Investigation of the influence of sex and prenatal steroids on synapse formation in human cerebral organoids.

一些突出的神经发育障碍在男性和女性之间的患病率不同（McCarthy 2016）。例如，在自闭症谱系条件（ASC）中似乎存在男性偏见，ASC患者的男女比例估计为3:1 （Loomes, Hull, and Mandy 2017）。目前尚不清楚这种差异存在的原因，尽管越来越多的证据表明，产前类固醇（包括雄激素和雌激素）与自闭症的可能性增加有关（Baron-Cohen等人，2020），睾丸激素水平升高与ASC的可能性或特征增加有关（Baron-Cohen等人，2011；Bos等人，2016）。产前类固醇在大脑发育和性别分化中起着关键作用。男性在妊娠18至24周以及出生后的头几个月血清中睾酮水平升高，与神经发育的关键阶段相吻合（Hines, Constantinescu, and Spencer 2015）。胎儿类固醇可能导致啮齿类动物的潜在性别差异，因此最终结果是相同的，但雄性和雌性的发育机制不同（Sellers etal . 2020）。用雄激素治疗人类神经干细胞可增加其增殖并影响约200个基因的表达，包括与ASC相关或参与的基因（Quartier等，2018）。Kelava等人表明，类固醇，特别是雄激素，会影响人类大脑类器官的早期皮质生成（2020）。然而，尚不清楚类固醇如何影响突触发育，这在ASC中受到影响。一些与ASC相关的高渗透性突变与突触功能的调节有关，包括SHANK3和NEUREXIN （NRXN1）基因的突变（Zoghbi和Bear 2012）。新出现的证据表明，类固醇也可以作为神经递质，影响哺乳动物的神经元活动（Rudolph et al. 2016）。然而，人们对类固醇在发育中的人类皮质中的作用知之甚少。现在已经建立了可重复生长的脑类器官的方案（Lancaster et al. 2013; Velasco et al. 2019），可以作为早期人类大脑发育的模型（Camp et al. 2015）来研究这些问题。考虑到类固醇在ASC可能性中的作用，研究产前类固醇对皮质和突触发育的影响是值得的。asc相关基因SHANK3和类固醇之间有一个有趣的联系，性激素调节SHANK的表达（Berkel et al. 2018）。Srivastava实验室现有的已发表和未发表的数据表明，男性人类诱导多能干细胞衍生（hiPSC）前脑神经元可以对一系列胎儿类固醇（如17b -雌二醇）产生反应，影响神经突生长、突触蛋白表达和突触基因表达，如与NRXN1相互作用的突触蛋白（Shum etal . 2015）。来自SHANK3和NRXN1突变的雄性和雌性hiPSC系的实验室数据表明，在神经网络活性（SHANK3 hiPSC系）或基因表达差异（NRXN1 hiPSC系）上，雄性和雌性可能存在差异。

Several prominent neurodevelopmental disorders have differing prevalence between males and females (McCarthy 2016). For example, there appears to be a male bias in autism spectrum condition (ASC), with an estimated 3:1 ratio of males to females with ASC (Loomes, Hull, and Mandy 2017). It is still unclear why this difference exists, although there is increasing evidence that prenatal steroids including androgens and estrogens are associated with increased likelihood of autism (Baron-Cohen et al. 2020), with increased testosterone levels associated with higher ASC likelihood or traits (Baron-Cohen et al. 2011; Bos et al. 2016). Prenatal steroids have key roles in the development and sexual differentiation of the brain. Levels of testosterone in serum are elevated in males between 18 and 24 weeks of gestation and in the first months after birth, coinciding with key stages of neurodevelopment (Hines, Constantinescu, and Spencer 2015). Fetal steroids may contribute to latent sex differences in rodents, such that the end result is the same but the developmental mechanisms differ in males and females (Sellers et al. 2020). Human neural stem cell treatment with androgens increases their proliferation and affects expression of ~200 genes, including genes associated with or involved in ASC (Quartier et al. 2018). Kelava et al. show that steroids, specifically androgens, affect early corticogenesis in human cerebral organoids (2020). However, it is not known how steroids affect synapse development, which is affected in ASC. Several highly penetrant mutations associated with ASC have been linked to the regulation of synaptic function, including mutations in the SHANK3 and NEUREXIN (NRXN1) genes (Zoghbi and Bear 2012). Emerging evidence shows steroids can also act as neurotransmitters and influence neuronal activity in mammals (Rudolph et al. 2016). However, little is known about steroid action in the developing human cortex. There are now established protocols for reproducibly growing cerebral organoids (Lancaster et al. 2013; Velasco et al. 2019), which can be used as a model of early human brain development (Camp et al. 2015) to study such questions. Given also the proposed role of steroids in ASC likelihood, an investigation of the effect of prenatal steroids on cortical and synapse development is worthwhile. An intriguing link between the ASC-linked gene SHANK3 and steroids has been reported, whereby sex hormones regulate SHANK expression (Berkel et al. 2018). Existing published and unpublished data from the Srivastava lab suggests that male human induced pluripotent stem cell-derived (hiPSC) forebrain neurons can respond to a range of fetal steroids, for example 17B-estradiol, with effects on neurite outgrowth, synaptic protein expression, and synaptic gene expression, such as synaptic proteins interacting with NRXN1 (Shum et al. 2015). Lab data from male and female hiPSC lines with mutations in SHANK3 and NRXN1 indicates potential male-female differences in neuronal network activity (SHANK3 hiPSC lines) or gene expression differences (NRXN1 hiPSC lines).