Endocrine Abstracts

The pituitary gland is the master gland of the endocrine system, controlling important physiological steps like growth, puberty or reproduction. There are different endocrine cell types within the adenopituitary, each one producing a specific hormone. Adaptation to different life stages and moments requires a plastic capacity based in proliferation and differentiation of pituitary stem cells. We ans others discovered the existence of a stem cell niche in the pituitary. Parenchymal stem cells from this niche are called GPS, as they co-express especific markers such as GFRa2, Prop1, Sox2 and Sox9 together with Cytokeratins and b-catenin, which are not co-expressed in any other pituitary cell. The objective of this study is to investigate about the role of GFRa2 in pituitary stem cells. To do so, we have used the GFRa2 knockout (KO) mouse strain compared to wild-type (WT) littermates. Characterization and validation for pituitary stem cell study was performed by postnatal growth assessment, serum hormone assays, qRT-PCR for gene expression and also Western Blot and image techniques for protein expression. Pituitary Gfra2 knockout was validated as we found absence of gene expression at mRNA and protein levels in comparison with littermate WT mice. Adult KO mice present a significant and marked difference in weight and size; those differences appear postnatally and increases during childhood to puberty. Gfra2 KO have decreased pituitary volume with significant less cells per section in the adenopituitary. Molecular analysis consisted on PCR and Western Blot to study gene and protein expression of RET pathway members and also different markers related to stem cells. Further research involving image techniques was also performed, demonstrating different distribution of stem cells in adenopituitary from KO mice in comparison to WT. Our data suggest an increased in proportion of Sox2 positive cells within the adenopituitary in KO mice. Moreover, Sox2+ cells in adenopituitary from KO mice are grouped. However, there is no difference in Sox+2 positive cells in the stem cell niche. Finally, we studied cell proliferation using the EdU click chemistry technique, suggesting that proliferation rates in KO mice are increased when compared to WT. In conclusion, absence of Gfra2 produces pituitary phenotype in mice, however, further investigation about the biology and cellular mechanisms is needed.