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The integrator complex subunit 6 (Ints6) confines the dorsal organizer in vertebrate embryogenesis.

Kapp LD, Abrams EW, Marlow FL, Mullins MC - PLoS Genet. (2013)

Bottom Line: We have isolated a recessive dorsalizing maternal-effect mutation disrupting the gene encoding Integrator Complex Subunit 6 (Ints6).Limiting Nodal signaling or restoring BMP signaling restores wild-type patterning to affected embryos.Our results are consistent with a novel role for Ints6 in restricting the vertebrate organizer to a dorsal domain in embryonic patterning.

View Article: PubMed Central - PubMed

Affiliation: Perelman School of Medicine at the University of Pennsylvania, Department of Cell and Developmental Biology, Philadelphia, Pennsylvania, United States of America.

ABSTRACT
Dorsoventral patterning of the embryonic axis relies upon the mutual antagonism of competing signaling pathways to establish a balance between ventralizing BMP signaling and dorsal cell fate specification mediated by the organizer. In zebrafish, the initial embryo-wide domain of BMP signaling is refined into a morphogenetic gradient following activation dorsally of a maternal Wnt pathway. The accumulation of β-catenin in nuclei on the dorsal side of the embryo then leads to repression of BMP signaling dorsally and the induction of dorsal cell fates mediated by Nodal and FGF signaling. A separate Wnt pathway operates zygotically via Wnt8a to limit dorsal cell fate specification and maintain the expression of ventralizing genes in ventrolateral domains. We have isolated a recessive dorsalizing maternal-effect mutation disrupting the gene encoding Integrator Complex Subunit 6 (Ints6). Due to widespread de-repression of dorsal organizer genes, embryos from mutant mothers fail to maintain expression of BMP ligands, fail to fully express vox and ved, two mediators of Wnt8a, display delayed cell movements during gastrulation, and severe dorsalization. Consistent with radial dorsalization, affected embryos display multiple independent axial domains along with ectopic dorsal forerunner cells. Limiting Nodal signaling or restoring BMP signaling restores wild-type patterning to affected embryos. Our results are consistent with a novel role for Ints6 in restricting the vertebrate organizer to a dorsal domain in embryonic patterning.

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Dorsal organizer gene expression is expanded in p18ahub mutants.In situ hybridization using goosecoid (gsc) probe (A–D). Animal pole views, dorsal to right for (A) and (B); dorsal view, animal pole up in (C) and (D). WT embryos at early gastrula (A, n = 27) and mid gastrula stages (C, n = 41). p18ahub embryos (B, n = 33 and D, n = 10) displayed radially expanded gsc expression at the same stages. The embryo in (D) is tilted toward the viewer to show radial gsc expression. WT (E, n = 18) and p18ahub (F, n = 18) blastula stage embryos showed no obvious differences in the number or distribution of β-catenin immunopositive nuclei (arrows). (G–J) In situ hybridization for bozozok (boz), lateral views, dorsal to right; insets show animal pole views. WT and p18ahub embryos showed normal boz expression at late blastula (G, n = 19 and H, n = 18) and early gastrula stages (I, n = 14 and J, n = 16, respectively). As described in the text, epiboly progression was delayed in p18ahub embryos. At 6 hpf WT embryos form a morphologically apparent organizer, indicated by a thickening of the blastoderm on the dorsal side of the embryo and boz expression within the hypoblast. In contrast, at 6 hpf p18ahub embryos still appeared to be in a late blastula stage, although their boz expression was similar to WT.
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pgen-1003822-g003: Dorsal organizer gene expression is expanded in p18ahub mutants.In situ hybridization using goosecoid (gsc) probe (A–D). Animal pole views, dorsal to right for (A) and (B); dorsal view, animal pole up in (C) and (D). WT embryos at early gastrula (A, n = 27) and mid gastrula stages (C, n = 41). p18ahub embryos (B, n = 33 and D, n = 10) displayed radially expanded gsc expression at the same stages. The embryo in (D) is tilted toward the viewer to show radial gsc expression. WT (E, n = 18) and p18ahub (F, n = 18) blastula stage embryos showed no obvious differences in the number or distribution of β-catenin immunopositive nuclei (arrows). (G–J) In situ hybridization for bozozok (boz), lateral views, dorsal to right; insets show animal pole views. WT and p18ahub embryos showed normal boz expression at late blastula (G, n = 19 and H, n = 18) and early gastrula stages (I, n = 14 and J, n = 16, respectively). As described in the text, epiboly progression was delayed in p18ahub embryos. At 6 hpf WT embryos form a morphologically apparent organizer, indicated by a thickening of the blastoderm on the dorsal side of the embryo and boz expression within the hypoblast. In contrast, at 6 hpf p18ahub embryos still appeared to be in a late blastula stage, although their boz expression was similar to WT.

Mentions: Dorsalization can also be caused by a ventral expansion of dorsal organizer gene expression. To investigate the organizer in p18ahub mutant embryos, we examined expression of the organizer gene goosecoid (gsc)[55]. We found that, although gsc expression was induced normally at the mid blastula stage (data not shown), it was expanded in p18ahub embryos by early gastrulation (Figure 3A,B) and remained ectopically expressed through mid gastrula stages (Figure 3C,D) compared to WT embryos. Therefore, the dorsalization of p18ahub embryos involves a prominent expansion of gsc expression by early gastrulation, contrasting dorsalization resulting solely from defective BMP signaling [5].


The integrator complex subunit 6 (Ints6) confines the dorsal organizer in vertebrate embryogenesis.

Kapp LD, Abrams EW, Marlow FL, Mullins MC - PLoS Genet. (2013)

Dorsal organizer gene expression is expanded in p18ahub mutants.In situ hybridization using goosecoid (gsc) probe (A–D). Animal pole views, dorsal to right for (A) and (B); dorsal view, animal pole up in (C) and (D). WT embryos at early gastrula (A, n = 27) and mid gastrula stages (C, n = 41). p18ahub embryos (B, n = 33 and D, n = 10) displayed radially expanded gsc expression at the same stages. The embryo in (D) is tilted toward the viewer to show radial gsc expression. WT (E, n = 18) and p18ahub (F, n = 18) blastula stage embryos showed no obvious differences in the number or distribution of β-catenin immunopositive nuclei (arrows). (G–J) In situ hybridization for bozozok (boz), lateral views, dorsal to right; insets show animal pole views. WT and p18ahub embryos showed normal boz expression at late blastula (G, n = 19 and H, n = 18) and early gastrula stages (I, n = 14 and J, n = 16, respectively). As described in the text, epiboly progression was delayed in p18ahub embryos. At 6 hpf WT embryos form a morphologically apparent organizer, indicated by a thickening of the blastoderm on the dorsal side of the embryo and boz expression within the hypoblast. In contrast, at 6 hpf p18ahub embryos still appeared to be in a late blastula stage, although their boz expression was similar to WT.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3814294&req=5

pgen-1003822-g003: Dorsal organizer gene expression is expanded in p18ahub mutants.In situ hybridization using goosecoid (gsc) probe (A–D). Animal pole views, dorsal to right for (A) and (B); dorsal view, animal pole up in (C) and (D). WT embryos at early gastrula (A, n = 27) and mid gastrula stages (C, n = 41). p18ahub embryos (B, n = 33 and D, n = 10) displayed radially expanded gsc expression at the same stages. The embryo in (D) is tilted toward the viewer to show radial gsc expression. WT (E, n = 18) and p18ahub (F, n = 18) blastula stage embryos showed no obvious differences in the number or distribution of β-catenin immunopositive nuclei (arrows). (G–J) In situ hybridization for bozozok (boz), lateral views, dorsal to right; insets show animal pole views. WT and p18ahub embryos showed normal boz expression at late blastula (G, n = 19 and H, n = 18) and early gastrula stages (I, n = 14 and J, n = 16, respectively). As described in the text, epiboly progression was delayed in p18ahub embryos. At 6 hpf WT embryos form a morphologically apparent organizer, indicated by a thickening of the blastoderm on the dorsal side of the embryo and boz expression within the hypoblast. In contrast, at 6 hpf p18ahub embryos still appeared to be in a late blastula stage, although their boz expression was similar to WT.
Mentions: Dorsalization can also be caused by a ventral expansion of dorsal organizer gene expression. To investigate the organizer in p18ahub mutant embryos, we examined expression of the organizer gene goosecoid (gsc)[55]. We found that, although gsc expression was induced normally at the mid blastula stage (data not shown), it was expanded in p18ahub embryos by early gastrulation (Figure 3A,B) and remained ectopically expressed through mid gastrula stages (Figure 3C,D) compared to WT embryos. Therefore, the dorsalization of p18ahub embryos involves a prominent expansion of gsc expression by early gastrulation, contrasting dorsalization resulting solely from defective BMP signaling [5].

Bottom Line: We have isolated a recessive dorsalizing maternal-effect mutation disrupting the gene encoding Integrator Complex Subunit 6 (Ints6).Limiting Nodal signaling or restoring BMP signaling restores wild-type patterning to affected embryos.Our results are consistent with a novel role for Ints6 in restricting the vertebrate organizer to a dorsal domain in embryonic patterning.

View Article: PubMed Central - PubMed

Affiliation: Perelman School of Medicine at the University of Pennsylvania, Department of Cell and Developmental Biology, Philadelphia, Pennsylvania, United States of America.

ABSTRACT
Dorsoventral patterning of the embryonic axis relies upon the mutual antagonism of competing signaling pathways to establish a balance between ventralizing BMP signaling and dorsal cell fate specification mediated by the organizer. In zebrafish, the initial embryo-wide domain of BMP signaling is refined into a morphogenetic gradient following activation dorsally of a maternal Wnt pathway. The accumulation of β-catenin in nuclei on the dorsal side of the embryo then leads to repression of BMP signaling dorsally and the induction of dorsal cell fates mediated by Nodal and FGF signaling. A separate Wnt pathway operates zygotically via Wnt8a to limit dorsal cell fate specification and maintain the expression of ventralizing genes in ventrolateral domains. We have isolated a recessive dorsalizing maternal-effect mutation disrupting the gene encoding Integrator Complex Subunit 6 (Ints6). Due to widespread de-repression of dorsal organizer genes, embryos from mutant mothers fail to maintain expression of BMP ligands, fail to fully express vox and ved, two mediators of Wnt8a, display delayed cell movements during gastrulation, and severe dorsalization. Consistent with radial dorsalization, affected embryos display multiple independent axial domains along with ectopic dorsal forerunner cells. Limiting Nodal signaling or restoring BMP signaling restores wild-type patterning to affected embryos. Our results are consistent with a novel role for Ints6 in restricting the vertebrate organizer to a dorsal domain in embryonic patterning.

Show MeSH
Related in: MedlinePlus