Wiget Franziska, van Dijk R Maarten, Louet Estelle R, Slomianka Lutz, Amrein Irmgard
Division of Functional Neuroanatomy, Institute of Anatomy, University of Zurich, Zurich, Switzerland.
Institute of Pharmacology, Toxicology and Pharmacy, Ludwig-Maximilian-University, Munich, Germany.
Front Neurosci. 2017 Dec 19;11:719. doi: 10.3389/fnins.2017.00719. eCollection 2017.
The functional septo-temporal (dorso-ventral) differentiation of the hippocampus is accompanied by gradients of adult hippocampal neurogenesis (AHN) in laboratory rodents. An extensive septal AHN in laboratory mice suggests an emphasis on a relation of AHN to tasks that also depend on the septal hippocampus. Domestication experiments indicate that AHN dynamics along the longitudinal axis are subject to selective pressure, questioning if the septal emphasis of AHN in laboratory mice is a rule applying to rodents in general. In this study, we used C57BL/6 and DBA2/Crl mice, wild-derived F1 house mice and wild-captured wood mice and bank voles to look for evidence of strain and species specific septo-temporal differences in AHN. We confirmed the septal > temporal gradient in C57BL/6 mice, but in the wild species, AHN was low septally and high temporally. Emphasis on the temporal hippocampus was particularly strong for doublecortin positive (DCX+) young neurons and more pronounced in bank voles than in wood mice. The temporal shift was stronger in female wood mice than in males, while we did not see sex differences in bank voles. AHN was overall low in DBA and F1 house mice, but they exhibited the same inversed gradient as wood mice and bank voles. DCX+ young neurons were usually confined to the subgranular zone and deep granule cell layer. This pattern was seen in all animals in the septal and intermediate dentate gyrus. In bank voles and wood mice however, the majority of temporal DCX+ cells were radially dispersed throughout the granule cell layer. Some but not all of the septo-temporal differences were accompanied by changes in the DCX+/Ki67+ cell ratios, suggesting that new neuron numbers can be regulated by both proliferation or the time course of maturation and survival of young neurons. Some of the septo-temporal differences we observe have also been found in laboratory rodents after the experimental manipulation of the molecular mechanisms that control AHN. Adaptations of AHN under natural conditions may operate on these or similar mechanisms, adjusting neurogenesis to the requirements of hippocampal function.
在实验啮齿动物中，海马体的功能性隔颞（背腹）分化伴随着成年海马神经发生（AHN）的梯度变化。实验小鼠广泛的隔区AHN表明，AHN与同样依赖隔区海马体的任务之间的关系受到重视。驯化实验表明，沿纵轴的AHN动态受到选择压力的影响，这引发了一个问题，即实验小鼠中AHN的隔区重点是否适用于一般啮齿动物。在本研究中，我们使用了C57BL/6和DBA2/Crl小鼠、野生来源的F1家鼠以及野生捕获的林姬鼠和棕背䶄，以寻找AHN中品系和物种特异性隔颞差异的证据。我们证实了C57BL/6小鼠中隔区>颞区的梯度，但在野生物种中，AHN在隔区较低，在颞区较高。对于双皮质素阳性（DCX+）的年轻神经元，对颞叶海马体的重视尤为强烈，并且在棕背䶄中比在林姬鼠中更为明显。雌性林姬鼠的颞区转移比雄性更强，而在棕背䶄中我们未观察到性别差异。DBA和F1家鼠的AHN总体较低，但它们表现出与林姬鼠和棕背䶄相同的反向梯度。DCX+年轻神经元通常局限于颗粒下区和深层颗粒细胞层。在隔区和齿状回中部的所有动物中都观察到了这种模式。然而，在棕背䶄和林姬鼠中，大多数颞区DCX+细胞呈放射状分散在整个颗粒细胞层中。部分但并非所有的隔颞差异都伴随着DCX+/Ki67+细胞比率的变化，这表明新神经元数量可以通过增殖或年轻神经元成熟和存活的时间进程来调节。我们观察到的一些隔颞差异在对控制AHN的分子机制进行实验操作后的实验啮齿动物中也有发现。自然条件下AHN的适应性可能作用于这些或类似的机制，根据海马体功能的需求调整神经发生。
