Folliculogenesis-specific basic helix-loop-helix, also known as factor in the germline alpha (FIGalpha) or transcription factor FIGa, is a protein that in humans is encoded by the FIGLA gene. [5] [6] The FIGLA gene is a germ cell-specific transcription factor preferentially expressed in oocytes that can be found on human chromosome 2p13.3.
This gene encodes a protein that functions in postnatal oocyte-specific gene expression. The protein is a basic helix-loop-helix transcription factor that regulates multiple oocyte-specific genes, including genes involved in folliculogenesis, oocyte differentiation, and those that encode the zona pellucida. [5] FIGLA is related to the zona pellucida genes ZP1, ZP2, and ZP3.
Mutation in the FIGLA gene are associated with premature ovarian failure. [7] Premature ovarian failure is a genetic disorder that leads to hypergonadotropic ovarian failure and infertility. It is believed that premature ovarian failure in humans is caused by FIGLA haploninsuffciency, which disrupts the formation of the primordial follicles. [7] [8] This was observed in FIGLA mice knockouts which had diminished follicular endowment and accelerated oocyte loss throughout their reproductive life span. [7] [8] Women with mutations in their FIGLA were shown to have a form of premature ovarian failure. [7] [8] As well as the failure to form primordial follicles, knockout mice also lacked zona pellucida genes Zp1, Zp2, and ZP3 expression. [8]
The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary found on each side of the body. The ovaries also secrete hormones that play a role in the menstrual cycle and fertility. The ovary progresses through many stages beginning in the prenatal period through menopause. It is also an endocrine gland because of the various hormones that it secretes.
An ovarian follicle is a roughly spheroid cellular aggregation set found in the ovaries. It secretes hormones that influence stages of the menstrual cycle. At the time of puberty, women have approximately 200,000 to 300,000 follicles, each with the potential to release an egg cell (ovum) at ovulation for fertilization. These eggs are developed once every menstrual cycle with around 450–500 being ovulated during a woman's reproductive lifetime.
The zona pellucida is a specialized extracellular matrix that surrounds the plasma membrane of mammalian oocytes. It is a vital constitutive part of the oocyte. The zona pellucida first appears in unilaminar primary oocytes. It is secreted by both the oocyte and the ovarian follicles. The zona pellucida is surrounded by the corona radiata. The corona is composed of cells that care for the egg when it is emitted from the ovary.
A granulosa cell or follicular cell is a somatic cell of the sex cord that is closely associated with the developing female gamete in the ovary of mammals.
Anti-Müllerian hormone (AMH), also known as Müllerian-inhibiting hormone (MIH), is a glycoprotein hormone structurally related to inhibin and activin from the transforming growth factor beta superfamily, whose key roles are in growth differentiation and folliculogenesis. In humans, it is encoded by the AMH gene, on chromosome 19p13.3, while its receptor is encoded by the AMHR2 gene on chromosome 12.
In biology, folliculogenesis is the maturation of the ovarian follicle, a densely packed shell of somatic cells that contains an immature oocyte. Folliculogenesis describes the progression of a number of small primordial follicles into large preovulatory follicles that occurs in part during the menstrual cycle.
Growth/differentiation factor 9 is a protein that in humans is encoded by the GDF9 gene.
Human fertilization is the union of a human egg and sperm, occurring in the ampulla of the fallopian tube. The result of this union leads to the production of a zygote cell, or fertilized egg, initiating prenatal development. Scientists discovered the dynamics of human fertilization in the nineteenth century.
Follicular atresia refers to the process in which a follicle fails to develop, thus preventing it from ovulating and releasing an egg. It is a normal, naturally occurring progression that occurs as mammalian ovaries age. Approximately 1% of mammalian follicles in ovaries undergo ovulation and the remaining 99% of follicles go through follicular atresia as they cycle through the growth phases. In summary, follicular atresia is a process that leads to the follicular loss and loss of oocytes, and any disturbance or loss of functionality of this process can lead to many other conditions.
Bone morphogenetic protein 15 (BMP-15) is a protein that in humans is encoded by the BMP15 gene. It is involved in folliculogenesis, the process in which primordial follicles develop into pre-ovulatory follicles.
Zona pellucida sperm-binding protein 3, also known as zona pellucida glycoprotein 3 (Zp-3) or the sperm receptor, is a ZP module-containing protein that in humans is encoded by the ZP3 gene. ZP3 is the receptor in the zona pellucida which binds sperm at the beginning of fertilization.
An antral follicle, also known as Graafian follicle and tertiary follicle, is an ovarian follicle during a certain latter stage of folliculogenesis.
In vitro maturation (IVM) is the technique of letting the contents of ovarian follicles and the oocytes inside mature in vitro. It can be offered to women with infertility problems, combined with In Vitro Fertilization (IVF), offering women pregnancy without ovarian stimulation.
Zona pellucida sperm-binding protein 2 is a protein that in humans is encoded by the ZP2 gene.
Zona pellucida sperm-binding protein 4, ZP-4 or avilesine, named after its discoverer Manuel Avilés Sánchez is a protein that in humans is encoded by the ZP4 gene.
Homeobox protein NOBOX, also known as newborn ovary homeobox protein, is a protein that in humans is encoded by the NOBOX gene. The official symbol (NOBOX) and the official full name are maintained by the HGNC. The NOBOX gene is conserved in chimpanzee, Rhesus monkey, cow, mouse, and rat. There are 175 organisms that have orthologs with human gene NOBOX. It is capable of regulating other genes that are important in the development of follicles. Follicles do not develop and oocytes decrease in its absence which lead to infertility.
Primordial follicle initiation and development varies by species; in the canine primordial follicle formation occurs 17–54 days post birth. At 17 days, primordial follicles, each of consists of a small oocyte and a single layer of flattened pre-granulosa cells, can first be observed in the cortical layer of the ovary. The follicles begin to proliferate, and are abundant by day 22. Even though primordial follicles will continue to form, between days 33 and 54 increasing numbers begin to degenerate, along with a decrease in ovarian cortical width. By day 36, primordial follicles occupy a narrow peripheral region of the ovarian cortex, while the rest of the cortical tissue is composed of degenerate primordial follicles, anovular cords and epitheloid cells.
Ovarian follicle activation can be defined as primordial follicles in the ovary moving from a quiescent (inactive) to a growing phase. The primordial follicle in the ovary is what makes up the “pool” of follicles that will be induced to enter growth and developmental changes that change them into pre-ovulatory follicles, ready to be released during ovulation. The process of development from a primordial follicle to a pre-ovulatory follicle is called folliculogenesis.
TATA-box binding protein like 2 is a protein that in humans is encoded by the TBPL2 gene. The TBPL2 protein is also known as TBP-related factor 3 (TRF3) and TATA binding protein 2 (TBP2). The protein was independently discovered in three laboratories as a vertebrate-specific family member of TATA-binding protein (TBP). Orthologs have been identified in mouse, frog and fish. Whereas the TBP gene is found in all eukaryotes, TBPL2 is only found in vertebrates.
Oocytes are immature egg cells that develop to maturity within a follicle in the ovary. Oocyte abnormalities can occur due to several factors, including premature ovarian insufficiency (POI), other maturation abnormalities, maternal ageing, and mitochondrial abnormalities.
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