title: A thyroid hormone receptor/KLF9 axis in human hepatocytes and pluripotent stem cells.
abstract: Biological processes require close cooperation of multiple transcription factors that integrate different signals. Thyroid hormone receptors (TRs) induce Krüppel-like factor 9 (KLF9) to regulate neurogenesis. Here, we show that triiodothyronine (T3) also works through TR to induce KLF9 in HepG2 liver cells, mouse liver, and mouse and human primary hepatocytes and sought to understand TR/KLF9 network function in the hepatocyte lineage and stem cells. Knockdown experiments reveal that KLF9 regulates hundreds of HepG2 target genes and modulates T3 response. Together, T3 and KLF9 target genes influence pathways implicated in stem cell self-renewal and differentiation, including Notch signaling, and we verify that T3 and KLF9 cooperate to regulate key Notch pathway genes and work independently to regulate others. T3 also induces KLF9 in human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSC) and this effect persists during differentiation to definitive endoderm and hiPSC-derived hepatocytes. Microarray analysis reveals that T3 regulates hundreds of hESC and hiPSC target genes that cluster into many of the same pathways implicated in TR and KLF9 regulation in HepG2 cells. KLF9 knockdown confirms that TR and KLF9 cooperate to regulate Notch pathway genes in hESC and hiPSC, albeit in a partly cell-specific manner. Broader analysis of T3 responsive hESC/hiPSC genes suggests that TRs regulate multiple early steps in ESC differentiation. We propose that TRs cooperate with KLF9 to regulate hepatocyte proliferation and differentiation and early stages of organogenesis and that TRs exert widespread and important influences on ESC biology.
authors.affiliation: Genomic Medicine, Houston Methodist Research Institute, Houston, Texas, USA.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Cvoro
authors.forename: Liani
authors.initials: L
authors.lastname: Devito
authors.forename: Flora A
authors.initials: FA
authors.lastname: Milton
authors.forename: Laila
authors.initials: L
authors.lastname: Noli
authors.forename: Aijun
authors.initials: A
authors.lastname: Zhang
authors.forename: Celine
authors.initials: C
authors.lastname: Filippi
authors.forename: Keiko
authors.initials: K
authors.lastname: Sakai
authors.forename: Ji Ho
authors.initials: JH
authors.lastname: Suh
authors.forename: Douglas
authors.initials: D
authors.lastname: H Sieglaff
authors.forename: Anil
authors.initials: A
authors.lastname: Dhawan
authors.forename: Takao
authors.initials: T
authors.lastname: Sakai
authors.forename: Dusko
authors.initials: D
authors.lastname: Ilic
authors.forename: Paul
authors.initials: P
authors.lastname: Webb
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D005260:Female; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000378:metabolism*; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism; D011988:Receptors, Thyroid Hormone / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014284:Triiodothyronine / Q000235:genetics / Q000378:metabolism
chemical_list: C489676:KLF9 protein, human; C489675:Klf9 protein, mouse; D051741:Kruppel-Like Transcription Factors; D051880:Receptors, Notch; D011988:Receptors, Thyroid Hormone; D014284:Triiodothyronine
keywords: Human embryonic stem cell; Induced pluripotent stem cell; Krüppel-like factor 9; Notch; Thyroid receptor