The "four core genotypes" (FCG) model comprises mice in which sex chromosome complement (XX vs. XY) is unrelated to the animal's gonadal sex. The four genotypes are XX gonadal males or females, and XY gonadal males or females. The model allows one to measure (1) the differences in phenotypes caused by sex chromosome complement (XX vs. XY), (2) the differential effects of ovarian and testicular secretions, and (3) the interactive effects of (1) and (2). Thus, the FCG model provides new information regarding the origins of sex differences in phenotype that has not been available from studies that manipulate gonadal hormone levels in normal XY males and XX females. Studies of the FCG model have uncovered XX vs. XY differences in behaviors (aggression, parenting, habit formation, nociception, social interactions), gene expression (septal vasopressin), and susceptibility to disease (neural tube closure and autoimmune disease) not mediated by gonadal hormones. Some sex chromosome effects are mediated by sex differences in dose of X genes or their parental imprint. Future studies will identify the genes involved and their mechanisms of action.

中文翻译：

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关于大脑和其他组织的性别差异，“四种核心基因型”小鼠模型告诉我们什么？

“四个核心基因型”(FCG) 模型包括性染色体补体（XX 与 XY）与动物性腺性别无关的小鼠。这四种基因型是XX性腺雄性或雌性，以及性腺雄性或雌性XY。该模型允许人们测量 (1) 由性染色体补体引起的表型差异 (XX vs. XY)，(2) 卵巢和睾丸分泌物的不同影响，以及 (3) (1) 和 ( 2）。因此，FCG 模型提供了有关表型性别差异起源的新信息，而这些信息是从操纵正常 XY 男性和 XX 女性的性腺激素水平的研究中无法获得的。FCG 模型的研究发现了 XX 与 XY 行为（攻击性、育儿、习惯形成、伤害感受、社交互动）的差异，基因表达（室间隔加压素）和对非性腺激素介导的疾病（神经管闭合和自身免疫性疾病）的易感性。一些性染色体效应是由 X 基因剂量或其父母印记的性别差异介导的。未来的研究将确定所涉及的基因及其作用机制。