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.

中文翻译：

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非洲大甘蔗大鼠新皮质神经发生和成熟

新皮质发育已在小鼠和大鼠等晚熟啮齿动物中进行了广泛研究。为了更好地模拟和理解新皮质的发育，有必要沿着“晚熟-早熟”谱鉴定替代动物模型。大甘蔗鼠（GCR，Thyronomys swinderianus）是一种本土的早熟非洲啮齿动物。尽管 GCR 中大脑发育的基本方面已被记录，但缺乏新皮质发育的详细信息，包括 GCR 中不同类型神经祖细胞 (NPC) 的出现和丰度。GCR 胚胎和胎儿是从妊娠 50-140 天之间的定时怀孕母鼠中获得的，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分析其新皮质。将数据与密切相关的早熟和晚熟物种（即豚鼠和侏儒兔）的现有数据进行了比较。神经和胶质生成以及神经元成熟的主要序列保留在产前 GCR 新皮质中。我们发现 GCR 表现出相对较长的皮质神经发生周期（70 天）。在神经发生的中期阶段，室下区成为主要的 NPC 池，Pax6 + NPC 构成 GCR 新皮质中的主要基底祖细胞亚型。虽然 GCR 皮层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体发生的主要方面直到神经发生中期才开始。与豚鼠相似，GCR新皮质表现出高度成熟状态，在出生时含有发育良好的树突、有髓轴突和星形胶质细胞的神经元，从而为早熟哺乳动物的新皮质生长和成熟很大一部分发生的观点提供了进一步的证据出生前。总之，这项工作加深了我们对 GCR 新皮质发育、晚熟-早熟谱系中调节大脑生长和发育的时间和细胞差异及其作为神经发育研究模型的适用性的理解。这项研究提供的大脑发育时间表可以作为未来研究的经验参考数据和基础，以便建模和更好地理解神经发育和相关的改变。