Single-Cell Analysis of Murine Long-Term Hematopoietic Stem Cells Reveals Distinct Patterns of Gene Expression during Fetal Migration

Abstract

<div><h3>Background</h3><p>Long-term hematopoietic stem cells (LT-HSCs) migrate from the fetal liver (FL) to the fetal bone marrow (FBM) during development. Various adhesion and chemotactic receptor genes have been implicated in the migration of adult LT-HSCs. However, their role in the migration of fetal LT-HSCs is not clearly understood due, in part, to the rare number of these cells in fetal tissues, which preclude classical gene expression analysis. The aim of this study is to characterize the expression of migration related genes in fetal LT-HSC across different anatomical locations during development.</p> <h3>Methodology/Principal Findings</h3><p>We isolated fetal LT-HSC from different developmental stages, as well as different anatomical locations, and performed single-cell multiplex RT-qPCR and flow cytometry analysis of eight molecules involved in adult LT-HSC migration. Our results show that the gene expression of the chemokine receptor <em>Cxcr4</em> in LT-HSC varies across developmental microenvironments and times, while the cadherin <em>Cdh2</em> (<em>Ncad</em>) and the calcium receptor <em>Casr</em> show higher gene expression and variability only in FBM at 17.5 days post coitum (dpc). The cadherin <em>Cdh5</em> (<em>Vecad</em>) maintains high expression variability only during fetal development, while the integrin subunit <em>Itga5 (α5)</em> increases its variability after 14.5 dpc. The integrin subunits <em>Itga4</em> (<em>α4</em>) and <em>Itgal</em> (<em>Lfa1</em>), as well as the selectin ligand <em>Selplg (Psgl1)</em>, did not show differences in their expression in single LT-HSCs irrespective of the developmental times or anatomical microenvironments studied.</p> <h3>Conclusions/Significance</h3><p>Our data demonstrate that the expression pattern of phenotypically identical, single LT-HSCs fluctuates as a function of developmental stage and anatomical microenvironment. This is the first exhaustive gene expression comparison of migration-related molecules in fetal tissues across developmental times, enhancing the understanding of LT-HSC migration fate decisions during development.</p> </div