Runx1 exon 6-related alternative splicing isoforms differentially regulate hematopoiesis in mice.
RUNX1 is an important transcription factor for hematopoiesis. There are multiple alternatively spliced isoforms of RUNX1. The best known isoforms are RUNX1a from use of exon 7A and RUNX1b and c from use of exon 7B. RUNX1a has unique functions due to its lack of C-terminal regions common to RUNX1b and c. Here, we report that the ortholog of human RUNX1a was only found in primates. Furthermore, we characterized 3 Runx1 isoforms generated by exon 6 alternative splicing. Runx1bEx6(-) (Runx1b without exon 6) and a unique mouse Runx1bEx6e showed higher colony-forming activity than the full-length Runx1b (Runx1bEx6(+)). They also facilitated the transactivation of Runx1bEx6(+). To gain insight into in vivo functions, we analyzed a knock-in (KI) mouse model that lacks isoforms Runx1b/cEx6(-) and Runx1bEx6e. KI mice had significantly fewer lineage-Sca1(+)c-Kit(+) cells, short-term hematopoietic stem cells (HSCs) and multipotent progenitors than controls. In vivo competitive repopulation assays demonstrated a sevenfold difference of functional HSCs between wild-type and KI mice. Together, our results show that Runx1 isoforms involving exon 6 support high self-renewal capacity in vitro, and their loss results in reduction of the HSC pool in vivo, which underscore the importance of fine-tuning RNA splicing in hematopoiesis.
Moores University California San Diego Cancer Center.
Yukiko
Y
Komeno
Moores University California San Diego Cancer Center.
Ming
M
Yan
Moores University California San Diego Cancer Center.
Shinobu
S
Matsuura
Biomedical Science Graduate Program, and.
Kentson
K
Lam
Moores University California San Diego Cancer Center.
Miao-Chia
MC
Lo
Division of Biological Sciences, University of California San Diego, La Jolla, CA;
Yi-Jou
YJ
Huang
Harvard Stem Cell Institute, Harvard Medical School, Boston, MA;
Daniel G
DG
Tenen
Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN; and.
James R
JR
Downing
Moores University California San Diego Cancer Center, Biomedical Science Graduate Program, and Division of Biological Sciences, University of California San Diego, La Jolla, CA; Department of Pathology, University of California San Diego, La Jolla, CA.
Dong-Er
DE
Zhang
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D050676:Core Binding Factor Alpha 2 Subunit / Q000235:genetics / Q000502:physiology*; D005091:Exons; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006410:Hematopoiesis / Q000235:genetics*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000235:genetics / Q000502:physiology; D022821:RNA Splice Sites; D017385:Sequence Homology
D050676:Core Binding Factor Alpha 2 Subunit; D020033:Protein Isoforms; D022821:RNA Splice Sites; C493726:Runx1 protein, mouse