Gene expression in the developing nemertean brain indicates convergent evolution of complex brains in Spiralia

AbstractBackgroundNemertea is a clade of worm-like animals, which belongs to a larger animal group called Spiralia (together with e.g. annelids, flatworms and mollusks). Many of the nemertean species possess a complex central nervous system (CNS) with a prominent brain, and elaborated chemosensory and neuroglandular cerebral organs, which have been suggested as homologues to the annelid mushroom bodies. In order to understand the developmental and evolutionary origins of complex nemertean brain, we investigated details of neuroanatomy and gene expression in the brain and cerebral organs of the juveniles of nemertean Lineus ruber.ResultsIn the hatched juveniles the CNS is already composed of all major elements present in the adults, including the brain (with dorsal and ventral lobes), paired longitudinal lateral nerve cords and an unpaired dorsal nerve cord. The TEM investigation of the juvenile cerebral organ revealed that the structure is already composed of several distinct cell types present also in the adults. We further investigated the expression of twelve transcription factors commonly used as brain and cell type markers in bilaterian brains, including genes specific for annelid mushroom bodies. The expression of the investigated genes in the brain is region-specific and divides the entire organ into several molecularly distinct areas, partially overlapping with the morphological compartments. Additionally, we detected expression of mushroom body specific genes in the developing cerebral organs.ConclusionsAt the moment of hatching, the juveniles of L. ruber already have a similar neuroarchitecture as adult worms, which suggests that further neural development is mostly related with increase in the size but not in complexity. Comparison in the gene expression between L. ruber and the annelid Platynereis dumerilii and other spiralians, indicates that the complex brains present in those two species evolved convergently by independent expansion of non-homologues regions of the simpler brain present in their common ancestor. The similarities in gene expression in mushroom bodies and cerebral organs might be a result of the convergent recruitment of the same genes into patterning of non-homologues organs or the results of more complicated evolutionary processes, in which conserved and novel cell types contribute to the non-homologues structures.

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Molecular and morphological analysis of the developing nemertean brain indicates convergent evolution of complex brains in Spiralia

BMC Biology ◽

10.1186/s12915-021-01113-1 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Ludwik Gąsiorowski ◽

Aina Børve ◽

Irina A. Cherneva ◽

Andrea Orús-Alcalde ◽

Andreas Hejnol

Keyword(s):

Neural Development ◽

Evolutionary Process ◽

Cell Types ◽

Major Elements ◽

Brain Cell ◽

Mushroom Bodies ◽

Brain Anatomy ◽

Last Common Ancestor ◽

Specific Expression ◽

The Brain

Abstract Background The brain anatomy in the clade Spiralia can vary from simple, commissural brains (e.g., gastrotrichs, rotifers) to rather complex, partitioned structures (e.g., in cephalopods and annelids). How often and in which lineages complex brains evolved still remains unclear. Nemerteans are a clade of worm-like spiralians, which possess a complex central nervous system (CNS) with a prominent brain, and elaborated chemosensory and neuroglandular cerebral organs, which have been previously suggested as homologs to the annelid mushroom bodies. To understand the developmental and evolutionary origins of the complex brain in nemerteans and spiralians in general, we investigated details of the neuroanatomy and gene expression in the brain and cerebral organs of the juveniles of nemertean Lineus ruber. Results In the juveniles, the CNS is already composed of all major elements present in the adults, including the brain, paired longitudinal lateral nerve cords, and an unpaired dorsal nerve cord, which suggests that further neural development is mostly related with increase in the size but not in complexity. The ultrastructure of the juvenile cerebral organ revealed that it is composed of several distinct cell types present also in the adults. The 12 transcription factors commonly used as brain cell type markers in bilaterians show region-specific expression in the nemertean brain and divide the entire organ into several molecularly distinct areas, partially overlapping with the morphological compartments. Additionally, several of the mushroom body-specific genes are expressed in the developing cerebral organs. Conclusions The dissimilar expression of molecular brain markers between L. ruber and the annelid Platynereis dumerilii indicates that the complex brains present in those two species evolved convergently by independent expansions of non-homologous regions of a simpler brain present in their last common ancestor. Although the same genes are expressed in mushroom bodies and cerebral organs, their spatial expression within organs shows apparent differences between annelids and nemerteans, indicating convergent recruitment of the same genes into patterning of non-homologous organs or hint toward a more complicated evolutionary process, in which conserved and novel cell types contribute to the non-homologous structures.

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Glucocorticoid receptor action in metabolic and neuronal function

F1000Research ◽

10.12688/f1000research.11375.1 ◽

2017 ◽

Vol 6 ◽

pp. 1208 ◽

Cited By ~ 19

Author(s):

Michael J. Garabedian ◽

Charles A. Harris ◽

Freddy Jeanneteau

Keyword(s):

Gene Expression ◽

Glucocorticoid Receptor ◽

Metabolic Diseases ◽

Cell Types ◽

Health And Disease ◽

And Behavior ◽

External Signals ◽

The Brain

Glucocorticoids via the glucocorticoid receptor (GR) have effects on a variety of cell types, eliciting important physiological responses via changes in gene expression and signaling. Although decades of research have illuminated the mechanism of how this important steroid receptor controls gene expression using in vitro and cell culture–based approaches, how GR responds to changes in external signals in vivo under normal and pathological conditions remains elusive. The goal of this review is to highlight recent work on GR action in fat cells and liver to affect metabolism in vivo and the role GR ligands and receptor phosphorylation play in calibrating signaling outputs by GR in the brain in health and disease. We also suggest that both the brain and fat tissue communicate to affect physiology and behavior and that understanding this “brain-fat axis” will enable a more complete understanding of metabolic diseases and inform new ways to target them.

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Tanycyte-independent control of hypothalamic leptin signaling

10.1101/528794 ◽

2019 ◽

Author(s):

Sooyeon Yoo ◽

David Cha ◽

Dong Won Kim ◽

Thanh V. Hoang ◽

Seth Blackshaw

Keyword(s):

Gene Expression ◽

Single Molecule ◽

Leptin Receptor ◽

Cell Types ◽

Leptin Signaling ◽

And Function ◽

Induced Changes ◽

The Brain ◽

Specific Deletion

AbstractLeptin is secreted by adipocytes to regulate appetite and body weight. Recent studies have reported that tanycytes actively transport circulating leptin across the brain barrier into the hypothalamus, and are required for normal levels of hypothalamic leptin signaling. However, direct evidence for leptin receptor (LepR) expression is lacking, and the effect of tanycyte-specific deletion of LepR has not been investigated. In this study, we analyze the expression and function of the tanycytic LepR in mice. Using single-molecule fluorescent in situ hybridization (smfISH), RT-qPCR, single-cell RNA sequencing (scRNA-Seq), and selective deletion of the LepR in tanycytes, we are unable to detect expression of LepR in the tanycytes. Tanycyte-specific deletion of LepR likewise did not affect leptin-induced pSTAT3 expression in hypothalamic neurons, regardless of whether leptin was delivered by intraperitoneal or intracerebroventricular injection. Finally, we use activity-regulated scRNA-Seq (act-Seq) to comprehensively profile leptin-induced changes in gene expression in all cell types in mediobasal hypothalamus. Clear evidence for leptin signaling is only seen in endothelial cells and subsets of neurons, although virtually all cell types show leptin-induced changes in gene expression. We thus conclude that LepR expression in tanycytes is either absent or undetectably low, that tanycytes do not directly regulate hypothalamic leptin signaling through a LepR-dependent mechanism, and that leptin regulates gene expression in diverse hypothalamic cell types through both direct and indirect mechanisms.

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Drosophila mef2 is essential for normal mushroom body and wing development

10.1101/311845 ◽

2018 ◽

Cited By ~ 1

Author(s):

Jill R. Crittenden ◽

Efthimios M. C. Skoulakis ◽

Elliott. S. Goldstein ◽

Ronald L. Davis

Keyword(s):

Nuclear Localization ◽

Mushroom Body ◽

Normal Development ◽

Cell Types ◽

Mushroom Bodies ◽

Wing Development ◽

Myocyte Enhancer Factor 2 ◽

Multiple Cell ◽

The Brain ◽

Enhancer Factor

ABSTRACTMEF2 (myocyte enhancer factor 2) transcription factors are found in the brain and muscle of insects and vertebrates and are essential for the differentiation of multiple cell types. We show that in the fruitfly Drosophila, MEF2 is essential for normal development of wing veins, and for mushroom body formation in the brain. In embryos mutant for D-mef2, there was a striking reduction in the number of mushroom body neurons and their axon bundles were not detectable. D-MEF2 expression coincided with the formation of embryonic mushroom bodies and, in larvae, expression onset was confirmed to be in post-mitotic neurons. With a D-mef2 point mutation that disrupts nuclear localization, we find that D-MEF2 is restricted to a subset of Kenyon cells that project to the α/β, and γ axonal lobes of the mushroom bodies, but not to those forming the α’/β’ lobes. Our findings that ancestral mef2 is specifically important in dopamine-receptive neurons has broad implications for its function in mammalian neurocircuits.

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Synaptic and peptidergic connectome of a neurosecretory centre in the annelid brain

10.1101/115204 ◽

2017 ◽

Cited By ~ 4

Author(s):

Elizabeth A. Williams ◽

Csaba Verasztó ◽

Sanja Jasek ◽

Markus Conzelmann ◽

Réza Shahidi ◽

...

Keyword(s):

Gene Expression ◽

Electron Microscopy ◽

Cell Types ◽

Peptide Receptor ◽

Neurosecretory Neurons ◽

Platynereis Dumerilii ◽

The Brain ◽

Gene Expression Mapping ◽

Synaptic Signalling

AbstractNeurosecretory centres in animal brains use peptidergic signalling to influence physiology and behaviour. Understanding neurosecretory centre function requires mapping cell types, synapses, and peptidergic networks. Here we use electron microscopy and gene expression mapping to analyse the synaptic and peptidergic connectome of an entire neurosecretory centre. We mapped 78 neurosecretory neurons in the brain of larval Platynereis dumerilii, a marine annelid. These neurons form an anterior neurosecretory organ expressing many neuropeptides, including hypothalamic peptide orthologues and their receptors. Analysis of peptide-receptor pairs revealed sparsely connected networks linking specific neuronal subsets. We experimentally analysed one peptide-receptor pair and found that a neuropeptide can couple neurosecretory and synaptic brain signalling. Our study uncovered extensive non-synaptic signalling within a neurosecretory centre and its connection to the synaptic brain.

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Brain composition in Heliconius butterflies, post-eclosion growth and experience dependent neuropil plasticity

10.1101/017913 ◽

2015 ◽

Author(s):

Stephen H Montgomery ◽

Richard M Merrill ◽

Swidbert R Ott

Keyword(s):

Behavioral Ecology ◽

Neural Development ◽

Mushroom Body ◽

Brain Regions ◽

Mushroom Bodies ◽

Heliconius Butterflies ◽

Sensory Adaptations ◽

Differential Expansion ◽

The Brain

Behavioral and sensory adaptations are often based in the differential expansion of brain components. These volumetric differences represent changes in investment, processing capacity and/or connectivity, and can be used to investigate functional and evolutionary relationships between different brain regions, and between brain composition and behavioral ecology. Here, we describe the brain composition of two species of Heliconius butterflies, a long-standing study system for investigating ecological adaptation and speciation. We confirm a previous report of striking mushroom body expansion, and explore patterns of post-eclosion growth and experience-dependent plasticity in neural development. This analysis uncovers age- and experience-dependent post-emergence mushroom body growth comparable to that in foraging hymenoptera, but also identifies plasticity in several other neuropil. An interspecific analysis indicates that Heliconius display remarkable levels of investment in mushroom bodies for a lepidopteran, and indeed rank highly compared to other insects. Our analyses lay the foundation for future comparative and experimental analyses that will establish Heliconius as a useful case study in evolutionary neurobiology.

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Transposon-mediated, cell type-specific transcription factor recording in the mouse brain

10.1101/538504 ◽

2019 ◽

Cited By ~ 1

Author(s):

Alexander J. Cammack ◽

Arnav Moudgil ◽

Tomas Lagunas ◽

Michael J. Vasek ◽

Mark Shabsovich ◽

...

Keyword(s):

Gene Expression ◽

Mouse Brain ◽

Regulation Of Gene Expression ◽

Cell Types ◽

Mouse Tissue ◽

Specific Cell ◽

Cell Type ◽

Cell Fate Decisions ◽

Cell Type Specific ◽

The Brain

AbstractTranscription factors (TFs) play a central role in the regulation of gene expression, controlling everything from cell fate decisions to activity dependent gene expression. However, widely-used methods for TF profiling in vivo (e.g. ChIP-seq) yield only an aggregated picture of TF binding across all cell types present within the harvested tissue; thus, it is challenging or impossible to determine how the same TF might bind different portions of the genome in different cell types, or even to identify its binding events at all in rare cell types in a complex tissue such as the brain. Here we present a versatile methodology, FLEX Calling Cards, for the mapping of TF occupancy in specific cell types from heterogenous tissues. In this method, the TF of interest is fused to a hyperactive piggyBac transposase (hypPB), and this bipartite gene is delivered, along with donor transposons, to mouse tissue via a Cre-dependent adeno-associated virus (AAV). The fusion protein is expressed in Cre-expressing cells where it inserts transposon “Calling Cards” near to TF binding sites. These transposons permanently mark TF binding events and can be mapped using high-throughput sequencing. Alternatively, unfused hypPB interacts with and records the binding of the super enhancer (SE)-associated bromodomain protein, Brd4. To demonstrate the FLEX Calling Card method, we first show that donor transposon and transposase constructs can be efficiently delivered to the postnatal day 1 (P1) mouse brain with AAV and that insertion profiles report TF occupancy. Then, using a Cre-dependent hypPB virus, we show utility of this tool in defining cell type-specific TF profiles in multiple cell types of the brain. This approach will enable important cell type-specific studies of TF-mediated gene regulation in the brain and will provide valuable insights into brain development, homeostasis, and disease.

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Gut-derived Metabolites Influence Neurodevelopmental Gene Expression and Wnt Signalling Events in a Germ-free Zebrafish Model

10.21203/rs.3.rs-1250656/v1 ◽

2022 ◽

Author(s):

Terry Van Raay ◽

Victoria Rea ◽

Ian Bell

Keyword(s):

Gene Expression ◽

Neural Development ◽

Morphological Changes ◽

Wnt Signalling ◽

Gene Ontology Analysis ◽

Rna Seq ◽

Zebrafish Model ◽

Germ Free ◽

The Impact ◽

The Brain

Abstract Background : Small molecule metabolites produced by the microbiome are known to be neuroactive and are capable of directly impacting the brain and central nervous system, yet there is little data on the contribution of these metabolites to the earliest stages of neural development and neural gene expression. Here, we explore the impact of deriving zebrafish embryos in the absence of microbes on early neural development as well as investigate whether any potential changes can be rescued with treatment of metabolites derived from the zebrafish gut microbiota. Results : Overall, we did not observe any gross morphological changes between treatments but did observe a significant decrease in neural gene expression in embryos raised germ-free, which was rescued with the addition of zebrafish metabolites. Specifically, we identified 354 genes significantly down regulated in germ-free embryos compared to conventionally raised embryos via RNA-Seq analysis. Of these, 42 were rescued with a single treatment of zebrafish gut-derived metabolites to germ-free embryos. Gene ontology analysis revealed that these genes are involved in prominent neurodevelopmental pathways including transcriptional regulation and Wnt signalling. Consistent with the ontology analysis, we found alterations in the development of Wnt dependent events which was rescued in the germ-free embryos treated with metabolites. Conclusions : These findings demonstrate that gut-derived metabolites are in part responsible for regulating critical signalling pathways in the brain, especially during neural development.

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Gut-derived metabolites influence neurodevelopmental gene expression and Wnt signalling events in a germ-free zebrafish model

10.1101/2021.07.06.451297 ◽

2021 ◽

Author(s):

Victoria Rea ◽

Ian Bell ◽

Terence J Van Raay

Keyword(s):

Gene Expression ◽

Neural Development ◽

Morphological Changes ◽

Wnt Signalling ◽

Gene Ontology Analysis ◽

Rna Seq ◽

Zebrafish Model ◽

Germ Free ◽

The Impact ◽

The Brain

Small molecule metabolites produced by the microbiome are known to be neuroactive and are capable of directly impacting the brain and central nervous system, yet there is little data on the contribution of these metabolites to the earliest stages of neural development and neural gene expression. Here, we explore the impact of rearing zebrafish embryos in the absence of microbes on early neural development as well as investigate whether any potential changes can be rescued with treatment of metabolites derived from the zebrafish gut microbiota. Overall, we did not observe any gross morphological changes between treatments but did observe a significant decrease in neural gene expression in embryos raised germ-free, which was rescued with the addition of zebrafish metabolites. Specifically, we identified 361 genes significantly down regulated in GF embryos compared to conventionally raised embryos via RNA-Seq analysis. Of these, 42 were rescued with the treatment of zebrafish gut-derived metabolites to GF embryos. Gene ontology analysis revealed that these genes are involved in prominent neurodevelopmental pathways including transcriptional regulation and Wnt signalling. Consistent with the ontology analysis, we found alterations in the development of Wnt dependent events which is rescued in the GF embryos treated with metabolites.

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In utero gene transfer system for embryos before neural tube closure reveals a role for Hmga2 in the onset of neurogenesis

10.1101/2020.05.14.086330 ◽

2020 ◽

Author(s):

Naohiro Kuwayama ◽

Yusuke Kishi ◽

Yurie Maeda ◽

Yurie Nishiumi ◽

Yutaka Suzuki ◽

...

Keyword(s):

Gene Expression ◽

Neural Tube ◽

Neural Development ◽

Viral Vectors ◽

Early Stage ◽

Cell Types ◽

In Utero ◽

Polycomb Group ◽

Neural Tube Closure ◽

Tube Closure

AbstractDuring the early stage of mammalian neural development, neuroepithelial cells (NECs) proliferate and increase their pool size before switching their fate to become neurogenic radial glial progenitors (RGPs). The timing of this expansion-to-neurogenic phase transition is strictly regulated so as to determine the proper number of progenitors and differentiated cell types that constitute the brain. The molecular mechanism underlying this switch has remained poorly understood, however, in part because of the difficulty associated with manipulation of gene expression in NECs before their transition to RGPs, which occurs before neural tube closure. We have now developed a simple and efficient method to manipulate gene expression in mouse neocortical NECs in the expansion phase by in utero injection of viral vectors at embryonic day 7.0 to 8.0. With the use of this method, we found that knockdown of the chromatin-associated protein Hmga2 in NECs inhibited the onset of the neurogenic phase in the neocortex. This effect of Hmga2 knockdown was accompanied by inhibition of the expression of a set of genes targeted by Polycomb group proteins, which repress neurogenic genes in cortical progenitors. Our study thus establishes a novel method for manipulation of gene expression in the early stage of mouse brain development as well as uncovers a key molecular player in the generation of neurogenic progenitors in the developing mouse neocortex.

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