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In cell biology a centriole is a cylindrical organelle composed mainly of a protein called tubulin. Centrioles are found in most eukaryotic cells, but are not present in conifers (Pinophyta), flowering plants (angiosperms) and most fungi, and are only present in the male gametes of charophytes, bryophytes, seedless vascular plants, cycads, and Ginkgo. A bound pair of centrioles, surrounded by a highly ordered mass of dense material, called the pericentriolar material (PCM), makes up a structure called a centrosome.
A gamete is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual that produces the larger type of gamete—called an ovum— and a male produces the smaller type—called a sperm. Sperm cells or spermatozoa are small and motile due to the flagellum, a tail-shaped structure that allows the cell to propel and move. In contrast, each egg cell or ovum is relatively large and non-motile. In short a gamete is an egg cell or a sperm. In animals, ova mature in the ovaries of females and sperm develop in the testes of males. During fertilization, a spermatozoon and ovum unite to form a new diploid organism. Gametes carry half the genetic information of an individual, one ploidy of each type, and are created through meiosis, in which a germ cell undergoes two fissions, resulting in the production of four gametes. In biology, the type of gamete an organism produces determines the classification of its sex.
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote.
The cilium is an organelle found on eukaryotic cells in the shape of a slender protuberance that projects from the much larger cell body.
Fertilisation or fertilization, also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Processes such as insemination or pollination which happen before the fusion of gametes are also sometimes informally called fertilisation. The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation.
In cell biology, the centrosome is an organelle that serves as the main microtubule organizing center (MTOC) of the animal cell, as well as a regulator of cell-cycle progression. The centrosome provides structure for the cell. The centrosome is thought to have evolved only in the metazoan lineage of eukaryotic cells. Fungi and plants lack centrosomes and therefore use other structures to organize their microtubules. Although the centrosome has a key role in efficient mitosis in animal cells, it is not essential in certain fly and flatworm species.
Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. This process starts with the mitotic division of the stem cells located close to the basement membrane of the tubules. These cells are called spermatogonial stem cells. The mitotic division of these produces two types of cells. Type A cells replenish the stem cells, and type B cells differentiate into primary spermatocytes. The primary spermatocyte divides meiotically into two secondary spermatocytes; each secondary spermatocyte divides into two equal haploid spermatids by Meiosis II. The spermatids are transformed into spermatozoa (sperm) by the process of spermiogenesis. These develop into mature spermatozoa, also known as sperm cells. Thus, the primary spermatocyte gives rise to two cells, the secondary spermatocytes, and the two secondary spermatocytes by their subdivision produce four spermatozoa and four haploid cells.
An oocyte, oöcyte, ovocyte, or rarely ocyte, 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 germ cells produce a primordial germ cell (PGC), which then undergoes mitosis, forming oogonia. During oogenesis, the oogonia become primary oocytes. An oocyte is a form of genetic material that can be collected for cryoconservation.
A pronucleus is the nucleus of a sperm or an egg cell during the process of fertilization. The sperm cell becomes a pronucleus after the sperm enters the ovum, but before the genetic material of the sperm and egg fuse. Contrary to the sperm cell, the egg cell has a pronucleus once it becomes haploid, and not when the sperm cell arrives. Sperm and egg cells are haploid, meaning they carry half the number of chromosomes of somatic cells, so in humans, haploid cells have 23 chromosomes, while somatic cells have 46 chromosomes. The male and female pronuclei don't fuse, although their genetic material does. Instead, their membranes dissolve, leaving no barriers between the male and female chromosomes. Their chromosomes can then combine and become part of a single diploid nucleus in the resulting embryo, containing a full set of chromosomes.
Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction. Animals produce motile sperm with a tail known as a flagellum, which are known as spermatozoa, while some red algae and fungi produce non-motile sperm cells, known as spermatia. Flowering plants contain non-motile sperm inside pollen, while some more basal plants like ferns and some gymnosperms have motile sperm.
Spermiogenesis is the final stage of spermatogenesis, which sees the maturation of spermatids into mature spermatozoa. The spermatid is a more or less circular cell containing a nucleus, Golgi apparatus, centriole and mitochondria. All these components take part in forming the spermatozoon.
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.
Male infertility refers to a sexually mature male's inability to impregnate a fertile female. In humans it accounts for 40–50% of infertility. It affects approximately 7% of all men. Male infertility is commonly due to deficiencies in the semen, and semen quality is used as a surrogate measure of male fecundity. More recently, advance sperm analyses that examine intracellular sperm components are being developed.
An asymmetric cell division produces two daughter cells with different cellular fates. This is in contrast to symmetric cell divisions which give rise to daughter cells of equivalent fates. Notably, stem cells divide asymmetrically to give rise to two distinct daughter cells: one copy of the original stem cell as well as a second daughter programmed to differentiate into a non-stem cell fate.
Sperm motility describes the ability of sperm to move properly through the female reproductive tract or through water to reach the egg. Sperm motility can also be thought of as the quality, which is a factor in successful conception; sperm that do not "swim" properly will not reach the egg in order to fertilize it. Sperm motility in mammals also facilitates the passage of the sperm through the cumulus oophorus and the zona pellucida, which surround the mammalian oocyte.
Centromere protein J is a protein that in humans is encoded by the CENPJ gene. It is also known as centrosomal P4.1-associated protein (CPAP). During cell division, this protein plays a structural role in the maintenance of centrosome integrity and normal spindle morphology, and it is involved in microtubule disassembly at the centrosome. This protein can function as a transcriptional coactivator in the Stat5 signaling pathway and also as a coactivator of NF-kappaB-mediated transcription, likely via its interaction with the coactivator p300/CREB-binding protein.
Pericentriolar material is a highly structured, dense mass of protein which makes up the part of the animal centrosome that surrounds the two centrioles. The PCM contains proteins responsible for microtubule nucleation and anchoring including γ-tubulin, pericentrin and ninein.
Centrosomal protein of 152 kDa, also known as Cep152, is a protein that in humans is encoded by the CEP152 gene. It is the ortholog of the Drosophila melanogaster gene asterless (asl) and both are required for centriole duplication.
Centrosomes are the major microtubule organizing centers (MTOC) in mammalian cells. Failure of centrosome regulation can cause mistakes in chromosome segregation and is associated with aneuploidy. A centrosome is composed of two orthogonal cylindrical protein assemblies, called centrioles, which are surrounded by a protein dense amorphous cloud of pericentriolar material (PCM). The PCM is essential for nucleation and organization of microtubules. The centrosome cycle is important to ensure that daughter cells receive a centrosome after cell division. As the cell cycle progresses, the centrosome undergoes a series of morphological and functional changes. Initiation of the centrosome cycle occurs early in the cell cycle in order to have two centrosomes by the time mitosis occurs.
Ciliogenesis is defined as the building of the cell's antenna or extracellular fluid mediation mechanism. It includes the assembly and disassembly of the cilia during the cell cycle. Cilia are important organelles of cells and are involved in numerous activities such as cell signaling, processing developmental signals, and directing the flow of fluids such as mucus over and around cells. Due to the importance of these cell processes, defects in ciliogenesis can lead to numerous human diseases related to non-functioning cilia. Ciliogenesis may also play a role in the development of left/right handedness in humans.
References
- 1 2 3 Blachon, S; Cai, X; Roberts, K. A; Yang, K; Polyanovsky, A; Church, A; Avidor-Reiss, T (2009). "A Proximal Centriole-Like Structure is Present in Drosophila Spermatids and Can Serve as a Model to Study Centriole Duplication". Genetics. 182 (1): 133–44. doi:10.1534/genetics.109.101709. PMC 2674812 . PMID 19293139.
- 1 2 Khire, Atul; Jo, Kyoung H; Kong, Dong; Akhshi, Tara; Blachon, Stephanie; Cekic, Anthony R; Hynek, Sarah; Ha, Andrew; Loncarek, Jadranka; Mennella, Vito; Avidor-Reiss, Tomer (2016). "Centriole Remodeling during Spermiogenesis in Drosophila". Current Biology. 26 (23): 3183–3189. doi:10.1016/j.cub.2016.07.006. PMC 5245371 . PMID 28094036.
- ↑ Blachon, Stephanie; Khire, Atul; Avidor-Reiss, Tomer (2014). "The Origin of the Second Centriole in the Zygote of Drosophila melanogaster". Genetics. 197 (1): 199–205. doi:10.1534/genetics.113.160523. PMC 4012480 . PMID 24532732.
- ↑ Fishman, E. L; Jo, Kyoung; Ha, Andrew; Royfman, Rachel; Zinn, Ashtyn; Krishnamurthy, Malathi; Avidor-Reiss, Tomer (2017). "Atypical centrioles are present in Tribolium sperm". Open Biology. 7 (3): 160334. doi:10.1098/rsob.160334. PMC 5376708 . PMID 28298310.
- 1 2 Fishman, Emily L; Jo, Kyoung; Nguyen, Quynh P. H; Kong, Dong; Royfman, Rachel; Cekic, Anthony R; Khanal, Sushil; Miller, Ann L; Simerly, Calvin; Schatten, Gerald; Loncarek, Jadranka; Mennella, Vito; Avidor-Reiss, Tomer (2018). "A novel atypical sperm centriole is functional during human fertilization". Nature Communications. 9 (1): 2210. doi:10.1038/s41467-018-04678-8. PMC 5992222 . PMID 29880810.
- ↑ Khanal, S., M.R. Leung, A. Royfman, E.L. Fishman, B. Saltzman, H. Bloomfield-Gadelha, T. Zeev-Ben-Mordehai, and T. Avidor-Reiss. 2021. A dynamic basal complex modulates mammalian sperm movement. Nat Commun. 12:3808.. https://doi.org/10.1038/s41467-021-24011-0