scholarly journals Drosophila embryonic type II neuroblasts: origin, temporal patterning, and contribution to the adult central complex

2017 ◽  
Author(s):  
Kathleen T. Walsh ◽  
Chris Q. Doe
Keyword(s):  
Transcription Factors ◽  
Complex Function ◽  
Neural Progenitors ◽  
Central Complex ◽  
Type I ◽  
Type Ii ◽  
Neuronal Diversity ◽  
Temporal Patterning ◽  
Larval Type ◽  
Mother Cells

ABSTRACTDrosophila neuroblasts are an excellent model for investigating how neuronal diversity is generated. Most brain neuroblasts generate a series of ganglion mother cells (GMCs) that each make two neurons (type I lineage), but sixteen brain neuroblasts generate a series of intermediate neural progenitors (INPs) that each produce 4-6 GMCs and 8-12 neurons (type II lineage). Thus, type II lineages are similar to primate cortical lineages, and may serve as models for understanding cortical expansion. Yet the origin of type II neuroblasts remains mysterious: do they form in the embryo or larva? If they form in the embryo, do their progeny populate the adult central complex, as do the larval type II neuroblast progeny? Here we present molecular and clonal data showing that all type II neuroblasts form in the embryo, produce INPs, and express known temporal transcription factors. Embryonic type II neuroblasts and INPs undergo quiescence, and produce embryonic-born progeny that contribute to the adult central complex. Our results provide a foundation for investigating the development of the central complex, and tools for characterizing early-born neurons in central complex function.

scholarly journals NanoDam identifies novel temporal transcription factors conserved between the Drosophila central brain and visual system

2021 ◽  
Author(s):  
Jocelyn L. Y. Tang ◽  
Anna Hakes ◽  
Robert Krautz ◽  
Takumi Suzuki ◽  
Esteban Contreras ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Visual System ◽  
Neural Progenitors ◽  
Adult Brain ◽  
Neuronal Diversity ◽  
Temporal Patterning ◽  
Genome Wide ◽  
Temporal Factors ◽  
Central Brain

Temporal patterning of neural progenitors is an evolutionarily conserved strategy for generating neuronal diversity. Type II neural stem cells in the Drosophila central brain produce transit-amplifying intermediate neural progenitors (INPs) that exhibit temporal patterning. However, the known temporal factors cannot account for the neuronal diversity in the adult brain. To search for new temporal factors, we developed NanoDam, which enables rapid genome-wide profiling of endogenously-tagged proteins in vivo with a single genetic cross. Mapping the targets of known temporal transcription factors with NanoDam identified Homeobrain and Scarecrow (ARX and NKX2.1 orthologues) as novel temporal factors. We show that Homeobrain and Scarecrow define middle-aged and late INP temporal windows and play a role in cellular longevity. Strikingly, Homeobrain and Scarecrow have conserved functions as temporal factors in the developing visual system. NanoDam enables rapid cell type-specific genome-wide profiling with temporal resolution and can be easily adapted for use in higher organisms.

scholarly journals A comprehensive series of temporal transcription factors in the fly visual system

2021 ◽  
Author(s):  
Nikolaos Konstantinides ◽  
Anthony M. Rossi ◽  
Aristides Escobar ◽  
Liébaut Dudragne ◽  
Yen-Chung Chen ◽  
...  
Keyword(s):  
Stem Cells ◽  
Transcription Factors ◽  
Single Cell ◽  
Neuronal System ◽  
Neuronal Diversity ◽  
Temporal Patterning ◽  
Neuronal Stem Cells ◽  
Mrna Sequencing ◽  
Neuronal Types ◽  
Cell Type Specific

AbstractThe brain consists of thousands of different neuronal types that are generated through multiple divisions of neuronal stem cells. These stem cells have the capacity to generate different neuronal types at different stages of their development. In Drosophila, this temporal patterning is driven by the successive expression of temporal transcription factors (tTFs). While a number of tTFs are known in different animals and across various parts of the nervous system, these have been mostly identified by informed guesses and antibody availability. We used single-cell mRNA sequencing to identify the complete series of tTFs that specify most Drosophila medulla neurons in the optic lobe. We tested the genetic interactions among these tTFs. While we verify the general principle that tTFs regulate the progression of the series by activating the next tTFs in the series and repressing the previous ones, we also identify more complex regulations. Two of the tTFs, Eyeless and Dichaete, act as hubs integrating the input of several upstream tTFs before allowing the series to progress and in turn regulating the expression of several downstream tTFs. Moreover, we show that tTFs not only specify neuronal identity by controlling the expression of cell type-specific genes. Finally, we describe the very first steps of neuronal differentiation and find that terminal differentiation genes, such as neurotransmitter-related genes, are present as transcripts, but not as proteins, in immature larval neurons days before they are being used in functioning neurons; we show that these mechanisms are conserved in humans. Our results offer a comprehensive description of a temporal series of tTFs in a neuronal system, offering mechanistic insights into the regulation of the progression of the series and the regulation of neuronal diversity. This represents a proof-of-principle for the use of single-cell mRNA sequencing for the comparison of temporal patterning across phyla that can lead to an understanding of how the human brain develops and how it has evolved.

scholarly journals Extrinsic Activin signaling cooperates with an intrinsic temporal program to increase mushroom body neuronal diversity

2019 ◽  
Author(s):  
Anthony M. Rossi ◽  
Claude Desplan
Keyword(s):  
Mushroom Body ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Neural Progenitors ◽  
Neuronal Diversity ◽  
Temporal Patterning ◽  
Activin Signaling ◽  
Extrinsic Cues ◽  
Neuronal Types ◽  
Temporal Program

SummaryTemporal patterning of neural progenitors leads to the sequential production of diverse neuronal types. To better understand how extrinsic cues interact with intrinsic temporal programs to contribute to temporal patterning, we studied the Drosophila mushroom body neural progenitors (neuroblasts). Each of these four neuroblasts divides ~250 times to sequentially produce only three main neuronal types over the course of ~9 days of development: γ, followed by α’β’, and finally αβ neurons. The intrinsic temporal clock is composed of two RNA-binding proteins, IGF-II mRNA binding protein (Imp) and Syncrip (Syp), that are expressed in opposing temporal gradients. Activin signaling affects the production of α’β’ neurons but whether and how this extrinsic cue interacts with the intrinsic temporal program was not known. We show that the Activin ligand Myoglianin produced from glia regulates the levels of the intrinsic temporal factor Imp in mushroom body neuroblasts. In neuroblasts mutant for the Activin signaling receptor baboon, Imp levels are higher than normal during the α’β’ temporal window, leading to the specific loss of the α’β’ neurons. The intrinsic temporal clock still progresses but with a delay, skipping the α’β’ window without affecting the total number of neurons produced: The number of γ neurons increases, α’β’ disappear and the number of αβ neurons decreases. Our results illustrate that an extrinsic cue modifies an intrinsic temporal program to increase neuronal diversity.

scholarly journals Endosperm evolution by duplicated and neofunctionalized Type I MADS-box transcription factors

2021 ◽  
Author(s):  
Yichun Qiu ◽  
Claudia Köhler
Keyword(s):  
Transcription Factors ◽  
Flowering Plants ◽  
Type I ◽  
Type Ii ◽  
Mads Box ◽  
Endosperm Tissue ◽  
Angiosperm Evolution ◽  
Functional Roles ◽  
Rates Of Evolution

MADS-box transcription factors (TFs) are present in nearly all major eukaryotic groups. They are divided into Type I and Type II that differ in domain structure, functional roles, and rates of evolution. In flowering plants, major evolutionary innovations like flowers, ovules and fruits have been closely connected to Type II MADS-box TFs. The role of Type I MADS-box TFs in angiosperm evolution remains to be identified. Here, we show that the formation of angiosperm-specific Type I MADS-box clades of Mγ and Mγ-interacting Mα genes (Mα*) can be tracked back to the ancestor of all angiosperms. Angiosperm-specific Mγ and Mα* genes were preferentially expressed in the endosperm, consistent with their proposed function as heterodimers in the angiosperm-specific embryo-nourishing endosperm tissue. We propose that duplication and diversification of Type I MADS-genes underpins the evolution of the endosperm, a developmental innovation closely connected to the origin and success of angiosperms.

scholarly journals A repressor-decay timer for robust temporal patterning in embryonic Drosophila neuroblast lineages

2018 ◽  
Author(s):  
Inna Averbukh ◽  
Sen-Lin Lai ◽  
Chris Q. Doe ◽  
Naama Barkai
Keyword(s):  
Transcription Factors ◽  
Embryonic Development ◽  
Neural Progenitors ◽  
Evolutionary Design ◽  
Temporal Patterning ◽  
Regulatory Circuit ◽  
Parameter Variations ◽  
Theory And Experiments

AbstractBiological timers synchronize patterning processes during embryonic development. In the Drosophila embryo, neural progenitors (neuroblasts; NBs) produce a sequence of unique neurons whose identities depend on the sequential expression of temporal transcription factors (TTFs). The stereotypy and precision of the NB lineages indicate reproducible temporal progression of the TTF timer. To examine the basis of this robustness, we combine theory and experiments. The TTF timer is commonly described as a relay of activators, but its regulatory circuit is also consistent with a repressor-decay timer, in which expression of each TTF begins once its repressor is sufficiently reduced. We find that repressor-decay timers are more robust to parameter variations compared to activator-relay timers. This suggests that the in-vivo TTF sequence progresses primarily by repressor-decay, a prediction that we support experimentally. Our results emphasize the role of robustness in the evolutionary design of patterning circuits.

Heat-Etching with a Bullivant Type II Simple Freeze-Cleave Device

1970 ◽  
Vol 28 ◽  
pp. 106-107 ◽  
Author(s):  
Ronald S. Weinstein ◽  
N. Scott McNutt
Keyword(s):  
New Zealand ◽  
General Hospital ◽  
Massachusetts General Hospital ◽  
Type I ◽  
Type Ii ◽  
Collaborative Effort ◽  
Temperature And Pressure ◽  
The University

The Type I simple cold block device was described by Bullivant and Ames in 1966 and represented the product of the first successful effort to simplify the equipment required to do sophisticated freeze-cleave techniques. Bullivant, Weinstein and Someda described the Type II device which is a modification of the Type I device and was developed as a collaborative effort at the Massachusetts General Hospital and the University of Auckland, New Zealand. The modifications reduced specimen contamination and provided controlled specimen warming for heat-etching of fracture faces. We have now tested the Mass. General Hospital version of the Type II device (called the “Type II-MGH device”) on a wide variety of biological specimens and have established temperature and pressure curves for routine heat-etching with the device.

Labelling of non-A, non-B hepatitis infected chimpanzee hepatocytes with nuclease-gold conjugates

1984 ◽  
Vol 42 ◽  
pp. 250-251
Author(s):  
G. D. Gagne ◽  
M. F. Miller ◽  
D. A. Peterson
Keyword(s):  
Endoplasmic Reticulum ◽  
Experimental Infection ◽  
Uranyl Acetate ◽  
Type I ◽  
Cellular Injury ◽  
Type Ii ◽  
Tubular Structures ◽  
Type Iii ◽  
Type Iv ◽  
Infected Chimpanzee

Experimental infection of chimpanzees with non-A, non-B hepatitis (NANB) or with delta agent hepatitis results in the appearance of characteristic cytoplasmic alterations in the hepatocytes. These alterations include spongelike inclusions (Type I), attached convoluted membranes (Type II), tubular structures (Type III), and microtubular aggregates (Type IV) (Fig. 1). Type I, II and III structures are, by association, believed to be derived from endoplasmic reticulum and may be morphogenetically related. Type IV structures are generally observed free in the cytoplasm but sometimes in the vicinity of type III structures. It is not known whether these structures are somehow involved in the replication and/or assembly of the putative NANB virus or whether they are simply nonspecific responses to cellular injury. When treated with uranyl acetate, type I, II and III structures stain intensely as if they might contain nucleic acids. If these structures do correspond to intermediates in the replication of a virus, one might expect them to contain DNA or RNA and the present study was undertaken to explore this possibility.

Comparative surface and ultrastructural views of methylotrophic bacteria by TEM, STEM, SE, and freeze-etch electron microscopy.

1987 ◽  
Vol 45 ◽  
pp. 792-793
Author(s):  
T.A. Fassel ◽  
M.J. Schaller ◽  
M.E. Lidstrom ◽  
C.C. Remsen
Keyword(s):  
Cytoplasmic Membrane ◽  
Structural Features ◽  
Methylotrophic Bacteria ◽  
Type I ◽  
Type Ii ◽  
Membrane Complex ◽  
Oxidation Of Methane ◽  
Methane Oxidizing Bacteria ◽  
Wall Structures ◽  
Methylomonas Albus

Methylotrophic bacteria play an Important role in the environment in the oxidation of methane and methanol. Extensive intracytoplasmic membranes (ICM) have been associated with the oxidation processes in methylotrophs and chemolithotrophic bacteria. Classification on the basis of ICM arrangement distinguishes 2 types of methylotrophs. Bundles or vesicular stacks of ICM located away from the cytoplasmic membrane and extending into the cytoplasm are present in Type I methylotrophs. In Type II methylotrophs, the ICM form pairs of peripheral membranes located parallel to the cytoplasmic membrane. Complex cell wall structures of tightly packed cup-shaped subunits have been described in strains of marine and freshwater phototrophic sulfur bacteria and several strains of methane oxidizing bacteria. We examined the ultrastructure of the methylotrophs with particular view of the ICM and surface structural features, between representatives of the Type I Methylomonas albus (BG8), and Type II Methylosinus trichosporium (OB-36).

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