Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 4 complete abstracts (711 words), 10 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
An early non-mammalian embryo that follows the morula stage. A blastula resembles a hollow ball with the layer of cells surrounding a fluid-filled cavity (blastocele). The layer of cells is called blastoderm.
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: Blastulae.
Where it fits in the MeSH classification
- Broader topics
- Embryo, Nonmammalian
Related concepts
- Morula
- Blastoderm
Research landscape
PubMed indexes 549 records tagged with the MeSH heading “Blastula” (counts retrieved 2026-10-31). 65 of them (11.8%) were published from 2020 onward, and the busiest period so far is 2010-2019 with 244 records.
Reviews account for 27 records (4.9%) and meta-analyses for 0. Randomized controlled trials number 1 (0.2%) as a share of all records on the topic. Randomized trials make up only a small share of this literature, so much of what is known comes from laboratory, observational or descriptive work.
Show the data
| Period | Records |
|---|---|
| through 1999 | 11 |
| 2000-2009 | 229 |
| 2010-2019 | 244 |
| 2020 onward | 65 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 27 | 4.9% |
| Meta-analyses | 0 | 0.0% |
| Randomized controlled trials | 1 | 0.2% |
Method: PubMed query "Blastula"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.
Reading the evidence in anatomy and physiology
Anatomy describes how body structures are built and physiology describes how they normally work, so most findings here are descriptive or mechanistic rather than evidence about treatment. Much of what is known comes from dissection, imaging, tissue studies and experiments in animals, and measurements in healthy volunteers can differ from those in people with disease or at different ages. Normal ranges vary between individuals and populations. Check whether a result was measured in people or in another species, the age and health of the participants, and the method used.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
| Study / authors | Year | Source label / design | Europe PMC citations | Licence / source |
|---|---|---|---|---|
| A global change in RNA polymerase II pausing during the Drosophila midblastula transition | 2013 | Research article Design not recorded in structured metadata | 143 | cc by PMID 23951546 · DOI · PMC3743134 |
| High-resolution analysis of gene activity during the Xenopus mid-blastula transition | 2014 | Research article Design not recorded in structured metadata | 83 | cc by PMID 24757007 · DOI · PMC3994770 |
| Rif1 prolongs the embryonic S phase at the Drosophila mid-blastula transition | 2018 | Research article Design not recorded in structured metadata | 75 | cc by PMID 29746464 · DOI · PMC5963817 |
| Changes in repair pathways of radiation-induced DNA double-strand breaks at the midblastula transition in Xenopus embryo | 2024 | Research article Design not recorded in structured metadata | 4 | cc by PMID 38648785 · DOI · PMC11115444 |
A global change in RNA polymerase II pausing during the Drosophila midblastula transition [1]
Abstract reading summary — source excerpts
- Opening excerpt
- Massive zygotic transcription begins in many organisms during the midblastula transition when the cell cycle of the dividing egg slows down.
- Closing excerpt
- 001.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (149 words)
Massive zygotic transcription begins in many organisms during the midblastula transition when the cell cycle of the dividing egg slows down. A few genes are transcribed before this stage but how this differential activation is accomplished is still an open question. We have performed ChIP-seq experiments on tightly staged Drosophila embryos and show that massive recruitment of RNA polymerase II (Pol II) with widespread pausing occurs de novo during the midblastula transition. However, ∼100 genes are strongly occupied by Pol II before this timepoint and most of them do not show Pol II pausing, consistent with a requirement for rapid transcription during the fast nuclear cycles. This global change in Pol II pausing correlates with distinct core promoter elements and associates a TATA-enriched promoter with the rapid early transcription. This suggests that promoters are differentially used during the zygotic genome activation, presumably because they have distinct dynamic properties. DOI:http://dx.doi.org/10.7554/eLife.00861.001.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 23951546 · DOI · PMC3743134
High-resolution analysis of gene activity during the Xenopus mid-blastula transition [2]
Abstract reading summary — source excerpts
- Opening excerpt
- The Xenopus mid-blastula transition (MBT) marks the onset of large-scale zygotic transcription, as well as an increase in cell cycle length and a loss of synchronous cell divisions.
- Closing excerpt
- Together, our high-resolution time series and experimental studies have yielded a deeper understanding of the temporal organisation of gene regulatory networks in the early Xenopus embryo.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (202 words)
The Xenopus mid-blastula transition (MBT) marks the onset of large-scale zygotic transcription, as well as an increase in cell cycle length and a loss of synchronous cell divisions. Little is known about what triggers the activation of transcription or how newly expressed genes interact with each other. Here, we use high-resolution expression profiling to identify three waves of gene activity: a post-fertilisation wave involving polyadenylation of maternal transcripts; a broad wave of zygotic transcription detectable as early as the seventh cleavage and extending beyond the MBT at the twelfth cleavage; and a shorter post-MBT wave of transcription that becomes apparent as development proceeds. Our studies have also allowed us to define a set of maternal mRNAs that are deadenylated shortly after fertilisation, and are likely to be degraded thereafter. Experimental analysis indicates that the polyadenylation of maternal transcripts is necessary for the establishment of proper levels of zygotic transcription at the MBT, and that genes activated in the second wave of expression, including Brachyury and Mixer, contribute to the regulation of genes expressed in the third. Together, our high-resolution time series and experimental studies have yielded a deeper understanding of the temporal organisation of gene regulatory networks in the early Xenopus embryo.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 24757007 · DOI · PMC3994770
Rif1 prolongs the embryonic S phase at the Drosophila mid-blastula transition [3]
Abstract reading summary — source excerpts
- Opening excerpt
- In preparation for dramatic morphogenetic events of gastrulation, rapid embryonic cell cycles slow at the mid-blastula transition (MBT).
- Closing excerpt
- In addition, we describe how onset of late replication fits into the progressive maturation of heterochromatin during development.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (186 words)
In preparation for dramatic morphogenetic events of gastrulation, rapid embryonic cell cycles slow at the mid-blastula transition (MBT). In Drosophila melanogaster embryos, down-regulation of cyclin-dependent kinase 1 (Cdk1) activity initiates this slowing by delaying replication of heterochromatic satellite sequences and extending S phase. We found that Cdk1 activity inhibited the chromatin association of Rap1 interacting factor 1 (Rif1), a candidate repressor of replication. Furthermore, Rif1 bound selectively to satellite sequences following Cdk1 down-regulation at the MBT. In the next S phase, Rif1 dissociated from different satellites in an orderly schedule that anticipated their replication. Rif1 lacking potential phosphorylation sites failed to dissociate and dominantly prevented completion of replication. Loss of Rif1 in mutant embryos shortened the post-MBT S phase and rescued embryonic cell cycles disrupted by depletion of the S phase-promoting kinase, cell division cycle 7 (Cdc7). Our work shows that Rif1 and S phase kinases compose a replication timer controlling first the developmental onset of late replication and then the precise schedule of replication within S phase. In addition, we describe how onset of late replication fits into the progressive maturation of heterochromatin during development.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 29746464 · DOI · PMC5963817
Changes in repair pathways of radiation-induced DNA double-strand breaks at the midblastula transition in Xenopus embryo [4]
Abstract reading summary — source excerpts
- Opening excerpt
- Ionizing radiation (IR) causes DNA damage, particularly DNA double-strand breaks (DSBs), which have significant implications for genome stability.
- Closing excerpt
- These results suggest that the MBT plays a crucial role in altering DSB repair mechanisms, thereby influencing the IR sensitivity of developing embryos.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (174 words)
Ionizing radiation (IR) causes DNA damage, particularly DNA double-strand breaks (DSBs), which have significant implications for genome stability. The major pathways of repairing DSBs are homologous recombination (HR) and nonhomologous end joining (NHEJ). However, the repair mechanism of IR-induced DSBs in embryos is not well understood, despite extensive research in somatic cells. The externally developing aquatic organism, Xenopus tropicalis, serves as a valuable model for studying embryo development. A significant increase in zygotic transcription occurs at the midblastula transition (MBT), resulting in a longer cell cycle and asynchronous cell divisions. This study examines the impact of X-ray irradiation on Xenopus embryos before and after the MBT. The findings reveal a heightened X-ray sensitivity in embryos prior to the MBT, indicating a distinct shift in the DNA repair pathway during embryo development. Importantly, we show a transition in the dominant DSB repair pathway from NHEJ to HR before and after the MBT. These results suggest that the MBT plays a crucial role in altering DSB repair mechanisms, thereby influencing the IR sensitivity of developing embryos.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 38648785 · DOI · PMC11115444
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article From egg to gastrula: how the cell cycle is remodeled during the Drosophila mid-blastula transition [5]
- Research article Analysis of chromosome segregation during preimplantation genetic diagnosis in both male and female translocation heterozygotes [6]
- Research article Ca2+ signaling and early embryonic patterning during the blastula and gastrula periods of zebrafish and Xenopus development [7]
- Research article Life at the edge: epiboly and involution in the zebrafish [8]
- Research article The Caenorhabditis elegans Q neuroblasts: A powerful system to study cell migration at single-cell resolution in vivo [9]
- Research article The guts of endoderm formation [10]
References
- Chen K, Johnston J, Shao W, Meier S, Staber C, Zeitlinger J. A global change in RNA polymerase II pausing during the Drosophila midblastula transition. . 2013. PMID 23951546 · DOI · PMC3743134
- Collart C, Owens ND, Bhaw-Rosun L, Cooper B, De Domenico E, Patrushev I, et al.. High-resolution analysis of gene activity during the Xenopus mid-blastula transition. . 2014. PMID 24757007 · DOI · PMC3994770
- Seller CA, O'Farrell PH. Rif1 prolongs the embryonic S phase at the Drosophila mid-blastula transition. . 2018. PMID 29746464 · DOI · PMC5963817
- Morozumi R, Shimizu N, Tamura K, Nakamura M, Suzuki A, Ishiniwa H, et al.. Changes in repair pathways of radiation-induced DNA double-strand breaks at the midblastula transition in Xenopus embryo. . 2024. PMID 38648785 · DOI · PMC11115444
- Farrell JA, O'Farrell PH. From egg to gastrula: how the cell cycle is remodeled during the Drosophila mid-blastula transition. Annu Rev Genet. 2014. PMID 25195504 · DOI · PMC4484755
- Munné S. Analysis of chromosome segregation during preimplantation genetic diagnosis in both male and female translocation heterozygotes. Cytogenet Genome Res. 2005. PMID 16192709 · DOI
- Webb SE, Miller AL. Ca2+ signaling and early embryonic patterning during the blastula and gastrula periods of zebrafish and Xenopus development. Biochim Biophys Acta. 2006. PMID 16962186 · DOI
- Kane D, Adams R. Life at the edge: epiboly and involution in the zebrafish. Results Probl Cell Differ. 2002. PMID 12353473 · DOI
- Rella L, Fernandes Póvoa EE, Korswagen HC. The Caenorhabditis elegans Q neuroblasts: A powerful system to study cell migration at single-cell resolution in vivo. Genesis. 2016. PMID 26934462 · DOI
- Warga RM, Stainier DY. The guts of endoderm formation. Results Probl Cell Differ. 2002. PMID 12353482 · DOI
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-10-31.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.