3D Atlas of the Pituitary Gland of the Model Fish Medaka ().

In vertebrates, the anterior pituitary plays a crucial role in regulating several essential physiological processes the secretion of at least seven peptide hormones by different endocrine cell types. Comparative and comprehensive knowledge of the spatial distribution of those endocrine cell types is required to better understand their physiological functions. Using medaka as a model and several combinations of multi-color fluorescence hybridization, we present the first 3D atlas revealing the gland-wide distribution of seven endocrine cell populations: lactotropes, thyrotropes, Lh and Fsh gonadotropes, somatotropes, and -expressing cells (corticotropes and melanotropes) in the anterior pituitary of a teleost fish. By combining hybridization and immunofluorescence techniques, we deciphered the location of corticotropes and melanotropes within the -expressing cell population. The 3D localization approach reveals sexual dimorphism of -, -, and -expressing cells in the adult medaka pituitary. Finally, we show the existence of bi-hormonal cells co-expressing -, - and - using single-cell transcriptomics analysis and hybridization. This study offers a solid basis for future comparative studies of the teleost pituitary and its functional plasticity.