Tiling mechanisms of the compound eye through geometrical tessellation

Tilling patterns are observed in many biological structures. Hexagonal tilling, commonly observed in the compound eyes of wild-type Drosophila, is dominant in nature; this dominance can probably be attributed to physical restrictions such as structural robustness, minimal boundary length, and space filling efficiency. Surprisingly, tetragonal tiling patterns are also observed in some Drosophila small eye mutants and aquatic crustaceans. Herein, geometrical tessellation is shown to determine the ommatidial tiling patterns. In small eye mutants, the hexagonal pattern is transformed into a tetragonal pattern as the relative positions of neighboring ommatidia are stretched along the dorsal-ventral axis. Hence, the regular distribution of ommatidia and their uniform growth collectively play an essential role in the establishment of tetragonal and hexagonal tiling patterns in compound eyes.

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Essential role of glucose transporter GLUT3 for post-implantation embryonic development

Journal of Endocrinology ◽

10.1677/joe-08-0262 ◽

2008 ◽

Vol 200 (1) ◽

pp. 23-33 ◽

Cited By ~ 27

Author(s):

S Schmidt ◽

A Hommel ◽

V Gawlik ◽

R Augustin ◽

N Junicke ◽

...

Keyword(s):

Essential Role ◽

Glucose Transporter ◽

Growth Arrest ◽

Complete Loss ◽

Transporter Gene ◽

Wild Type ◽

Post Implantation ◽

Time Point

Deletion of glucose transporter geneSlc2a3(GLUT3) has previously been reported to result in embryonic lethality. Here, we define the exact time point of growth arrest and subsequent death of the embryo.Slc2a3−/−morulae and blastocysts developed normally, implantedin vivo, and formed egg-cylinder-stage embryos that appeared normal until day 6.0. At day 6.5, apoptosis was detected in the ectodermal cells ofSlc2a3−/−embryos resulting in severe disorganization and growth retardation at day 7.5 and complete loss of embryos at day 12.5. GLUT3 was detected in placental cone, in the visceral ectoderm and in the mesoderm of 7.5-day-old wild-type embryos. Our data indicate that GLUT3 is essential for the development of early post-implanted embryos.

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IC138 Defines a Subdomain at the Base of the I1 Dynein That Regulates Microtubule Sliding and Flagellar Motility

Molecular Biology of the Cell ◽

10.1091/mbc.e09-04-0277 ◽

2009 ◽

Vol 20 (13) ◽

pp. 3055-3063 ◽

Cited By ~ 43

Author(s):

Raqual Bower ◽

Kristyn VanderWaal ◽

Eileen O'Toole ◽

Laura Fox ◽

Catherine Perrone ◽

...

Keyword(s):

Double Mutant ◽

Essential Role ◽

Null Allele ◽

Flagellar Motility ◽

Wild Type ◽

Gene Encoding ◽

Radial Spoke ◽

Mutant Strains ◽

Dynein Arms ◽

Image Averaging

To understand the mechanisms that regulate the assembly and activity of flagellar dyneins, we focused on the I1 inner arm dynein (dynein f) and a null allele, bop5-2, defective in the gene encoding the IC138 phosphoprotein subunit. I1 dynein assembles in bop5-2 axonemes but lacks at least four subunits: IC138, IC97, LC7b, and flagellar-associated protein (FAP) 120—defining a new I1 subcomplex. Electron microscopy and image averaging revealed a defect at the base of the I1 dynein, in between radial spoke 1 and the outer dynein arms. Microtubule sliding velocities also are reduced. Transformation with wild-type IC138 restores assembly of the IC138 subcomplex and rescues microtubule sliding. These observations suggest that the IC138 subcomplex is required to coordinate I1 motor activity. To further test this hypothesis, we analyzed microtubule sliding in radial spoke and double mutant strains. The results reveal an essential role for the IC138 subcomplex in the regulation of I1 activity by the radial spoke/phosphorylation pathway.

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Spreading of hemiretinal projections in the ipsilateral tectum following unilateral enucleation: a study of optic nerve regeneration in Xenopus with one compound eye

Development ◽

10.1242/dev.61.1.259 ◽

1981 ◽

Vol 61 (1) ◽

pp. 259-276

Author(s):

Charles Straznicky ◽

David Tay

Keyword(s):

Optic Nerve ◽

Nerve Regeneration ◽

Compound Eye ◽

Rapid Expansion ◽

Compound Eyes ◽

Optic Nerve Regeneration ◽

Xenopus Embryos ◽

Retinotectal Projections ◽

Optic Fibre

Right compound eyes were formed in Xenopus embryos at stages 32–33 by the fusion of two nasal (NN), two ventral (VV) or two temporal (TT) halves. Shortly after metamorphosis the optic nerve from the compound eye was sectioned and the left intact eye removed. The retinotectal projections from the compound eye to the contralateral and ipsilateral tecta were studied by [3H]proline autoradiography and electrophysiological mapping between 6 weeks and 5 months after the postmetamorphic surgery. The results showed that NN and VV eyes projected to the entire extent of both tecta. In contrast, optic fibre projection from TT eyes, although more extensive than the normal temporal hemiretinal projection, failed to cover the caudomedial portion of the tecta. The visuotectal projections in all three combinations corresponded to typical reduplicated maps to be expected from such compound eyes, where each of the hemiretinae projected across the contralateral and ipsilateral tecta in an overlapping fashion. The rapid expansion of the hemiretinal projections of the compound eyes in the ipsilateral tectum following the removal of the resident optic fibre projection suggests that tectal markers may be carried and deployed by the incoming optic fibres themselves.

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Insights on the mechanisms of Ca2+ regulation of connexin26 hemichannels revealed by human pathogenic mutations (D50N/Y)

The Journal of General Physiology ◽

10.1085/jgp.201210893 ◽

2013 ◽

Vol 142 (1) ◽

pp. 23-35 ◽

Cited By ~ 41

Author(s):

William Lopez ◽

Jorge Gonzalez ◽

Yu Liu ◽

Andrew L. Harris ◽

Jorge E. Contreras

Keyword(s):

Essential Role ◽

Negative Charge ◽

Salt Bridge ◽

Cysteine Residue ◽

Wild Type ◽

Closed State ◽

Large Size ◽

Deactivation Kinetics ◽

Connexin Hemichannel

Because of the large size and modest selectivity of the connexin hemichannel aqueous pore, hemichannel opening must be highly regulated to maintain cell viability. At normal resting potentials, this regulation is achieved predominantly by the physiological extracellular Ca2+ concentration, which drastically reduces hemichannel activity. Here, we characterize the Ca2+ regulation of channels formed by wild-type human connexin26 (hCx26) and its human mutations, D50N/Y, that cause aberrant hemichannel opening and result in deafness and skin disorders. We found that in hCx26 wild-type channels, deactivation kinetics are accelerated as a function of Ca2+ concentration, indicating that Ca2+ facilitates transition to, and stabilizes, the closed state of the hemichannels. The D50N/Y mutant hemichannels show lower apparent affinities for Ca2+-induced closing than wild-type channels and have more rapid deactivation kinetics, which are Ca2+ insensitive. These results suggest that D50 plays a role in (a) stabilizing the open state in the absence of Ca2+, and (b) facilitating closing and stabilization of the closed state in the presence of Ca2+. To explore the role of a negatively charged residue at position 50 in regulation by Ca2+, this position was substituted with a cysteine residue, which was then modified with a negatively charged methanethiosulfonate reagent, sodium (2-sulfanoethyl) methanethiosulfonate (MTSES)−. D50C mutant hemichannels display properties similar to those of D50N/Y mutants. Recovery of the negative charge with chemical modification by MTSES− restores the wild-type Ca2+ regulation of the channels. These results confirm the essential role of a negative charge at position 50 for Ca2+ regulation. Additionally, charge-swapping mutagenesis studies suggest involvement of a salt bridge interaction between D50 and K61 in the adjacent connexin subunit in stabilizing the open state in low extracellular Ca2+. Mutant cycle analysis supports a Ca2+-sensitive interaction between these two residues in the open state of the channel. We propose that disruption of this interaction by extracellular Ca2+ destabilizes the open state and facilitates hemichannel closing. Our data provide a mechanistic understanding of how mutations at position 50 that cause human diseases are linked to dysfunction of hemichannel gating by external Ca2+.

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Differences in orthodenticle expression promote ommatidial size variation between Drosophila species

10.1101/2021.03.17.435774 ◽

2021 ◽

Author(s):

Montserrat Torres-Oliva ◽

Elisa Buchberger ◽

Alexandra D. Buffry ◽

Maike Kittelmann ◽

Lauren Sumner-Rooney ◽

...

Keyword(s):

Natural Variation ◽

Gene Expression Analysis ◽

Compound Eye ◽

Chromosomal Region ◽

Size Variation ◽

Compound Eyes ◽

Positional Candidate ◽

Eye Size ◽

Drosophila Mauritiana ◽

Differential Timing

The compound eyes of insects exhibit extensive variation in ommatidia number and size, which affects how they see and underlies adaptations in their vision to different environments and lifestyles. However, very little is known about the genetic and developmental bases underlying differences in compound eye size. We previously showed that the larger eyes of Drosophila mauritiana compared to D. simulans is caused by differences in ommatidia size rather than number. Furthermore, we identified an X-linked chromosomal region in D. mauritiana that results in larger eyes when introgressed into D. simulans. Here, we used a combination of fine-scale mapping and gene expression analysis to further investigate positional candidate genes on the X chromosome. We found that orthodenticle is expressed earlier in D. mauritiana than in D. simulans during ommatidial maturation in third instar larvae, and we further show that this gene is required for the correct organisation and size of ommatidia in D. melanogaster. Using ATAC-seq, we have identified several candidate eye enhancers of otd as well as potential direct targets of this transcription factor that are differentially expressed between D. mauritiana and D. simulans. Taken together, our results suggest that differential timing of otd expression contributes to natural variation in ommatidia size between D. mauritiana and D. simulans, which provides new insights into the mechanisms underlying the regulation and evolution of compound eye size in insects.

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The development of the retinotectal projection in Xenopus with one compound eye

Development ◽

10.1242/dev.33.3.775 ◽

1975 ◽

Vol 33 (3) ◽

pp. 775-787

Author(s):

Joan D. Feldman ◽

R. M. Gaze

Keyword(s):

Compound Eye ◽

Contralateral Side ◽

Compound Eyes ◽

Stages Of Development ◽

Ipsilateral Side ◽

Retinotectal Projection ◽

Xenopus Embryos ◽

Donor Embryo

Double-nasal and double-temporal compound eyes were constructed in Xenopus embryos at stages 32 and 37/38. A particular half was removed from the host eye anlage and replaced with the opposite half-eye from the contralateral side of a donor embryo. Control operations consisted of removing a half-eye and replacing it with a similar half from the ipsilateral side of the donor embryo. Whereas in control animals, each half-eye projected its fibres to the appropriate half-tectum, in operated animals each half of the compound eye spread its optic teiminals across the entire rostrocaudal extent of the dorsal tectal surface. The area of tectal surface covered by ganglion fibre terminals was similar in operated animals mapped at successive stages of development to that previously observed in normal animals at equivalent stages. Therefore the factors responsible for the extended distribution of fibre terminals from each half of a compound eye must exist at least from mid-tadpole life, and thereafter be continuously present throughout development.

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Interactions between compound and normal eye projections in dually innervated tectum: a study of optic nerve regeneration in Xenopus

Development ◽

10.1242/dev.66.1.159 ◽

1981 ◽

Vol 66 (1) ◽

pp. 159-174

Author(s):

Charles Straznicky ◽

David Tay

Keyword(s):

Optic Nerve ◽

Nerve Regeneration ◽

Compound Eye ◽

Compound Eyes ◽

Lateral Region ◽

Optic Nerve Regeneration ◽

Xenopus Embryos ◽

Retinotectal Projections ◽

Two Populations

Right compound eyes were formed in Xenopus embryos at tailbud stages by the fusion of two nasal (NN), two temporal (TT) or two ventral (VV) halves. The left eye was kept intact. Two to four weeks after metamorphosis the optic nerve from the intact eye was severed to induce bilateral optic nerve regeneration. The contralateral retinotectal projections from the compound eye and the induced ipsilateral projections from the intact eye to the same (dually innervated) tectum were studied by [3H]proline autoradiography and visuotectal mapping from 3 to 6 months after the postmetamorphic surgery. The results showed that the NN, TT and VV projections, in the presence of optic fibres from the intact eye failed to spread across the whole extent of the dually innervated tectum. Unexpectedly the bulk of the regenerating projection from the intact eye was confined to the previously uninnervated parts of the dually innervated tecta, the caudomedial region in TT, the rostrolateral region in NN and the lateral region in VV eye animals. The partial segregation of the two populations of optic fibres in the dually innervated tectum has been taken as a further indication of the role of fibre-fibre and fibre-tectum interactions in retinotectal map formation.

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Regional Specialization for Control of Ocular Movements in the Compound Eyes of a Stomatopod Crustacean

Journal of Experimental Biology ◽

10.1242/jeb.171.1.373 ◽

1992 ◽

Vol 171 (1) ◽

pp. 373-393 ◽

Cited By ~ 1

Author(s):

THOMAS W. CRONIN ◽

HONG Y. YAN ◽

KAY D. BIDLE

Keyword(s):

Compound Eye ◽

Compound Eyes ◽

University Of Maryland ◽

Regional Specialization ◽

Ocular Movements ◽

Maryland College ◽

Ocular Tracking ◽

College Park ◽

Direct Tracking ◽

The University

1. Regional specialization within the triple compound eyes of the gonodactyloid stomatopod Gonodactylus oerstedii (Hansen) was studied by examining how ocular tracking of a small target was affected after occluding vision in particular ommatidial regions with black enamel paint. 2. Complete occlusion of one eye did not prevent the other eye from tracking, indicating that the two eyes act somewhat independently. However, following such treatment, the angular extent over which the seeing eye moved while tracking was reduced. 3. An eye was able to continue tracking a moving target even after occlusion of the anterior tip or after painting over all of its posterior surface except the anterior tip (restricting the visual field to a patch about 40° in diameter). Similarly, occlusion of only the midband, the medial half or the lateral half of an eye did not prevent tracking. 4. Tracking was also possible, although with decreased amplitude, when either the dorsal or the ventral hemisphere was occluded. However, when both the dorsal and ventral hemispheres were occluded, leaving only the midband for vision, the ability of an eye to track was abolished. 5. A computer model was used to investigate whether the midband alone had the potential to direct tracking in our experiments. The model's output predicts that, in spite of its restricted field of view, if the midband is oriented within 20° of the horizontal, an eye could track using the midband alone. Conditions favoring such potential tracking occurred in our experiments, but neither tracking nor targetting movements were observed. 6. We conclude that ommatidia of the dorsal and ventral hemispheres of each compound eye are essential for ocular tracking in G. oerstedii. The midband appears to play no major role in this activity. Note: Present address: Department of Zoology, The University of Maryland College Park, College Park, MD 20742, USA.

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Disparate compound eyes of Cambrian radiodonts reveal their developmental growth mode and diverse visual ecology

Science Advances ◽

10.1126/sciadv.abc6721 ◽

2020 ◽

Vol 6 (49) ◽

pp. eabc6721

Author(s):

John R. Paterson ◽

Gregory D. Edgecombe ◽

Diego C. García-Bellido

Keyword(s):

Crucial Role ◽

Compound Eye ◽

Marine Ecosystems ◽

Growth Mode ◽

Compound Eyes ◽

Suspension Feeding ◽

Ecological Diversity ◽

Crown Group ◽

Developmental Growth

Radiodonts are nektonic stem-group euarthropods that played various trophic roles in Paleozoic marine ecosystems, but information on their vision is limited. Optical details exist only in one species from the Cambrian Emu Bay Shale of Australia, here assigned to Anomalocaris aff. canadensis. We identify another type of radiodont compound eye from this deposit, belonging to ‘Anomalocaris’ briggsi. This ≤4-cm sessile eye has >13,000 lenses and a dorsally oriented acute zone. In both taxa, lenses were added marginally and increased in size and number throughout development, as in many crown-group euarthropods. Both species’ eyes conform to their inferred lifestyles: The macrophagous predator A. aff. canadensis has acute stalked eyes (>24,000 lenses each) adapted for hunting in well-lit waters, whereas the suspension-feeding ‘A.’ briggsi could detect plankton in dim down-welling light. Radiodont eyes further demonstrate the group’s anatomical and ecological diversity and reinforce the crucial role of vision in early animal ecosystems.

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Essential roles for Pot1b in HSC self-renewal and survival

Blood ◽

10.1182/blood-2011-06-361527 ◽

2011 ◽

Vol 118 (23) ◽

pp. 6068-6077 ◽

Cited By ~ 22

Author(s):

Yang Wang ◽

Mei-Feng Shen ◽

Sandy Chang

Keyword(s):

Progenitor Cell ◽

Essential Role ◽

Dyskeratosis Congenita ◽

Telomere Maintenance ◽

Wild Type ◽

Telomere Shortening ◽

Damage Response ◽

First Time

Abstract Maintenance of mammalian telomeres requires both the enzyme telomerase and shelterin, which protect telomeres from inappropriately activating DNA damage response checkpoints. Dyskeratosis congenita is an inherited BM failure syndrome disorder because of defects in telomere maintenance. We have previously shown that deletion of the shelterin component Pot1b in the setting of telomerase haploinsufficiency results in rapid telomere shortening and fatal BM failure in mice, eliciting phenotypes that strongly resemble human syskeratosis congenita. However, it was unclear why BM failure occurred in the setting of Pot1b deletion. In this study, we show that Pot1b plays an essential role in HSC survival. Deletion of Pot1b results in increased apoptosis, leading to severe depletion of the HSC reserve. BM from Pot1bΔ/Δ mice cannot compete with BM from wild-type mice to provide multilineage reconstitution, indicating that there is an intrinsic requirement for Pot1b the maintenance of HSC function in vivo. Elimination of the p53-dependent apoptotic function increased HSC survival and significantly extended the lifespan of Pot1b-null mice deficient in telomerase function. Our results document for the first time the essential role of a component of the shelterin complex in the maintenance of HSC and progenitor cell survival.

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