title: Maternal thyroid hormones are essential for neural development in zebrafish.
abstract: Teleost eggs contain an abundant store of maternal thyroid hormones (THs), and early in zebrafish embryonic development, all the genes necessary for TH signaling are expressed. Nonetheless the function of THs in embryonic development remains elusive. To test the hypothesis that THs are fundamental for zebrafish embryonic development, an monocarboxilic transporter 8 (Mct8) knockdown strategy was deployed to prevent maternal TH uptake. Absence of maternal THs did not affect early specification of the neural epithelia but profoundly modified later dorsal specification of the brain and spinal cord as well as specific neuron differentiation. Maternal THs acted upstream of pax2a, pax7, and pax8 genes but downstream of shha and fgf8a signaling. The lack of inhibitory spinal cord interneurons and increased motoneurons in the mct8 morphants is consistent with their stiff axial body and impaired mobility. The mct8 mutations are associated with X-linked mental retardation in humans, and the cellular and molecular consequences of MCT8 knockdown during embryonic development in zebrafish provides new insight into the potential role of THs in this condition.
authors.affiliation: Comparative Endocrinology and Integrative Biology Group (M.A.C., J.S., D.M.P.), Centre of Marine Sciences, and Departamento de Ciências Biomédicas e Medicina and Centro de Biomedicina Molecular e Estrutural (C.F.), Universidade do Algarve, 8005-139 Faro, Portugal.
authors.forename: Marco A
authors.initials: MA
authors.lastname: Campinho
authors.forename: João
authors.initials: J
authors.lastname: Saraiva
authors.forename: Claudia
authors.initials: C
authors.lastname: Florindo
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Power
mesh_terms: D000818:Animals; D001921:Brain / Q000196:embryology; D002454:Cell Differentiation / Q000235:genetics; D027501:Monocarboxylic Acid Transporters / Q000235:genetics*; D060172:Morpholinos / Q000235:genetics; D055495:Neurogenesis / Q000235:genetics*; D009474:Neurons / Q000166:cytology*; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics; D015398:Signal Transduction; D013116:Spinal Cord / Q000196:embryology; D037021:Thyroid Hormone Receptors alpha / Q000096:biosynthesis / Q000378:metabolism; D037042:Thyroid Hormone Receptors beta / Q000096:biosynthesis / Q000378:metabolism; D013963:Thyroid Hormones / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins / Q000235:genetics
chemical_list: D027501:Monocarboxylic Acid Transporters; D060172:Morpholinos; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors; C494467:Pax8 protein, zebrafish; C570017:Slc16a2 protein, zebrafish; D037021:Thyroid Hormone Receptors alpha; D037042:Thyroid Hormone Receptors beta; D013963:Thyroid Hormones; D029961:Zebrafish Proteins