Role of Notch signaling on the differentiation of early lymphoid progenitors ce...

• Author(s): Moreira, Pedro Miguel Lopes
• Date: 2014
• Persistent ID: http://hdl.handle.net/10362/13012
• Origin: Repositório Institucional da UNL
• Subject(s): Notch signaling – Delta1; Organogenesis; Thymus; Spleen; Hematopoietic progenitors; B cells
• Document Type: Master Thesis
• Language: English
• Advisor(s): Henriques, Isabel; Zilhão, Rita

Description

Dissertação para a obtenção do grau de Mestre em Genética Molecular e Biomedicina The lymphoid organs, thymus and spleen, are essential for the differentiation of T and B cells, respectively. One of the signaling pathways involved in processes of cell differentiation is the Notch signaling pathway. Work conducted by our group demonstrated that Notch ligands, receptors and target genes are expressed in the thymic epithelium. In this work, we aimed: 1) to study the organogenesis of the thymus and spleen in chicken embryos; 2) phenotypically characterize the cells present in both organs; 3) to study the role of Notch signaling in the differentiation of hematopoietic progenitors (PH) isolated from thymus and spleen of the chicken embryo. To study the formation of the thymus and spleen and characterize the cell populations present within them during embryonic development, we stained histological sections of the organs and citospins with Hematoxylin-Eosin (HE). To elucidate the role of Notch signaling in the differentiation of the PH, we used a co-culture system of PH with stromal cells that express specific Notch ligands, Delta 1 (Dl1) and Delta 4 (Dl4). The results confirm that, the spleen is an early (E6) vascularized organ and the number of PH in the spleen increases after day E10. In the thymus, the regionalization in cortex and medulla occurs at day E8 and there are no visible neural crest cells during the several embryonic stages studied. We conclude that hematopoietic cells collected from the thymus at day E15 are more differentiated than cells collected from thymus E13. The co-cultures results demonstrated that the Notch ligand Dl1 appears to favor the lymphoid progenitor cells (LPC) proliferation/survival. Thus, the Dl1 ligand may have an important role at the early stages of T cell differentiation. Moreover, these evidences seem to confirm that the undifferentiated LPCs are able to respond more effectively to external stimulus and differentiate into T cells more efficiently.