Investigating the Potential Role of Protocadherin-7 in Determining the Fate of Long-Term Hematopoietic Stem Cells

Abstract

Hematopoietic stem cells (HSCs) exhibit self-renewal and can differentiate into mature blood cells. Long-term HSCs (LT-HSCs) have long-term reconstitution potential to replenish the HSC pool. Based on reaction to stress, LT-HSCs have been categorized into quiescent reserve HSCs (rHSCs) located near N-Cadherin+ Mesenchymal Stem Cells in the endosteal niche and primed HSCs (pHSCs), which differentiate into short-term HSCs (ST-HSCs) and are located throughout the central marrow. Bulk-RNA sequencing of HSCs and their progeny revealed differential expression of Pcdh7, a non-clustered delta-1 protocadherin, with higher levels in pHSCs as compared to rHSCs. Pcdh7 can interact with other adhesion proteins to cause cell migration, which suggests a potential role in guiding LT-HSC migration away from the endosteal niche due to its increased expression. Flow cytometry analysis in transgenic mice with Pcdh7 tagged to ZsGreen indicates less expression of Pcdh7 protein in rHSCs and pHSCs, but notable expression in ST-HSCs. To confirm Pcdh7 expression within these HSCs, ZsGreen was observed within sorted cells which requires further validation. Immunofluorescence staining of femur sections identified a few ZsGreen+ cells within the bone marrow. This project aims to check if Pcdh7 plays a role in determining the fate that a LT-HSC attains.