Department of Psychology and Center for Neuroendocrine Studies, University of Massachusetts, Amherst, MA 01003, USA.
Biol Sex Differ. 2012 Feb 15;3:5. doi: 10.1186/2042-6410-3-5.
Calbindin-D28 has been used as a marker for the sexually dimorphic nucleus of the preoptic area (SDN-POA). Males have a distinct cluster of calbindin-immunoreactive (ir) cells in the medial preoptic area (CALB-SDN) that is reduced or absent in females. However, it is not clear whether the sex difference is due to the absolute number of calbindin-ir cells or to cell position (that is, spread), and the cellular mechanisms underlying the sex difference are not known. We examined the number of cells in the CALB-SDN and surrounding regions of C57Bl/6 mice and used mice lacking the pro-death gene, Bax, to test the hypothesis that observed sex differences are due to cell death.
Experiment 1 compared the number of cells in the CALB-SDN and surrounding regions in adult males, females, and females injected with estradiol benzoate on the day of birth. In experiment 2, cell number in the CALB-SDN and adjacent regions were compared in wild-type and Bax knockout mice of both sexes. In addition, calbindin-ir cells were quantified within the principal nucleus of the bed nucleus of the stria terminalis (BNSTp), a nearby region that is larger in males due to Bax-dependent cell death.
Males had more cells in the CALB-SDN as well as in surrounding regions than did females, and estradiol treatment of females at birth masculinized both measures. Bax deletion had no effect on cell number in the CALB-SDN or surrounding regions but increased calbindin-ir cell number in the BNSTp.
The sex difference in the CALB-SDN of mice results from an estrogen-dependent difference in cell number with no evidence found for greater spread of cells in females. Blocking Bax-dependent cell death does not prevent sex differences in calbindin-ir cell number in the BNST or CALB-SDN but increases calbindin-ir cell number in the BNSTp of both sexes.
钙结合蛋白 D28（Calbindin-D28）已被用作视前区性别二态核（SDN-POA）的标志物。雄性动物的视前内侧区（CALB-SDN）有一个明显的钙结合蛋白免疫反应（ir）细胞簇，而雌性动物的则减少或不存在。然而，目前尚不清楚这种性别差异是由于钙结合蛋白-ir 细胞的绝对数量还是由于细胞位置（即扩散）造成的，也不知道导致这种性别差异的细胞机制。我们检查了 C57Bl/6 小鼠的 CALB-SDN 和周围区域的细胞数量，并使用缺乏促死亡基因 Bax 的小鼠来检验这样一个假设，即观察到的性别差异是由于细胞死亡造成的。
实验 1 比较了成年雄性、雌性和出生当天注射苯甲酸雌二醇的雌性小鼠的 CALB-SDN 和周围区域的细胞数量。在实验 2 中，比较了雄性和雌性野生型和 Bax 基因敲除小鼠的 CALB-SDN 和相邻区域的细胞数量。此外，还在雄性 Bax 依赖性细胞死亡导致体积增大的附近终纹床核主核（BNSTp）内量化了钙结合蛋白-ir 细胞。
雄性小鼠的 CALB-SDN 以及周围区域的细胞数量均多于雌性小鼠，而出生时注射苯甲酸雌二醇的雌性小鼠的这两个指标均呈现雄性化。Bax 缺失对 CALB-SDN 或周围区域的细胞数量没有影响，但增加了 BNSTp 中的钙结合蛋白-ir 细胞数量。
小鼠 CALB-SDN 的性别差异是由于雌激素依赖性的细胞数量差异造成的，而没有发现雌性细胞扩散程度更大的证据。阻止 Bax 依赖性细胞死亡并不能防止 BNST 或 CALB-SDN 中钙结合蛋白-ir 细胞数量的性别差异，但会增加两性 BNSTp 中的钙结合蛋白-ir 细胞数量。
