Dictyate
Encyclopedia
The dictyate or dictyotene is a prolonged resting phase in oogenesis
. It occurs in the stage of meiotic prophase I in ootidogenesis. It starts late in fetal life and is terminated shortly before ovulation
by the LH surge. Thus, although the majority of oocytes are produced in female fetuses before birth, these pre-eggs remain arrested in the Dictyate stage until puberty
commences and the cells complete ootidogenesis.
Translation of mRNA in dictyate is partly explained by molecules binding to sites on the mRNA strain, which results in that initiation factor
s of translation can not bind to that site. Two such molecules, that impedes initiation factors, are CPEB
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 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, and thus translation starts, which contributes to the end of dictyate and further maturation of the oocyte.
Oogenesis
Oogenesis, ovogenesis or oögenesis is the creation of an ovum . It is the female form of gametogenesis. The male equivalent is spermatogenesis...
. It occurs in the stage of meiotic prophase I in ootidogenesis. It starts late in fetal life and is terminated shortly before ovulation
Ovulation
Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...
by the LH surge. Thus, although the majority of oocytes are produced in female fetuses before birth, these pre-eggs remain arrested in the Dictyate stage until puberty
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
commences and the cells complete ootidogenesis.
Translation halt
There are a lot of mRNAs that have been transcribed but not translated during dictyate. 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 factor
Initiation factors are proteins that bind to the small subunit of the ribosome during the initiation of translation, a part of protein biosynthesis.They are divided into three major groups:*Prokaryotic initiation factors*Archaeal initiation factors...
s of translation can not bind to that site. Two such molecules, that impedes initiation factors, are CPEB
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 can also act as a repressor, dependent on its...
and maskin, which bind to CPE
Cytoplasmic polyadenylation element
The cytoplasmic polyadenylation element is a sequence element found in the 3' untranslated region of messenger RNA. Binding of CPE binding protein to this region promotes the extension of the polyadenine tail and, in general, activation of the mRNA for protein translation. Among other functions, a...
(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 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, and thus translation starts, which contributes to the end of dictyate and further maturation of the oocyte.