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Rxivist combines preprints from bioRxiv with data from Twitter to help you find the papers being discussed in your field. Currently indexing 70,182 bioRxiv papers from 306,477 authors.

Most downloaded bioRxiv papers, all time

in category developmental biology

2,064 results found. For more information, click each entry to expand.

101: Tracing the Transitions from Pluripotency to Germ Cell Fate with CRISPR Screening
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Posted to bioRxiv 22 Feb 2018

Tracing the Transitions from Pluripotency to Germ Cell Fate with CRISPR Screening
1,327 downloads developmental biology

Jamie A. Hackett, Yun Huang, Ufuk Günesdogan, Kristjan Holm-Gretarsson, Toshihiro Kobayashi, M. Azim Surani

Early mammalian development entails a series of cell fate transitions that includes transit through naive pluripotency to post-implantation epiblast. This subsequently gives rise to primordial germ cells (PGC), the founding population of the germline lineage. To investigate the gene regulatory networks that control these critical cell fate decisions, we developed a compound-reporter system to track cellular identity in a model of PGC specification (PGC-like cells; PGCLC), and coupled it with unbiased genome-wide CRISPR screening. This enabled identification of key genes both for exit from pluripotency and for acquisition of PGC fate, with further characterisation revealing a central role for the transcription factors Nr5a2 and Zfp296 in germline ontogeny. Abrogation of these genes results in significantly impaired PGCLC development due to widespread activation (Nr5a2-/-) or inhibition (Zfp296-/-) of WNT pathway components. This leads to aberrant upregulation of the somatic programme or failure to appropriately activate germline genes in PGCLC, respectively, and consequently loss of germ cell identity. Overall our study places Zfp296 and Nr5a2 as key components of an expanded PGC gene regulatory network, and outlines a transferable strategy for identifying critical regulators of complex cell fate transitions.

102: Finding cell-specific expression patterns in the early Ciona embryo with single cell RNA-seq
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Posted to bioRxiv 03 Oct 2017

Finding cell-specific expression patterns in the early Ciona embryo with single cell RNA-seq
1,326 downloads developmental biology

Garth R Ilsley, Ritsuko Suyama, Takeshi Noda, Nori Satoh, Nicholas M. Luscombe

Gene expression studies have typically focused on finding differentially expressed genes or pathways between two or more conditions. More recently, single-cell RNA-seq has been established as a reliable and accessible technique enabling new types of analyses, such as the study of gene expression variation within cell types from cell lines or from relatively similar cells in tissues, organs or tumors. However, although single-cell RNA-seq provides quantitative and comprehensive expression data in a developing embryo, it is not yet clear whether this can replace conventional in situ screens for finding developmentally important genes; moreover, current single-cell data analysis approaches typically cluster cells into types based on a common set of genes or identify more variable or differentially expressed genes using predefined groups of cells, limiting their use for finding genes with novel expression patterns. Here we present a method that comprehensively finds cell-specific patterns of developmentally important regulators directly from single-cell gene expression data of the Ciona embryo, a marine chordate. We recover many of the known expression patterns directly from our single-cell RNA-seq data and despite extensive previous screens, we succeed in finding new cell-specific patterns and genes, which we validate by in situ and single-cell qPCR.

103: Dissecting the dynamics of signaling events in the BMP, WNT, and NODAL cascade during self-organized fate patterning in human gastruloids.
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Posted to bioRxiv 10 Oct 2018

Dissecting the dynamics of signaling events in the BMP, WNT, and NODAL cascade during self-organized fate patterning in human gastruloids.
1,321 downloads developmental biology

Sapna Chhabra, Lizhong Liu, Ryan Goh, Aryeh Warmflash

During gastrulation, the pluripotent epiblast is patterned into the three germ layers, which form the embryo proper. This patterning requires a signaling cascade involving the BMP, WNT and NODAL pathways; however, how these pathways regulate one another in space and time to generate cell-fate patterns remains unknown. Using a human gastruloid model, we show that BMP signaling initiates a wave of WNT signaling, which, in turn, initiates a wave of NODAL signaling. While WNT propagation depends on continuous BMP activity, NODAL propagates independently of upstream signals. We further show that the duration of BMP signaling determines the position of mesodermal differentiation while WNT and NODAL synergize to achieve maximal differentiation. The waves of both WNT and NODAL signaling activity extend farther into the colony than mesodermal differentiation. Combining dynamic measurements of signaling activity with mathematical modeling revealed that the formation of signaling waves is inconsistent with WNT and NODAL forming a stable spatial pattern in signaling activities, and the final signaling state is spatially homogeneous. Thus, dynamic eventsin the BMP, WNT, and NODAL signaling cascade, in the absence of a signaling gradient, have the potential to mediate epiblast patterning.

104: Micro computed tomography as an accessible imaging platform for exploring organism development and human disease modeling
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Posted to bioRxiv 13 Aug 2018

Micro computed tomography as an accessible imaging platform for exploring organism development and human disease modeling
1,320 downloads developmental biology

Todd A. Schoborg, Samantha L. Smith, Lauren N. Smith, H. Douglas Morris, Nasser M Rusan

Understanding how events at the molecular and cellular scales contribute to tissue form and function is key to uncovering mechanisms driving animal development, physiology and disease. Elucidating these mechanisms has been enhanced through the study of model organisms and the use of sophisticated genetic, biochemical and imaging tools. Here we present an optimized method for non-invasive imaging of Drosophila melanogaster at high resolution using micro computed tomography (μ-CT). Our method allows for rapid processing of intact animals at any developmental stage, provides precise quantitative assessment of tissue size and morphology, and permits analysis of inter-organ relationships. We then use the power of μ-CT imaging to model human diseases through the characterization of microcephaly in the fly. Our work demonstrates that μ-CT is a versatile and accessible tool that complements standard imaging techniques, capable of uncovering novel biological mechanisms that have remained undocumented due to limitations of current methods.

105: Epigenetic analyses of planarian stem cells demonstrate conservation of bivalent histone modifications in animal stem cells.
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Posted to bioRxiv 29 Mar 2017

Epigenetic analyses of planarian stem cells demonstrate conservation of bivalent histone modifications in animal stem cells.
1,314 downloads developmental biology

Anish Dattani, Damian Kao, Yuliana Mihaylova, Prasad Abnave, Samantha Hughes, Alvina Lai, Sounak Sahu, Aziz Aboobaker

Planarian flatworms have an indefinite capacity to regenerate missing or damaged body parts owing to a population of pluripotent adult stems cells called neoblasts (NBs). Currently, little is known about the importance of the epigenetic status of NBs and how histone modifications regulate homeostasis and cellular differentiation. We have developed an improved and optimized ChIP-seq protocol for NBs in Schmidtea mediterranea and have generated genome-wide profiles for the active marks H3K4me3 and H3K36me3, and suppressive marks H3K4me1 and H3K27me3. The genome-wide profiles of these marks were found to correlate well with NB gene expression profiles. We found that genes with little transcriptional activity in the NB compartment but which switch on in post-mitotic progeny during differentiation are bivalent, being marked by both H3K4me3 and H3K27me3 at promoter regions. In further support of this hypothesis bivalent genes also have a high level of paused RNA Polymerase II at the promoter-proximal region. Overall, this study confirms that epigenetic control is important for the maintenance of a NB transcriptional program and makes a case for bivalent promoters as a conserved feature of animal stem cells and not a vertebrate specific innovation. By establishing a robust ChIP-seq protocol and analysis methodology, we further promote planarians as a promising model system to investigate histone modification mediated regulation of stem cell function and differentiation.

106: The Ly6/uPAR protein Bouncer is necessary and sufficient for species-specific fertilization
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Posted to bioRxiv 24 Jun 2018

The Ly6/uPAR protein Bouncer is necessary and sufficient for species-specific fertilization
1,292 downloads developmental biology

Sarah Herberg, Krista R Gert, Alexander Schleiffer, Andrea Pauli

Fertilization is fundamental for sexual reproduction, yet its molecular mechanisms are poorly understood. Here, we identify an oocyte-expressed Ly6/uPAR protein, which we call Bouncer, as a crucial fertilization factor in zebrafish. We show that membrane-bound Bouncer mediates sperm-egg binding and is thus essential for sperm entry into the egg. Remarkably, Bouncer is not only required for sperm-egg interaction, but also sufficient to allow cross-species fertilization between zebrafish and medaka, two fish species that diverged over 150 million years ago. Our study thus identifies Bouncer as a key determinant of species-specific fertilization in fish. Bouncer's closest homolog in tetrapods, SPACA4, is restricted to the male gonad in internally fertilizing vertebrates, suggesting that our findings in fish have relevance to human biology.

107: In vitro characterization of the human segmentation clock
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Posted to bioRxiv 04 Nov 2018

In vitro characterization of the human segmentation clock
1,283 downloads developmental biology

Margarete Diaz-Cuadros, Daniel E. Wagner, Christoph Budjan, Alexis Hubaud, Jonathan Touboul, Arthur Michaut, Ziad Al Tanoury, Kumiko Yoshioka-Kobayashi, Yusuke Niino, Ryoichiro Kageyama, Atsushi Miyawaki, Olivier Pourquié

The vertebral column is characterized by the periodic arrangement of vertebrae along the anterior-posterior (AP) axis. This segmental or metameric organization is established early in embryogenesis when pairs of embryonic segments called somites are rhythmically produced by the presomitic mesoderm (PSM). The tempo of somite formation is controlled by a molecular oscillator known as the segmentation clock. While this oscillator has been well characterized in model organisms whether a similar oscillator exists in humans remains unknown. We have previously shown that human embryonic stem (ES) cells or induced pluripotent stem (iPS) cells can differentiate in vitro into PSM upon activation of the Wnt signaling pathway combined with BMP inhibition. Here, we show that these human PSM cells exhibit Notch and YAP-dependent oscillations of the cyclic gene HES7 with a 5-hour period. Single cell RNA-sequencing comparison of the differentiating iPS cells with mouse PSM reveals that human PSM cells follow a similar differentiation path and exhibit a remarkably coordinated differentiation sequence. We also demonstrate that FGF signaling controls the phase and period of the oscillator. This contrasts with classical segmentation models such as the Clock and Wavefront where FGF merely implements a signaling threshold specifying where oscillations stop. Overall, our work identifying the human segmentation clock represents an important breakthrough for human developmental biology.

108: Self-organised symmetry breaking in zebrafish reveals feedback from morphogenesis to pattern formation
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Posted to bioRxiv 14 Sep 2019

Self-organised symmetry breaking in zebrafish reveals feedback from morphogenesis to pattern formation
1,274 downloads developmental biology

Vikas Trivedi, Timothy Fulton, Andrea Attardi, Kerim Anlas, Chaitanya Dingare, Alfonso Martinez-Arias, Benjamin Steventon

A fundamental question in developmental biology is how the early embryo breaks initial symmetry to establish the spatial coordinate system later important for the organisation of the embryonic body plan. In zebrafish, this is thought to depend on the inheritance of maternal mRNAs [[1][1]–[3][2]], cortical rotation to generate a dorsal pole of beta-catenin activity [[4][3]–[8][4]] and the release of Nodal signals from the yolk syncytial layer (YSL) [[9][5]–[12][6]]. Recent work aggregating mouse embryonic stem cells has shown that symmetry breaking can occur in the absence of extra-embryonic tissue [[19][7],[20][8]]. To test whether this is also true in zebrafish, we separated embryonic cells from the yolk and allowed them to develop as aggregates. These aggregates break symmetry autonomously to form elongated structures with an anterior-posterior pattern. Extensive cell mixing shows that any pre-existing asymmetry is lost prior to the breaking morphological symmetry, revealing that the maternal pre-pattern is not strictly required for early embryo patterning. Following early signalling events after isolation of embryonic cells reveals that a pole of Nodal activity precedes and is required for elongation. The blocking of PCP-dependent convergence and extension movements disrupts the establishment of opposing poles of BMP and Wnt/TCF activity and the patterning of anterior-posterior neural tissue. These results lead us to suggest that convergence and extension plays a causal role in the establishment of morphogen gradients and pattern formation during zebrafish gastrulation. [1]: #ref-1 [2]: #ref-3 [3]: #ref-4 [4]: #ref-8 [5]: #ref-9 [6]: #ref-12 [7]: #ref-19 [8]: #ref-20

109: Micropattern differentiation of mouse pluripotent stem cells recapitulates embryo regionalized fates and patterning
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Posted to bioRxiv 19 Dec 2017

Micropattern differentiation of mouse pluripotent stem cells recapitulates embryo regionalized fates and patterning
1,267 downloads developmental biology

Sophie M. Morgani, Jakob J Metzger, Jennifer Nichols, E.D. Siggia, Anna-Katerina Hadjantonakis

During gastrulation epiblast cells exit pluripotency as they specify and spatially arrange the three germ layers of the embryo. Similarly, human pluripotent stem cells (PSCs) undergo spatially organized fate specification on micropatterned surfaces. Since in vivo validation is not possible for the human, we developed a mouse PSC micropattern system and, with direct comparisons to mouse embryos, reveal the robust specification of distinct regional identities. BMP, WNT, ACTIVIN and FGF directed mouse epiblast-like cells to undergo an epithelial-to-mesenchymal transition and radially pattern posterior mesoderm fates. Conversely, WNT, ACTIVIN and FGF patterned anterior identities, including definitive endoderm. By contrast, epiblast stem cells, a developmentally advanced state, only specified anterior identities, but without patterning. The mouse micropattern system offers a robust scalable method to generate regionalized cell types present in vivo, resolve how signals promote distinct identities and generate patterns, and compare mechanisms operating in vivo and in vitro and across species.

110: Partial reprogramming induces a steady decline in epigenetic age before loss of somatic identity
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Posted to bioRxiv 31 Mar 2018

Partial reprogramming induces a steady decline in epigenetic age before loss of somatic identity
1,262 downloads developmental biology

Nelly Olova, Daniel J Simpson, Riccardo Marioni, Tamir Chandra

Induced pluripotent stem cells (IPSCs), with their unlimited regenerative capacity, carry the promise for tissue replacement to counter age-related decline. However, attempts to realise in vivo iPSC have invariably resulted in the formation of teratomas. Partial reprogramming in prematurely aged mice has shown promising results in alleviating age-related symptoms without teratoma formation. Does partial reprogramming lead to rejuvenation (i.e. "younger" cells), rather than dedifferentiation, which bears the risk of cancer? Here we analyse cellular age during iPSC reprogramming and find that partial reprogramming leads to a reduction in the biological age of cells. We also find that the loss of somatic gene expression and epigenetic age follow different kinetics, suggesting that rejuvenation can be achieved with a minimised risk of cancer.

111: TET1 drives global DNA demethylation via DPPA3-mediated inhibition of maintenance methylation
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Posted to bioRxiv 15 May 2018

TET1 drives global DNA demethylation via DPPA3-mediated inhibition of maintenance methylation
1,259 downloads developmental biology

Christopher B. Mulholland, Joel Ryan, Weihua Qin, Michael D. Bartoschek, Franziska R Traube, Edris Parsa, Miha Modic, Daniel Nixdorf, Christoph Ziegenhain, Thomas Carell, Wolfgang Enard, Sebastian Bultmann, Heinrich Leonhardt

DNA modifications undergo genome-wide changes during development, play a central role in epigenetic gene regulation and preserve genome stability. Ten-eleven translocation (TET) proteins catalyze the oxidation of 5-methylcytosine (5mC) and are implicated in DNA demethylation and the regulation of gene expression. However, to which degree the gene regulatory effects of TET proteins depend on catalytic functions and to which extent oxidative cytosine modifications represent intermediates of active DNA demethylation or serve as stable epigenetic marks still remains unclear. Here, we dissect the stage-specific catalytic and non-catalytic contributions of TET1 to the regulation of the methylome and transcriptome in the transition from naive to primed pluripotency. Whereas non-catalytic functions of TET1 prevent the premature exit from pluripotency, we find that the catalytic activity of TET1 is necessary for the expression of the naive pluripotency marker DPPA3 (STELLA/PGC7). DPPA3 in turn binds and displaces UHRF1 from nuclear methylation sites to the cytoplasm, thereby impairing the recruitment and activity of the maintenance DNA methyltransferase DNMT1. Collectively, our work delineates catalytic and non-catalytic functions of TET1, uncovers the mechanism of TET1-governed DNA hypomethylation, and reveals the mechanistic basis by which DPPA3 antagonizes global DNA methylation.

112: Implantation-Competent Blastocyst-Like Structures from Mouse Pluripotent Stem Cells
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Posted to bioRxiv 30 Apr 2018

Implantation-Competent Blastocyst-Like Structures from Mouse Pluripotent Stem Cells
1,256 downloads developmental biology

Cody Kime, Hiroshi Kiyonari, Satoshi Ohtsuka, Eiko Kohbayashi, Michio Asahi, Shinya Yamanaka, Masayo Takahashi, Kiichiro Tomoda

Soon after fertilization, the few totipotent cells of mammalian embryos diverge to form a structure called the blastocyst (BC). Although numerous types of cells, including germ cells and extended pluripotency stem cells, have been generated from pluripotent stem cells (PSCs) in-vitro, generating functional BCs only from PSCs has not yet been reported. Here we describe induced self-organizing 3D BC-like structures (iBCs) generated from mouse PSC culture in-vitro. Resembling natural BCs, iBCs have a blastocoel-like cavity and were formed with outer cells that are positive for trophectoderm lineage markers and with inner cells that are positive for pluripotency markers. iBCs transplanted to pseudopregnant mice uteruses implanted, induced decidualization, and exhibited growth and development before resorption, demonstrating that iBCs are implantation-competent. iBC production required the transcription factor Prdm14 and iBC precursor intermediates concomitantly activate the MERVL totipotency related cleavage stage reporter. Thus, our system may contribute to understanding molecular mechanisms underpinning totipotency, embryogenesis, and implantation.

113: A toolkit for tissue-specific protein degradation in C. elegans
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Posted to bioRxiv 30 Jan 2017

A toolkit for tissue-specific protein degradation in C. elegans
1,249 downloads developmental biology

Shaohe Wang, Ngang Heok Tang, Pablo Lara-Gonzalez, Bram Prevo, Dhanya K Cheerambathur, Andrew D Chisholm, Arshad Desai, Karen Oegema

Proteins essential for embryo production, cell division, and early embryonic events are frequently re-utilized later in embryogenesis, during organismal development, or in the adult. Examining protein function across these different biological contexts requires tissue-specific perturbation. Here, we describe a method that utilizes expression of a fusion between a GFP-targeting nanobody and SOCS-box containing ubiquitin ligase adaptor to target GFP tagged proteins for degradation. When combined with endogenous locus GFP tagging by CRISPR-Cas9 or rescue of a null mutant with a GFP fusion, this approach enables routine and efficient tissue-specific protein ablation. We show that this approach works in multiple tissues-the epidermis, intestine, body wall muscle, sensory neurons, and touch neurons-where it recapitulates expected loss-of-function mutant phenotypes. The transgene toolkit and the strain set described here will complement existing approaches to enable routine analysis of the tissue-specific roles of C. elegans proteins.

114: Emergence of neuronal diversity during vertebrate brain development
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Posted to bioRxiv 12 Nov 2019

Emergence of neuronal diversity during vertebrate brain development
1,248 downloads developmental biology

Bushra Raj, Jeffrey A. Farrell, Aaron McKenna, Jessica L Leslie, Alexander F. Schier

Neurogenesis in the vertebrate brain comprises many steps ranging from the proliferation of progenitors to the differentiation and maturation of neurons. Although these processes are highly regulated, the landscape of transcriptional changes and progenitor identities underlying brain development are poorly characterized. Here, we describe the first developmental single-cell RNA-seq catalog of more than 200,000 zebrafish brain cells encompassing 12 stages from 12 hours post-fertilization to 15 days post-fertilization. We characterize known and novel gene markers for more than 800 clusters across these timepoints. Our results capture the temporal dynamics of multiple neurogenic waves from embryo to larva that expand neuronal diversity from ~20 cell types at 12 hpf to ~100 cell types at 15 dpf. We find that most embryonic neural progenitor states are transient and transcriptionally distinct from long-lasting neural progenitors of post-embryonic stages. Furthermore, we reconstruct cell specification trajectories for the retina and hypothalamus, and identify gene expression cascades and novel markers. Our analysis reveal that late-stage retinal neural progenitors transcriptionally overlap cell states observed in the embryo, while hypothalamic neural progenitors become progressively distinct with developmental time. These data provide the first comprehensive single-cell transcriptomic time course for vertebrate brain development and suggest distinct neurogenic regulatory paradigms between different stages and tissues.

115: Modeling the Human Segmentation Clock with Pluripotent Stem Cells
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Posted to bioRxiv 27 Feb 2019

Modeling the Human Segmentation Clock with Pluripotent Stem Cells
1,248 downloads developmental biology

Mitsuhiro Matsuda, Yoshihiro Yamanaka, Maya Uemura, Mitsujiro Osawa, Megumu K. Saito, Ayako Nagahashi, Megumi Nishio, Long Guo, Shiro Ikegawa, Satoko Sakurai, Shunsuke Kihara, Michiko Nakamura, Tomoko Matsumoto, Hiroyuki Yoshitomi, Makoto Ikeya, Takuya Yamamoto, Knut Woltjen, Miki Ebisuya, Junya Toguchida, Cantas Alev

Pluripotent stem cells (PSCs) have increasingly been used to model different aspects of embryogenesis and organ formation. Despite recent advances in the in vitro induction of major mesodermal lineages and mesoderm-derived cell types experimental model systems that can recapitulate more complex biological features of human mesoderm development and patterning are largely missing. Here, we utilized induced pluripotent stem cells (iPSCs) for the stepwise in vitro induction of presomitic mesoderm (PSM) and its derivatives to model distinct aspects of human somitogenesis. We focused initially on modeling the human segmentation clock, a major biological concept believed to underlie the rhythmic and controlled emergence of somites, which give rise to the segmental pattern of the vertebrate axial skeleton. We succeeded to observe oscillatory expression of core segmentation clock genes, including HES7 and DKK1, and identified novel oscillatory genes in human iPSC-derived PSM. We furthermore determined the period of the human segmentation clock to be around five hours and showed the presence of dynamic traveling wave-like gene expression within in vitro induced human PSM. Utilizing CRISPR/Cas9-based genome editing technology, we then targeted genes, for which mutations in patients with abnormal axial skeletal development such as spondylocostal dysostosis (SCD) (HES7, LFNG and DLL3) or spondylothoracic dysostosis (STD) (MESP2) have been reported. Subsequent analysis of patient-like iPSC knock-out lines as well as patient-derived iPSCs together with their genetically corrected isogenic controls revealed gene-specific alterations in oscillation, synchronization or differentiation properties, validating the overall utility of our model system, to recapitulate not only key features of human somitogenesis but also to provide novel insights into diseases associated with the formation and patterning of the human axial skeleton.

116: Skeletal Cell YAP And TAZ Redundantly Promote Bone Development By Regulation Of Collagen I Expression And Organization
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Posted to bioRxiv 30 May 2017

Skeletal Cell YAP And TAZ Redundantly Promote Bone Development By Regulation Of Collagen I Expression And Organization
1,226 downloads developmental biology

Christopher D. Kegelman, Devon E. Mason, James H. Dawahare, Genevieve D. Vigil, Scott S. Howard, Teresita M. Bellido, Alexander G. Robling, Joel D Boerckel

The functions of the transcriptional co-activators YAP and TAZ in bone are controversial. Each has been observed to either promote or inhibit osteogenesis in vitro, while their roles in bone development are unknown. Here we report that combinatorial YAP/TAZ deletion from skeletal cells in mice caused osteogenesis imperfecta with severity dependent on targeted cell lineage and allele dosage. Osteocyte-conditional deletion impaired bone accrual and matrix collagen, while allele dosage-dependent deletion from all osteogenic lineage cells caused spontaneous fractures, with neonatal lethality only in dual homozygous knockouts. We identified putative target genes whose mutation in humans causes osteogenesis imperfecta and which contain promoter-proximate binding domains for the YAP/TAZ co-effector, TEAD4. Two candidates, Col1a1 and SerpinH1, exhibited reduced expression upon either YAP/TAZ deletion or YAP/TAZ-TEAD inhibition by verteporfin. Together, these data demonstrate that YAP and TAZ redundantly promote bone matrix development and implicate YAP/TAZ-mediated transcriptional regulation of collagen in osteogenesis imperfecta.

117: Transcriptome landscape of the developing olive fruit fly embryo delineated by Oxford Nanopore long-read RNA-Seq
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Posted to bioRxiv 24 Nov 2018

Transcriptome landscape of the developing olive fruit fly embryo delineated by Oxford Nanopore long-read RNA-Seq
1,219 downloads developmental biology

Anthony Bayega, Spyros Oikonomopoulos, Eleftherios Zorbas, Yu Chang Wang, Maria-Eleni Gregoriou, Konstantina T Tsoumani, Kostas D Mathiopoulos, Jiannis Ragoussis

The olive fruit fly or olive fly (Bactrocera oleae) is the most important pest of cultivated olive trees. Like all insects the olive fly undergoes complete metamorphosis. However, the transcription dynamics that occur during early embryonic development have not been explored, while detailed transcriptomic analysis in the absence of a fully annotated genome is challenging. We collected olive fly embryos at hourly intervals for the first 6 hours of development and performed full-length cDNA-Seq using a purpose designed SMARTer cDNA synthesis protocol followed by sequencing on the MinION (Oxford Nanopore Technologies). We generated 31 million total reads across the timepoints (median yield 4.2 million per timepoint). The reads showed 98 % alignment rate to the olive fly genome and 91 % alignment rate to the NBCI predicted B. oleae gene models. Over 50 % of the expressed genes had at least one read covering its entire length validating our full-length RNA-Seq procedure. Expression of 68 % of the predicted B. oleae genes was detected in the first six hours of development. We generated a de novo transcriptome assembly of the olive fly and identified 3553 novel genes and a total of 79,810 transcripts; a fourfold increase in transcriptome diversity compared to the NCBI predicted transcriptome. On a global scale, the first six hours of embryo development were characterized by dramatic transcriptome changes with the total number of transcripts per embryo dropping to half from the first hour to the second hour of embryo development. Clustering of genes based on temporal co-expression followed by gene-set enrichment analysiss of genes expressed in the first six hours of embryo development showed that genes involved in transcription and translation, macro-molecule biosynthesis, and neurodevelopment were highly enriched. These data provide the first insight into the transcriptome landscape of the developing olive fly embryo. The data also reveal transcript signatures of sex development. Overall, full-length sequencing of the cDNA molecules permitted a detailed characterization of the isoform complexity and the transcriptional dynamics of the first embryonic stages of the B. oleae.

118: Stage-specific transcriptomes and DNA methylomes indicate an early and transient loss of transposon control in Arabidopsis shoot stem cells
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Posted to bioRxiv 29 Sep 2018

Stage-specific transcriptomes and DNA methylomes indicate an early and transient loss of transposon control in Arabidopsis shoot stem cells
1,217 downloads developmental biology

Ruben Gutzat, Klaus Rembart, Thomas Nussbaumer, Rahul Pisupati, Falko Hofmann, Gabriele Bradamante, Nina Daubel, Angelika Gaidora, Nicole Lettner, Mattia Donà, Magnus Nordborg, Michael D. Nodine, Ortrun Mittelsten Scheid

In contrast to animals, postembryonic development in plants is modular, and aerial organs originate from stem cells in the center of the shoot apical meristem (SAM) throughout life. Descendants of SAM stem cells in the subepidermal layer (L2) will give also rise to male and female gametes 1and therefore can be considered primordial germ cells. In these cells, transmission of somatic mutations including virus and TE insertions must be avoided. Despite their essential role for plant development and intergenerational continuity, a comprehensive molecular analysis of SAM plant stem cells has been missing, due to their low number, deep embedding among non-stem cells and difficult isolation. Here we present a comprehensive analysis of stage-specific gene expression and DNA methylation dynamics in Arabidopsis SAM stem cells. This revealed that stem cell expression signatures are mostly defined by development, but we also identified a core set of differentially expressed stemness genes. Surprisingly, vegetative SAM stem cells showed increased expression of transposable elements (TEs) relative to surrounding cells, despite high expression of genes connected to epigenetic silencing. We also find increasing methylation at CHG and a drop in CHH methylation at TEs before stem cells enter the reproductive lineage, indicating an onset of epigenetic reprogramming at an early stage. Transiently elevated TE expression is reminiscent of that in animal primordial germ cells (PGCs) 2 and demonstrates commonality of transposon biology. Our results connect SAM stem cells with germline development and transposon evolution and will allow future experiments to determine the degree of epigenetic heritability between generations.

119: Lipoproteins carry endocannabinoids that inhibit the Hedgehog pathway
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Posted to bioRxiv 18 Nov 2013

Lipoproteins carry endocannabinoids that inhibit the Hedgehog pathway
1,213 downloads developmental biology

Helena Khaliullina, Mesut Bilgin, Julio L Sampaio, Andrej Shevchenko, Suzanne Eaton

Hedgehog proteins are lipid-modified secreted signaling molecules that regulate tissue development and homeostasis. Lipids contained in circulating lipoproteins repress the Hedgehog signaling pathway in the absence of Hedgehog ligand, but the identity of these lipids is unknown. Here, using biochemical fractionation and lipid mass spectrometry, we identify these inhibitory lipids as endocannabinoids. Endocannabinoids are present in lipoproteins of both flies and humans, and repress the pathway in both mammalian signaling assays and Drosophila wing imaginal discs. In Drosophila, endocannabinoids are required in vivo to keep the levels of Smoothened and full-length Cubitus interruptus (Ci155) low in the absence of Hedgehog. Furthermore, elevating their endogenous levels inhibits Hedgehog-dependent accumulation of Smoothened and Ci155. Interestingly, cannabis-derived phytocannabinoids are also potent pathway inhibitors in flies and mammals. These findings constitute a novel link between organismal metabolism and local Hedgehog signaling, and suggest previously unsuspected mechanisms for the broad physiological activities of cannabinoids.

120: Motility-gradient induced elongation of the vertebrate embryo
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Posted to bioRxiv 12 Sep 2017

Motility-gradient induced elongation of the vertebrate embryo
1,192 downloads developmental biology

Ido Regev, Karine Guevorkian, Olivier Pourquie, L. Mahadevan

The body of vertebrate embryos forms by posterior elongation from a terminal growth zone called the Tail Bud (TB). The TB produces highly motile cells forming the presomitic mesoderm (PSM), a tissue playing an important role in elongation movements. PSM cells establish an anterior-posterior cell motility gradient which parallels the degradation of a specific cellular signal (Fgf8) known to be implicated in cell motility. Here, we combine electroporation of fluorescent reporters in the PSM to time-lapse imaging in the chicken embryo to quantify cell diffusive movements along the motility gradient. We show that simple microscopic and macroscopic mechano-chemical models for tissue extension that couple Fgf activity, cell motility and tissue rheology at both the cellular and continuum levels suffice to capture the speed and extent of elongation. These observations explain how the continuous addition of cells that exhibit a gradual reduction in motility combined with lateral confinement can be converted into an oriented movement that drives body elongation. The results of the models compare well with our experimental results, with implications for other elongation processes in the embryo.

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