Neuroprotective cold-shock proteins (CSPs) are abundant in the normothermic neonatal rodent brain but decrease with advancing neurodevelopmental age and are low or absent in the adult brain. It has not been established if neurodevelopmental age alters the baseline expression of CSPs in the human brain. Here, we tested the hypothesis that protein levels of RNA-binding motif 3 (RBM3), reticulon-3 (RTN3), and cold-induced RNA-binding protein (CIRBP) are abundant in the normothermic developing human brain but low-to-absent in adults. We also tested if β-klotho (KLB) is expressed in the developing brain; KLB functions as a coreceptor that controls tissue-specific binding and activity of the systemically circulating thermogenic hormone fibroblast growth factor 21 (FGF21), and is predominantly expressed in the liver, pancreas, and in adipose cells. Methods: Hippocampi and anterior prefrontal cortices (aPFCs/BA10) from a total of 20 male and 20 female subjects were obtained from the NIH NeuroBioBank. CSP and KLB levels were measured in: infants < 1 year old (n = 8), toddlers aged 1-2 years (n = 8), children aged 3-5 years (n = 7), 18-year-old adolescents (n = 8), and adults aged 31-34 years (n = 8). An equal number of male and female (n = 4 each) samples were pooled into each age group, except in the 3- to 5-year-olds which comprised 3 male and 4 female specimens due to sample availability. In total, 78 whole-brain tissues were dissociated using a bead-based Precellys homogenizer to generate equivalent homogenates, and levels of protein targets subsequently analyzed by Western blotting. Results: Infants had the highest levels of RBM3 and other CSPs in the brain compared to all other ages. In the hippocampus, CSPs were detected predominantly in infants. In the aPFC, CSP levels were highest in infants, moderate-to-low in toddlers/children, and below assay detection limits in adolescents/adults. Germane to the thermogenic FGF21/KLB signaling axis, our results confirm that KLB is absent in the adult hippocampus/aPFC as reported by others. In contrast, we report for the first time that KLB is abundant in the early developing human brain; KLB levels were highest in the infant hippocampus/aPFC and moderately expressed in toddlers. RBM3 is a potent neuroprotective CSP. Thus, the impact of these findings on the observed efficacy of therapeutic hypothermia in neonatal brain injury merits further investigation.

中文翻译：

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婴儿在人脑中独特地表达高水平的RBM3和其他冷适应性神经保护蛋白。

神经保护性冷休克蛋白（CSP）在常温新生啮齿动物脑中丰富，但随着神经发育年龄的增加而降低，而在成年脑中则低或缺乏。神经发育年龄是否会改变人脑中CSP的基线表达尚无定论。在这里，我们测试了以下假设：正常发育中的人脑中RNA结合基序3（RBM3），网状蛋白3（RTN3）和冷诱导的RNA结合蛋白（CIRBP）的蛋白质水平丰富。在成年人中不存在。我们还测试了发育中的大脑是否表达了β-klotho（KLB）。KLB发挥共受体作用，控制组织特异性结合和全身循环产热激素成纤维细胞生长因子21（FGF21）的活性，并主要在肝脏，胰腺和脂肪细胞中表达。方法：从NIH NeuroBioBank获得了总共20位男性和20位女性受试者的海马和前额叶前皮质（aPFCs / BA10）。CSP和KLB水平的测量对象为：<1岁以下的婴儿（n = 8），1-2岁的幼儿（n = 8），3-5岁的儿童（n = 7），18岁的青少年（ n = 8），以及31-34岁的成年人（n = 8）。将相同数量的男性和女性样本（每个n = 4）合并到每个年龄组中，但由于样本的可用性，在3至5岁的儿童中，包括3个男性和4个女性样本。总共，使用基于珠子的Precellys匀浆器解离了78个全脑组织，以生成等效的匀浆，随后通过蛋白质印迹分析了蛋白质靶标的水平。结果：与所有其他年龄段相比，婴儿的大脑中RBM3和其他CSP的含量最高。在海马中，主要在婴儿中检测到CSP。在aPFC中，婴儿的CSP水平最高，幼儿/儿童的CSP水平中等至低，而青少年/成人的CSP水平低于检测限。与成热的FGF21 / KLB信号轴密切相关，我们的研究结果证实，成年海马/ aPFC中不存在KLB，如其他人所报道。相比之下，我们首次报道了KLB在人类早期发育的大脑中含量丰富。KLB水平在婴儿海马/ aPFC中最高，在幼儿中中等水平。RBM3是有效的神经保护性CSP。因此，这些发现对观察到的治疗性低温治疗新生儿脑损伤的效果的影响值得进一步研究。幼儿/儿童的中度至低级，以及青少年/成人的检测限以下。与成热的FGF21 / KLB信号轴密切相关，我们的研究结果证实，成年海马/ aPFC中不存在KLB，如其他人所报道。相比之下，我们首次报道了KLB在人类早期发育的大脑中含量丰富。KLB水平在婴儿海马/ aPFC中最高，在幼儿中中等水平。RBM3是有效的神经保护性CSP。因此，这些发现对观察到的低温治疗新生儿脑损伤的疗效的影响值得进一步研究。幼儿/儿童的中度至低级，以及青少年/成人的检测限以下。与成热的FGF21 / KLB信号轴密切相关，我们的研究结果证实，成年海马/ aPFC中不存在KLB，如其他人所报道。相比之下，我们首次报道了KLB在人类早期发育的大脑中含量丰富。KLB水平在婴儿海马/ aPFC中最高，在幼儿中中等水平表达。RBM3是有效的神经保护性CSP。因此，这些发现对观察到的低温治疗新生儿脑损伤的疗效的影响值得进一步研究。我们首次报道了KLB在人类早期大脑中含量丰富；KLB水平在婴儿海马/ aPFC中最高，在幼儿中中等水平。RBM3是有效的神经保护性CSP。因此，这些发现对观察到的低温治疗新生儿脑损伤的疗效的影响值得进一步研究。我们首次报道了KLB在人类早期大脑中含量丰富；KLB水平在婴儿海马/ aPFC中最高，在幼儿中中等水平。RBM3是有效的神经保护性CSP。因此，这些发现对观察到的低温治疗新生儿脑损伤的疗效的影响值得进一步研究。