The dictyate or dictyotene
[Medical Physiology, Boron & Boulpaep, , Elsevier Saunders 2005. Updated edition. 1300 pages.] is a prolonged resting phase in
oogenesis
Oogenesis, ovogenesis, or oögenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated in the embryonic stage.
...
. It occurs in the stage of
meiotic
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately res ...
prophase I
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately res ...
in
ootidogenesis
Oogenesis, ovogenesis, or oögenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated in the embryonic stage.
O ...
. It starts late in fetal life
[ and is terminated shortly before ]ovulation
Ovulation is the release of eggs from the ovaries. In women, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells. After ovulation, during the luteal phase, the egg will be available to be fertilize ...
by the LH surge. Thus, although the majority of oocytes
An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female g ...
are produced in female fetuses before birth, these pre-eggs remain arrested in the dictyate stage until puberty
Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a ...
commences and the cells complete ootidogenesis
Oogenesis, ovogenesis, or oögenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated in the embryonic stage.
O ...
.
In both mouse and human, oocyte DNA of older individuals has substantially more double-strand breaks than that of younger individuals.[{{cite journal , vauthors=Titus S, Li F, Stobezki R, Akula K, Unsal E, Jeong K, Dickler M, Robson M, Moy F, Goswami S, Oktay K , title=Impairment of BRCA1-related DNA double-strand break repair leads to ovarian aging in mice and humans , journal=Sci Transl Med , volume=5 , issue=172 , pages=172ra21 , year=2013 , pmid=23408054 , doi=10.1126/scitranslmed.3004925 , pmc=5130338]
The dictyate appears to be an adaptation for efficiently removing damages in germ line DNA by homologous recombination
Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may ...
al repair.[Stringer JM, Winship A, Zerafa N, Wakefield M, Hutt K. Oocytes can efficiently repair DNA double-strand breaks to restore genetic integrity and protect offspring health. Proc Natl Acad Sci U S A. 2020 May 26;117(21):11513-11522. doi: 10.1073/pnas.2001124117. Epub 2020 May 7. PMID 32381741; PMCID: PMC7260990.] Prophase arrested oocytes have a high capability for efficient repair of DNA damages.[ DNA repair capability appears to be a key quality control mechanism in the female germ line and a critical determinant of ]fertility
Fertility is the capability to produce offspring through reproduction following the onset of sexual maturity. The fertility rate is the average number of children born by a female during her lifetime and is quantified demographically. Ferti ...
.[
]
Translation halt
There are a lot of mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein.
mRNA is created during the ...
s that have been transcribed but not translated
Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...
during dictyate.[Molecule.org - Maskin Is a CPEB-Associated Factor that Transiently Interacts with eIF-4E]
Barbara Stebbins-Boaz,1 Quiping Cao,1 Cornelia H de Moor,1 Raul Mendez,1 and Joel D Richter1 Shortly before ovulation, the oocyte of interest activates these mRNA strains.
Biochemistry mechanism
Translation of mRNA in dictyate is partly explained by molecules binding to sites on the mRNA strain, which results in that initiation factor Initiation factors are proteins that bind to the small subunit of the ribosome during the initiation of translation, a part of protein biosynthesis.
Initiation factors can interact with repressors to slow down or prevent translation. They have t ...
s of translation can not bind to that site. Two such molecules, that impedes initiation factors, are CPEB
CPEB, or cytoplasmic polyadenylation element binding protein, is a highly conserved RNA-binding protein that promotes the elongation of the polyadenine tail of messenger RNA. CPEB most commonly activates the target RNA for translation, but c ...
and ''maskin'', which bind to CPE (cytoplasmic polyadenylation element). When these two molecules remain together, then maskin binds the initiation factor eIF-4E,[ and thus eIF4E can no longer interact with the other initiation factors][Lodish 2008, p.351] and no translation occurs. On the other hand, dissolution of the CPEB/maskin complex leads to eIF-4E binding to the initiation factor eIF-4G Eukaryotic initiation factors (eIFs) are proteins or protein complexes involved in the initiation phase of eukaryotic translation. These proteins help stabilize the formation of ribosomal preinitiation complexes around the start codon and are an im ...
,[ and thus translation starts, which contributes to the end of dictyate and further maturation of the oocyte.
]
See also
*Oogenesis
Oogenesis, ovogenesis, or oögenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated in the embryonic stage.
...
*Immature ovum
An immature ovum is a cell that goes through the process of oogenesis to become an ovum. It can be an oogonium, an oocyte, or an ootid. An oocyte, in turn, can be either primary or secondary, depending on how far it has come in its process of me ...
*Embryo
An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
*Zygote
A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism.
In multicell ...
References
Developmental biology