PT  - JOURNAL ARTICLE
AU  - Cristina Porcheri
AU  - Ohad Golan
AU  - Fernando J. Calero-Nieto
AU  - Roshana Thambyrajah
AU  - Cristina Ruiz-Herguido
AU  - Xiaonan Wang
AU  - Francesca Catto
AU  - Yolanda Guillen
AU  - Roshani Sinha
AU  - Jessica González
AU  - Sarah J. Kinston
AU  - Samanta A. Mariani
AU  - Antonio Maglitto
AU  - Chris Vink
AU  - Elaine Dzierzak
AU  - Pierre Charbord
AU  - Bertie Göttgens
AU  - Lluis Espinosa
AU  - David Sprinzak
AU  - Anna Bigas
TI  - Notch ligand Dll4 impairs cell recruitment into aortic clusters and limits hematopoietic stem cells
AID  - 10.1101/2019.12.16.877407
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 2019.12.16.877407
4099  - http://biorxiv.org/content/early/2019/12/16/2019.12.16.877407.short
4100  - http://biorxiv.org/content/early/2019/12/16/2019.12.16.877407.full
AB  - Hematopoietic stem cells (HSCs) develop from the hemogenic endothelium in cluster structures that protrude into the embryonic aortic lumen. Although much is known about the molecular characteristics of the developing hematopoietic cells, we lack a complete understanding of their origin and the three-dimensional organization of the niche. Here we use advanced live imaging techniques of organotypic slice cultures, clonal analysis, and mathematical modelling to show the two-step process of intra-aortic hematopoietic cluster (IACH) formation. First, a hemogenic progenitor buds up from the endothelium and undergoes division forming the monoclonal core of the IAHC. Next, surrounding hemogenic cells are recruited into the IAHC, increasing their size and heterogeneity. We identified the Notch ligand Dll4 as a negative regulator of the recruitment phase of IAHC. Blocking of Dll4 promotes the entrance of new hemogenic Gfi1+ cells into the IAHC and increases the number of cells that acquire HSC activity. Mathematical modelling based on our data provides estimation of the cluster lifetime and the average recruitment time of hemogenic cells to the cluster under physiologic and Dll4-inhibited conditions.