Segmental repetition of neuronal phenotype sets in the chick embryo hindbrain

Development ◽  
1993 ◽  
Vol 118 (1) ◽  
pp. 151-162 ◽  
Author(s):  
J.D. Clarke ◽  
A. Lumsden

The neurons within the segmented hindbrain of the early chick embryo have been mapped with the neuronal tracers HRP and fluorescent lysinated dextran. We have categorised neurons according to their axonal pathways and have then compared rhombomeres with respect to the number and class of neurons present. The results indicate that most rhombomeres are similar in that they contain the same set of basic neuronal types but differ in that particular neuronal types are more abundant in some rhombomeres than others. The data support the concept that the hindbrain develops according to ‘variations on a segmental theme’ rather than ‘each segment is unique’. Many of the cell types occupy distinct mediolateral domains that are probably established by both the differential migration of some neuronal classes and the spatial segregation of distinct precursors. The caudal rhombomeres 7 and 8 are exceptional in that they do not have the full set of basic neuronal types and also contain two additional medial cell types that are not present rostrally. The mechanisms that may generate the regional diversity apparent in the more mature hindbrain are discussed.

Development ◽  
1994 ◽  
Vol 120 (10) ◽  
pp. 2879-2889 ◽  
Author(s):  
Y. Hatada ◽  
C.D. Stern

We have used carbocyanine dyes (DiI and DiO) to generate fate maps for the epiblast layer of the chick embryo between stage X and the early primitive streak stage (stages 2–3). The overall distribution of presumptive cell types in these maps is similar to that described for other laboratory species (zebrafish, frog, mouse). Our maps also reveal certain patterns of movement for these presumptive areas. Most areas converge towards the midline and then move anteriorly along it. Interestingly, however, some presumptive tissue types do not take part in these predominant movements, but behave in a different way, even if enclosed within an area that does undergo medial convergence and anterior movement. The apparently independent behaviour of certain cell populations suggests that at least some presumptive cell types within the epiblast are already specified at preprimitive streak stages.


2020 ◽  
Author(s):  
Yang-Sun Hwang ◽  
Catherine Maclachlan ◽  
Jérôme Blanc ◽  
Anaëlle Dubois ◽  
Carl C H Petersen ◽  
...  

Abstract Synapses are the fundamental elements of the brain’s complicated neural networks. Although the ultrastructure of synapses has been extensively studied, the difference in how synaptic inputs are organized onto distinct neuronal types is not yet fully understood. Here, we examined the cell-type-specific ultrastructure of proximal processes from the soma of parvalbumin-positive (PV+) and somatostatin-positive (SST+) GABAergic neurons in comparison with a pyramidal neuron in the mouse primary visual cortex (V1), using serial block-face scanning electron microscopy. Interestingly, each type of neuron organizes excitatory and inhibitory synapses in a unique way. First, we found that a subset of SST+ neurons are spiny, having spines on both soma and dendrites. Each of those spines has a highly complicated structure that has up to eight synaptic inputs. Next, the PV+ and SST+ neurons receive more robust excitatory inputs to their perisoma than does the pyramidal neuron. Notably, excitatory synapses on GABAergic neurons were often multiple-synapse boutons, making another synapse on distal dendrites. On the other hand, inhibitory synapses near the soma were often single-targeting multiple boutons. Collectively, our data demonstrate that synaptic inputs near the soma are differentially organized across cell types and form a network that balances inhibition and excitation in the V1.


Cells ◽  
2018 ◽  
Vol 7 (2) ◽  
pp. 9 ◽  
Author(s):  
José Serrado Marques ◽  
Vera Teixeira ◽  
António Jacinto ◽  
Ana Tavares

1948 ◽  
Vol 68 (2) ◽  
pp. 263-266 ◽  
Author(s):  
A. M. Schechtman

1987 ◽  
Vol 88 (4) ◽  
pp. 521-526
Author(s):  
R.M. Brown ◽  
C.A. Middleton

The behaviour in culture of dissociated epithelial cells from chick embryo pigmented retina epithelium (PRE), corneal epithelium (CE) and epidermis has been studied using time-lapse cinematography. The analysis concentrated on the contact behaviour of 60 previously isolated cells of each type during a 24 h period starting 3.5 h after the cells were plated out. During the period analysed the number of isolated cells in cultures of all three types gradually decreased as they became incorporated into islands and sheets of cells. However, there were significant differences in behaviour between the cell types during the establishment of these sheets and islands. In PRE cell cultures, islands of cells developed because, throughout the period of analysis, collisions involving previously isolated cells almost invariably resulted in the development of a stable contact. Once having established contact with another cell these cells rarely broke away again to become reisolated. In contrast the contacts formed between colliding CE and epidermal cells were, at least initially, much less stable and cells of both these types were frequently seen to break away and become reisolated after colliding with other cells. Sheets and islands of cells eventually developed in these cultures because the frequency with which isolated cells become reisolated decreased with increasing time in culture. The possible reasons underlying the different behaviour of PRE cells, when compared with that of CE and epidermal cells, are discussed. It is suggested that the decreasing tendency of isolated CE and epidermal cells to become reisolated may be related to the formation of desmosomes.


1988 ◽  
Vol 222 (1) ◽  
pp. 90-94 ◽  
Author(s):  
Masao Nakamura ◽  
Takashi Kuwana ◽  
Yukihiko Miyayama ◽  
Toyoaki Fujimoto

2021 ◽  
Vol 44 (1) ◽  
Author(s):  
Anthony M. Rossi ◽  
Shadi Jafari ◽  
Claude Desplan

During the approximately 5 days of Drosophila neurogenesis (late embryogenesis to the beginning of pupation), a limited number of neural stem cells produce approximately 200,000 neurons comprising hundreds of cell types. To build a functional nervous system, neuronal types need to be produced in the proper places, appropriate numbers, and correct times. We discuss how neural stem cells (neuroblasts) obtain so-called area codes for their positions in the nervous system (spatial patterning) and how they keep time to sequentially produce neurons with unique fates (temporal patterning). We focus on specific examples that demonstrate how a relatively simple patterning system (Notch) can be used reiteratively to generate different neuronal types. We also speculate on how different modes of temporal patterning that operate over short versus long time periods might be linked. We end by discussing how specification programs are integrated and lead to the terminal features of different neuronal types. Expected final online publication date for the Annual Review of Neuroscience, Volume 44 is July 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.


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