title: The basic helix-loop-helix transcription factor Hand1 regulates mouse development as a homodimer.
abstract: Hand1 is a basic helix-loop-helix transcription factor that is essential for development of the placenta, yolk sac and heart during mouse development. While Hand1 is essential for trophoblast giant cell (TGC) differentiation, its potential heterodimer partners are not co-expressed in TGCs. To test the hypothesis that Hand1 functions as homodimer, we generated knock-in mice in which the Hand1 gene was altered to encode a tethered homodimer (TH). Some Hand1(TH/-) conceptuses in which the only form of Hand1 is Hand1(TH) are viable and fertile, indicating that homodimer Hand1 is sufficient for mouse survival. ~2/3 of Hand1(TH/-) and all Hand1(TH/TH) mice died in utero and displayed severe placental defects and variable cardial and cranial-facial abnormalities, indicating a dosage-dependent effect of Hand1(TH). Meanwhile, expression of the Hand1(TH) protein did not have negative effects on viability or fertility in all Hand1(TH/+) mice. These data imply that Hand1 homodimer plays a dominant role during development and its expression dosage is critical for survival, whereas Hand1 heterodimers can be either dispensable or play a regulatory role to modulate the activity of Hand1 homodimer in vivo.
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Calgary, Calgary, AB, Canada; Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada; Center for Stem Cell Application and Research, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China. Electronic address: dhu2007@gmail.com.
authors.forename: Dong
authors.initials: D
authors.lastname: Hu
authors.forename: Ian C
authors.initials: IC
authors.lastname: Scott
authors.forename: Fran
authors.initials: F
authors.lastname: Snider
authors.forename: Colleen
authors.initials: C
authors.lastname: Geary-Joo
authors.forename: Xiang
authors.initials: X
authors.lastname: Zhao
authors.forename: David G
authors.initials: DG
authors.lastname: Simmons
authors.forename: James C
authors.initials: JC
authors.lastname: Cross
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000378:metabolism; D002454:Cell Differentiation; D004622:Embryo, Mammalian / Q000002:abnormalities / Q000378:metabolism; D018628:Gene Dosage; D018507:Gene Expression Regulation, Developmental; D055879:Gene Knock-In Techniques; D017403:In Situ Hybridization; D051379:Mice; D055503:Protein Multimerization
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; C095572:Hand1 protein, mouse
keywords: Basic helix-loop-helix; Hand1; Homodimer; Mouse development; Transcription factor; Trophoblast