SEARCH · bioRxiv Science

Results for “Developmental Biology”

Search indexed bioRxiv preprints in genomics, neuroscience, cell biology and bioinformatics. Read source abstracts and check manuscript versions; preprints are not peer reviewed.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,153 records · Page 64Linked to original sources

bioRxiv2018

Retinoic acid and androgens interact to regulate spermatogenesis in a non-mammalian vertebrate lacking stra8

In mammals, retinoic acid (RA) signaling is critical for spermatogonial differentiation and for entering meiosis, the latter depending on RA-induced Stra8 gene expression. Many fish species, including zebrafish, do not contain a stra8 gene, but RA signaling nevertheless is important for sperm production. However, it is not known which stages of spermatogenesis respond to RA. Here, we show in zebrafish that RA promotes spermatogonial differentiation and reduces the apoptotic loss of spermatids, but is not required for meiosis. Some of the RA effects are mediated by other genes, in particular rec8a. Surprisingly, androgens can partially compensate for the loss of RA signaling, and we identify a link between the endocrine system and RA signaling: follicle-stimulating hormone (Fsh) stimulates testicular RA production. While RA signaling is relevant at the basis of the vertebrates, it also targets processes and mechanisms that are different from those known in mammals so far.

developmental biology↗

bioRxiv2018

Inter-organ growth coordination is mediated by the Xrp1/Dilp8 axis in Drosophila

How organs scale with other body parts is not mechanistically understood. We have addressed this question using the Drosophila imaginal disc model. When growth of one disc domain is perturbed, other parts of the disc and other discs slow down their growth, maintaining proper inter-disc and intra-disc proportions. We show here that the relaxin-like Dilp8 is required for this inter-organ coordination. Our work also reveals that the stress-response transcription factor Xrp1 plays a key role upstream of dilp8 in linking organ growth status with non-autonomous/systemic growth response. In addition, we show that the small ribosomal subunit protein RpS12 is required to trigger Xrp1-dependent non-autonomous response. Our work demonstrates that RpS12, Xrp1 and Dilp8 constitute a new, independent regulatory module that ensures intra- and inter-organ growth coordination during development.

developmental biology↗

bioRxiv2018

Prolonged quiescence delays somatic stem cell-like division in Caenorhabditis elegans and is controlled by insulin signalling

Cells can enter quiescence in adverse conditions and resume proliferation when the environment becomes favourable. Prolonged quiescence comes with a cost, reducing proliferation potential and survival. Interestingly, cellular quiescence also occurs in normal development, with many cells spending most of their lifetime at this state. Elucidating the mechanisms involved in surviving long-term quiescence and in maintenance of cellular proliferation potential will contribute to a better understanding of the process of tissue regeneration. Developmental arrest of C. elegans at the L1 stage is an emerging model for the study of cellular quiescence and reactivation. During arrest, L1 larvae undergo a process that shares phenotypic hallmarks with the ageing of the adult. Interestingly, insulin signalling, a prominent pathway in the regulation of ageing, also balances cell proliferation and activation of stress resistance pathways during quiescence, becoming a candidate regulator of proliferation potential. Here we report that prolonged L1 quiescence delays reactivation of blast cell divisions in C. elegans, leading to a delay in the initiation of postembryonic development. This delay is accompanied by increased inter-individual variability. We propose that the delay in cell division results from the decline that animals suffer during L1 arrest. To that end, we show that insulin signalling modulates the rate of L1 ageing, affecting proliferative potential after quiescence. These findings support that the insulin signalling pathway has a comparable role in L1 arrest to that in ageing adults. Furthermore, we show that variable yolk provisioning to the embryos as a consequence of maternal age is one of the sources of inter-individual variability in recovery after quiescence of genetically identical animals. Taken together, these results support the relevance of L1 arrest as a model to study in vivo proliferation after quiescence and to understand the mechanisms for maintenance of proliferation potential.

developmental biology↗

bioRxiv2018

Iron deficiency affects early stages of embryonic hematopoiesis but not the endothelial to hematopoietic transition

Iron is an essential micronutrient for hematopoiesis and previous research suggested that iron deficiency in the pregnant female could cause anemia in the offspring. Since the development of all embryonic and adult blood cells begins in the embryo, we aimed to resolve the role of iron in embryonic hematopoiesis. For this purpose, we used an experimental system of mouse embryonic stem cells differentiation into embryonic hematopoietic progenitors. We modulated the iron status in cultures by adding either an iron chelator DFO for iron deficiency, or ferric ammonium citrate for iron excess, and followed the emergence of developing hematopoietic progenitors by flow cytometry. We found interestingly that iron deficiency by DFO did not block the endothelial to hematopoietic transition, the first step of hematopoiesis. However, it had a differential effect on the proliferation, survival and clonogenic capacity of hematopoietic progenitors. Surprisingly, iron deficiency affected erythro-myeloid Kitpos CD41+ progenitors significantly more than the primitive erythroid Kitneg CD41+. The Kitpos progenitors paradoxically died more, proliferated less and had more reduction in colony formation than Kitneg after 24 hours of DFO treatment. Kitpos progenitors expressed less transferrin-receptor on the cell surface and had less labile iron compared to Kitneg, which could reduce their capacity to compete for scarce iron and survive iron deficiency. We suggest that iron deficiency could disturb hematopoiesis already at an early embryonic stage by compromising survival, proliferation and differentiation of definitive hematopoietic progenitors.

developmental biology↗

bioRxiv2018

Desmoplakin is required for epidermal integrity and morphogenesis in the Xenopus laevis embryo

Desmoplakin (Dsp) is a unique and critical desmosomal protein, however, it is unclear whether this protein and desmosomes themselves are required for epidermal morphogenesis. Using morpholinos or Crispr/Cas9 mutagenesis we decreased the function of Dsp in frog embryos to better understand its role during epidermal development. Dsp morphant and mutant embryos had developmental defects that mimicked what has been reported in mammals. Such defects included epidermal fragility which correlated with reduction in cortical keratin and junctional e-cadherin in the developing epidermis. Dsp protein sequence and expression are also highly similar with mammals and suggest shared function across vertebrates. Most importantly, we also uncovered a novel function for Dsp in the morphogenesis of the epidermis in X. laevis. Specifically, Dsp is required during the process of radial intercalation where basally located cells move into the outer epidermal layer. Once inserted these newly intercalated cells expand their apical surface and then they differentiate into specific epidermal cell types. Decreased levels of Dsp resulted in the failure of the radially intercalating cells to expand their apical surface, thereby reducing the number of differentiated multiciliated and secretory cells. Dsp is also required in the development of other ectodermally derived structures such as the mouth, eye and fin that utilize intercalating-like cell movements. We have developed a novel system, in the frog, to demonstrate for the first time that desmosomes not only protect against mechanical stress but are also critical for epidermal morphogenesis.\n\nSummary StatementCritical desmosomal protein, desmoplakin, is required for proper distribution and levels of cytoskeletal elements and e-cadherin. Thus embryos with decreased desmoplakin have defects in epidermal integrity and morphogenesis.

developmental biology↗

bioRxiv2018

Genetic dissection of Nodal and Bmp signalling requirements during primordial germ cell development

The essential roles played by Nodal and Bmp signalling during early mouse development have been extensively documented. Here we used conditional deletion strategies to investigate functional contributions made by Nodal, Bmp and Smad downstream effectors during primordial germ cell (PGC) development. We demonstrate that Nodal and its target gene Eomes provide early instructions during formation of the PGC lineage. We discovered that Smad2 inactivation in the visceral endoderm results in increased numbers of PGCs due to an expansion of the PGC niche. Smad1 is required for specification, whereas in contrast Smad4 controls the maintenance and migration of PGCs. Importantly we found that beside Blimp1, down-regulated phosphoSmad159 levels also distinguishes PGCs from their somatic neighbours so that emerging PGCs become refractory to Bmp signalling that otherwise promotes mesodermal development in the posterior epiblast. Thus balanced Nodal/Bmp signalling cues regulate germ cell versus somatic cell fate decisions in the early posterior epiblast.

developmental biology↗

bioRxiv2018

Plastic multicellular development of Myxococcus xanthus: genotype-environment interactions in a physical gradient

In order to investigate the contribution of the physical environment to variation in multicellular development of Myxococcus xanthus, phenotypes developed by different genotypes in a gradient of substrate stiffness conditions were quantitatively characterized. Statistical analysis showed that plastic phenotypes result from the genotype, the substrate conditions and the interaction between them. Also, phenotypes were expressed with scale- and trait-specificity. Overall, the presented information highlights the constructive role of the physical context in the development of microbial multicellularity, with both ecological and evolutionary implications.

developmental biology↗

bioRxiv2018

Efficient GFP-labeling and analysis of spermatogenic cells using the IRG transgene and flow cytometry

Spermatogenesis is a highly ordered developmental program that produces haploid male germ cells. The study of male germ cell development in the mouse has provided unique perspectives into the molecular mechanisms that control cell development and differentiation in mammals, including tissue-specific gene regulatory programs. An intrinsic challenge in spermatogenesis research is the heterogeneity of germ and somatic cell types present in the testis. Techniques to separate and isolate distinct mouse spermatogenic cell types have great potential to shed light on molecular mechanisms controlling mammalian cell development, while also providing new insights into cellular events important for human reproductive health. Here, we detail a versatile strategy that combines Cre-lox technology to fluorescently label germ cells, with flow cytometry to discriminate and isolate germ cells in different stages of development for cellular and molecular analyses.

developmental biology↗

bioRxiv2018

Developmental regulators FlbE/D orchestrate the polarity site-to-nucleus dynamics of the fungal bZIP FlbB

Permanently polarized cells have developed transduction mechanisms linking polarity-sites with gene regulation in the nucleus. In neurons, one mechanism is based on long-distance retrograde migration of transcription factors (TFs). Aspergillus nidulans FlbB is the only known fungal TF shown to migrate retrogradely to nuclei from the polarized region of fungal cells known as hyphae. There, FlbB controls developmental transitions by triggering the production of asexual multicellular structures. FlbB dynamics in hyphae is orchestrated by regulators FlbE and FlbD. At least three FlbE domains are involved in the acropetal transport of FlbB, with a final MyoE/actin filament-dependent step from the subapex to the apex. Experiments employing a T2A viral peptide-containing chimera (FlbE::mRFP::T2A::FlbB::GFP) suggest that apical FlbB/FlbE interaction is inhibited in order to initiate a dynein-dependent FlbB transport to nuclei. FlbD controls the nuclear accumulation of FlbB through a cMyb domain and a C-terminal LxxLL motif. Overall, results elucidate a highly dynamic pattern of FlbB interactions, which enable timely developmental induction. Furthermore, this system establishes a reference for TF-based long-distance signaling in permanently polarized cells.

developmental biology↗

bioRxiv2018

Reevaluation of the Role of ERK3 in Perinatal Survival and Post-Natal Growth Using New Genetically-Engineered Mouse Models

The physiological functions of the atypical MAP kinase ERK3 remain poorly characterized. Previous analysis of mice with a targeted insertion of the lacZ reporter in the Mapk6 locus (Mapk6lacZ) showed that inactivation of ERK3 in Mapk6lacZ mice leads to perinatal lethality associated with intrauterine growth restriction, defective lung maturation, and neuromuscular anomalies. To further explore the role of ERK3 in physiology and disease, we generated novel mouse models expressing a catalytically-inactive (Mapk6KD) or conditional (Mapk6{Delta}) allele of ERK3. Surprisingly, we found that mice devoid of ERK3 kinase activity or expression survive the perinatal period without any observable lung or neuromuscular phenotype. ERK3 mutant mice reached adulthood, were fertile and showed no apparent health problem. However, analysis of growth curves revealed that ERK3 kinase activity is ncessary for optimal post-natal growth. To gain insight into the genetic basis underlying the discrepancy in phenotypes of different Mapk6 mutant mouse models, we analyzed the regulation of genes flanking the Mapk6 locus by quantitative PCR. We found that expression of several Mapk6 neighboring genes is deregulated in Mapk6lacZ mice, but not in Mapk6KD or Mapk6{Delta} mutant mice. Our genetic analysis suggests that off-target effects of the targeting construct on local gene expression are likely to be responsible for the perinatal lethality phenotype of Mapk6lacZ mutant mice.

developmental biology↗

bioRxiv2018

Neuropilin 1 mediates epicardial activation and revascularization in the regenerating zebrafish heart

Unlike adult mammals, zebrafish are able to naturally regenerate their heart. A key mechanism in zebrafish heart regeneration is the activation of the epicardium, leading to the establishment of a supporting scaffold for newly formed cardiomyocytes, angiogenesis and cytokine secretion. Neuropilins (NRPs) are cell surface co-receptors mediating functional signaling of kinase receptors for cytokines known to play critical roles in zebrafish heart regeneration, including Platelet-Derived growth factor (PDGF), Vascular Endothelial growth factor (VEGF), and Fibroblast growth factor (FGF). Herein, we investigated the role of neuropilins in the response of the zebrafish heart to injury and its subsequent regeneration. All four zebrafish neuropilin isoforms, nrp 1a, 1b, 2a, and 2b, were upregulated following cardiac cryoinjury and were strongly expressed by the activated epicardium. A nrp1a mutant, coding for a truncated, non-functional protein, showed a significant delay in heart regeneration in comparison to Wild-Type fish and displayed persistent collagen deposition. The regenerating hearts of nrp1a mutants were less vascularized and epicardial-derived cell migration and re-expression of the developmental gene Wilms tumor 1 was severely impaired in nrp1a mutants. Moreover, cryoinjury-induced activation and migration of epicardial cells in heart explants was strongly reduced in nrp1a mutant zebrafish. These results identify a key role for Nrp1 in zebrafish heart regeneration, mediated through epicardial activation, migration and revascularization.

developmental biology↗

bioRxiv2018

Maintenance of spatial gene expression by Polycomb-mediated repression after formation of a vertebrate body plan

Polycomb group proteins are transcriptional repressors that are important regulators of cell fate during embryonic development. Among them, Ezh2 is responsible for catalyzing the epigenetic repressive mark H3K27me3 and is essential for animal development. The ability of zebrafish embryos lacking both maternal and zygotic ezh2 to form a normal body plan provides a unique model to comprehensively study Ezh2 function during early development in vertebrates. By using a multi-omics approach, we found that Ezh2 is required for the recruitment of H3K27me3 and Polycomb group protein Rnf2. However, in absence of Ezh2, only minor changes in global H3K4me3 levels and gene and protein expression occurred. These changes were mainly due to local deregulation of transcription factors outside their normal expression boundaries. Altogether, our results in zebrafish show that Polycomb-mediated gene repression is important only after the body plan is formed to maintain spatially restricted transcriptional profiles of Polycomb-targeted transcription factors.

developmental biology↗

bioRxiv2018

Body composition and growth in full-term small for gestational age and large for gestational age Swedish infants assessed with air displacement plethysmography at birth and at 3-4 months of age.

BackgroundBeing born small for gestational age (SGA) or large for gestational age (LGA) has short and long term metabolic consequences. There is a growing interest in the extent to which body composition, both in the short and the long term, differs in infants born at the extremes of these birth weights.\n\nMethodsBody composition in 25 SGA and 25 LGA infants were assessed during the first days of life and at 3-4 months of age using air displacement plethysmography.\n\nResultsSGA infants had significantly lower body fat (%) at birth compared to LGA infants. SGA infants increased their body weight and length at a significantly higher rate between birth and 3-4 months than LGA infants. Fat mass (g) in SGA infants increased 23 times between birth and 3-4 months of age compared to 2.8 times for LGA infants. At 3-4 months of age LGA infants reached a threshold in body fat (%) while SGA infants were still gaining body fat (%).\n\nConclusionSeveral significant differences have been identified between SGA and LGA infants, indicating that the effects of intrauterine life continues to play an important role in body composition and growth during the first 3-4 months of life.

developmental biology↗

bioRxiv2018

Culling less fit neurons protects against amyloid-β induced brain damage and cognitive and motor decline

Alzheimers disease (AD) is the most common form of dementia, impairing cognitive and motor functions. One of the pathological hallmarks of AD is neuronal loss, which is not reflected in mouse models of AD. Therefore, the role of neuronal death is still uncertain. Here, we used a Drosophila AD model expressing a secreted form of human amyloid-{beta}42 peptide and show that it recapitulates key aspects of AD pathology, including neuronal death and impaired long-term memory. We found that neuronal apoptosis is mediated by cell fitness-driven neuronal culling, which selectively eliminates impaired neurons from brain circuits. We show that removal of less fit neurons delays amyloid-{beta}42-induced brain damage and protects against cognitive and motor decline, suggesting that - contrary to common knowledge - neuronal death may have a beneficial effect in AD.

developmental biology↗

bioRxiv2018

ABC-transporter activity and eicosanoid-signaling are required for germ cell migration a basal chordate

In the colonial ascidian Botryllus schlosseri, long-lived germline stem cells (GSCs) migrate to new germline niches as they develop during repetitive cycles of asexual reproduction. ABC-transporters are involved in the export of lipid-signaling molecules, but their roles in germ cell migration are poorly understood. Here, we show that in Botryllus, abcc1 and abcb1 are highly expressed in germ cells, and inhibition of ABC-transporter activity leads to failure of germ cell migration. Phospholipase A2 (PLA2) produces arachidonic acid, which is further metabolized to eicosanoid signaling molecules. In humans, 12-lipoxygenase (LOX) metabolizes arachidonic acid to12-Hydroxyeicosatetraenoic acid (12-S-HETE), which stimulates migration of mammalian cancer cells and smooth muscle cells. We show that PLA2 and LOX activity are required for germ cell migration. A potential homolog to the human receptor for 12-S-HETE, BSgpr31, is expressed in germ cells. 12-S-HETE rescues migration towards S1P in the presence of inhibitors of ABCC1, ABCB1, PLA2 or LOX, and a gradient of 12-S-HETE enhances chemotaxis towards S1P and stimulates motility. We conclude that 12-S-HETE is a secondary chemoattractant exported by ACB-transporters that is required for migration of germ cells towards S1P. We also find that in the presence of S1P, detection of an 12-S-HETE gradient initiates an autologous positive feedback loop that may sustain migration. This is the first report of an eicosanoid-signaling molecule regulating germ cell migration.

developmental biology↗

bioRxiv2018

A Scube2-Shh feedback loop links morphogen release to morphogen signaling to enable scale invariant patterning of the ventral neural tube

To enable robust patterning, morphogen systems should be resistant to variations in gene expression and tissue size. Here we explore how the Sonic Hedgehog (Shh) morphogen gradient in the ventral neural tube enables scaled patterning in embryos of varying sizes. Using zebrafish eggs that have been surgically reduced in size, we find that ventral neural tube patterning remains proportional in smaller embryos. Intriguingly, a secreted protein implicated in Shh release, Scube2, is expressed in the dorsal-intermediate neural tube far from Shh producing cells. Overexpression of scube2 expands the Shh gradient whereas loss of scube2 causes gradient contraction. Conversely, upregulation of Shh represses scube2 expression while Shh downregulation increases scube2 expression thus establishing a negative feedback loop. This regulatory feedback is necessary for scaling, as demonstrated by its loss in scube2 overexpressing embryos. Using mathematical modeling, we show that feedback control on diffusion and release rates of Shh allows the morphogen gradient to be robust to differences in field length and Shh gene dosage. We conclude that Scube2 promotes release and diffusion of Shh to allow gradient scaling in an extension to the expander-repressor model. Summary StatementThe Shh morphogen gradient can scale to different size tissues by feedback between Scube2 mediated release and diffusion of Shh and Shh based inhibition of Scube2 expression

developmental biology↗

bioRxiv2018

Single-cell RNA-seq of the Developing Cardiac Outflow Tract Reveals Convergent Development of the Vascular Smooth Muscle Cells at the Base of the Great Arteries

RationaleCardiac outflow tract (OFT) is a major hotspot for congenital heart diseases (CHDs). A thorough understanding of the cellular diversity, transitions and regulatory networks of normal OFT development is essential to decipher the etiology of OFT malformations.\n\nObjectiveWe sought to explore the cellular diversity and transitions between cell lineages during OFT development.\n\nMethods and ResultsWe performed single-cell transcriptomic sequencing of 55,611 mouse OFT cells from three developmental stages that generally correspond to the early, middle and late stages of OFT remodeling and septation. We identified 17 cell clusters that could be assigned to six cell lineages. Among these lineages, the macrophage and VSMC lineages of the developing OFT have seldom been previously described. Known cellular transitions, such as endothelial to mesenchymal transition, have been recapitulated. In particular, we identified convergent development of the VSMC lineage, where intermediate cell subpopulations were found to be involved in either myocardial to VSMC trans-differentiation or mesenchymal to VSMC transition. Through single-molecule in situ hybridization, we observed that cells expressing the myocardial marker Myh7 co-expressed the VSMC marker gene Cxcl12 in OFT walls, thus confirming the existence of myocardial to VSMC trans-differentiation. Moreover, we found that the Penk+ cluster c8, a relatively small mesenchymal subpopulation that was undergoing mesenchymal to VSMC transition, was associated with the fusion of OFT cushions. We also uncovered the expression dynamics and critical transcriptional regulators potentially governing cell state transitions. Finally, we developed web-based interactive interfaces to facilitate further data exploration.\n\nConclusionsWe provide a single-cell reference map of cell states for normal OFT development, which will be a valuable resource for the CHD community. Our data support the existence of myocardial to VSMC trans-differentiation and convergent development of the VSMC lineage at the base of the great arteries.

developmental biology↗

bioRxiv2018

A dual function of FGF signaling in Xenopus left-right axis formation

Organ left-right (LR) asymmetry is a conserved vertebrate feature, which is regulated by left-sided activation of Nodal signaling. Nodal asymmetry is established by a leftward fluid-flow generated at the ciliated LR organizer (LRO). While the role of fibroblast growth factor (FGF) signaling pathways during mesoderm development are conserved, diverging results from different model organisms suggested a non-conserved function in LR asymmetry. Here, we demonstrate that FGF is required during gastrulation in a dual function at consecutive stages of Xenopus embryonic development. In the early gastrula, FGF is necessary for LRO precursor induction, acting in parallel to FGF-mediated mesoderm induction. During late gastrulation, the FGF/Ca2+-branch is required for specification of the flow sensing lateral LRO cells, a function related to FGF-mediated mesoderm morphogenesis. This second function in addition requires input from the calcium channel Polycystin-2. Thus, analogous to mesoderm development, FGF activity is required in a dual role for laterality specification, namely for generating and sensing of leftward flow. Moreover, our data show that FGF functions in LR asymmetric development are conserved across vertebrate species, from fish to mammals.

developmental biology↗