Two consecutive microtubule-based epithelial seaming events mediate dorsal closure in the scuttle fly Megaselia abdita
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Spain
- Universitat Pompeu Fabra, Spain
- Konrad Lorenz Institute for Evolution and Cognition Research (KLI), Austria
Figures
Figure 1 with 4 supplements
The extraembryonic serosa ruptures and accumulates dorsally previous to epidermal seaming in Megaselia abdita.
(A) Nuclear staining of M. abdita embryos prior to dorsal closure reveals three types of tissues: the extraembryonic serosa (magenta), the extraembryonic amnion (blue), and the embryonic epidermis …
Figure 1—figure supplement 1
Identification of extraembryonic tissues in Megaselia abdita.
(A) Confocal projection of nuclear staining in an intact M. abdita embryo stained with DAPI. (A’) Confocal projection and image processing of nuclear staining from A to separate the extraembryonic …
Figure 1—figure supplement 2
Description of the three-tissue system anatomy in Megaselia abdita prior to dorsal closure.
(A) Nuclear staining (DAPI) of serosa cells (magenta) attached to the vitelline membrane after devitellinization. (B) Phalloidin staining (green) of a devitellinized embryo (dorsal view) showing a …
Figure 1—figure supplement 3
Anatomical landmarks during dorsal closure progression and serosa internalization.
(A–A’’) Dorsal views from a time-lapse sequence of dorsal closure in a M. abdita embryo labeled with the fluorescent dye FM 4–64. Magenta bands depict the position and fusion of the dorsal ridge …
Figure 1—figure supplement 4
Tissue topology at anterio-posterior positions of different stages of dorsal closure in fixed embryos of Megaselia abdita.
(A) Dorsal view of a M. abdita embryo during serosa dorsal accumulation. (a) A stack reslicing along the anterio-posterior (AP) midline (yellow dashed line) shows a sagittal view of the embryo …
Figure 2 with 1 supplement
JNK (bsk) is required for dpp expression and the completion of dorsal closure without affecting serosa rupture or retraction in Megaselia abdita.
(A) Wild-type expression of Mab_dpp (purple stain, black arrowheads) along the dorsal leading edge of the epidermis in a M. abdita embryo (lateral view) during dorsal closure. (A’) Cuticle …
Figure 2—figure supplement 1
Mab_bsk RNAi results in a lack of dorsal closure progression after serosa rupture.
(A–A’’) Detection of the serosa edge in the bright-field time-lapse sequence of Mab_bsk knock-down embryo from Figure 2C was obtained by image subtraction (a–a’’) to render the retracting serosa …
Figure 3 with 2 supplements
An actomyosin-enriched epidermal cable is necessary for the completion of dorsal closure upon contraction, retraction, and internalization of the serosa in Megaselia abdita.
(A) F-actin enrichment (as observed by inverted intensity of phalloidin staining) and (B) PhosphoMyosin enrichment (inverted intensity of immunostaining) in the epidermal leading edge (green …
Figure 3—figure supplement 1
Actin accumulates apically in contracting serosa cells and filopodial protrusions are present in the epidermal actin cable of Megaselia abdita.
(A) Lateral view of a M. abdita embryo showing F-actin accumulation at the epidermal leading edge and the internalizing serosa (red arrowheads), but not in the extraembryonic amnion (blue …
Figure 3—figure supplement 2
The epidermal actomyosin cable is a contractile structure controlled by JNK (Mab_bsk) expression during dorsal closure.
(A) An actomyosin cable (white arrowhead) at the epidermal leading edge of a wild-type M. abdita embryo. (B) Mab_bsk RNAi results in the absence of an actomyosin cable (white arrowhead) in M. abdita …
Figure 4 with 5 supplements
Microtubule-dependent seaming of the extraembryonic amnion is required for subsequent epidermal seaming during dorsal closure in Megaselia abdita.
(A) Confocal projections of microtubules in the extraembryonic amnion orienting toward the internalizing serosa during early amniotic seaming. (B) As amniotic seaming progresses, microtubules …
Figure 4—figure supplement 1
Microtubule alignment is present in both the epidermis and the amnion and correlates with enlarged amniotic cells in Megaselia abdita.
(A) Microtubule bundles orient toward the dorsal midline (white dashed line) in both the epidermis (white arrowhead) and the amnion (blue arrowhead) of M. abdita embryos during dorsal closure. Note …
Figure 4—figure supplement 2
Colcemid treatment prevents microtubule polymerization without affecting serosa retraction or epidermal actomyosin cable in Megaselia abdita.
(A) Average area of serosa during retraction in wild-type control embryos (blue, n = 10 embryos) and colcemid-injected (red, n = 10 embryos). Kinetics of serosa retraction did not show an apparent …
Figure 4—figure supplement 3
UV-deactivation of colcemid in the amnion region allows dorsal closure progression in treated Megaselia abdita embryos.
(A) (Left panel) Dorsal view of a M. abdita wild-type control embryo injected with FM 4–64 during serosa accumulation at the dorsal opening. Yellow dashed line represents the edge of the epidermal …
Figure 4—figure supplement 4
Landmarks of amniotic seaming during dorsal closure progression in Megaselia abdita.
(A–A’’) Lateral view from two time-lapse sequences of dorsal closure progression in M. abdita embryos labeled with FM 4–64 (from Video 9). Top panels show a wild-type embryo undergoing serosa …
Figure 4—figure supplement 5
Schematics of dorsal closure in Megaselia abdita.
(A) Schematics depicting in transverse view the organization of the serosa cells (magenta), amnion cells (blue), and embryonic epidermis (green) prior to dorsal closure. The black dashed line …
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Videos
Video 1
Dorsal closure in Megaselia abdita involves the rupture and retraction of the serosa and advancement of the epidermal flanks to the dorsal midline.
Time-lapse sequence of dorsal closure in two M. abdita embryos injected with the fluorescent label FM 4–64. Top: serosa rupture and retraction in lateral view. Rupture initiates at a …
Video 2
The extraembryonic serosa of Megaselia abdita embryos internalizes into the yolk prior to epidermal seaming.
Time-lapse sequence of a dorsal (top) and orthogonal view (bottom) of an FM 4–64-labeled embryo. After serosa rupture and accumulation at the dorsal opening, the extraembryonic tissue internalizes …
Video 3
Knock-down of Mab_bsk by RNAi does not prevent serosa rupture and retraction despite preventing epidermal flanks from closing in Megaselia abdita embryos.
Bright-field time-lapse sequence of serosa retraction in a M. abdita embryo injected with Mab_bsk dsRNA at early stages of development. Embryo in lateral view. Anterior is to the left, dorsal to the …
Video 4
Injection of the Rho kinase inhibitor Y-27632 prevents dorsal closure and slows down serosa retraction in Megaselia abdita.
Time-lapse sequence of dorsal closure in a FM 4–64-labeled M. abdita embryo injected with the Rho kinase (ROCK) inhibitor Y-27632, which downregulates actomyosin-based contractility. Note the slow …
Video 5
Injection of the Rho kinase inhibitor Y-27632 prevents internalization of the serosa in Megaselia abdita embryos.
Time-lapse sequence of a dorsal (top) and orthogonal view (bottom) of serosa rupture in an FM 4–64-labeled M. abdita embryo. Injection of the Rho kinase (ROCK) inhibitor Y-27632 (to downregulate …
Video 6
Amniotic seaming followed by epidermal seaming during the late stage of dorsal closure in Megaselia abdita.
Time-lapse sequence of the final stage of dorsal closure in a M. abdita embryo fluorescently labeled with FM 4–64. The amnion flanks are brought together and seamed at the dorsal midline upon serosa …
Video 7
The initial stages of serosa internalization in colcemid-injected embryos of Megaselia abdita occur as in wild-type embryos.
Time-lapse sequence in orthogonal view of dorsal closure during serosa internalization in FM 4–64-labeled M. abdita embryos. The inward bending of the extraembryonic tissue and apicobasal cell …
Video 8
Colcemid injection prevents dorsal closure in Megaselia abdita.
Time-lapse sequence of impaired dorsal closure in an FM 4–64-labeled M. abdita embryo after injection of colcemid to induce microtubule depolymerization. The initial stages of dorsal closure …
Video 9
Colcemid injection impairs amniotic flank seaming during dosal closure in Megaselia abdita.
Time-lapse sequence in lateral view of the latest stages of dorsal closure in FM 4–64-labeled M. abdita embryos. Amnion cell elongation can be observed in a wild-type embryo (top) resulting in the …
Video 10
UV-deactivation of colcemid in the amnion region of treated Megaselia abdita embryos rescues amnion seaming.
Time-lapse sequence in dorsal view of dorsal closure in FM 4–64-labeled M. abdita embryos during serosa accumulation and internalization. Colcemid-injected embryos do not complete dorsal closure …
Additional files
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Transparent reporting form
- https://doi.org/10.7554/eLife.33807.029
