Identification of ephrin-A3 and novel genes specific to the midbrain-MHB in embryonic zebrafish by ordered differential display.
Development of the tectum and the cerebellum is induced by a reciprocal inductive signaling between their respective primordia, the midbrain and the midbrain/hindbrain boundary (MHB). We set out to identify molecules that function in and downstream of this reciprocal signaling. Overexpression of LIM domain of the transcription factor Islet-3 (LIM(Isl-3)) leads to inhibition of this reciprocal signaling and to resultant defects in tectal and cerebellar development. We therefore searched for genes that may be either up- or down-regulated by overexpression of LIM(Isl-3) by comparing the gene expression profiles in the midbrain and the MHB of normal embryos and embryos in which Islet-3 function was repressed, using a combination of ordered differential display and whole-mount in situ hybridization. Among genes identified in this search, two cDNA fragments encoded Wnt1 and FGF8, which are already known to be essential for the reciprocal signaling between the midbrain and the MHB, confirming the effectiveness of our strategy. We identified four other partial cDNA clones that were specifically expressed around the MHB, ten cDNAs specifically expressed in the tectum, and three cDNAs expressed in neural crest cells including those derived from the midbrain level. The ephrin-A3 gene was specifically expressed in posterior tectum in a gradient that decreased anteriorly. Although ephrin-A2 and ephrin-A5 have been reported to be expressed in the corresponding region in mouse embryos, the superior/inferior colliculi, mouse ephrin-A3 is not expressed prominently in this region, suggesting that the role of ephrin-A3 in brain development may have been altered in the process of brain evolution.
Hirate
Y
Y
Laboratory for Developmental Gene Regulation, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.
Mieda
M
M
Harada
T
T
Yamasu
K
K
Okamoto
H
H
D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004625:Embryo, Nonmammalian / Q000378:metabolism; D036384:Ephrin-A3; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D017403:In Situ Hybridization; D060850:LIM-Homeodomain Proteins; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics*; D008636:Mesencephalon / Q000196:embryology* / Q000378:metabolism; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins; D012249:Rhombencephalon / Q000196:embryology* / Q000378:metabolism; D016415:Sequence Alignment; D014157:Transcription Factors; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics / Q000378:metabolism
D018076:DNA, Complementary; D036384:Ephrin-A3; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D014157:Transcription Factors; C063843:insulin gene enhancer binding protein Isl-1; C558563:isl2b protein, zebrafish