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Mech Dev
2001 Feb 01;1002:275-89. doi: 10.1016/s0925-4773(00)00541-4.
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Functional characterization and genetic mapping of alk8.
Payne TL
,
Postlethwait JH
,
Yelick PC
.
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The novel type I TGFbeta family member receptor alk8 is expressed both maternally and zygotically. Functional characterization of alk8 was performed using microinjection studies of constitutively active (CA), kinase modified/dominant negative (DN), and truncated alk8 mRNAs. CA Alk8 expression produces ventralized embryos while DN Alk8 expression results in dorsalized phenotypes. Truncated alk8 expressing embryos display a subtle dorsalized phenotype closely resembling that of the identified zebrafish dorsalized mutant, lost-a-fin (laf). Single-strand conformation polymorphism (SSCP) analysis was used to map alk8 to zebrafish LG02 in a region demonstrating significant conserved synteny to Hsa2, and which contains the human alk2 gene, ACVRI. Altogether, these functional, gene mapping and phylogenetic analyses suggest that alk8 may be the zebrafish orthologue to human ACVRI (alk2), and therefore extend previous studies of Alk2 conducted in Xenopus.
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11165484
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Fig. 2. Expression of bmp2b, bmp4 and chordin mRNAs in CA and KM Alk8 expressing embryos. For all three markers, bmp2b, bmp4 and chordin, GFP control embryos are presented in the center panels, KM alk8 RNA injected embryos are presented in the lefthand panels and CA alk8 RNA injected embryos are presented in the righthand panels. Bmp2b mRNA expression patterns are presented in panels (A–F). CA Alk8 up regulates ventralbmp2b and bmp4 mRNA expression, while KM Alk8 causes reduced bmp2b and bmp4 mRNA expression in ventral domains. Panels (A–C) depict lateral views of 80% epiboly stage embryos, with dorsal to the right. Panels (D–F) present lateraltail views of 24 hpf embryos, with anterior to the left. Bmp4 mRNA expression patterns are presented in panels (G-L′). Panels (G–I) depict lateral views of 80% epiboly staged embryos, with dorsal to the right. Panels (J–L) present dorsal head views and Panels (J′–L′) present lateraltail views of the same, 24 hpf embryos. Chordin expression is shown in Panels (M-U′). Panels (M–O) depict anterior views of shield stage embryos oriented with dorsal to the right. Panels (P–R) present dorsal views of 80% epiboly stage embryos with anterior to the top; Panels (S–U) present lateral views of early somite stage embryos, and Panels (S′–U′) present dorsal tail views of the same embryos.
Fig. 3. Alk8 regulation of ntl1 expression in the developing embryo. Gfp RNA control embryos are shown in the center panels, KM Alk8 expressing embryos are shown on the left and CA Alk8 expressing embryos are shown in the righthand panels. Panels (A–C) present dorsal views of 80% epiboly staged embryos, anterior to the top. Panels (D–F) present dorsal views of early somite staged embryos, with anterior to the left. Panels (G–I) present lateral views of 24 hpf embryos, anterior to the left.
Fig. 4. Alk8 influences the patterning of adaxial and somitic mesoderm. The expression of myoD was used to examine Alk8 patterning of somitic mesoderm. Gfp RNA control embryos are shown in the center panels, KM Alk8 expressing embryos are presented in lefthand panels, and CA Alk8 expressing embryos are displayed in righthand panels. Panels (A–C) present dorsal views of 80% epiboly staged embryos. Panels (D–F, F′) present dorsal views of early somite staged embryos; Panels (G–I) present dorsal views of 24 hpf embryos.
Fig. 5. Alk8 patterning of neural tissues. The expression of otx2 and krox20 was used to assess Alk8 pattering of neural tissues. Gfp RNA control embryos are shown in the center panels; KM Alk8 expressing embryos are shown in the lefthand panels; and KM Alk8 expressing embryos are displayed in righthand panels. Panels (A–C) present lateral views of 80% epiboly staged embryos, dorsal to the right. Panels (A′–C′) present anterior views of the same embryos, with dorsal to the bottom. Panels (D–F) present lateral views of early somite staged embryos, with dorsal to the right. Panels (G–I) present lateral views of 24 hpf embryos, with dorsal to the right. Insets in panels (G–I) present dorsal head views. Panels (J–L) present dorsal anterior views of otx2 and krox20 double stained, early somite staged embryos.
Fig. 6. Alk8 regulates the expression of taramA. Control gfp RNA injected embryos are shown in center panels, KM alk8 RNA injected embryos are shown on the left side and CA alk8 RNA injected embryos are shown on the right. Panels A, B and C present dorsal views of 80% epiboly staged embryos; Panels (A′–C′) present lateral views of the same embryos, with dorsal to the right.
