Maternal and Zygotic Expression of a nanos-Class Gene in the Leech Helobdella robusta: Primordial Germ Cells Arise from Segmental Mesoderm

Developmental Biology

Marc Pilon¹  David A. Weisblat¹  Dongmin Kang¹ 

[1] Department of Biological Sciences, Stanford University, Stanford, California, 94305-5020

关键词: annelid;    leech;    Helobdella;    germline;    nanos;   

DOI  :  10.1006/dbio.2002.0615

学科分类：生物科学（综合）

来源: Academic Press

【 摘 要 】

Thenanos-classgeneoftheleechHelobdellarobusta(Hro-nos)ispresentasamaternaltranscriptwhoselevelsdecayduringcleavage;HRO-NOSproteinismoreabundantintheDquadrantcellsrelativetotheA,B,andCquadrants;andHRO-NOSismoreabundantintheectodermalprecursorcell(DNOPQ)thaninitssistermesodermalprecursor(DM)(PilonandWeisblat,1997).Here,usinginsituhybridization,weshowthatHro-nosmRNAisbroadlydistributedthroughoutthezygote,isconcentratedinbothanimalandvegetalteloplasmduringstage1andisathigherlevelsinDNOPQthaninDMatstage4b.Hro-nosexpressionincreasesafterstage7,asjudgedbyinsituhybridization,developmentalRT-PCR,andwesternblots;thisincreasemustthereforerepresentlaterzygoticexpression.Ofparticularinterest,duringstages9and10,eachof11mid-bodysegments(M8-M18)hasapairofHro-nospositive“spots”comprisingofoneortwolargecellseach.Thesespotslaterdisappearinananteroposteriorprogression.WefindthattheseHro-nos-expressingcellsareofmesodermalorigin,arisinginasegmentallyiteratedmannerfromtheMlineage,andcorrespondtocellspreviouslyproposedasprimordialgermcells(PGCs;Bürger,1891;WeisblatandShankland,1985).Theseresultssupporttheproposalthatnanos-classgenesfunctionedinthespecificationofgermlinecellsintheancestralbilaterianandpossiblyinaseparateprocessrelatedtoembryonicpolarityintheancestralprotostome.

【 授权许可】

Unknown