Pitx genes in Tunicates provide new molecular insight into the evolutionary origin of pituitary.
We have initiated a project aimed at documenting molecular and cellular changes underlying the emergence of the hypothalamo-hypophyseal axis in Chordates. Considering the phylogenetic position of Tunicates and the 'pan-hypophyseal' expression pattern of Pitx genes in Vertebrate pituitary, we searched for a Pitx-related homeobox gene in the ascidian Ciona intestinalis, and identified Ci-Pitx (ona intestinalis uitary homeobo gene). We also isolated Cs-Pitx and Bs-Pitx, the Ci-Pitx respective counterparts of Ciona savignyi and Botryllus schlosseri, two other Tunicate species. Ci-Pitx mRNA encodes a putative protein exhibiting the diagnostic K50-Paired-class homeodomain and a conserved C-terminal Aristaless domain. Embryonic expression pattern of Ci-Pitx revealed a conserved expression domain in the anterior neural ridge and subsequently in the pharyngeal primordium, defined in Vertebrates as the stomodeal ectomere, which encompasses the presumptive pituitary territory. This shows that expression at early steps of pituitary development is a feature of Pitx-related genes that was already present in the last common ancestor of Chordates.
Christiaen
Lionel
L
INRA Junior Group Morphogenèse du Système Nerveux des Chordés, UPR2197 DEPSN, Institut de Neurobiologie Alfred Fessard, CNRS, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France. christia@iaf.cnrs-gif.fr
Burighel
Paolo
P
Smith
William C
WC
Vernier
Philippe
P
Bourrat
Franck
F
Joly
Jean-Stéphane
JS
D000595:Amino Acid Sequence; D000818:Animals; D002938:Ciona intestinalis / Q000196:embryology / Q000235:genetics*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000378:metabolism; D047108:Embryonic Development; D019143:Evolution, Molecular; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D010802:Phylogeny; D010902:Pituitary Gland / Q000378:metabolism*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014561:Urochordata / Q000196:embryology / Q000235:genetics*
D018076:DNA, Complementary; D018398:Homeodomain Proteins