Lineage-specific, fast-evolving GATA-like gene regulates zygotic gene activation to promote endoderm specification and pattern formation in the Theridiidae spider.

Background: The process of early development varies across the species-rich phylum Arthropoda. Owing to the limited research strategies for dissecting lineage-specific processes of development in arthropods, little is known about the variations in early arthropod development at molecular resolution. The Theridiidae spider, Parasteatoda tepidariorum, has its genome sequenced and could potentially contribute to dissecting early embryonic processes.

Virtual spherical-shaped multicellular platform for simulating the morphogenetic processes of spider-like body axis formation.

Remodeling of multicellular architecture is a critical developmental process for shaping the axis of a bilaterally symmetric animal body and involves coordinated cell-cell interactions and cell rearrangement. In arthropods, the early embryonic process that leads to the segmented body axis varies at the cellular and molecular levels depending on the species. Developmental studies using insect and spider model species have provided specific examples of these diversified mechanisms that regulate axis formation and segmentation in arthropod embryos.

Reconstruction of the Global Polarity of an Early Spider Embryo by Single-Cell and Single-Nucleus Transcriptome Analysis.

Patterning along an axis of polarity is a fundamental step in the development of a multicellular animal embryo. In the cellular field of an early spider embryo, Hedgehog signaling operates to specify a "fuzzy" French-flag-like pattern along the primary axis, which is related to the future anterior-posterior (A-P) axis. However, details regarding the generation and development of a diversity of cell states based on the embryo polarity are not known.

Hedgehog signaling controls segmentation dynamics and diversity via in a spider embryo.

Hedgehog (Hh) signaling plays fundamental roles in animal body patterning. Understanding its mechanistic complexity requires simple tractable systems that can be used for these studies. In the early spider embryo, Hh signaling mediates the formation of overall anterior-posterior polarity, yet it remains unclear what mechanisms link the initial Hh signaling activity with body axis segmentation, in which distinct periodic stripe-forming dynamics occur depending on the body region.

Dataset on gene expressions affected by simultaneous knockdown of Hedgehog and Dpp signaling components in embryos of the spider .

Simultaneous, parental RNA interference (pRNAi) mediated knockdown of Hedgehog and Decapentaplegic (Dpp) signaling components, () and , respectively, exhibited serious defects in the formation of the major embryonic axes in the model spider . This paper describes a dataset of a custom oligonucleotide two-color microarray analysis that was carried out to compare the transcript expression levels between untreated (normal) and  +  double pRNAi embryos at late stage 5. Array spots that showed the intensity ratio of [ +  double pRNAi]/[normal] <0.

The common house spider .

The common house spider belonging to the Chelicerata in the phylum Arthropoda, has emerged as an experimental system for studying mechanisms of development from an evolutionary standpoint. In this article, we review the distinct characteristics of , the major research questions relevant to this organism, and the available key methods and resources. has a relatively short lifecycle and, once mated, periodically lays eggs.

Microarray data on the comparison of transcript expression between normal and RNAi embryos in the common house spider .

We conducted a custom microarray experiment to detect the differences in the transcript expression levels between untreated (normal) and -RNAi embryos at late stage 6 in the common house spider . The array probes were designed based on accumulated EST and cDNA sequences. The microarray dataset has been deposited in the Gene Expression Omnibus (GEO) Database at the National Center for Biotechnology Information (NCBI) under the accession GSE113064.

Experimental duplication of bilaterian body axes in spider embryos: Holm's organizer and self-regulation of embryonic fields.

Bilaterally symmetric body plans of vertebrates and arthropods are defined by a single set of two orthogonal axes, the anterior-posterior (or head-tail) and dorsal-ventral axes. In vertebrates, and especially amphibians, complete or partial doubling of the bilaterian body axes can be induced by two different types of embryological manipulations: transplantation of an organizer region or bi-sectioning of an embryo. Such axis doubling relies on the ability of embryonic fields to flexibly respond to the situation and self-regulate toward forming a whole body.

Homeobox Gene Duplication and Divergence in Arachnids.

Homeobox genes are key toolkit genes that regulate the development of metazoans and changes in their regulation and copy number have contributed to the evolution of phenotypic diversity. We recently identified a whole genome duplication (WGD) event that occurred in an ancestor of spiders and scorpions (Arachnopulmonata), and that many homeobox genes, including two Hox clusters, appear to have been retained in arachnopulmonates. To better understand the consequences of this ancient WGD and the evolution of arachnid homeobox genes, we have characterized and compared the homeobox repertoires in a range of arachnids.

Genome-scale embryonic developmental profile of gene expression in the common house spider .

We performed RNA sequencing (RNA-Seq) at ten successive developmental stages in embryos of the common house spider . Two independent datasets from two pairs of parents represent the normalized coverage of mapped RNA-Seq reads along scaffolds of the genome assembly. Transcript abundance was calculated against existing AUGUSTUS gene models.

A quantitative study of the diversity of stripe-forming processes in an arthropod cell-based field undergoing axis formation and growth.

One of the conserved traits of arthropod embryonic development is striped expression of homologs of Drosophila segment polarity genes, including hedgehog (hh). Although a diversity of stripe-forming processes is recognized among arthropod embryos, such varied stripe-forming processes have not been well characterized from cellular and quantitative perspectives. The spider Parasteatoda tepidariorum embryo, which has a hh-dependent mechanism of axis formation, offers a cell-based field where the stripes of Pt-hh (a hh homolog) expression dynamically develop in accordance with axis formation and growth, with the patterning processes varying among the regions of the field.

Evolutionary origin of type IV classical cadherins in arthropods.

Background: Classical cadherins are a metazoan-specific family of homophilic cell-cell adhesion molecules that regulate morphogenesis. Type I and type IV cadherins in this family function at adherens junctions in the major epithelial tissues of vertebrates and insects, respectively, but they have distinct, relatively simple domain organizations that are thought to have evolved by independent reductive changes from an ancestral type III cadherin, which is larger than derived paralogs and has a complicated domain organization. Although both type III and type IV cadherins have been identified in hexapods and branchiopods, the process by which the type IV cadherin evolved is still largely unclear.

Multi-color FISH facilitates analysis of cell-type diversification and developmental gene regulation in the Parasteatoda spider embryo.

The simultaneous and quantitative analysis of the expression of multiple genes helps to shed light on gene regulatory networks. We established a method for multi-color fluorescence in situ hybridization (mFISH) for the analysis of cell-type diversification and developmental gene regulation in the embryo of the spider Parasteatoda tepidariorum. This mFISH technique allowed quadruple staining using four types of labels for RNA probes, digoxigenin, fluorescein, biotin, and dinitrophenyl, together with different fluorescent tyramides.

Travelling and splitting of a wave of hedgehog expression involved in spider-head segmentation.

During development segmentation is a process that generates a spatial periodic pattern. Peak splitting of waves of gene expression is a mathematically predicted, simple strategy accounting for this type of process, but it has not been well characterized biologically. Here we show temporally repeated splitting of gene expression into stripes that is associated with head axis growth in the spider Achaearanea embryo.

Early embryonic development in the spider Achaearanea tepidariorum: Microinjection verifies that cellularization is complete before the blastoderm stage.

The spider Achaearanea tepidariorum is emerging as a non-insect model for studying developmental biology. However, the availability of microinjection into early embryos of this spider has not been reported. We defined the early embryonic stages in A.

Cell migration that orients the dorsoventral axis is coordinated with anteroposterior patterning mediated by Hedgehog signaling in the early spider embryo.

The early embryo of the spider Achaearanea tepidariorum is emerging as a model for the simultaneous study of cell migration and pattern formation. A cell cluster internalized at the center of the radially symmetric germ disc expresses the evolutionarily conserved dorsal signal Decapentaplegic. This cell cluster migrates away from the germ disc center along the basal side of the epithelium to the germ disc rim.

Differing strategies for forming the arthropod body plan: lessons from Dpp, Sog and Delta in the fly Drosophila and spider Achaearanea.

In the insect Drosophila embryo, establishment of maternal transcription factor gradients, rather than cell-cell interactions, is fundamental to patterning the embryonic axes. In contrast, in the chelicerate spider embryo, cell-cell interactions are thought to play a crucial role in the development of the embryonic axes. A grafting experiment by Holm using spider eggs resulted in duplication of the embryonic axes, similar to the Spemann's organizer experiment using amphibian eggs.

Progressive activation of Delta-Notch signaling from around the blastopore is required to set up a functional caudal lobe in the spider Achaearanea tepidariorum.

In the development of most arthropods, the caudal region of the elongating germ band (the growth zone) sequentially produces new segments. Previous work with the spider Cupiennius salei suggested involvement of Delta-Notch signaling in segmentation. Here, we report that, in the spider Achaearanea tepidariorum, the same signaling pathway exerts a different function in the presumptive caudal region before initiation of segmentation.

Axis specification in the spider embryo: dpp is required for radial-to-axial symmetry transformation and sog for ventral patterning.

The mechanism by which Decapentaplegic (Dpp) and its antagonist Short gastrulation (Sog) specify the dorsoventral pattern in Drosophila embryos has been proposed to have a common origin with the mechanism that organizes the body axis in the vertebrate embryo. However, Drosophila Sog makes only minor contributions to the development of ventral structures that hypothetically correspond to the vertebrate dorsum where the axial notochord forms. In this study, we isolated a homologue of the Drosophila sog gene in the spider Achaearanea tepidariorum, and characterized its expression and function.

Diversification of epithelial adherens junctions with independent reductive changes in cadherin form: identification of potential molecular synapomorphies among bilaterians.

The adherens junction (AJ) is the most universal junction found in bilaterian epithelia and may represent one of the earliest types of cell-cell junctions. The adhesion molecules responsible for forming AJs are the classic cadherins (referred to simply as cadherins), whose extracellular domain organization displays marked variety among species examined so far. In this study, we attempted to reconstruct the evolution of cadherin by analyzing new data from several arthropods (two insects, one non-insect hexapod, three crustaceans, and one chelicerate) and previously published sequences for Drosophila melanogaster and other animals.

Expression patterns of a twist-related gene in embryos of the spider Achaearanea tepidariorum reveal divergent aspects of mesoderm development in the fly and spider.

We cloned an Achaearanea tepidariorum (Chelicerata, Arachnida) gene related to Drosophila twist (twi), which encodes a basic helix-loop-helix transcription factor required to specify mesoderm fate in the Drosophila embryo. The cloned spider gene was designated At.twist (At.