Quality assurance of hematopoietic stem cells by macrophages determines stem cell clonality

Wattrus et al. establish that hematopoietic stem and progenitor cells (HSPC) are quality assured for stress levels during development. Calreticulin is revealed as an “eat-me” molecule that initiates macrophage-HSPC interaction and leads to programmed cell clearance or stem cell expansion. They used SORT-seq to characterize the macrophage and HSPC subpopulations involved.

A public antibody class recognizes an S2 epitope exposed on open conformations of SARS-CoV-2 spike

Claireaux et al. aimed to guide vaccine improvement by finding out how the unexposed immune system reacts to the SARS-CoV-2 spike protein. Single-cell RNA sequencing and flow cytometry helped them describe the reactive B cell repertoire. They identified a non-neutralizing antibody class as a main factor in the unexposed SARS-CoV-2 response.

Inflammatory response in hematopoietic stem and progenitor cells triggered by activating SHP2 mutations evokes blood defects

Hematopoietic stem and progenitor cells (HSPCs) are the disease-propagating cells of juvenile myelomonocytic leukemia (JMML). A SHP2 mutation is common in these patients, and Solman et al. reproduced it in zebrafish. Single-cell mRNA sequencing of HSPCs from mutant zebrafish embryos and bulk sequencing of HSPCs from JMML patients revealed an overlapping inflammatory gene expression pattern. Pharmacological inhibition of the inflammatory response positively impacted mutant zebrafish, suggesting therapeutic possibilities in JMML patients.