in hermaphrodites but reduced in males. LURY-1 also modulates male mating efficiency, influencing motor events during contact with a hermaphrodite. Our findings indicate sex-specific roles of this peptide in feeding and reproduction in C. elegans, providing further insight into neuromodulatory control of sexually dimorphic behaviours.

Identification and Characterization of Dimorphic Expression of Sex-Related Genes in Rock Bream, a Fish With Multiple Sex Chromosomes

The rock bream (Oplegnathus fasciatus) is a typical fish with a unique multiple sex chromosome system. In this study, we investigated the gene expression profiling in the gonads and brains of both males and females using RNA-Seq to identify sex-related genes and pathways. In accordance with the dimorphic expression profiles, combined with Gene ontology and KEGG enrichment analyses, a number of potential genes and pathways associated with sex determination were obtained from transcriptional analysis, especially some sex-biased genes and pathways. Next, we selected 18 candidate genes and analyzed their expression in different tissues and developmental stages. We found that the expression levels of Amh, Dmrt1, Sox9, Dmrtb1, and Nanos2 were significantly higher in the testis than those in the ovary or other tissues, whereas the expression levels of ZP4, Bouncer, RNF208, FoxH1, and TOB were significantly higher in the ovary than those in the testis. Furthermore, the expression levels of these genes in different developmental stages of gonads also showed sexually dimorphic patterns, suggesting that they might play important roles during gonadal development. These genes are useful markers for investigating sex determination and differentiation in rock bream. The findings of this study can provide insights into the molecular mechanisms of sex determination and differentiation in fish with multiple sex chromosome systems.

Comparison of Gonadal Transcriptomes Uncovers Reproduction-Related Genes with Sexually Dimorphic Expression Patterns in Diodon hystrix

Diodon hystrix is a new and emerging aquaculture species in south China. However, due to the lack of understanding of reproductive regulation, the management of breeding and reproduction under captivity remains a barrier for the commercial aquaculture of D. hystrix. More genetic information is needed to identify genes critical for gonadal development. Here, the first gonadal transcriptomes of D. hystrix were analyzed and 151.89 million clean reads were generated. All reads were assembled into 57,077 unigenes, and 24,574 could be annotated. By comparing the gonad transcriptomes, 11,487 differentially expressed genes were obtained, of which 4599 were upregulated and 6888 were downregulated in the ovaries. Using enrichment analyses, many functional pathways were found to be associated with reproduction regulation. A set of sex-biased genes putatively involved in gonad development and gametogenesis were identified and their sexually dimorphic expression patterns were characterized. The detailed transcriptomic data provide a useful resource for further research on D. hystrix reproductive manipulation.

Sexual Development of the Hermaphroditic Scallop Argopecten irradians Revealed by Morphological, Endocrine and Molecular Analysis

Simultaneous or functional hermaphrodites possessing both ovary and testis at the same time are good materials for studying sexual development. However, previous research on sex determination and differentiation was mainly conducted in gonochoristic species and studies on simultaneous hermaphrodites are still limited. In this study, we conducted a combined morphological, endocrine and molecular study on the gonadal development of a hermaphroditic scallop Argopecten irradians aged 2–10 month old. Morphological analysis showed that sex differentiation occurred at 6 months of age. By examining the dynamic changes of progesterone, testosterone and estradiol, we found testosterone and estradiol were significantly different between the ovaries and testes almost throughout the whole process, suggesting the two hormones may be involved in scallop sex differentiation. In addition, we identified two critical sex-related genes FoxL2 and Dmrt1L, and investigated their spatiotemporal expression patterns. Results showed that FoxL2 and Dmrt1L were female- and male-biased, respectively, and mainly localized in the germ cells and follicular cells, indicating their feasibility as molecular markers for early identification of sex. Further analysis on the changes of FoxL2 and Dmrt1L expression in juveniles showed that significant sexual dimorphic expression of FoxL2 occurred at 2 months of age, earlier than that of Dmrt1L. Moreover, FoxL2 expression was significantly correlated with estradiol/testosterone ratio (E2/T). All these results indicated that molecular sex differentiation occurs earlier than morphological sex differentiation, and FoxL2 may be a key driver that functions through regulating sex steroid hormones in the scallop. This study will deepen our understanding of the molecular mechanism underlying sex differentiation and development in spiralians.

A role for microRNAs in the epigenetic control of sexually dimorphic gene expression in the human placenta

Aim: The contribution of miRNAs as epigenetic regulators of sexually dimorphic gene expression in the placenta is unknown. Materials & methods: 382 placentas from the extremely low gestational age newborns (ELGAN) cohort were evaluated for expression levels of 37,268 mRNAs and 2,102 miRNAs using genome-wide RNA-sequencing. Differential expression analysis was used to identify differences in the expression based on the sex of the fetus. Results: Sexually dimorphic expression was observed for 128 mRNAs and 59 miRNAs. A set of 25 miRNA master regulators was identified that likely contribute to the sexual dimorphic mRNA expression. Conclusion: These data highlight sex-dependent miRNA and mRNA patterning in the placenta and provide insight into a potential mechanism for observed sex differences in outcomes.