title: FoxD5 mediates anterior-posterior polarity through upstream modulator Fgf signaling during zebrafish somitogenesis.
abstract: The transcription factor FoxD5 is expressed in the paraxial mesoderm of zebrafish. However, the roles of FoxD5 in anterior pre-somitic mesoderm (PSM) during somitogenesis are unknown. We knocked down FoxD5 in embryos, which resulted in defects of the newly formed somites, including loss of the striped patterns of anterior-posterior polarity genes deltaC, notch2, notch3 and EphB2a, as well as the absence of mespa expression in S-I. Also, the expression of mespb exhibited a 'salt and pepper' pattern, indicating that FoxD5 is necessary for somite patterning in anterior PSM. Embryos were treated with SU5402, an Fgf receptor (FGFR) inhibitor, resulting in reduction of FoxD5 expression. This finding was consistent with results obtained from Tg(hsp70l:dnfgfr1-EGFP)pd1 embryos, whose dominant-negative form of FGFR1 was produced by heat-induction. Loss of FoxD5 expression was observed in the embryos injected with fgf3-/fgf8-double-morpholinos (MOs). Excessive FoxD5 mRNA could rescue the defective expression levels of mespa and mespb in fgf3-/fgf8-double morphants, suggesting that Fgf signaling acts as an upstream modulator of FoxD5 during somitogenesis. We concluded that FoxD5 is required for maintaining anterior-posterior polarity within a somite and that the striped pattern of FoxD5 in anterior PSM is mainly regulated by Fgf. An Fgf-FoxD5-Mesps signaling network is therefore proposed.
authors.affiliation: Institute of Molecular and Cellular Biology, National Taiwan University, Room 307, Fisheries Science Building, No. 1, Section 4, Roosevelt Road, Taipei, Taiwan.
authors.forename: Hung-Chieh
authors.initials: HC
authors.lastname: Lee
authors.forename: Wei-An
authors.initials: WA
authors.lastname: Tseng
authors.forename: Fang-Yi
authors.initials: FY
authors.lastname: Lo
authors.forename: Tzu-Ming
authors.initials: TM
authors.lastname: Liu
authors.forename: Huai-Jen
authors.initials: HJ
authors.lastname: Tsai
mesh_terms: D000818:Animals; D001483:Base Sequence; D019521:Body Patterning; D017931:DNA Primers; D005346:Fibroblast Growth Factors / Q000378:metabolism*; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000502:physiology*; D055785:Gene Knockdown Techniques; D007150:Immunohistochemistry; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D015398:Signal Transduction; D019170:Somites / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins / Q000235:genetics / Q000502:physiology*
chemical_list: D017931:DNA Primers; D051858:Forkhead Transcription Factors; C545360:Foxd5 protein, zebrafish; D012333:RNA, Messenger; D029961:Zebrafish Proteins; D005346:Fibroblast Growth Factors