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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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Related in: MedlinePlus

Lefty misexpression suppresses patterning defects of p18ahub embryos.(A) Pie charts indicate fractions of embryos at 24 hpf with the indicated phenotypes. Number of embryos is at the center of each chart. Labels across indicate the amount of lefty1 (lft1) mRNA injected. Top row shows uninjected p18ahub control clutch for each experiment, middle row indicates p18ahub embryos injected with mRNA, and bottom row is WT embryos injected with mRNA. +1× lft mRNA corresponds to 1 pg mRNA. (B and C) In situ hybridization for lft1 in a mid gastrula stage WT (B, n = 12) and p18ahub (C, n = 13) embryos; lateral views, dorsal facing.
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pgen-1003822-g006: Lefty misexpression suppresses patterning defects of p18ahub embryos.(A) Pie charts indicate fractions of embryos at 24 hpf with the indicated phenotypes. Number of embryos is at the center of each chart. Labels across indicate the amount of lefty1 (lft1) mRNA injected. Top row shows uninjected p18ahub control clutch for each experiment, middle row indicates p18ahub embryos injected with mRNA, and bottom row is WT embryos injected with mRNA. +1× lft mRNA corresponds to 1 pg mRNA. (B and C) In situ hybridization for lft1 in a mid gastrula stage WT (B, n = 12) and p18ahub (C, n = 13) embryos; lateral views, dorsal facing.

Mentions: The secreted feedback inhibitor Lefty/Antivin (Lft1) regulates Nodal signaling [63], [64], [65], [79]. Misexpression of Lft1 in WT embryos severely limits mesendoderm induction with embryos closely resembling ndr1;ndr2 double mutants [62]. We found that injection of as little as 0.7 picograms (pg) of lft1 mRNA (Figure 6A, +0.7× middle row), a dose that only weakly perturbs WT embryos (Figure 6A, Minor head defects), could restore WT or nearly WT patterning in 33% of mutant embryos. Injection of 1 pg of lft1 mRNA (Figure 6A, +1× middle row) restored WT patterning in a larger fraction of mutant embryos and suppressed mesendoderm formation (oep-like) in 20% of mutant embryos. The same dose of lft1 mRNA injected into WT embryos blocked mesendoderm development in more than 50% of the embryos (Figure 6A, +1× bottom). Injection of 3 pg of lft1 mRNA into mutant and WT embryos inhibited mesendoderm induction in a similar fraction of embryos (Figure 6A, +3×). Thus, suppression of Nodal signaling can restore the balance between axial and non-axial fate specification in mutant embryos, similarly to restoring BMP signaling.


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

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

Lefty misexpression suppresses patterning defects of p18ahub embryos.(A) Pie charts indicate fractions of embryos at 24 hpf with the indicated phenotypes. Number of embryos is at the center of each chart. Labels across indicate the amount of lefty1 (lft1) mRNA injected. Top row shows uninjected p18ahub control clutch for each experiment, middle row indicates p18ahub embryos injected with mRNA, and bottom row is WT embryos injected with mRNA. +1× lft mRNA corresponds to 1 pg mRNA. (B and C) In situ hybridization for lft1 in a mid gastrula stage WT (B, n = 12) and p18ahub (C, n = 13) embryos; lateral views, dorsal facing.
© Copyright Policy
Related In: Results  -  Collection

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

pgen-1003822-g006: Lefty misexpression suppresses patterning defects of p18ahub embryos.(A) Pie charts indicate fractions of embryos at 24 hpf with the indicated phenotypes. Number of embryos is at the center of each chart. Labels across indicate the amount of lefty1 (lft1) mRNA injected. Top row shows uninjected p18ahub control clutch for each experiment, middle row indicates p18ahub embryos injected with mRNA, and bottom row is WT embryos injected with mRNA. +1× lft mRNA corresponds to 1 pg mRNA. (B and C) In situ hybridization for lft1 in a mid gastrula stage WT (B, n = 12) and p18ahub (C, n = 13) embryos; lateral views, dorsal facing.
Mentions: The secreted feedback inhibitor Lefty/Antivin (Lft1) regulates Nodal signaling [63], [64], [65], [79]. Misexpression of Lft1 in WT embryos severely limits mesendoderm induction with embryos closely resembling ndr1;ndr2 double mutants [62]. We found that injection of as little as 0.7 picograms (pg) of lft1 mRNA (Figure 6A, +0.7× middle row), a dose that only weakly perturbs WT embryos (Figure 6A, Minor head defects), could restore WT or nearly WT patterning in 33% of mutant embryos. Injection of 1 pg of lft1 mRNA (Figure 6A, +1× middle row) restored WT patterning in a larger fraction of mutant embryos and suppressed mesendoderm formation (oep-like) in 20% of mutant embryos. The same dose of lft1 mRNA injected into WT embryos blocked mesendoderm development in more than 50% of the embryos (Figure 6A, +1× bottom). Injection of 3 pg of lft1 mRNA into mutant and WT embryos inhibited mesendoderm induction in a similar fraction of embryos (Figure 6A, +3×). Thus, suppression of Nodal signaling can restore the balance between axial and non-axial fate specification in mutant embryos, similarly to restoring BMP signaling.

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