scholarly journals Loss of positional information when tracking multiple dots: The role of memory

2004 ◽  
Vol 4 (8) ◽  
pp. 361-361 ◽  
Author(s):  
S. Narasimhan ◽  
S. P. Tripathy ◽  
B. T. Barrett
Keyword(s):  
Positional Information

scholarly journals Successive specification of Drosophila neuroblasts NB 6-4 and NB 7-3 depends on interaction of the segment polarity genes wingless, gooseberry and naked cuticle

Development ◽  
2001 ◽  
Vol 128 (17) ◽  
pp. 3253-3261 ◽  
Author(s):  
Nirupama Deshpande ◽  
Rainer Dittrich ◽  
Gerhard M. Technau ◽  
Joachim Urban
Keyword(s):  
Cell Fate ◽  
Cell Lineage ◽  
Positional Information ◽  
Dorsoventral Patterning ◽  
Expression Domain ◽  
Direct Role ◽  
Segment Polarity Genes ◽  
Segment Polarity ◽  
Unique Identity

The Drosophila central nervous system derives from neural precursor cells, the neuroblasts (NBs), which are born from the neuroectoderm by the process of delamination. Each NB has a unique identity, which is revealed by the production of a characteristic cell lineage and a specific set of molecular markers it expresses. These NBs delaminate at different but reproducible time points during neurogenesis (S1-S5) and it has been shown for early delaminating NBs (S1/S2) that their identities depend on positional information conferred by segment polarity genes and dorsoventral patterning genes. We have studied mechanisms leading to the fate specification of a set of late delaminating neuroblasts, NB 6-4 and NB 7-3, both of which arise from the engrailed (en) expression domain, with NB 6-4 delaminating first. In contrast to former reports, we did not find any evidence for a direct role of hedgehog in the process of NB 7-3 specification. Instead, we present evidence to show that the interplay of the segmentation genes naked cuticle (nkd) and gooseberry (gsb), both of which are targets of wingless (wg) activity, leads to differential commitment to NB 6-4 and NB 7-3 cell fate. In the absence of either nkd or gsb, one NB fate is replaced by the other. However, the temporal sequence of delamination is maintained, suggesting that formation and specification of these two NBs are under independent control.

scholarly journals Loss of positional information when tracking multiple moving dots: The role of visual memory

2009 ◽  
Vol 49 (1) ◽  
pp. 10-27 ◽  
Author(s):  
Sathyasri Narasimhan ◽  
Srimant P. Tripathy ◽  
Brendan T. Barrett
Keyword(s):  
Visual Memory ◽  
Positional Information

Developmental Mechanisms for Evolutionary Novelties

2014 ◽  
Author(s):  
Günter P. Wagner
Keyword(s):  
Hind Limb ◽  
Positional Information ◽  
Morphological Characters ◽  
Mechanical Stimuli ◽  
Body Parts ◽  
Environmental Perturbations ◽  
Developmental Mechanisms ◽  
Evolutionary Changes ◽  
Evolutionary Novelties

This chapter examines the developmental mechanisms underlying evolutionary novelties. It first considers the role of the environment in evolutionary innovations, with particular emphasis on how environmental perturbations result in the release of cryptic genetic variation. It then explores where the positional information for novel characters comes from before explaining derived mechanical stimuli and the origin of novelties in the avian hind limb skeleton. It also discusses the origin of character identity networks and the evolution of novel signaling centers, focusing on two novel morphological characters: the butterfly eyespot and the turtle carapace. Finally, it reflects on the developmental biology of novelties, emphasizing the complex and multifaceted nature of the evolutionary changes in the developmental mechanisms that contribute to the origin of novel body parts.

scholarly journals Regenerative Models for the Integration and Regeneration of Head Skeletal Tissues

2018 ◽  
Vol 19 (12) ◽  
pp. 3752 ◽  
Author(s):  
Warren Vieira ◽  
Catherine McCusker
Keyword(s):  
Soft Tissues ◽  
Treatment Options ◽  
Positional Information ◽  
Cell Types ◽  
Model Organisms ◽  
Biological Targets ◽  
Tissue Integration ◽  
Repair Mechanisms

Disease of, or trauma to, the human jaw account for thousands of reconstructive surgeries performed every year. One of the most popular and successful treatment options in this context involves the transplantation of bone tissue from a different anatomical region into the affected jaw. Although, this method has been largely successful, the integration of the new bone into the existing bone is often imperfect, and the integration of the host soft tissues with the transplanted bone can be inconsistent, resulting in impaired function. Unlike humans, several vertebrate species, including fish and amphibians, demonstrate remarkable regenerative capabilities in response to jaw injury. Therefore, with the objective of identifying biological targets to promote and engineer improved outcomes in the context of jaw reconstructive surgery, we explore, compare and contrast the natural mechanisms of endogenous jaw and limb repair and regeneration in regenerative model organisms. We focus on the role of different cell types as they contribute to the regenerating structure; how mature cells acquire plasticity in vivo; the role of positional information in pattern formation and tissue integration, and limitations to endogenous regenerative and repair mechanisms.

The role of visual cues in learning escape behaviour in the little brown skink (Scincella lateralis)

Behaviour ◽  
2014 ◽  
Vol 151 (14) ◽  
pp. 2015-2028 ◽  
Author(s):  
Mark A. Paulissen
Keyword(s):  
Visual Cues ◽  
Small Animal ◽  
Positional Information ◽  
Learning Criterion ◽  
Forest Species ◽  
Escape Behaviour ◽  
Observation Chamber ◽  
Visual Cue ◽  
Scincella Lateralis

Many small animals escape predators by running under an escape retreat such as a rock, log, or pile of leaves. Rapid escape to a retreat would be facilitated if the animal already learned the location of the retreat before it ever had to flee from a predator. One way a small animal might do this is to attend to a prominent ‘local cue’, that is, a visual cue that is part of, or contiguous with, the retreat. I tested the hypothesis that a small lizard commonly known as the little brown skink, Scincella lateralis, can use a local visual cue to learn an escape behaviour. Little brown skinks were presented with two retreats side-by side in an observation chamber. One retreat was backed with a vertical striped cue and the other backed with a horizontal striped cue. Each lizard was induced to run from one end of the observation tank to the opposite end with the two retreats; the retreat that each lizard chose for escape was recorded through a series of 15 trials conducted over three days. Half of the lizards were trained to escape to the vertical cue retreat; half were trained to escape to the horizontal cue retreat. About one-third of little brown skinks met the learning criterion of escaping to the correct retreat in five consecutive trials. However, significantly more of the vertical cue lizards met the learning criterion than did horizontal cue lizards. Also, the vertical cue lizards escaped to the correct retreat significantly more often than expected by chance. Furthermore, even the horizontal cue lizards showed a preference for escaping to the vertical cue retreat. This suggests little brown skinks can use a local visual cue to learn an escape behaviour, but only if it a vertical cue. This may be related to the use of a vertical cue to obtain positional information to locate a retreat or perhaps to the tendency of this forest species to attend to abundant vertical cues in its habitat.

scholarly journals Molluscan dorsal-ventral patterning relying on BMP2/4 and Chordin provides insights into spiralian development and bilaterian body plan evolution

2020 ◽  
Author(s):  
Sujian Tan ◽  
Pin Huan ◽  
Baozhong Liu
Keyword(s):  
Nervous System ◽  
Molecular Mechanisms ◽  
Positional Information ◽  
Body Plan ◽  
Bmp Signaling ◽  
Functional Study ◽  
Development Mode ◽  
Larval Nervous System ◽  
Body Plan Evolution

AbstractThe molecular mechanisms of dorsal-ventral (DV) patterning in Spiralia are poorly understood. The few available studies indicate that derived DV patterning mechanisms occurred in particular spiralian lineages and likely were related to the loss of Chordin gene. Here, a functional study of the first spiralian Chordin showed that BMP2/4 and Chordin regulate DV patterning in the mollusk Lottia goshimai, thus revealing the first spiralian case that retains this conserved mechanism. We then showed that Chordin but not BMP2/4 transferred the positional information of the D-quadrant organizer to establish the BMP signaling gradient along the presumed DV axis. Further investigations on the molluscan embryos with influenced DV patterning suggested a role of BMP signaling in regulating the organization of the larval nervous system and indicated that the blastopore localization is correlated with the BMP signaling gradient. These findings provide insights into the evolution of animal DV patterning, the unique development mode of spiralians driven by the D-quadrant organizer, and the evolution of bilaterian body plans.

The expression of pannier and achaete-scute homologues in a mosquito suggests an ancient role of pannier as a selector gene in the regulation of the dorsal body pattern

Development ◽  
2002 ◽  
Vol 129 (16) ◽  
pp. 3861-3871 ◽  
Author(s):  
Corinna Wülbeck ◽  
Pat Simpson
Keyword(s):  
Expression Patterns ◽  
Ectopic Expression ◽  
Positional Information ◽  
New Class ◽  
Medial Dorsal ◽  
Duplication Events ◽  
Selector Genes ◽  
Bristle Pattern ◽  
Body Pattern

The Drosophila gene pannier (pnr) has recently been assigned to a new class of selector genes (Calleja, M., Herranz, H., Estella, C., Casal, J., Lawrence, P., Simpson, P. and Morata, G. (2000). Development 127, 3971-3980; (Mann, R. S. and Morata, G. (2000). Annu. Rev. Cell Dev. Biol. 16, 243-271). It specifies pattern in the dorsal body. On the dorsal notum it is expressed in a broad medial domain and directly regulates transcription of the achaete-scute (ac-sc) genes driving their expression in small discrete clusters within this domain at the sites of each future bristle. This spatial resolution is achieved through modulation of Pnr activity by specific co-factors and by a number of discrete cis-regulatory enhancers in the ac-sc gene complex. We have isolated homologues of pnr and ac-sc in Anopheles gambiae, a basal species of Diptera that diverged from Drosophila melanogaster (Dm) about 200 million years ago, and examined their expression patterns. We found that an ac-sc homologue of Anopheles, Ag-ASH, is expressed on the dorsal medial notum at the sites where sensory organs emerge in several domains that are identical to those of the pnr homologue, Ag-pnr. This suggests that activation of Ag-ASH by Ag-Pnr has been conserved. Indeed, when expressed in Drosophila, Ag-pnr is able to mimic the effects of ectopic expression of Dm-pnr and induce ectopic bristles. These results are discussed in the context of the gene duplication events and the acquisition of a modular promoter, that may have occurred at different times in the lineage leading to derived species such as Drosophila. The bristle pattern of Anopheles correlates in a novel fashion with the expression domains of Ag-pnr/Ag-ASH. While precursors for the sensory scales can arise anywhere within the expression domains, bristle precursors arise exclusively along the borders. This points to the existence of specific positional information along the borders, and suggests that Ag-pnr specifies pattern in the medial, dorsal notum, as in Drosophila, but via a different mechanism.

Effects of ultraviolet light on the activity of an avian limb positional signalling region

Development ◽  
1982 ◽  
Vol 71 (1) ◽  
pp. 223-232
Author(s):  
Lawrence S. Honig
Keyword(s):  
Ultraviolet Radiation ◽  
Ultraviolet Light ◽  
Single Cells ◽  
Positional Information ◽  
Limb Bud ◽  
Single Cell Suspension ◽  
Γ Radiation ◽  
Cell Pellet ◽  
Lethal Doses

Cells from a region on the posterior margin of the developing avian limb bud (the polarizing region) can signal positional information to responding anterior cells. Polarizing activity may be assayed by disaggregation of the tissue into single cells, followed by reaggregation and grafting of cell pellet. This method enables treatments of the cells while in single-cell suspension. The effects of ultraviolet radiation (254 nm) were studied to determine the role of nucleic acids in polarizing activity. Ultraviolet radiation eliminated quail polarizing activity over the same range of doses as it reduced cell spreading (20–60 J/m2). In contrast to the published effects of γ-radiation in which polarizing activity is affected only at doses much higher than those that are cell lethal, ultraviolet apparently abolishes cell survival and polarizing activity at comparable doses. Compared to other biological systems, polarizing activity is quite sensitive to ultraviolet light: the D37 is 18 J/m2; the extrapolation number, n, is 3·6. From pomparison of the effects of ultraviolet radiation to those published for ionizing X- or γ-radiation, one may conclude that ultraviolet and γ-radiation abolish limb polarizing activity at equivalent nucleic acid dosages, not at equivalent cell lethal doses.

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