Establishment of embryonic axes in larvae of the starfish, Asterina pectinifera

Development ◽  
1983 ◽  
Vol 75 (1) ◽  
pp. 87-100
Author(s):  
Tetsuya Kominami
Keyword(s):  
Cleavage Plane ◽  
Anterior Part ◽  
Polar Body ◽  
Cleavage Pattern ◽  
Early Cleavage ◽  
Embryonic Axes ◽  
Cell Stage ◽  
Polar Bodies ◽  
Asterina Pectinifera ◽  
Fertilized Egg

In order to clarify the relationships between the first cleavage plane and the embryonic axes, early cleavage pattern of the fertilized eggs of the starfish, Asterina pectinifera was reexamined . It was ascertained that the polar bodies were formed at the site to which the germinal vesicle had closely located before the initiation of the meiotic division, and that the first cleavage plane passed near this site of polar body formation. While some of the early embryos of this starfish were observed to show various cleavage patterns during early cleavage stage, more than 70% of the embryos developed according to, so to say, the ‘typical’ cleavage pattern. Next, horseradish peroxidase (HRP) was injected into one of the blastomeres of the 2-cellor 8-cell-stage embryos. The embryos were allowed to develop up to either the early gastrula or the early bipinnaria stage and stained to detect the descendants of the blastomere injected with HRP. In early gastrulae still retaining radial symmetry, the activity of HRP injected at the 2-cell stage was found only in one side of the embryo partitioned by one of the symmetrical planes. When one of the four blastomeres lying nearer to the polar bodies at the 8-cell stage was marked with HRP, its descendants constituted one quarter of the anterior part of the gastrula, and descendants of a blastomere opposite the polar bodies were found in the posterior region of the embryo. It was concluded that the animal-vegetal (AV) axis was preexisting in the fertilized egg and that the first cleavage plane contained this primary axis. In early bipinnariae with their dorsoventral (DV) axes already established, the region of activity of the HRP injected at the 2-cell stage was still demarcated by a plane which passed through the AV axis, but the plane of the boundary had no fixed relation to the DV axis. The results indicate that the first cleavage plane does not necessarily correspond to the median plane of the starfish larva, unlike the case in sea-urchin eggs (Hörstadius & Wolsky, 1936). In other words, the DV axis of the starfish embryo is not predetermined in the fertilized egg, and might be established in the course of development through cell-to-cell interactions, while the AV axis is established mainly according to the pre-existing egg polarity.

Centrosome inheritance in starfish zygotes: behaviour and duplicating capacity of the meiotic centrosomes in maturation division

Zygote ◽  
1999 ◽  
Vol 8 (S1) ◽  
pp. S12-S13
Author(s):  
Miwa Tamura ◽  
Shin-ichi Nemoto
Keyword(s):  
Polar Body ◽  
Ionophore A23187 ◽  
Differential Interference Contrast Microscopy ◽  
Centriole Duplication ◽  
Polar Bodies ◽  
Transmission Electron ◽  
Interference Contrast Microscopy ◽  
Almost All ◽  
Artificial Activation ◽  
Asterina Pectinifera

In zygotes of almost all animals, it has been believed that only the sperm centrosome acts as the mitotic spindle poles. As first proposed a century ago by Boveri (1887), this uniparental (paternal) inheritance of the centrosome must depend on the selective loss of the maternal centrosomes. To trace the fate and duplicating capacity of all the maternal centrosomes/centrioles, including those cast off into polar bodies, we used two kinds of procedures: (1) suppression of polar body (PB) extrusion and (2) transplantation of PB centro-somes into artificially activated eggs.Gametes used in this study were from the starfish, Asterina pectinifera. Oocyte maturation was induced with 1-methyladenine (Kanatani, 1969). Suppression of PB extrusion and artificial activation were done according to Washitani-Nemoto et al. (1994). Micromanipulation was performed by the method of Saiki & Hamaguchi (1993). Behaviour of the centrosomes was examined by staining with an antibody against α-tubulin, polarisation and differential interference-contrast microscopy and transmission electron microscopy.In starfish oocytes, no centriole duplication occurs in meiosis II, hence each pole of a meiosis II spindle is formed by the splitting of paired centrioles in the inner centrosome of a meiosis I spindle into singles. Eventually, each of a second PB (PB2) and a mature egg inherits only one centriole from a meiosis II spindle (a PB1 inherits a pair of centrioles). So, either PB2 and the mature egg inherit a single centriole (Fig. 1; cf. Sluder et al., 1989; Kato et al., 1990). When mature eggs were artificially activated with the Ca2+-ionophore A23187, a single monaster was formed.

scholarly journals In vitro aging of porcine oocytes

2011 ◽  
Vol 49 (No. 3) ◽  
pp. 93-98 ◽  
Author(s):  
I. Petrová ◽  
M. Sedmíková ◽  
E. Chmelíková ◽  
D. Švestková ◽  
R. Rajmon
Keyword(s):  
In Vitro Culture ◽  
Polar Body ◽  
Cell Stage ◽  
Subsequent Aging ◽  
Parthenogenetic Activation ◽  
In Vitro Aging ◽  
Polar Bodies ◽  
Porcine Oocyte ◽  
Parthenogenetic Embryos

Porcine oocytes matured in vitro develop in various ways if they are further cultivated. In our studies these oocytes were cultivated for 1 to 5 days (in vitro aging). During the 1st day of aging, most of them remained at the stage of metaphase II (98%). Then many oocytes underwent the spontaneous parthenogenetic activation. The portion of activated oocytes reached its peak after 2 or 3 days of aging in vitro (39 or 45%). The portion of fragmented oocytes peaked at the same time (28%). During subsequent aging in vitro (i.e. day 4 or 5 of aging), the portion of lysed oocytes significantly increased (30 or 37%). The highest portion of spontaneously activated parthenogenetic embryos at a pronuclear stage (35%) was observed during the 2nd day of aging in vitro. These pronuclear embryos had mainly one polar body with two pronuclei (47% of all pronuclear embryos) or two polar bodies with one pronucleus (38% of all pronuclear embryos). During the 3rd and 5th day of in vitro aging, there was a significant increase in the portion of parthenogenetic embryos cleaved to the 2-cell or 3-cell stage. When considering the prolonged in vitro culture of porcine oocyte, only the first day of aging should be taken into account, since beyond this time significant changes, i.e. parthenogenesis, fragmentation or lysis, occurred in oocytes under in vitro conditions.  

Development and Biology of the Larva of Saccoglossus Horsti (Enteropneusta)

1952 ◽  
Vol 236 (639) ◽  
pp. 553-589 ◽  
Keyword(s):  
Anterior Part ◽  
Cell Stage ◽  
Apical Tuft ◽  
Polar Bodies ◽  
The Family ◽  
Planktonic Phase ◽  
Mode Of Life ◽  
Fertilization Membrane ◽  
Mode Of Development ◽  
Dispersal Period

Larvae of Saccoglossus horsti were reared in the laboratory, and their developmental history from the egg to the five gill-slit stage studied. The immature eggs varied from 0.23 to 0.30 mm in length and from 0.15 to 0.22 mm in breadth. They were irregular, opaque, finely granular and creamish grey in colour. They became spherical on maturing. Fertilization resulted in the rapid erection of a fertilization membrane, making the eggs buoyant. Two similar polar bodies were extruded shortly afterwards, marking the plane of the first cleavage which, with the second, was holoblastic and meridional. Subsequent cleavages were different in the animal and vegetative tiers. There was evidence of radial cleavage during the 16- to 32-cell stage. A hollow blastula was formed at the 9th to 10th cleavage stage, and gastrulation by invagination followed. The blastocoele was completely obliterated and a typical archigastrula resulted. This rapidly became uniformly ciliated and developed a telotroch around the closing blastopore. The component cilia of the telotroch imparted a slow rotatory movement to the embryo. Axial elongation and the growth of an apical tuft were accompanied by the formation of a faint annular groove. This groove marked off the definitive proboscis and the anterior part of the collar. Hatching followed 30 to 36 h after fertilization, and the larva became planktonic. During its lecithotrophic existence the larva developed a second annular groove anterior to the first, marking off the definitive proboscis from the anterior region of the collar. No definite phototaxis was detectable. Swimming movements were spasmodic. The larva rotated in a clockwise direction when viewed from the apical tuft. The spiral mode of propulsion and the propelling action of the telotroch is discussed. Settlement occurred some 2 days after hatching. A post-telotrochal adhesive patch was developed just prior to settlement, enabling the larva to adhere tenaciously to the substratum. After settlement further elongation of the main axis occurred, a well-defined proboscis, collar and trunk were rapidly differentiated. Of particular interest is the development of a long, muscular strongly ciliated post-anal tail. A dispersal period of about 6 1 2 to 7 days occurred prior to settlement. The existence of this phase prior to the animal adopting the adult mode of life demands that the mode of development of certain members of the family Harrimanidae be regarded as indirect and comparable in many respects to that known for some of the family Ptychoderidae. The mouth, anus and gill apertures became functional at much the same period, viz., at the onset of the burrowing phase. Remarkable growth movements initiated during the late planktonic phase were accelerated after settlement. This resulted in the translation of the telotroch to a latero-ventral position on the trunk and tail. The behaviour of the tail during the process of ciliary feeding, as well as during the coursing through the burrow, was observed. Ciliary reversal occurred on collar, trunk and tail. This phenomenon is discussed. Special tactile cilia have been described. They occurred on the dorsal and latero-dorsal surfaces of the trunk and tail. There was some evidence of gregariousness. The possibility of this larval habit is briefly considered in relation to the dispersal of the adults in the field. The homologies of the Enteropneusta and the Pterobranchia are discussed in some detail, with particular reference to the tail of the larval Saccoglossus horsti , and the stalk of the genus Cephalodiscus .

scholarly journals ALADIN is Required for the Production of Fertile Mouse Oocytes.

2016 ◽  
Author(s):  
Sara Carvalhal ◽  
Michelle Stevense ◽  
Katrin Koehler ◽  
Ronald Naumann ◽  
Angela Huebner ◽  
...  
Keyword(s):  
Polar Body ◽  
Spindle Assembly ◽  
Cell Periphery ◽  
Cell Stage ◽  
Spindle Positioning ◽  
Asymmetric Cell Divisions ◽  
Cell Divisions ◽  
Polar Bodies ◽  
Polar Body Extrusion

Asymmetric cell divisions depend upon the precise placement of the mitotic spindle. In mammalian oocytes, spindles assemble close to the cell center but chromosome segregation takes place at the cell periphery where half of the chromosomes are expelled into small, non-developing polar bodies at anaphases. By dividing so asymmetrically, most of the cytoplasmic content within the oocyte is preserved, which is critical for successful fertilization and early development. Recently, we determined that the nucleoporin ALADIN participates in spindle assembly in somatic cells, and we have also shown that female mice homozygous deficient for ALADIN are sterile. In this study we show that this protein is involved in specific meiotic stages including meiotic resumption, spindle assembly, and spindle positioning. In the absence of ALADIN, polar body extrusion is impaired in a majority of oocytes due to problems in spindle orientation prior to the first meiotic anaphase. Those few oocytes that can mature far enough to be fertilized in vitro are unable to support embryonic development beyond the two-cell stage. Overall, we find that ALADIN is critical for oocyte maturation and appears to be far more essential for this process than for somatic cell divisions.

scholarly journals Animal and vegetal poles of the mouse egg predict the polarity of the embryonic axis, yet are nonessential for development

Development ◽  
2000 ◽  
Vol 127 (16) ◽  
pp. 3467-3474 ◽  
Author(s):  
M.A. Ciemerych ◽  
D. Mesnard ◽  
M. Zernicka-Goetz
Keyword(s):  
Fluorescent Protein ◽  
Polar Body ◽  
Lineage Tracing ◽  
Embryonic Axes ◽  
Cell Stage ◽  
Adult Mice ◽  
Vegetal Pole ◽  
Mammalian Embryos ◽  
Pole Cells ◽  
Green Fluorescent

Recent studies suggest early (preimplantation) events might be important in the development of polarity in mammalian embryos. We report here lineage tracing experiments with green fluorescent protein showing that cells located either near to or opposite the polar body at the 8-cell stage of the mouse embryo retain their same relative positions in the blastocyst. Thus they come to lie on either end of an axis of symmetry of the blastocyst that has recently been shown to correlate with the anterior-posterior axis of the postimplantation embryo (see R. J. Weber, R. A. Pedersen, F. Wianny, M. J. Evans and M. Zernicka-Goetz (1999). Development 126, 5591–5598). The embryonic axes of the mouse can therefore be related to the position of the polar body at the 8-cell stage, and by implication, to the animal-vegetal axis of the zygote. However, we also show that chimeric embryos constructed from 2-cell stage blastomeres from which the animal or the vegetal poles have been removed can develop into normal blastocysts and become fertile adult mice. This is also true of chimeras composed of animal or vegetal pole cells derived through normal cleavage to the 8-cell stage. We discuss that although polarity of the postimplantation embryo can be traced back to the 8-cell stage and in turn to the organisation of the egg, it is not absolutely fixed by this time.

scholarly journals Role of PB1 Midbody Remnant Creating Tethered Polar Bodies during Meiosis II

Genes ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1394
Author(s):  
Alex McDougall ◽  
Celine Hebras ◽  
Gerard Pruliere ◽  
David Burgess ◽  
Vlad Costache ◽  
...  
Keyword(s):  
Polar Body ◽  
Dynamic Imaging ◽  
Meiotic Spindle ◽  
Left Behind ◽  
Meiotic Chromosomes ◽  
Polar Bodies ◽  
The Future ◽  
Previous Round ◽  
Small Structure ◽  
Fertilized Egg

Polar body (PB) formation is an extreme form of unequal cell division that occurs in oocytes due to the eccentric position of the small meiotic spindle near the oocyte cortex. Prior to PB formation, a chromatin-centered process causes the cortex overlying the meiotic chromosomes to become polarized. This polarized cortical subdomain marks the site where a cortical protrusion or outpocket forms at the oocyte surface creating the future PBs. Using ascidians, we observed that PB1 becomes tethered to the fertilized egg via PB2, indicating that the site of PB1 cytokinesis directed the precise site for PB2 emission. We therefore studied whether the midbody remnant left behind following PB1 emission was involved, together with the egg chromatin, in defining the precise cortical site for PB2 emission. During outpocketing of PB2 in ascidians, we discovered that a small structure around 1 µm in diameter protruded from the cortical outpocket that will form the future PB2, which we define as the “polar corps”. As emission of PB2 progressed, this small polar corps became localized between PB2 and PB1 and appeared to link PB2 to PB1. We tested the hypothesis that this small polar corps on the surface of the forming PB2 outpocket was the midbody remnant from the previous round of PB1 cytokinesis. We had previously discovered that Plk1::Ven labeled midbody remnants in ascidian embryos. We therefore used Plk1::Ven to follow the dynamics of the PB1 midbody remnant during meiosis II. Plk1::Ven strongly labeled the small polar corps that formed on the surface of the cortical outpocket that created PB2. Following emission of PB2, this polar corps was rich in Plk1::Ven and linked PB2 to PB1. By labelling actin (with TRITC-Phalloidin) we also demonstrated that actin accumulates at the midbody remnant and also forms a cortical cap around the midbody remnant in meiosis II that prefigured the precise site of cortical outpocketing during PB2 emission. Phalloidin staining of actin and immunolabelling of anti-phospho aPKC during meiosis II in fertilized eggs that had PB1 removed suggested that the midbody remnant remained within the fertilized egg following emission of PB1. Dynamic imaging of microtubules labelled with Ens::3GFP, MAP7::GFP or EB3::3GFP showed that one pole of the second meiotic spindle was located near the midbody remnant while the other pole rotated away from the cortex during outpocketing. Finally, we report that failure of the second meiotic spindle to rotate can lead to the formation of two cortical outpockets at anaphase II, one above each set of chromatids. It is not known whether the midbody remnant of PB1 is involved in directing the precise location of PB2 since our data are correlative in ascidians. However, a review of the literature indicates that PB1 is tethered to the egg surface via PB2 in several species including members of the cnidarians, lophotrochozoa and echinoids, suggesting that the midbody remnant formed during PB1 emission may be involved in directing the precise site of PB2 emission throughout the invertebrates.

Spontaneous Activation of the Hamster Egg in vivo

1973 ◽  
Vol 31 ◽  
pp. 548-549
Author(s):  
F. J. Longo
Keyword(s):  
Polar Body ◽  
Light And Electron Microscopy ◽  
Microscopic Level ◽  
Estrus Cycle ◽  
Light Microscopic Level ◽  
Cell Stage ◽  
Spontaneous Activation ◽  
Second Polar Body ◽  
Fertilized Egg

Spontaneous activation of the hamster ovum is a normal occurence in oviducal eggs that are not inseminated. Many aspects comprising this process of parthenogenesis mimic events characteristic of fertilization and include for example, the formation of the second polar body and the development of one or two pronuclei. Occasionally the activated egg cleaves to form a two-cell stage. The similarity between the spontaneously activated hamster ovum and the inseminated egg has been previously documented at the light microscopic level of investigation; however, further investigation is warranted for the study of parthenogenesis in mammals provides an opportunity of elucidating developmental mechanisms of the fertilized egg. Accordingly, unfertilized eggs were flushed from the oviducts of hamsters at different intervals during the estrus cycle (6 to 70 hours postovulation), prepared for light and electron microscopy, and compared with fertilized eggs obtained at corresponding periods.

Evolutionary dissociation between cleavage, cell lineage and embryonic axes in sea urchin embryos

Development ◽  
1992 ◽  
Vol 114 (4) ◽  
pp. 931-938 ◽  
Author(s):  
J.J. Henry ◽  
K.M. Klueg ◽  
R.A. Raff
Keyword(s):  
Sea Urchin ◽  
Cleavage Plane ◽  
Cell Lineage ◽  
Frontal Plane ◽  
Individual Species ◽  
Cleavage Pattern ◽  
Embryonic Axes ◽  
Animal Pole ◽  
Dorsoventral Axis ◽  
The Relationship

Using vital dye staining and the microinjection of fluorescent cell lineage-autonomous tracers, the relationship between the first cleavage plane and the prospective larval dorsoventral axis was examined in several sea urchin species, including: Strongylocentrotus purpuratus, S. droebachiensis, Lytechinus pictus, Clypeaster rosaceus, Heliocidaris tuberculata and H. erythrogramma. The results indicate that there is no single relationship between the early cleavage pattern and the dorsoventral axis for all sea urchins; however, specific relationships exist for individual species. In S. purpuratus the first cleavage plane occurs at an angle 45 degrees clockwise with respect to the prospective dorsoventral axis in most cases, as viewed from the animal pole. On the other hand, in S. droebachiensis, L. pictus and H. tuberculata, the first cleavage plane generally corresponds with the plane of bilateral symmetry. There does not appear to be a predominant relationship between the first cleavage plane and the dorsoventral axis in C. rosaceus. In the direct-developing sea urchin H. erythrogramma the first cleavage plane bisects the dorsoventral axis through the frontal plane. Clearly, evolutionary differences have arisen in the relationship between cleavage pattern and developmental axes. Therefore, the mechanism of cell determination is not necessarily tied to any particular pattern of cell cleavage, but to an underlying framework of axial systems resident within sea urchin eggs and embryos.

The establishment of the oral-aboral axis in the ctenophore embryo

Development ◽  
1977 ◽  
Vol 42 (1) ◽  
pp. 237-260
Author(s):  
Gary Freeman
Keyword(s):  
Polar Body ◽  
Causal Role ◽  
Cleavage Furrow ◽  
Cell Stage ◽  
Body Formation ◽  
Cleavage Initiation ◽  
Polar Bodies ◽  
Polar Body Formation ◽  
A Site

In a small percentage of normal embryos and in a higher percentage of embryos centrifuged prior to the first cleavage the positions of the polar bodies and the site of the first cleavage furrow do not coincide. These cases have been used to establish whether polar body formation sites or first cleavage initiation sites correlate best with the oral-aboral axis of the embryo. In all cases when the first cleavage is initiated at a site different from the site where the polar bodies were given off, the pattern of the first four cleavages is normal, the segregation of comb plate potential at these stages is normal, and the larvae that form are normal. The extent to which comb plate potential is localized along the oral-aboral axis of the embryo prior to the first cleavage, during the first cleavage and at the 2-cell stage was also examined. These experiments demonstrate that the oral-aboral axis is established at the time of the first cleavage, that cleavage plays a causal role in setting up the axis, and that comb plate-forming potential begins to be localized in the aboral region of the embryo at this time.

scholarly journals Deletion of Orc4 during oogenesis severely reduces polar body extrusion and blocks zygotic DNA replication

2022 ◽  
Author(s):  
Hieu Nguyen ◽  
Hongwen Wu ◽  
Anna Ung ◽  
Yukiko Yamazaki ◽  
Ben Fogelgren ◽  
...  
Keyword(s):  
Dna Replication ◽  
Dna Synthesis ◽  
Origin Recognition Complex ◽  
Polar Body ◽  
Full Length ◽  
Primary Follicle ◽  
Cell Stage ◽  
Polar Bodies ◽  
Polar Body Extrusion

Abstract Origin Recognition Complex subunit 4 (ORC4) is a DNA binding protein required for DNA replication. During oocyte maturation, after the last oocyte DNA replication step and before zygotic DNA replication, the oocyte undergoes two meiotic cell divisions in which half the DNA is ejected in much smaller polar bodies. We previously demonstrated that ORC4 forms a cytoplasmic cage around the DNA that is ejected in both polar body extrusion (PBE) events. Here, we used ZP3 activated Cre to delete exon 7 of Orc4 during oogenesis to test how it affected both predicted functions of ORC4: its recently discovered role in PBE and its well-known role in DNA synthesis. Orc4 deletion severely reduced PBE. Almost half of Orc4-depleted GV oocytes cultured in vitro arrested before anaphase I (48%), and only 25% produced normal first polar bodies. This supports the role of ORC4 in PBE and suggests that transcription of the full length Orc4 during oogenesis is required for efficient PBE. Orc4 deletion also abolished zygotic DNA synthesis. A reduced number of Orc4-depleted oocytes developed to the MII stage and after activation these oocytes arrested at the 2-cell stage, without undergoing DNA synthesis. This confirms that transcription of full length Orc4 after the primary follicle stage is required for zygotic DNA replication. The data also suggest that MII oocytes do not have a replication licensing checkpoint since cytokinesis progressed without DNA synthesis. Together the data confirm that oocyte ORC4 is important for both PBE and zygotic DNA synthesis.

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