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- Title
Zebrafish gonad mutant models reveal neuroendocrine mechanisms of brain sexual dimorphism and male mating behaviors of different brain regions.
- Authors
Dai, Xiangyan; Pradhan, Ajay; Liu, Jiao; Liu, Ruolan; Zhai, Gang; Zhou, Linyan; Dai, Jiyan; Shao, Feng; Yuan, Zhiyong; Wang, Zhijian; Yin, Zhan
- Abstract
Background: Sexually dimorphic mating behaviors differ between sexes and involve gonadal hormones and possibly sexually dimorphic gene expression in the brain. However, the associations among the brain, gonad, and sexual behavior in teleosts are still unclear. Here, we utilized germ cells-free tdrd12 knockout (KO) zebrafish, and steroid synthesis enzyme cyp17a1-deficient zebrafish to investigate the differences and interplays in the brain–gonad–behavior axis, and the molecular control of brain dimorphism and male mating behaviors. Methods: Tdrd12+/−; cyp17a1+/− double heterozygous parents were crossed to obtain tdrd12−/−; cyp17a1+/+ (tdrd12 KO), tdrd12+/+; cyp17a1−/− (cyp17a1 KO), and tdrd12−/−; cyp17a1−/− (double KO) homozygous progenies. Comparative analysis of mating behaviors were evaluated using Viewpoint zebrafish tracking software and sexual traits were thoroughly characterized based on anatomical and histological experiments in these KOs and wild types. The steroid hormone levels (testosterone, 11-ketotestosterone and 17β-estradiol) in the brains, gonads, and serum were measured using ELISA kits. To achieve a higher resolution view of the differences in region-specific expression patterns of the brain, the brains of these KOs, and control male and female fish were dissected into three regions: the forebrain, midbrain, and hindbrain for transcriptomic analysis. Results: Qualitative analysis of mating behaviors demonstrated that tdrd12−/− fish behaved in the same manner as wild-type males to trigger oviposition behavior, while cyp17a1−/− and double knockout (KO) fish did not exhibit these behaviors. Based on the observation of sex characteristics, mating behaviors and hormone levels in these mutants, we found that the maintenance of secondary sex characteristics and male mating behavior did not depend on the presence of germ cells; rather, they depended mainly on the 11-ketotestosterone and testosterone levels secreted into the brain–gonad regulatory axis. RNA-seq analysis of different brain regions revealed that the brain transcript profile of tdrd12−/− fish was similar to that of wild-type males, especially in the forebrain and midbrain. However, the brain transcript profiles of cyp17a1−/− and double KO fish were distinct from those of wild-type males and were partially biased towards the expression pattern of the female brain. Our results revealed important candidate genes and signaling pathways, such as synaptic signaling/neurotransmission, MAPK signaling, and steroid hormone pathways, that shape brain dimorphism and modulate male mating behavior in zebrafish. Conclusions: Our results provide comprehensive analyses and new insights regarding the endogenous interactions in the brain–gonad–behavior axis. Moreover, this study revealed the crucial candidate genes and neural signaling pathways of different brain regions that are involved in modulating brain dimorphism and male mating behavior in zebrafish, which would significantly light up the understanding the neuroendocrine and molecular mechanisms modulating brain dimorphism and male mating behavior in zebrafish and other teleost fish. Highlights: Germ cells disruption does not change androgen levels and male mating behavior. The maintenance of SSCs and male mating behavior are depended mainly on the concentrations of 11-KT and T secreted into the brain–gonad regulatory axis. Germ cells loss does not have severe effects on brain functions, but disruption of homeostasis in gonadal somatic cells can have a more significant impact. Moreover, a proper interaction between germ cells and gonadal somatic cells is not only crucial for gonads but also for gene regulation in the brain. This study revealed the crucial candidate genes and neural signaling pathways of different brain regions that are involved in modulating brain dimorphism and male mating behavior in zebrafish.
- Subjects
GONADS; ANIMAL sexual behavior; BRACHYDANIO; HUMAN sexuality; STEROID synthesis; NEURAL pathways; ANIMAL courtship; SEXUAL dimorphism
- Publication
Biology of Sex Differences, 2023, Vol 14, Issue 1, p1
- ISSN
2042-6410
- Publication type
Article
- DOI
10.1186/s13293-023-00534-7