Effects of Delta1 and Jagged1 on early human hematopoiesis: correlation with expression of Notch-signaling-related genes in CD34⁺ cells

¹ Instituto de Medicina Molecular, Faculdade de Medicina de Lisboa, Lisboa, Portugal; Instituto Gulbenkian de Ciência, Oeiras, Portugal
² Department of Immunology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
³ Serviço de Hematologia, Instituto Português de Oncologia Francisco Gentil, Lisboa, Portugal
⁴ Instituto Gulbenkian de Ciência, Oeiras, Portugal
⁵ Serviço de Obstetrícia, Hospital de Santa Maria, Lisboa, Portugal

^* To whom correspondence should be addressed. E-mail: hleonor{at}fm.ul.pt.

	Abstract

It has been shown that Notch-signaling mediated by ligands of both Jagged and Delta families expands the hematopoietic stem cell compartment while blocking or delaying terminal myeloid differentiation. Here we show that Delta1- and Jagged1- expressing stromal cells have distinct effects on the clonogenic and differentiation capacities of human CD34⁺CD38⁺ cells. Jagged1 increases the number of bi- (CFUGM) and uni-potent progenitors (CFU-G and CFU-M), without quantitatively affecting terminal cell differentiation, whereas Delta1 reduces the number of CFU-GM and differentiated monocytic cells. Expression analysis of genes coding for Notch-receptors, Notch-targets and Notch-signaling modulators in supernatant CD34⁺ cells arising upon contact with Jagged1 and Delta1, shows dynamic and differential gene expression profiles over time. At early time-points, modest up-regulation of Notch1, Notch3 and Hes1 is observed in Jagged1- CD34⁺ cells whereas those in contact with Delta1 strikingly up-regulate Notch3 and Hes1. Later, myeloid progenitors with strong clonogenic potential emerging upon contact with Jagged1 up-regulate Notch1 and Deltex and down-regulate Notch-signaling modulators, whereas T/NK progenitors originated by Delta1 strikingly up-regulate Notch3 and Deltex and, to a lesser extent, Hes1, Lunatic Fringe and Numb. Together, the data unravels previously unrecognized expression patterns of Notch-signaling-related genes in CD34⁺CD38⁺ cells as they develop in Jagged1 or Delta1-stromal cell environments, which appear to reflect sequential maturational stages of CD34⁺ cells into distinct cell-lineages.