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David Bodznick




The majority of neurons in the mammalian brain reside within the cerebellum. The cerebellum has several functions, including motor control, sensory processing and cognition. Despite its anatomical and functional significance, the evolutionary origins of the cerebellum are not well understood. There are several sensory nuclei present across vertebrate phylogeny collectively termed cerebellum-like structures due to a shared anatomy and physiology with the cerebellum. Common structure and function may arise due to a shared genetic and developmental toolkit. If this is true, the cerebellum may have evolved as a duplication or expansion of the cerebellum-like structures and these structures would be considered generatively homologous. In Chapter 1, I review what is known about cerebellar anatomy and development, cerebellum-like structures and candidate genes that may play a role in this common developmental genetic toolkit. In Chapter 2, I describe the morphological and temporal developmental relationships between the cerebellum and cerebellum-like structures in a representative of the most basal extant vertebrate lineage that possesses a cerebellum, the little skate Leucoraja erinacea. In Chapter 3, I test the hypothesis that the cerebellum and cerebellum-like structures develop using a shared developmental genetic toolkit by determining if homologs of candidate genes important for parallel-fiber-Purkinje cell synaptogenesis are expressed in the same respective cell types between both structures. I have also shown that major elements of gnathostome cerebellar development are conserved. Based on these findings, it is possible that the cerebellum evolved as a result of a duplication or expansion of the cerebellum-like developmental genetic toolkit.



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