Brain-specific homeobox Bsx specifies identity of pineal gland between serially homologous photoreceptive organs in zebrafish

• Published in: Communications biology Vol. 2; no. 1; p. 364
• Main Authors: Mano, Hiroaki, Asaoka, Yoichi, Kojima, Daisuke, Fukada, Yoshitaka
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 07.10.2019; Nature Publishing Group
• Subjects: 13/31; 14/19; 38/39; 38/77; 38/90; 631/181/2806; 631/378/2571/2573; 631/378/2613/1786; 631/378/87; 64/116; Animals; Animals, Genetically Modified; Biology; Biomedical and Life Sciences; Danio rerio; Ectopic expression; Endocrine system; Gene expression; Gene Expression Regulation, Developmental; Homeobox; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; Life Sciences; Otx Transcription Factors - metabolism; PAX6 Transcription Factor - metabolism; Pineal gland; Pineal Gland - cytology; Pineal Gland - growth & development; Pineal Gland - metabolism; Promoter Regions, Genetic; Retina; Rhodopsin - metabolism; Trans-Activators - metabolism; Transcription Factors - metabolism; Zebrafish; Zebrafish Proteins - genetics; Zebrafish Proteins - metabolism; Cell type diversity; Retina; Cellular neuroscience; Evolutionary developmental biology
• ISSN: 2399-3642; 2399-3642
• DOI: 10.1038/s42003-019-0613-1

The pineal gland functioning as a photoreceptive organ in non-mammalian species is a serial homolog of the retina. Here we found that Brain-specific homeobox (Bsx) is a key regulator conferring individuality on the pineal gland between the two serially homologous photoreceptive organs in zebrafish. Bsx knock-down impaired the pineal development with reduced expression of exorh , the pineal-specific gene responsible for the photoreception, whereas it induced ectopic expression of rho , a retina-specific gene, in the pineal gland. Bsx remarkably transactivated the exorh promoter in combination with Otx5, but not with Crx, through its binding to distinct subtypes of PIRE, a DNA cis -element driving Crx/Otx-dependent pineal-specific gene expression. These results demonstrate that the identity of pineal photoreceptive neurons is determined by the combinatorial code of Bsx and Otx5, the former confers the pineal specificity at the tissue level and the latter determines the photoreceptor specificity at the cellular level. Hiroaki Mano et al. show that brain-specific homeobox, Bsx, is a regulator in pineal gland development. They show that Bsx depletion in zebrafish reduces the expression of a pineal-specific gene responsible for photoreception, affecting the identity of pineal photoreceptive neurons.