title: Identification of a novel role of ZIC3 in regulating cardiac development.
abstract: Mutations in ZIC3 cause X-linked heterotaxy, a disorder characterized by abnormal lateralization of normally asymmetric thoracic and abdominal organs. Animal models demonstrate an early role for ZIC3 in embryonic left-right (LR) patterning. ZIC3 mutations have also been described in patients with isolated cardiovascular malformations. We wished to address the hypothesis that ZIC3 has plieotropic effects in development and may regulate cardiac development independent of its role in LR patterning. We observed significantly reduced expression of several markers of cardiac lineage commitment in Zic3(null/y) embryonic stem cells including atrial natriuretic factor (ANF), Nkx2.5 and Tbx5. Likewise, ANF expression-a molecular marker of trabecular myocardium and a direct target of multiple cardiac-specific transcription factors-was severely reduced in E9.5 Zic3 null hearts. Trabecular myocardium was reduced in these embryos. This finding was similar to that observed in embryos with cardiac-specific ablation of serum response factor (SRF), a direct transcriptional regulator of ANF expression. While ZIC3 by itself had no effect on the ANF promoter, it could bind to and inhibit a cardiac alpha-actin promoter through its zinc finger domains. We observed that ZIC3 could function as a coactivator of SRF on both cardiac alpha-actin and ANF promoters. The zinc fingers of ZIC3 and the mcm1, agamous deficiens SRF (MADS) box motif of SRF were found to mediate their physical and functional interactions. These findings reveal a novel role of ZIC3 in regulating cardiac gene expression and may explain, in part, the association of ZIC3 mutation with cardiovascular malformations.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
authors.forename: Lirong
authors.initials: L
authors.lastname: Zhu
authors.forename: Karine G
authors.initials: KG
authors.lastname: Harutyunyan
authors.forename: Jian Lan
authors.initials: JL
authors.lastname: Peng
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Schwartz
authors.forename: John W
authors.initials: JW
authors.lastname: Belmont
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D019521:Body Patterning; D053595:Embryonic Stem Cells / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006367:HeLa Cells; D006321:Heart / Q000196:embryology*; D018398:Homeodomain Proteins / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D051379:Mice; D008954:Models, Biological; D009154:Mutation; D009206:Myocardium / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*
chemical_list: D000199:Actins; D018398:Homeodomain Proteins; D014157:Transcription Factors; C491595:ZIC3 protein, human; C491594:Zic3 protein, mouse