The mid-developmental transition and the evolution of animal body plans
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ABSTRACT:
PROVIDER: PRJNA287810 | ENA |
REPOSITORIES: ENA
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Project description:Animals are grouped into ~35 'phyla' based upon the notion of distinct body plans. Morphological and molecular analyses have revealed that a stage in the middle of development--known as the phylotypic period--is conserved among species within some phyla. Although these analyses provide evidence for their existence, phyla have also been criticized as lacking an objective definition, and consequently based on arbitrary groupings of animals. Here we compare the developmental transcriptomes of ten species, each annotated to a different phylum, with a wide range of life histories and embryonic forms. We find that in all ten species, development comprises the coupling of early and late phases of conserved gene expression. These phases are linked by a divergent 'mid-developmental transition' that uses species-specific suites of signalling pathways and transcription factors. This mid-developmental transition overlaps with the phylotypic period that has been defined previously for three of the ten phyla, suggesting that transcriptional circuits and signalling mechanisms active during this transition are crucial for defining the phyletic body plan and that the mid-developmental transition may be used to define phylotypic periods in other phyla. Placing these observations alongside the reported conservation of mid-development within phyla, we propose that a phylum may be defined as a collection of species whose gene expression at the mid-developmental transition is both highly conserved among them, yet divergent relative to other species.
| S-EPMC4817236 | biostudies-literature
Project description:This SuperSeries is composed of the SubSeries listed below.
2016-02-18 | GSE70185 | GEO
Project description:Evolutionary theory assumes that genetic variation is uniform and gradual in nature, yet morphological and gene expression studies have revealed that different life-stages exhibit distinct levels of cross-species conservation. In particular, a stage in mid-embryogenesis is highly conserved across species of the same phylum, suggesting that this stage is subject to developmental constraints, either by increased purifying selection or by a strong mutational bias. An alternative explanation, however, holds that the same ‘hourglass’ pattern of variation may result from increased positive selection at the earlier and later stages of development. To distinguish between these scenarios, we examined gene expression variation in a population of the nematode C. elegans using an experimental design that eliminated the influence of positive selection. By measuring gene expression for all genes throughout development in twenty strains, we found that variations were dramatically uneven throughout development, with a significant depletion during mid-embryogenesis. In particular, the family of homeodomain transcription factors, whose expression generally coincides with mid-embryogenesis, evolved under high constraint. Our data further shows that genes responsible for the integration of germ layers during morphogenesis are the most constrained class of genes. Together, these results provide the first evidence for developmental constraints as the mechanism underlying the hourglass model of animal evolution. Understanding the pattern and mechanism of developmental constraints provides a framework to understand how evolutionary processes have interacted with embryogenesis and led to the diversity of animal life on earth.
2017-04-04 | GSE87528 | GEO
Project description:Sox31 is a member of the zebrafish SoxB1 subfamily, and its expression can be detected both pre- and post-MBT. To distinguish the function of its maternal and zygotic transcripts, a splice blocking morpholino (Sb MO) was designed to interfere with the processing of new, zygotically synthesised mRNAs without interfering with mRNAs of maternal origin. Developmental arrest was observed in Sb MO which could not bypass MBT. Mid-Blastula Transition (MBT) functions as a time window for zygotic genome activation and maternal mRNA degradation. To uncover whether the “zygotic up” and “maternal down” event during MBT is retarded in Sb morphants, we performed microarray experiment at the end of MBT (about 4.3 hours post fertilication/4.3 hpf) to compare mRNAs from Sb morphants and control embryos.
2011-10-13 | GSE32914 | GEO
Project description:Nascent transcriptome of Xenopus laevis embryos at mid-blastula transition (MBT) stages
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Project description:In mammals, a key transition in spermatogenesis is the exit from spermatogonial differentiation and mitotic proliferation and the entry into spermatocyte differentiation and meiosis. Although several genes that regulate this transition have been identified, how it is controlled and coordinated remains poorly understood. Here we examine the role in male gametogenesis of the Doublesex-related gene Dmrt6 (Dmrtb1) and find that Dmrt6 plays a critical role in directing germ cells through the mitotic to meiotic germ cell transition. DMRT6 protein is expressed in late mitotic spermatogonia. In mice of the C57BL/6J strain a null mutation in Dmrt6 disrupts spermatogonial differentiation, causing expression in inappropriate cell types of spermatogonial differentiation factors including SOHLH1, SOHLH2 and DMRT1 and the meiotic initiation factor STRA8 and causing most late spermatogonia to undergo apoptosis. In mice of the 129Sv background, most Dmrt6 mutant spermatogonia can complete differentiation and enter meiosis, but they show defects in chromosome pairing, establishment of the XY body, and processing of recombination foci, and mainly arrest in mid-pachynema. mRNA profiling of Dmrt6 mutant testes together with DMRT6 ChIP-seq suggest that DMRT6 represses genes involved in spermatogonial differentiation and activates genes required for meiotic prophase. Our results indicate that Dmrt6 plays a key role in coordinating the transition in gametogenic programs from spermatogonial differentiation and mitosis to spermatocyte development and meiosis. Six samples for RNA-Seq with three biological replicates in each group. Two samples for ChIP-Seq (one input and one ChIP).
2014-10-31 | E-GEOD-60440 | biostudies-arrayexpress
Project description:Gradual evolution of cell cycle regulation by cyclin-dependant kinases during the transition to animal multicellularity
| PRJNA592365 | ENA
Project description:In mammals, a key transition in spermatogenesis is the exit from spermatogonial differentiation and mitotic proliferation and the entry into spermatocyte differentiation and meiosis. Although several genes that regulate this transition have been identified, how it is controlled and coordinated remains poorly understood. Here we examine the role in male gametogenesis of the Doublesex-related gene Dmrt6 (Dmrtb1) and find that Dmrt6 plays a critical role in directing germ cells through the mitotic to meiotic germ cell transition. DMRT6 protein is expressed in late mitotic spermatogonia. In mice of the C57BL/6J strain a null mutation in Dmrt6 disrupts spermatogonial differentiation, causing expression in inappropriate cell types of spermatogonial differentiation factors including SOHLH1, SOHLH2 and DMRT1 and the meiotic initiation factor STRA8 and causing most late spermatogonia to undergo apoptosis. In mice of the 129Sv background, most Dmrt6 mutant spermatogonia can complete differentiation and enter meiosis, but they show defects in chromosome pairing, establishment of the XY body, and processing of recombination foci, and mainly arrest in mid-pachynema. mRNA profiling of Dmrt6 mutant testes together with DMRT6 ChIP-seq suggest that DMRT6 represses genes involved in spermatogonial differentiation and activates genes required for meiotic prophase. Our results indicate that Dmrt6 plays a key role in coordinating the transition in gametogenic programs from spermatogonial differentiation and mitosis to spermatocyte development and meiosis.
2014-10-31 | GSE60440 | GEO
Project description:Sox31 is a member of the zebrafish SoxB1 subfamily, and its expression can be detected both pre- and post-MBT. To distinguish the function of its maternal and zygotic transcripts, a splice blocking morpholino (Sb MO) was designed to interfere with the processing of new, zygotically synthesised mRNAs without interfering with mRNAs of maternal origin. Developmental arrest was observed in Sb MO which could not bypass MBT. Mid-Blastula Transition (MBT) functions as a time window for zygotic genome activation and maternal mRNA degradation. To uncover whether the “zygotic up” and “maternal down” event during MBT is retarded in Sb morphants, we performed microarray experiment at the end of MBT (about 4.3 hours post fertilication/4.3 hpf) to compare mRNAs from Sb morphants and control embryos. In one experiment, three flocks of zebrafish eggs were injected with the Sox19b morpholino immediately after fertilization, while another three control populations were injected with placebo. At 4.3 hpf, these six flocks of embryos were sent for gene expression profiling with six Affymetrix Zebrafish Genome Arrays. In another experiment, we compared two wildtype embryo samples at 4h (post-MBT) against two wildtype samples at 2.5 h (pre-MBT).
2011-10-12 | E-GEOD-32914 | biostudies-arrayexpress
Project description:To validate that EU-RNA imaging provides a direct readout of wide-spread zygotic transcription, we sought to identify the nascent transcriptome using RNA-seq. We micoinjected 5-ethynyl uridine (EU) into 1-cell Xenopus embryos, isolated total RNA from embryos at mid-blastula transition (MBT), biotinylated EU-RNA and purified it to generate cDNA libraries for sequencing. Total RNA from normal embyros were used as control. We found over 25,000 nascent genes in this EU-RNA dataset at mid-ZGA. The nascent transcriptome dataset captures nearly 90% of the transcripts present in the whole-embryo dataset and with similar or better read-depth, indicating that our EU-RNA imaging is truly representative of wide-spread zygotic transcription. Furthermore, of the known zygotic genes that are most highly induced at MBT, we detected all of them and at much higher levels than in the whole-embryo dataset. These results show that our labeling captures the nascent zygotic transcriptome. We found ~ 4-fold higher sensitivity for nascent transcripts in the EU-RNA dataset compared to the whole embryo dataset, and as excepted we did not detect thousands of maternal-only transcripts in the nascent dataset. Together, these results suggest that EU-labeling provides a visual readout of bona fide nascent zygotic transcripts.
2019-05-31 | GSE131962 | GEO