Neuroscience Unit, Department of Veterinary Anatomy, College of Veterinary Medicine, Federal University of Agriculture Abeokuta, Abeokuta, Ogun State, Nigeria.
Institute of Veterinary Anatomy, Histology and Embryology, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, Germany.
Neural Dev. 2023 Oct 13;18(1):7. doi: 10.1186/s13064-023-00175-x.
Neocortex development has been extensively studied in altricial rodents such as mouse and rat. Identification of alternative animal models along the "altricial-precocial" spectrum in order to better model and understand neocortex development is warranted. The Greater cane rat (GCR, Thyronomys swinderianus) is an indigenous precocial African rodent. Although basic aspects of brain development in the GCR have been documented, detailed information on neocortex development including the occurrence and abundance of the distinct types of neural progenitor cells (NPCs) in the GCR are lacking.
GCR embryos and fetuses were obtained from timed pregnant dams between gestation days 50-140 and their neocortex was analyzed by immunofluorescence staining using characteristic marker proteins for NPCs, neurons and glia cells. Data were compared with existing data on closely related precocial and altricial species, i.e. guinea pig and dwarf rabbit.
The primary sequence of neuro- and gliogenesis, and neuronal maturation is preserved in the prenatal GCR neocortex. We show that the GCR exhibits a relatively long period of cortical neurogenesis of 70 days. The subventricular zone becomes the major NPC pool during mid-end stages of neurogenesis with Pax6 + NPCs constituting the major basal progenitor subtype in the GCR neocortex. Whereas dendrite formation in the GCR cortical plate appears to initiate immediately after the onset of neurogenesis, major aspects of axon formation and maturation, and astrogenesis do not begin until mid-neurogenesis. Similar to the guinea pig, the GCR neocortex exhibits a high maturation status, containing neurons with well-developed dendrites and myelinated axons and astrocytes at birth, thus providing further evidence for the notion that a great proportion of neocortex growth and maturation in precocial mammals occurs before birth.
Together, this work has deepened our understanding of neocortex development of the GCR, of the timing and the cellular differences that regulate brain growth and development within the altricial-precocial spectrum and its suitability as a research model for neurodevelopmental studies. The timelines of brain development provided by this study may serve as empirical reference data and foundation in future studies in order to model and better understand neurodevelopment and associated alterations.
在晚成性啮齿动物（如小鼠和大鼠）中，对新皮质发育进行了广泛的研究。为了更好地模拟和理解新皮质发育，有必要沿着“晚成性-早成性”谱系确定替代动物模型。大颊囊鼠（GCR，Thyronomys swinderianus）是一种本土的早成性非洲啮齿动物。尽管已经记录了 GCR 中大脑发育的基本方面，但关于新皮质发育的详细信息，包括 GCR 中不同类型神经祖细胞（NPC）的发生和丰度，仍然缺乏。
在妊娠第 50-140 天之间，从定时怀孕的母鼠中获得 GCR 胚胎和胎儿，并使用 NPC、神经元和神经胶质细胞的特征标记蛋白通过免疫荧光染色对其新皮质进行分析。将数据与密切相关的早成性和晚成性物种（即豚鼠和矮兔）的现有数据进行比较。
在产前 GCR 新皮质中，神经发生和神经胶质发生以及神经元成熟的主要序列得以保留。我们表明，GCR 表现出相对较长的 70 天皮质神经发生期。室下区在神经发生的中晚期成为主要的 NPC 池，GCR 新皮质中 Pax6+NPC 构成主要的基底祖细胞亚型。尽管 GCR 皮质板中的树突形成似乎在神经发生开始后立即开始，但轴突形成和成熟以及星形胶质发生的主要方面直到神经发生中期才开始。与豚鼠一样，GCR 新皮质具有较高的成熟状态，在出生时就含有具有发育良好的树突和髓鞘化轴突的神经元和星形胶质细胞，这进一步证明了一个观点，即早成性哺乳动物的大部分新皮质生长和成熟发生在出生前。
总之，这项工作加深了我们对 GCR 新皮质发育的理解，加深了我们对在晚成性-早成性谱系内调节大脑生长和发育的时间和细胞差异的理解，以及它作为神经发育研究模型的适宜性。本研究提供的大脑发育时间线可以作为未来研究的经验参考数据和基础，以模拟和更好地理解神经发育和相关变化。
