Evolutionary Changes in the Developmental Origin of Hatching Gland Cells in Basal Ray-Finned Fishes.
Hatching gland cells (HGCs) originate from different germ layers between frogs and teleosts, although the hatching enzyme genes are orthologous. Teleostei HGCs differentiate in the mesoendodermal cells at the anterior end of the involved hypoblast layer (known as the polster) in late gastrula embryos. Conversely, frog HGCs differentiate in the epidermal cells at the neural plate border in early neurula embryos. To infer the transition in the developmental origin of HGCs, we studied two basal ray-finned fishes, bichir (Polypterus) and sturgeon. We observed expression patterns of their hatching enzyme (HE) and that of three transcription factors that are critical for HGC differentiation: KLF17 is common to both teleosts and frogs; whereas FoxA3 and Pax3 are specific to teleosts and frogs, respectively. We then inferred the transition in the developmental origin of HGCs. In sturgeon, the KLF17, FoxA3, and HE genes were expressed during the tailbud stage in the cell mass at the anterior region of the body axis, a region corresponding to the polster in teleost embryos. In contrast, the bichir was suggested to possess both teleost- and amphibian-type HGCs, i.e. the KLF17 and FoxA3 genes were expressed in the anterior cell mass corresponding to the polster, and the KLF17, Pax3 and HE genes were expressed in dorsal epidermal layer of the head. The change in developmental origin is thought to have occurred during the evolution of basal ray-finned fish, because bichir has two HGCs, while sturgeon only has the teleost-type.
['Nagasawa|Tatsuki|T|', 'Kawaguchi|Mari|M|', 'Yano|Tohru|T|', 'Sano|Kaori|K|', 'Okabe|Masataka|M|', 'Yasumasu|Shigeki|S|']
D000818:Animals D001001:Anura D005075:Biological Evolution D002454:Cell Differentiation D004625:Embryo, Nonmammalian D004707:Endoderm D029941:Fish Proteins D005399:Fishes D018507:Gene Expression Regulation, Developmental D008666:Metalloendopeptidases D054258:Neural Plate D010802:Phylogeny D014157:Transcription Factors
hatching gland cell germ layer hatching enzyme bichir sturgeon Forkhead box Krüppel-like factor Paired box