Chandwani, Paul; (2002) A study of the developing pituitary gland in zebrafish. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The pituitary gland is an endocrine organ with roles in growth, maturation and homeostasis. It is derived from two distinct cell populations in the embryo, which give rise to a mature gland with six distinct hormone secreting cell types. This organ, combined with the attributes of the zebrafish, provides an ideal model system in which to study cell differentiation and intercellular communication, fundamentals of developmental biology. Initially a characterisation of gene expression within the anterior pituitary gland over the first four days of development was carried out using in situ hybridisation and antibody labelling. This provides a description of normal development. This information was used to identify mutant zebrafish lines in which anterior pituitary development was in some way disrupted. Two such lines investigated in this work carry novel alleles. A novel zebrafish gene, ptx1/3, with expression in the developing anterior pituitary gland was studied, firstly to determine the identity of the gene in relation to a number of possible homologues from other species and then to assess its role in pituitary development. An anti-sense approach was used to address function by preventing translation of the protein within the zebrafish embryo. Large-scale genetic screening is an invaluable method of isolating novel mutant lines. I contributed to two such screens were conducted during the course of my studies; the first was at UCL and the second in Tuebingen, Germany, co-ordinated by Artemis pharmaceuticals. Both focused on isolating mutants with defects in early neurogenesis and axon pathway patterning in the embryonic forebrain. Embryos were screened by morphology and anti-tubulin antibody labelling, with more than 100 mutant lines being identified. Novel mutant lines are useful tools in the study of development. One such line studied here, named u320, was genetically mapped to identify the location of the mutant locus. A phenotypic characterisation of the line was conducted including gene expression analysis and transplantation experiments. This work provides information as to the likely activity of the mutated locus in this novel zebrafish line and the role of the affected gene in the context of development, with a focus on the anterior pituitary. The work described here provides an outline of the developing pituitary gland in the zebrafish embryo. A number of studies then provide examples as to how this information can be used to understand the role of specific genes in a more general developmental context

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