Melatonin receptor genes (mel-1a, mel-1b, mel-1c) are differentially expressed in the avian germ line.
The presence of melatonin receptor transcripts (mel-1a, mel-1b and mel-1c) was investigated in primordial germ cells (PGCs), immature and mature oocytes, and sperm of Japanese quail by reverse transcription--polymerase chain reaction (RT-PCR). The mel-1a transcript was detected in as few as in a thousand PGCs. Significant differences in the expression of melatonin receptor genes were found in differentiating germ cells: in PGCs only the mel-1a receptor was expressed, in blastoderms and immature oocytes all three transcripts (mel-1a, mel-1b, mel-1c) were present, while in mature ovulated oocytes the predominant transcript was mel-1c (with sporadic occurrence of mel-1a and mel-1b). In sperm, mel-1a and mel-1c were present but mel-1b was absent. This indicates that the expression of melatonin receptor genes changes throughout the differentiation of PGCs into adult gametes: during oocyte differentiation two additional transcripts, mel-1b and mel-1c, are synthesized in addition to mel-1a, but at oocyte maturation, mel-1a and mel-1b are degraded and only mel-1c remains. During male line (spermatozoa) differentiation mel-1c is transcribed in addition to mel-1a, with mel-1b being completely absent. Since melatonin and the activities of enzymes participating in melatonin synthesis are present in the avian yolk, it is reasonable to suggest a role for this molecule in early avian development and germ line differentiation. We propose that melatonin may act as a signaling molecule regulating some differentiation processes (e.g., cell proliferation, migration, etc.) before the formation of neural and hormonal systems.
Kawashima
Takaharu
T
National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan.
Stepińska
Urszula
U
Kuwana
Takashi
T
Olszańska
Bozenna
B
D000818:Animals; D002642:Chick Embryo; D003370:Coturnix / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells / Q000166:cytology / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000302:isolation & purification / Q000378:metabolism; D044094:Receptors, Melatonin / Q000235:genetics* / Q000378:metabolism
D020033:Protein Isoforms; D012333:RNA, Messenger; D044094:Receptors, Melatonin