1. Smyd1 facilitates heart development by antagonizing oxidative and ER stress responses.
- Author
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Rasmussen TL, Ma Y, Park CY, Harriss J, Pierce SA, Dekker JD, Valenzuela N, Srivastava D, Schwartz RJ, Stewart MD, and Tucker HO
- Subjects
- Amino Acid Sequence, Animals, COS Cells, Cell Cycle Proteins chemistry, Cell Cycle Proteins metabolism, Cell Proliferation, Chlorocebus aethiops, DNA-Binding Proteins deficiency, DNA-Binding Proteins genetics, Embryo, Mammalian embryology, Gene Expression Regulation, Developmental, Gene Knockout Techniques, Humans, Methylation, Mice, Molecular Sequence Data, Muscle Proteins deficiency, Muscle Proteins genetics, Transcription Factors deficiency, Transcription Factors genetics, Transcription, Genetic, Up-Regulation, DNA-Binding Proteins metabolism, Endoplasmic Reticulum Stress, Heart growth & development, Muscle Proteins metabolism, Myocardium cytology, Myocardium metabolism, Oxidative Stress, Transcription Factors metabolism
- Abstract
Smyd1/Bop is an evolutionary conserved histone methyltransferase previously shown by conventional knockout to be critical for embryonic heart development. To further explore the mechanism(s) in a cell autonomous context, we conditionally ablated Smyd1 in the first and second heart fields of mice using a knock-in (KI) Nkx2.5-cre driver. Robust deletion of floxed-Smyd1 in cardiomyocytes and the outflow tract (OFT) resulted in embryonic lethality at E9.5, truncation of the OFT and right ventricle, and additional defects consistent with impaired expansion and proliferation of the second heart field (SHF). Using a transgenic (Tg) Nkx2.5-cre driver previously shown to not delete in the SHF and OFT, early embryonic lethality was bypassed and both ventricular chambers were formed; however, reduced cardiomyocyte proliferation and other heart defects resulted in later embryonic death at E11.5-12.5. Proliferative impairment prior to both early and mid-gestational lethality was accompanied by dysregulation of transcripts critical for endoplasmic reticulum (ER) stress. Mid-gestational death was also associated with impairment of oxidative stress defense-a phenotype highly similar to the previously characterized knockout of the Smyd1-interacting transcription factor, skNAC. We describe a potential feedback mechanism in which the stress response factor Tribbles3/TRB3, when directly methylated by Smyd1, acts as a co-repressor of Smyd1-mediated transcription. Our findings suggest that Smyd1 is required for maintaining cardiomyocyte proliferation at minimally two different embryonic heart developmental stages, and its loss leads to linked stress responses that signal ensuing lethality.
- Published
- 2015
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