Use features like bookmarks, note taking and highlighting while reading vertebrate development. The transition from maternal to zygotic control of the developing embryo requires not only the erasure of maternal rna and proteins, but the activation of zygotic transcription. We find that the zebrafish embryo undergoes at least 10 rounds of cell division in the absence of condensed chromatin ultrastructure. Maternalzygotic transition maternal control of development in. Production of maternalzygotic mutant zebrafish by germline replacement article pdf available in proceedings of the national academy of sciences 9923. Differential transcript isoform usage pre and post. Importantly, we also describe a novel biological function of tbp. The egg contains stored maternal genetic material mrna which controls embryo development until the onset of mzt. The reprogramming of parental dna, combined with the correct timing of gene expression from the zygotic dna requires major chromatin and transcriptional remodelling. Buy the maternal to zygotic transition, volume 1 current topics in developmental biology on free shipping on qualified orders. In the previous chapter, we discussed the known maternal proteins required for early cleavages and initial cell divisions of the fertilized vertebrate embryo. Maternal eomesodermin regulates zygotic nodal gene.
Dynamic rnaprotein interactions underlie the zebrafish maternal. By using a morpholino oligonucleotide that blocks primordial germ cell pgc development, we generate embryos devoid of endogenous pgcs to serve as hosts for the transplantation of germ cells derived from homozygous mutant donors. Considering the diverse and temporarily restricted roles of dazl in germ cell development and oocytetozygote transition 34, 35, it is tempting to speculate that the maternal and zygotic isoforms may be responsible for two biological processes. The maternal to zygotic transition regulates genomewide. Developmental changes are first driven by transcripts and proteins provided by the gametes, with a gradual involvement of zygotic gene products that are transcribed after zga. Giraldez,1,2 yuichiro mishima,3 jason rihel,1,2 russell j.
Transcript stability can be influenced by cis elements and trans factors, but how these inputs are integrated to determine the overall mrna stability is unclear. Zygotic genome activation during the maternal to zygotic transition miler t. Maternal ybx1 mybx1 mutant embryos fail to undergo normal cleavage and the maternal to zygotic. Moreover, the production of maternal zygotic mutants for oneeyedpinhead or lostafin have revealed previously unexpected roles for genes initially identified by zygotic mutant phenotype. Proteomics analysis of early developmental stages of zebrafish. Our group uses zebrafish to study transcriptional and epigenetic control of key transitions during embryogenesis. Degradation of maternal messenger rna mrna, which is required to activate zygotic genome transcription in maternal to zygotic transition, is controlled by the 3. Mishima and tomari show that codon usage determines the stability of maternal mrnas during the maternal to zygotic transition in zebrafish. Maternal to zygotic transition an overview sciencedirect topics. Pdf production of maternalzygotic mutant zebrafish by. This maternaltozygotic transition mzt has been extensively studied in model organisms. Maternal to zygotic transition mzt, also known as embryonic genome activation is the stage in embryonic development during which development comes under the exclusive control of the zygotic genome rather than the maternal egg genome.
The maternal to zygotic transition revisited nadine l. Zebrafish mir430 promotes deadenylation and clearance of. The maternaltozygotic transition, volume 1 1st edition. To understand the molecular mechanisms controlling this maternal to zygotic transition, it is important to distinguish between the maternal and zygotic transcriptomes during this period. Cytoplasmic polyadenylationmediated translational control. During the maternal to zygotic transition, transcription of zygotic genes commences, and developmental control starts to be regulated by zygotic gene products.
Zebrafish mir430 promotes deadenylation and clearance of maternal mrnas antonio j. This requires both zygotic genome activation zga and degradation of maternal products. In the 19501960s this concept was developed to a large extent due to. During the cleavage stages of early development there is no transcription and the cell cycles, which lack gap phases, are rapid. Maternal mrna degradation by tut4 and tut7 in the zebrafish maternal to zygotic transition during the maternal to zygotic transition mzt, maternal rnas are actively degraded and replaced by newlysynthesized zygotic transcripts in a highly coordinated manner. The temporally regulated degradation of maternal mrnas at and after the mbt is part of a general mechanism to regulate the maternal to zygotic transition and is required for normal development of the zebrafish embryo giraldez et al, 2006. The degradation of these maternal mrnas is critical for promoting the maternaltozygotic transition of developmental programs, although the underlying mechanisms are poorly understood in vertebrates. We are interested in the roles of nodal, fgf and wnt signaling pathways in germ layer formaton and patterning of zebrafish embryo. We reveal that tbp plays an important role in the degradation of a specific subset of maternal mrnas during late blastulationearly gastrulation, which involves targets of the mir.
Download it once and read it on your kindle device, pc, phones or tablets. Giraldez1,2, 1department of genetics, yale university school of medicine, new haven, ct 06510 2yale stem cell center, yale university school of medicine, new haven, ct 06520 abstract embryogenesis depends on a highly coordinated cascade of genetically encoded events. Zebrafish embryos also show a similar response to cleavage stage dna damage ikegami et al. Hence, tbp acts as a specific regulator of the key processes underlying the transition from maternal to zygotic regulation of embryogenesis. In their recent development paper, yuko sato, hiroshi kimura and collegues applied used fabs to analyse the relationship between chromatin and transcription in zebrafish zygotic. Rna 5methylcytosine facilitates the maternaltozygotic transition. The maternal to zygotic transition mzt involves both the clearance of maternal rnas and the initiation of transcription of the embryonic genome and is a tightly regulated process.
Lipshitz2, abstract the development of animal embryos is initially directed by maternal gene products. In some species, decay of maternal transcripts may be facilitated by the activity of micrornas. Production of maternalzygotic mutant zebrafish by germ. The maternaltozygotic transition mzt defines a developmental phase during which the embryo progressively emancipates itself from a developmental control relying largely on maternal information. Maternal factors in zebrafish development american association. During the maternaltozygotic transition mzt, transcriptionally silent embryos rely on posttranscriptional regulation of maternal mrnas until. The shift to zygotic control of transcription around the mbt is also referred to as the maternal zygotic transition. Even after the initiation of zygotic gene expression, perduring maternal products. It remains unclear which maternal factors activate zygotic expression of nodal genes in the ventrolateral blastodermal margin of the zebrafish blastulas. Here we use exome sequencing and rnaseq to achieve such discrimination and in doing so have identified the first zygotic genes to be expressed in the embryo.
Morpholino knockdown of ybx1 also results in mzt loss and epiboly failure, suggesting the postfertilization requirement of ybx1. Mzt is often thought to be synonymous with midblastula transition mbt, but these processes are, in fact, distinct. The maternaltozygotic transition, volume 1 current. Genes mediating nodal, fgf and wnt signals in zebrafish embryo have been identified by wholemount in situ hybridization screening, yeast two hybrid system and microarray assay, and their functions are being studied using various biochemical, genetic and molecular. In this study, we show that loss of maternal eomesodermin a eomesa, a tbox transcription factor, impairs zygotic expression of the nodal genes ndr1 and ndr2 as well as mesodermal and. The tatabinding protein regulates maternal mrna degradation and differential zygotic transcription in zebrafish marco ferg, remo sanges, jochen gehrig, janos kiss, matthias bauer, agnes lovas, monika szabo, lixin yang, uwe straehle, michael j. Dynamic rnaprotein interactions underlie the zebrafish maternalto. This codonmediated mrna decay is dependent on the ccr4not deadenylase complex and is promoted by short 3. Maternal to zygotic control advances in experimental medicine and biology book 953 kindle edition by francisco pelegri, michael danilchik, ann sutherland. The earliest events in zebrafish development are driven by maternal factors deposited in the egg during oogenesis that become activated upon fertilization and initiate cascades of events that drive early development. With intricate modulation of genetic and epigenetic regulators, the maternal to zygotic transition is concomitant with a dramatic reprogramming of gene expression and a series of cellular and molecular events, including degradation of maternal factors, dna demethylation, changes of histone modification and eventual zygotic genome activation. For example, the zygotic expression of mir430 in zebrafish embryos is. New insights into the maternal to zygotic transition. We showed here that tbp is required for a zygotic developmental programme, which.
During the maternaltozygotic transition mzt, transcriptionally silent embryos rely on posttranscriptional regulation of maternal mrnas until zygotic genome activation zga. Then, during the maternal to zygotic transition mzt, developmental control is handed to the zygotic genome. Schier1,2 micrornas mirnas comprise 1 to 3% of all vertebrate genes, but their in vivo functions and. This can also be called the maternal to zygotic transition. Various protein posttranslational modifications have been identified during the mzt. During oogenesis a maternal factor is localized to the vegetal pole of the oocyte that is a determinant of dorsal tissues. The mrna degradation machinery active during maternal to zygotic transition. New insights into the maternal to zygotic transition development. Activation of the maternaltozygotic transition mzt in. Maternal ybx1 mybx1 mutant embryos fail to undergo normal cleavage and the maternal to zygotic transition mzt. In zebrafish, selective degradation of maternal mrnas, rather than wholesale turnover of maternal mrnas, occurs at the midblastula transition mbt or upon zga. The maternal to zygotic transition mzt is essential for the developmental control handed from maternal products to newly synthesized zygotic genome in the earliest stages of embryogenesis, including maternal component mrnas and proteins degradation and zygotic genome activation zga. Liang et al identified a protein, zelda zld, as a key activator of the early zygotic genome, which was the first identified zygotic genomeactivator in any organism 1.
By analyzing zebrafish ybx1 mutants with a null allele, we demonstrate an essential role of maternal ybx1 in repressing global translation in oocytes and embryos. These results have demonstrated that, as in drosophila, maternally derived rnas and proteins can partially mask the effects of zygotic mutations in zebrafish. Valeria yartseva, phd senior scientific researcher. The maternal to zygotic transition mzt is one of the most profound and tightly orchestrated processes during the early life of embryos, yet factors that shape the temporal pattern of vertebrate. This is a universal transition in animal development when the embryo initiates the transcription of its genome zygotic phase. During drosophila development, the embryo undergoes. During the maternal to zygotic transition mzt, thousands of maternal transcripts are regulated upon fertilization and genome activation. Activation of zygotic gene transcription edit at this stage, the zygote starts producing its own mrnas that are made from its own dna, and no longer uses the maternal mrna. Dynamic rnaprotein interactions underlie the zebrafish. C in zebrafish embryos, transcripts that degrade have been assigned to three. Here, we demonstrate that genomewide establishment of heterochromatin is triggered by the maternal to zygotic transition mzt during zebrafish embryogenesis.
Grocock,4 stijn van dongen,4 kunio inoue,3 anton j. Posttranslational regulation of the maternaltozygotic. First we look at how transcription is activated in the embryo during the maternal to zygotic transition. The maternal to zygotic transition is still poorly understood. Genomescale gametic demethylation and remethylation occurs after fertilization, during blastula stages, but how zga relates to promoter dna methylation states is unknown. In the zebrafish blastula, the general delay in zygotic gene activity is followed by. Zygotic genome activation zga occurs at the midblastula transition mbt in zebrafish and is a period of extensive chromatin remodeling. Posttranscriptional regulation is crucial to shape gene expression. In the giraldez lab we study the regulatory code that governs gene expression during vertebrate development after fertilization. In drosophila, the transcription factor zelda specifically binds to promoters of the earliest zygotic genes and primes them for activation.
Rnabisseq revealed a dynamic rna m5c landscape during zebrafish embryogenesis. The maternaltozygotic transition mzt defines a developmental phase during which the embryo progressively emancipates. At a certain time point, the transition of developmental. Maternal and zygotic control of zebrafish dorsoventral. Abstract the idea of a major developmental transition that includes the activation of the embryonic genome has a long history. Identification of the zebrafish maternal and paternal. The maternal to zygotic transition is not a single event, but rather, a series of events. The maternal to zygotic transition mzt spans a period of early embryonic development starting just after fertilisation. Maternal to zygotic control brings together chapters from experts in various disciplines describing the latest advances related to this important developmental transition. We report a generally applicable strategy for transferring zygotic lethal mutations through the zebrafish germ line. A posttranscriptional regulatory code for mrna stability. Dynamic rnaprotein interactions underlie the zebrafish maternal to zygotic transition article pdf available in genome research 277 april 2017 with 1 reads how we measure reads.
Maternal to zygotic transition mzt is the stage in embryonic development during which development comes under the exclusive control of the zygotic genome. This maternaltozygotic transition mzt has been extensively studied in model. The book provides critical information on how maternal gene products program the initial development of all animal and plant embryos, then undergoing a series of events, termed the maternal to zygotic transition, during which maternal products are cleared and zygotic genome activation takes over the developmental control. Here, we characterized maternal mrna degradation pathways in zebrafish using a transcriptome analysis and systematic reporter assays. In drosophila, the mzt is known to occur hours postfertilization hpf of the zygote, however, how this process is temporally regulated was unclear until recent papers published by liang et al 1 and nien et al 2.
Maternal ybx1 safeguards zebrafish oocyte maturation and. For instance, mir430 is essential for mrna degradation in zebra fish oocytes 94. The preceding stage of development is driven by maternally deposited mrnas, and the genome is silent maternal phase. Loss of maternal ybx1 leads to impaired oocyte maturation and egg activation. Each chapter is a synthesis of knowledge relevant to all vertebrates, with details on.
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