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The democratization of genomic technologies has revealed profound sex biases in expression patterns in every adult tissue, even in organs with no conspicuous differences, such as the heart. With the increasing awareness of the disparities in cardiac pathophysiology between males and females, there are exciting opportunities to explore how sex differences in the heart are established developmentally. Although sexual dimorphism is traditionally attributed to hormonal influence, expression and epigenetic sex biases observed in early cardiac development can only be accounted for by the difference in sex chromosome composition, i.e., XX in females and XY in males. In fact, genes linked to the X and Y chromosomes, many of which encode regulatory factors, are expressed in cardiac progenitor cells and at every subsequent developmental stage. The effect of the sex chromosome composition may explain why many congenital heart defects originating before gonad formation exhibit sex biases in presentation, mortality, and morbidity. Some transcriptional and epigenetic sex biases established soon after fertilization persist in cardiac lineages, suggesting that early epigenetic events are perpetuated beyond early embryogenesis. Importantly, when sex hormones begin to circulate, they encounter a cardiac genome that is already functionally distinct between the sexes. Although there is a wealth of knowledge on the effects of sex hormones on cardiac function, we propose that sex chromosome-linked genes and their downstream targets also contribute to the differences between male and female hearts. Moreover, identifying how hormones influence sex chromosome effects, whether antagonistically or synergistically, will enhance our understanding of how sex disparities are established. We also explore the possibility that sexual dimorphism of the developing heart predicts sex-specific responses to environmental signals and foreshadows sex-biased health-related outcomes after birth.
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Male-Biased microRNA Discovery in the Pea Aphid
Epigenetic mechanisms modulate gene expression levels during development, shaping how a single genome produces a diversity of phenotypes. Here, we begin to explore the epigenetic regulation of sexual dimorphism in pea aphids (Acyrthosiphon pisum) by focusing on microRNAs. Previous analyses of microRNAs in aphids have focused solely on females, so we performed deep sequencing of a sample containing early-stage males. We used this sample, plus samples from Genbank, to find 207 novel pea aphid microRNA coding loci. We localized microRNA loci to a chromosome-level assembly of the pea aphid genome and found that those on the X chromosome have lower overall expression compared to those on autosomes. We then identified a set of 19 putative male-biased microRNAs and found them enriched on the X chromosome. Finally, we performed protein-coding RNA-Seq of first instar female and male pea aphids to identify genes with lower expression in males. 10 of these genes were predicted targets of the 19 male-biased microRNAs. Our study provides the most complete set of microRNAs in the pea aphid to date and serves as foundational work for future studies on the epigenetic control of sexual dimorphism.
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- Award ID(s):
- 1749514
- PAR ID:
- 10329727
- Date Published:
- Journal Name:
- Insects
- Volume:
- 12
- Issue:
- 6
- ISSN:
- 2075-4450
- Page Range / eLocation ID:
- 533
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/insects12060533
