Evidence for neurogenesis in the medial cortex of the leopard gecko, Eublepharis macularius

Rebecca P Mcdonald,Matthew K Vickaryous

doi:10.1038/s41598-018-27880-6

Abstract

Although lizards are often described as having robust neurogenic abilities, only a handful of the more than 6300 species have been explored. Here, we provide the first evidence of homeostatic neurogenesis in the leopard gecko (Eublepharis macularius). We focused our study on the medial cortex, homologue of the mammalian hippocampal formation. Using immunostaining, we identified proliferating pools of neural stem/progenitor cells within the sulcus septomedialis, the pseudostratified ventricular zone adjacent to the medial cortex. Consistent with their identification as radial glia, these cells expressed SOX2, glial fibrillary acidic protein, and Vimentin, and demonstrated a radial morphology. Using a 5-bromo-2′-deoxyuridine cell tracking strategy, we determined that neuroblast migration from the ventricular zone to the medial cortex takes ~30-days, and that newly generated neuronal cells survived for at least 140-days. We also found that cell proliferation within the medial cortex was not significantly altered following rupture of the tail spinal cord (as a result of the naturally evolved process of caudal autotomy). We conclude that the sulcus septomedialis of the leopard gecko demonstrates all the hallmarks of a neurogenic niche.

Highlights

Evolved examples of constitutive postnatal neurogenesis have been reported for representative members of most major vertebrate lineages[1,2]
This study provides the first evidence of postnatal neurogenesis in a representative, commercially bred lizard species, the leopard gecko
Using a BrdU pulse-chase strategy and a panel of protein markers, we determined that cells from the ventricular zone of the sulcus septomedialis constitutively proliferate and contribute new neurons to the medial cortex, homologue of the mammalian hippocampal formation[18,19,20]

Summary

Introduction

Evolved examples of constitutive postnatal neurogenesis have been reported for representative members of most major vertebrate (and even some invertebrate) lineages[1,2]. In Gallot’s lizards (Galloti gallotia) cells that have migrated to the medial cortex within 30 days still have ultrastructural features of neuroblasts (i.e., immature neurons), and do not take on characteristics of mature neurons until 90 days after their generation[26]. These findings provide intriguing evidence for unequal neurogenic potential across lizard species. It is worth noting that, where reported, studies to date involve wild-caught populations and rely on estimates of lizard ages, an important factor known to influence neurogenic capacity[27,28]

Methods

Results

Conclusion