Xenopus neurula left-right asymmetry is respeficied by microinjecting TGF-beta5 protein.
A variety of TGF-beta-related ligands regulate the left-right asymmetry of vertebrates but the involvement of TGF-betas in left-right specification has not been reported. We assessed whether TGF-beta signaling is involved in the left-right specification of Xenopus post-gastrula embryos by microinjecting Xenopus TGF-beta5 protein into the left or right flank of neurula-tailbud embryos. Injection on the right side of neurulae caused left-right reversal of the internal organs in 93% of the embryos, while injection on the left side caused less than 5% left-right reversal. Expression of Xenopus nodal related-1 (Xnr-1 ), Xenopus antivin and Xenopus Pitx2, which are normally expressed on the left, was unaltered by the left-side injection. In contrast, right-side injection into neurulae induced the expression of these genes predominantly on the right side. Right-side injection into tailbud embryos caused bilateral expression of these handed genes. Time course analysis of asymmetric gene expression revealed that Xnr-1 could be induced by TGF-beta5 at late neurula stage, while antivin and Pitx2 could be induced by TGF-beta5 at the latertail bud stage. Injection of the antisense morpholino oligonucleotide against Xenopus TGF-beta5 into the left dorsal blastomere inhibited the normal left-handed expression of Xnr-1 and Pitx2, and caused the organ reversal in the injected embryos. These results suggest that normal left-right balance of endogenous TGF-beta5 signaling in the neurula embryo may be needed to determine the laterality of the asymmetric genes and to generate the correct left-right axis.
Mogi
Kazue
K
Research Institute for Integrated Sciences and Department of Biological Sciences, Kanagawa University, Tsuchiya, Hiratsuka, Japan.
Goto
Madoka
M
Ohno
Eri
E
Azumi
Yoshitaka
Y
Takeuchi
Shigeo
S
Toyoizumi
Ryuji
R
D000818:Animals; D019521:Body Patterning / Q000187:drug effects / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D005775:Gastrula / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D006133:Growth Substances / Q000494:pharmacology; D018398:Homeodomain Proteins / Q000378:metabolism; D055458:Left-Right Determination Factors; D008297:Male; D008845:Microinjections; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D015398:Signal Transduction; D051899:Smad2 Protein; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D000097577:Homeobox Protein PITX2
D004268:DNA-Binding Proteins; D006133:Growth Substances; D018398:Homeodomain Proteins; D055458:Left-Right Determination Factors; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense; D051899:Smad2 Protein; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D029867:Xenopus Proteins; D000097577:Homeobox Protein PITX2; C497785:Smad2 protein, Xenopus; C404602:TGF-beta5 protein, Xenopus laevis; C492176:lefty protein, Xenopus; C512833:nodal1 protein, Xenopus