A single amphioxus and sea urchin runt-gene suggests that runt-gene duplications occurred in early chordate evolution.
Runt-homologous molecules are characterized by their DNA binding runt-domain which is highly conserved within bilaterians. The three mammalian runt-genes are master regulators in cartilage/bone formation and hematopoiesis. Historically these features evolved in Craniota and might have been promoted by runt-gene duplication events. The purpose of this study was therefore to investigate how many runt-genes exist in the stem species of chordates, by analyzing the number of runt-genes in what is likely to be the closest living relative of Craniota-amphioxus. To acquire further insight into the possible role of runt-genes in early chordate evolution we have determined the number of runt-genes in sea urchins and have analyzed the runt-expression pattern in this species. Our findings demonstrate the presence of a single runt-gene in amphioxus and sea urchin, which makes it highly likely that the stem species of chordates harbored only a single runt-gene. This suggests that runt-gene duplications occurred later in chordate phylogeny, and are possibly also associated with the evolution of features such as hematopoiesis, cartilage and bone development. In sea urchin embryos runt-expression involves cells of endodermal, mesodermal and ectodermal origin. This complex pattern of expression might reflect the multiple roles played by runt-genes in mammals. A strong runt-signal in the gastrointestinal tract of the sea urchin is in line with runt-expression in the intestine of nematodes and in the murine gastrointestinal tract, and seems to be one of the phylogenetically ancient runt-expression domains.
Stricker
S
S
Max Planck Institute Molecular Genetics, Ihnestr 73, 14195 Berlin, Germany.
Poustka
A J
AJ
Wiecha
U
U
Stiege
A
A
Hecht
J
J
Panopoulou
G
G
Vilcinskas
A
A
Mundlos
S
S
Seitz
V
V
D000595:Amino Acid Sequence; D000818:Animals; D015139:Blotting, Southern; D002816:Chordata, Nonvertebrate / Q000235:genetics*; D019143:Evolution, Molecular; D020440:Gene Duplication; D015870:Gene Expression; D006801:Humans; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D010802:Phylogeny; D012617:Sea Urchins / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics*
D009363:Neoplasm Proteins; D014157:Transcription Factors