Of dots and lines: Characterising the development of the adrenal gland in Xenopus laevis

Kerr, Amy Jessica MacLeod (2024) Of dots and lines: Characterising the development of the adrenal gland in Xenopus laevis. Doctoral thesis, University of East Anglia.

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Abstract

The adrenal glands (AGs) are vital endocrine organs, performing as key hormonal regulators of physiological processes such as maintaining homeostasis, immune system regulation, sex hormone production, and the "fight-or-flight" response. In mammals, the AGs sit on top of the kidneys and are composed of the mesoderm-derived outer adrenal cortex (AC), producing steroids, and the inner adrenal medulla (AM) containing neuroendocrine chromaffin cells (CCs). CCs produce and secrete catecholamines adrenaline and noradrenaline directly into the bloodstream, essentially functioning as a specialized sympathetic neuron. Despite the AGs crucial role in our physiology, their development remains poorly understood. Only recently it was shown that most CCs are in fact derived from Schwann Cell Precursors (SCPs), nerve associated glial progenitor cells derived from the neural crest (NC). The NC is a unique cell population in vertebrate embryos, giving rise to a remarkable variety of tissues in the body such as pigment cells, craniofacial cartilage and bone, the peripheral nervous system and more. Abnormal NC development can cause many syndromes (termed Neurocristopathies) some of which include tumours forming from the AM or near the AGs, like neuroblastoma. Although performing the same function across vertebrate species, the structure of AGs can differ greatly between different model species. Currently, little is known about AG development during embryogenesis in the model organism Xenopus. The cellular origin and biological processes governing CC development of the AM have remained particularly elusive.

In this project, marker genes were identified to create a temporal and spatial map of Xenopus AG development to help define the molecular landscape underlying specific functions of this organ. This information will provide fundamental knowledge to establish and utilise Xenopus laevis as a research model for exploring aspects of AG development and disease. Chromaffin-like cells were found interspersed across the anterior embryonic body, first appearing at the anteroventral side of the embryo. During embryogenesis, chromaffin-like cells were not found in close association with the developing pronephric kidney and marker genes for the AM and AC cells did not overlap, suggesting that the AM does not fully form during embryogenesis. NC knockdown experiments showed a significant decrease in chromaffin-like cells, indicating their NC origin and raising an interesting question on how far the NC migrates during early Xenopus embryogenesis.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	06 Jan 2025 15:02
Last Modified:	06 Jan 2025 15:02
URI:	https://ueaeprints.uea.ac.uk/id/eprint/98090
DOI:

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