Expression of the gene for ancestral glycoprotein hormone beta subunit in the nerve cord of amphioxus.
Amphioxus belongs to the subphylum cephalochordata, a clade of chordates phylogenetically placed at the most basal position. Despite many studies on the endocrine system of amphioxus, there were no confident lines of evidence on the presence of pituitary hormones, whereas recent amphioxus genome analysis reported that amphioxus has no pituitary hormone except for thyrostimulin, which is a glycoprotein hormone in the pituitary, brain, and other organs of vertebrates. In the present study, we cloned cDNA for one glycoprotein hormone beta subunit (GPB) from amphioxus, AmpGPB5, and phylogenetically indicated that AmpGPB5 is the ancestral molecule of glycoprotein hormone beta subunits of vertebrates including pituitary glycoprotein hormones. Synteny analyses showed conservation of chromosomal location of genes near GPB genes from amphioxus through human. The AmpGPB5 gene was expressed in a restricted region of the dorsal part of the nerve cord, glandular atrial cells of gills, and pre-vitellogenic oocytes in amphioxus. However, expression was not detected in the Hatschek's pit which is considered to be a primitive pituitary gland. On the basis of present results, we hypothesize that a portion of vertebrate pituitary hormones might be derived from an ancestral glycoprotein hormone of amphioxus that functions as a neuroendocrine hormone.
Tando
Yukiko
Y
Center for Advance Marine Research, Ocean Research Institute, The University of Tokyo, 1-15-1, Minamidai, Nakano, Tokyo 164-8639, Japan.
Kubokawa
Kaoru
K
D000595:Amino Acid Sequence; D000825:Animal Structures / Q000166:cytology / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002490:Central Nervous System / Q000166:cytology / Q000378:metabolism*; D002816:Chordata, Nonvertebrate / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D040461:Gene Components / Q000235:genetics; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005880:Gills / Q000166:cytology / Q000378:metabolism; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010053:Ovary / Q000166:cytology / Q000378:metabolism; D010802:Phylogeny; D011487:Protein Conformation; D021122:Protein Subunits / Q000235:genetics*; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D006023:Glycoproteins; D021122:Protein Subunits; C458339:thyrostimulin