title: Direct transcriptional regulation of Six6 is controlled by SoxB1 binding to a remote forebrain enhancer.
abstract: Six6, a sine oculis homeobox protein, plays a crucial and conserved role in the development of the forebrain and eye. To understand how the expression of Six6 is regulated during embryogenesis, we screened ~250 kb of genomic DNA encompassing the Six6 locus for cis-regulatory elements capable of directing reporter gene expression to sites of Six6 transcription in transgenic mouse embryos. Here, we describe two novel enhancer elements, that are highly conserved in vertebrate species and whose activities recapitulate Six6 expression in the ventral forebrain and eye, respectively. Cross-species comparisons of the Six6 forebrain enhancer sequences revealed highly conserved binding sites matching the consensus for homeodomain and SoxB1 transcription factors. Deletion of either of the binding sites resulted in loss of the forebrain enhancer activity in the ventral forebrain. Moreover, our studies show that members of the SoxB1 family, including Sox2 and Sox3, are expressed in the overlapping region of the ventral forebrain with Six6 and can bind to the Six6 forebrain enhancer. Loss of function of SoxB1 genes in vivo further emphasizes their role in regulating Six6 forebrain enhancer activity. Thus, our data strongly suggest that SoxB1 transcription factors are direct activators of Six6 expression in the ventral forebrain.
authors.affiliation: Department of Genetic Engineering, College of Life Sciences and Graduate School of Biotechnology, Kyung Hee University, Yongin-si 446-701, Republic of Korea.
authors.forename: Bumwhee
authors.initials: B
authors.lastname: Lee
authors.forename: Karine
authors.initials: K
authors.lastname: Rizzoti
authors.forename: David S
authors.initials: DS
authors.lastname: Kwon
authors.forename: Seon-Young
authors.initials: SY
authors.lastname: Kim
authors.forename: Sangtaek
authors.initials: S
authors.lastname: Oh
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Epstein
authors.forename: Youngsook
authors.initials: Y
authors.lastname: Son
authors.forename: Jaeseung
authors.initials: J
authors.lastname: Yoon
authors.forename: Kwanghee
authors.initials: K
authors.lastname: Baek
authors.forename: Yongsu
authors.initials: Y
authors.lastname: Jeong
mesh_terms: D000818:Animals; D004742:Enhancer Elements, Genetic; D005123:Eye / Q000196:embryology; D005136:Eye Proteins / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D051379:Mice; D016548:Prosencephalon / Q000196:embryology / Q000502:physiology*; D011485:Protein Binding; D012045:Regulatory Sequences, Nucleic Acid; D055748:SOXB1 Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics*
chemical_list: D005136:Eye Proteins; D018398:Homeodomain Proteins; D055748:SOXB1 Transcription Factors; C114419:Six6 protein, mouse; D015534:Trans-Activators