Oogenesis and germinal bed morphology of the brown anole (A. sagrei)

Background: The brown anole is a model species of the genus Anolis, a squamate (encompassing lizards and snakes) group widely studied in evolutionary, behavioral, and developmental biology. Full genome annotation, the establishment of gene editing techniques, and comprehensive description of reproductive tract morphology and embryogenesis in this species have laid the foundation for functional studies. However, analysis of brown anole oogenesis is still required and vital to optimize genome modification, mutant line establishment, and analyses of the evolution of reproductive developmental mechanisms. Results: Here, we characterize ovary morphology and gametogenesis in the female brown anole, Anolis sagrei, using brightfield imaging, microCT, histology staining, electron microscopy, and confocal imaging. We define 10 stages of oocyte maturation, which commences inside the oogonial nest within the germinal bed and concludes with the mature follicle ready to ovulate based on follicle size, yolk acquisition, and follicular, cellular, and basement membrane architecture. Conclusions: We describe the complete oogenesis of the brown anole in 10 stages and report that oogenesis is highly conserved within iguanians, a suborder of lizards. With our staging framework, we lay the foundation for functional studies of oogenesis and optimized gene-editing.