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Nature. 2018 Dec;564(7736):425-429. doi: 10.1038/s41586-018-0783-x. Epub 2018 Dec 5.

Complex mammalian-like haematopoietic system found in a colonial chordate.

Author information

1
Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA. rosentab@post.bgu.ac.il.
2
Department of Biology, Stanford University, Hopkins Marine Station, Pacific Grove, CA, USA. rosentab@post.bgu.ac.il.
3
Department of Physics, Stanford University, Stanford, CA, USA.
4
Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA.
5
AI based Healthcare and Medical Data Analysis Standardization Unit, Medical Sciences Innovation Hub Program, RIKEN, Tokyo, Japan.
6
Department of Biology, Stanford University, Hopkins Marine Station, Pacific Grove, CA, USA.
7
Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA.
8
Chan Zuckerberg Biohub, San Francisco, CA, USA.
9
Department of Bioengineering, Stanford University, Stanford, CA, USA.
10
Department of Molecular Cellular and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA, USA.
11
Dipartimento di Biologia, Università degli Studi di Padova, Padova, Italy.
12
Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA. irv@stanford.edu.
13
Department of Biology, Stanford University, Hopkins Marine Station, Pacific Grove, CA, USA. irv@stanford.edu.
14
Ludwig Center for Cancer Stem Cell Research and Medicine, Stanford University School of Medicine, Stanford, CA, USA. irv@stanford.edu.
15
Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA. ayeletv@stanford.edu.
16
Department of Biology, Stanford University, Hopkins Marine Station, Pacific Grove, CA, USA. ayeletv@stanford.edu.

Abstract

Haematopoiesis is an essential process that evolved in multicellular animals. At the heart of this process are haematopoietic stem cells (HSCs), which are multipotent and self-renewing, and generate the entire repertoire of blood and immune cells throughout an animal's life1. Although there have been comprehensive studies on self-renewal, differentiation, physiological regulation and niche occupation in vertebrate HSCs, relatively little is known about the evolutionary origin and niches of these cells. Here we describe the haematopoietic system of Botryllus schlosseri, a colonial tunicate that has a vasculature and circulating blood cells, and interesting stem-cell biology and immunity characteristics2-8. Self-recognition between genetically compatible B. schlosseri colonies leads to the formation of natural parabionts with shared circulation, whereas incompatible colonies reject each other3,4,7. Using flow cytometry, whole-transcriptome sequencing of defined cell populations and diverse functional assays, we identify HSCs, progenitors, immune effector cells and an HSC niche, and demonstrate that self-recognition inhibits allospecific cytotoxic reactions. Our results show that HSC and myeloid lineage immune cells emerged in a common ancestor of tunicates and vertebrates, and also suggest that haematopoietic bone marrow and the B. schlosseri endostyle niche evolved from a common origin.

PMID:
30518860
DOI:
10.1038/s41586-018-0783-x

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