Exploring embryonic germ line development in the water flea, Daphnia magna, by zinc-finger-containing VASA as a marker.
VASA is an ATP-dependent RNA helicase belonging to the DEAD-box family that, in many organisms, is specifically expressed in germ line cells throughout the life cycle, making it a powerful molecular marker to study germ line development. To obtain further information on germ line development in crustaceans, we cloned VASA cDNAs from three branchiopod species: water fleas Daphnia magna and Moina macrocopa, and brine shrimp Artemia franciscana. RNA helicase domains in branchiopod VASA were highly conserved among arthropod classes. However, N-terminal RNA-binding domains in branchiopod VASA were highly diverged and, unlike other arthropod VASA reported so far, possessed repeats of retroviral-type zinc finger (CCHC) motifs. Raising specific antibodies against Daphnia VASA revealed that the primordial germ cells (PGCs) in this organism segregate at a very early cleavage stage of embryogenesis in parthenogenetic and sexual eggs. Clusters of PGCs then start to migrate inside the embryo and finally settle at both sides of the intestine, the site of future gonad development. RNA analyses suggested that maternally supplied vasa mRNA was responsible for early VASA expression, while zygotic expression started during blastodermal stage of development.
Sagawa
Kazunori
K
School of Life Science, Tokyo University of Pharmacy and Life Science, Hachioji, Japan.
Yamagata
Hideo
H
Shiga
Yasuhiro
Y
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D003445:Crustacea; D003621:Daphnia / Q000166:cytology* / Q000196:embryology*; D004625:Embryo, Nonmammalian / Q000502:physiology*; D047108:Embryonic Development; D005260:Female; D005854:Germ Cells / Q000166:cytology*; D017403:In Situ Hybridization; D007413:Intestinal Mucosa / Q000378:metabolism; D008297:Male; D008957:Models, Genetic; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D020365:RNA Helicases / Q000096:biosynthesis* / Q000737:chemistry; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D016335:Zinc Fingers
D012333:RNA, Messenger; D020365:RNA Helicases