Parker Coltan G, Craig Sarah E, Histed Abigail R, Lee Joanne S, Ibanez Emma, Pronitcheva Veronica, Rhodes Justin S
Neuroscience Program, University of Illinois, Urbana-Champaign, 405 N Mathews Ave, Urbana, IL 61801, USA.
Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign, 405 N Mathews Ave, Urbana, IL 61801, USA.
Gen Comp Endocrinol. 2023 Mar 1;333:114185. doi: 10.1016/j.ygcen.2022.114185. Epub 2022 Dec 9.
Sex differences in cell number in the preoptic area of the hypothalamus (POA) are documented across all major vertebrate lineages and contribute to differential regulation of the hypothalamic-pituitary-gonad axis and reproductive behavior between the sexes. Sex-changing fishes provide a unique opportunity to study mechanisms underlying sexual differentiation of the POA. In anemonefish (clownfish), which change sex from male to female, females have approximately twice the number of medium-sized cells in the anterior POA compared to males. This sex difference transitions from male-like to female-like during sex change. However, it is not known how this sex difference in POA cell number is established. This study tests the hypothesis that new cell addition plays a role. We initiated adult male-to-female sex change in 30 anemonefish (Amphiprion ocellaris) and administered BrdU to label new cells added to the POA at regular intervals throughout sex change. Sex-changing fish added more new cells to the anterior POA than non-changing fish, supporting the hypothesis. The observed effects could be accounted for by differences in POA volume, but they are also consistent with a steady trickle of new cells being gradually accumulated in the anterior POA before vitellogenic oocytes develop in the gonads. These results provide insight into the unique characteristics of protandrous sex change in anemonefish relative to other modes of sex change, and support the potential for future research in sex-changing fishes to provide a richer understanding of the mechanisms for sexual differentiation of the brain.
下丘脑视前区（POA）细胞数量的性别差异在所有主要脊椎动物谱系中都有记录，并且导致下丘脑 - 垂体 - 性腺轴的差异调节以及两性之间的生殖行为差异。性逆转鱼类为研究POA性别分化的潜在机制提供了独特的机会。在从雄性转变为雌性的海葵鱼（小丑鱼）中，与雄性相比，雌性在前POA中中型细胞的数量大约是雄性的两倍。这种性别差异在性逆转过程中从雄性样转变为雌性样。然而，尚不清楚POA细胞数量的这种性别差异是如何形成的。本研究检验了新细胞添加起作用这一假设。我们诱导了30条海葵鱼（眼斑双锯鱼）从成年雄性转变为雌性，并在整个性逆转过程中定期给予BrdU以标记添加到POA的新细胞。性逆转的鱼比未发生性逆转的鱼向前POA添加了更多新细胞，支持了这一假设。观察到的效应可能是由POA体积差异导致的，但也与在性腺中卵黄生成卵母细胞发育之前，新细胞在前POA中逐渐稳定积累的情况一致。这些结果为海葵鱼相对于其他性逆转模式的雄性先熟性逆转的独特特征提供了见解，并支持了未来对性逆转鱼类的研究有可能更深入理解大脑性别分化机制的潜力。
