Sperm motility

Last updated
Video of human sperm cells moving under a microscope

Sperm motility describes the ability of sperm to move properly through the female reproductive tract (internal fertilization) or through water (external fertilization) 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 (a layer of cells) and the zona pellucida (a layer of extracellular matrix), which surround the mammalian oocyte.

Contents

In the wood mouse Apodemus sylvaticus, sperms aggregate in 'trains' that are better able to fertilize eggs because they are more capable of navigating the viscous environment of the female reproductive tract. The trains move in a sinusoidal motion.

Sperm motility is also affected by certain factors released by eggs. [1]

Sperm movement is activated by changes in intracellular ion concentration. [2] The changes in ion concentration that provoke motility are different among species. In marine invertebrates and sea urchins, the rise in pH to about 7.2–7.6 activates ATPase which leads to a decrease in intracellular potassium, and thus induces membrane hyperpolarization. As a result, sperm movement is activated. [3] The change in cell volume which alters intracellular ion concentration can also contribute to the activation of sperm motility. In some mammals, sperm motility is activated by increase in pH, calcium ion and cAMP, yet it is suppressed by low pH in the epididymis.

The tail of the sperm - the flagellum - confers motility upon the sperm, and has three principal components:

  1. a central skeleton constructed of 11 microtubules collectively termed the axoneme and similar to the equivalent structure found in cilia
  2. a thin cell membrane covering the axoneme
  3. mitochondria arranged spirally around the axoneme at the middle-piece,

Back and forth movement of the tail results from a rhythmical longitudinal sliding motion between the anterior and posterior tubules that make up the axoneme. The energy for this process is supplied by ATP produced by mitochondria. The velocity of a sperm in fluid medium is usually 1–4 mm/min. This allows the sperm to move towards an ovum in order to fertilize it.

The axoneme is attached at its base to a centriole known as the distal centriole and acts as a basal body. [4] In most animals, this distal centriole act as a shock absorber preventing the microtubules filaments from moving at the axoneme base. In contrast, in mammals, the distal centriole evolved an atypical structure, known as the atypical distal centriole. [5] The atypical centriole is made of splayed microtubules organized into left and right sides. During sperm movement, the two sides move relative to each other, helping to shape the waveform of the sperm tail. [5]

In mammals, spermatozoa mature functionally through a process which is known as capacitation. When spermatozoa reach the isthmic oviduct, their motility has been reported to be reduced as they attach to epithelium. Near the time of ovulation, hyperactivation occurs. During this process, the flagella move with high curvature and long wavelength. [6] Hyperactivation is initiated by extracellular calcium; however, the factors that regulate calcium level is unknown. [7]

Without technological intervention, a non-motile or abnormally-motile sperm is not going to fertilize. Therefore, the fraction of a sperm population that is motile is widely used as a measure of semen quality . Insufficient sperm motility is a common cause of subfertility or infertility. Several measures are available to improve sperm quality.

Axoneme movement

Sperm motility is dependent on several metabolic pathways and regulatory mechanisms.

The axonemal bend movement is based on the active sliding of axonemal doublet microtubules by the molecular motor dynein, which is divided into an outer and an inner arm. Outer and inner arm plays different roles in the production and regulation of flagellar motility: the outer arm increase the beat frequency, the inner arm is involved in the propulsion and propagation of flagellar bending. The bending of the flagellum is due to subsequent cycles of dynein arm attachment, generation of force and detachment on the B subunit. The binding of the axoneme is the result of the presence of a resistance to the microtubule sliding generated by dynein.

Dyneins on the two sides of the central pair apparatus are regulated in an opposite way by an activation/disactivation game made by the radialspoke-central pair apparatus, that regulates the flagellar bending. Sperm motility is regulated by several pathways and the most important are the Calcium pathway and the PKA pathway. This pathwaysinvolve ions, adenylyl cyclase, cAMP, membrane channels and phosphorylations.

The first event is the activation of a Na+/HCO3 − (NBC) co-transporter and the regulation of HCO3 − /Cl− by SLC26 transporters, that bring to an increase in HCO3 − levels.

The second event is the activation of an Na+/H+ exchanger and of the proton channel Hv-1, that leads to an increase in pH levels.

These increase in HCO3 − and pH levels bring to the activation of the CatSper channel, a sperm membrane specific calcium channel. CatSperm can be activated also by progesterone and albumine. CatSper, once activated, opens and let free calcium entrance inside the cell, with a global increase in calcium intracellular levels.

Together, the increase in HCO3 − , pH and calcium leads to the activation of a soluble adenylyl cyclase (SAC or SACY), that increases the production of cAMP and brings to the activation of PKA, a protein kinase that phosphorylates several tyrosine kinases and leads to a phosphorylation cascade that ends with the phosphorylation of the axonemal dynein and the start of flagellar movement. [8]

Sperm DNA damage

Sperm DNA damage is common in infertile men. [9] About 31% of men with sperm motility defects have high levels of sperm DNA fragmentation. [10]

Sperm Motility and Age

Sperm motility increases from puberty through one's mid-thirties. Research shows that from the age of 36 onwards, sperm motility decreases from 40% Grade A & B to 31% in one's 50s. The effects of aging on semen quality is summarized below based on a study of 1,219 subjects: [11]

Age group (years)Number of subjects (n)Motility (% Grade A+B)

[Min-Max]

21-285747.5 ± 25.4

[0-88]

29-3545048.1 ± 30.4

[0-95]

36-4253240.0 ± 27.1

[0-83]

43-4916533.1 ± 25.1

[0-84]

50-601531.3 ± 23.9

[0-59]

Classifications of motility

  1. Straight moving,
  2. Zig-zag moving,
  3. Vibrating,
  4. Non-motile

Related Research Articles

<span class="mw-page-title-main">Centriole</span> Organelle in eukaryotic cells that produces cilia and organizes the mitotic spindle

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.

<span class="mw-page-title-main">Spermatozoon</span> Motile sperm cell

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.

<span class="mw-page-title-main">Flagellum</span> Cellular appendage functioning as locomotive or sensory organelle

A flagellum is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are known as flagellates.

<span class="mw-page-title-main">Cilium</span> Organelle found on eukaryotic cells

The cilium, is a membrane-bound organelle found on most types of eukaryotic cell. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projection that extends from the surface of the much larger cell body. Eukaryotic flagella found on sperm cells and many protozoans have a similar structure to motile cilia that enables swimming through liquids; they are longer than cilia and have a different undulating motion.

<span class="mw-page-title-main">Fertilisation</span> Union of gametes of opposite sexes during the process of sexual reproduction to form a zygote

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. While processes such as insemination or pollination which happen before the fusion of gametes are also sometimes informally referred to as fertilisation, these are technically separate processes. 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.

The evolution of flagella is of great interest to biologists because the three known varieties of flagella – each represent a sophisticated cellular structure that requires the interaction of many different systems.

<span class="mw-page-title-main">Dynein</span> Class of enzymes

Dyneins are a family of cytoskeletal motor proteins that move along microtubules in cells. They convert the chemical energy stored in ATP to mechanical work. Dynein transports various cellular cargos, provides forces and displacements important in mitosis, and drives the beat of eukaryotic cilia and flagella. All of these functions rely on dynein's ability to move towards the minus-end of the microtubules, known as retrograde transport; thus, they are called "minus-end directed motors". In contrast, most kinesin motor proteins move toward the microtubules' plus-end, in what is called anterograde transport.

Capacitation is the penultimate step in the maturation of mammalian spermatozoa and is required to render them competent to fertilize an oocyte. This step is a biochemical event; the sperm move normally and look mature prior to capacitation. In vivo, capacitation occurs after ejaculation, when the spermatozoa leave the vagina and enter the upper female reproductive tract. The uterus aids in the steps of capacitation by secreting sterol-binding albumin, lipoproteins, and proteolytic and glycosidasic enzymes such as heparin.

<span class="mw-page-title-main">Axoneme</span>

An axoneme, also called an axial filament is the microtubule-based cytoskeletal structure that forms the core of a cilium or flagellum. Cilia and flagella are found on many cells, organisms, and microorganisms, to provide motility. The axoneme serves as the "skeleton" of these organelles, both giving support to the structure and, in some cases, the ability to bend. Though distinctions of function and length may be made between cilia and flagella, the internal structure of the axoneme is common to both.

<span class="mw-page-title-main">Sperm</span> Male reproductive cell in anisogamous forms of sexual reproduction

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.

<span class="mw-page-title-main">Spermiogenesis</span> Final stage of spermatogenesis, involving spermatid maturation

Spermiogenesis is the final stage of spermatogenesis, during which the spermatids develop into mature spermatozoa. At the beginning of the stage, the spermatid is a more or less circular cell containing a nucleus, Golgi apparatus, centriole and mitochondria; by the end of the process, it has radically transformed into an elongated spermatozoon, complete with a head, midpiece, and tail.

The cation channels of sperm also known as Catsper channels or CatSper, are ion channels that are related to the two-pore channels and distantly related to TRP channels. The four members of this family form voltage-gated Ca2+ channels that seem to be specific to sperm. As sperm encounter the more alkaline environment of the female reproductive tract, CatSper channels become activated by the altered ion concentration. These channels are required for proper fertilization. The study of these channels has been slow because they do not traffic to the cell membrane in many heterologous systems.

Tektins are cytoskeletal proteins found in cilia and flagella as structural components of outer doublet microtubules. They are also present in centrioles and basal bodies. They are polymeric in nature, and form filaments.

<span class="mw-page-title-main">Centrin</span> Family of calcium-binding phosphoproteins

Centrins, also known as caltractins, are a family of calcium-binding phosphoproteins found in the centrosome of eukaryotes. Centrins are small calcium binding proteins that are ubiquitous centrosome components. There are about 350 “signature” proteins that are unique to eukaryotic cells but have no significant homology to proteins in archaea and bacteria. They are a type of protein that is essential and present in almost all eukaryotic cells and are found in the centrioles and pericentriolar lattice. Human centrin genes are CETN1, CETN2 and CETN3.

<span class="mw-page-title-main">DNAI1</span> Protein-coding gene in the species Homo sapiens

Dynein axonemal intermediate chain 1 is a protein that in humans is encoded by the DNAI1 gene.

Oocyteactivation is a series of processes that occur in the oocyte during fertilization.

In biology, solenocytes are elongated, flagellated cells commonly found in lower invertebrates, such as flatworms, as well as in chordates and several other animal species. In terms of function, solenocytes play a significant role in the excretory systems of their host organism(s). For example, the lancelets, also referred to as amphioxus, utilize solenocytic protonephridia to perform excretion. In addition to excretion, these cells contribute to ion regulation and osmoregulation. With this in mind, solenocytes form subtypes of protonephridium and are often compared to another specialized excretory cell type, i.e., flame cells. Solenocytes have flagella, while flame cells are generally ciliated.

The proximal centriole-like or PCL is an atypical type of centriole found in the sperm cells of insects. The PCL name is due to some similarity to the Proximal centriole found in Vertebrates sperm and the hypothesis that the two structures are homologous. The PCL is an atypical type of centriole because it does not have microtubules, a defining feature of centrioles. However, the PCL is a type of centriole for several reasons. (1) the PCL formation is dependent upon the same genetic pathway that mediates the initiation of centriole formation. (2) The PCL is composed of centriolar proteins. (3) After fertilization, the sperm PCL function like a centriole. The PCL recruits pericentriolar material (PCM) forming a centrosome that acts as a microtubule-organizing center (MTOC). The PCL also serves as a platform to form a typical centriole in the zygote, as expected from a centriole. Also, the PCL is essential to form one of the two spindle poles of the dividing zygote.

<span class="mw-page-title-main">DNAH1</span> Protein-coding gene in the species Homo sapiens

Dynein axonemal heavy chain 1 is a protein that in humans is encoded by the DNAH1 gene.

References

  1. ↑ Quill, A. T., Garbers, L. D. (2002). "Sperm Motility Activation and Chemoattraction". In Daniel M. Hardy (ed.). Fertilization. California: Academic press. p. 29. ISBN   978-0-12-311629-1.{{cite book}}: CS1 maint: multiple names: authors list (link)
  2. ↑ Jensen, Martin Blomberg (March 2014). "Vitamin D and male reproduction". Nature Reviews Endocrinology. 10 (3): 175–186. doi:10.1038/nrendo.2013.262. PMID   24419359. S2CID   32394600.
  3. ↑ Darszon, Alberto; Labarca, Pedro; Nishigaki, Takuya; Espinosa, Felipe (1 April 1999). "Ion Channels in Sperm Physiology". Physiological Reviews. 79 (2): 481–510. doi:10.1152/physrev.1999.79.2.481. PMID   10221988. S2CID   30768971.
  4. ↑ Avidor-Reiss, Tomer; Carr, Alexa; Fishman, Emily Lillian (December 2020). "The sperm centrioles". Molecular and Cellular Endocrinology. 518: 110987. doi:10.1016/j.mce.2020.110987. PMC   7606549 . PMID   32810575.
  5. 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 (December 2018). "A novel atypical sperm centriole is functional during human fertilization". Nature Communications. 9 (1): 2210. Bibcode:2018NatCo...9.2210F. doi:10.1038/s41467-018-04678-8. PMC   5992222 . PMID   29880810.
  6. ↑ Mortimer, D; Aitken, Rj; Mortimer, St; Pacey, Aa (1995). "Workshop report: clinical CASA--the quest for consensus". Reproduction, Fertility and Development. 7 (4): 951–959. doi:10.1071/RD9950951. PMID   8711226.
  7. ↑ Yanagimachi, R. (1994). "Mammalian fertilization". In Knobil, E.; Neill, J. D. (eds.). The Physiology of Reproduction. New York: Raven Press. pp. 189–317.[ ISBN missing ]
  8. ↑ Sun, Xiang-hong; Zhu, Ying-ying; Wang, Lin; Liu, Hong-ling; Ling, Yong; Li, Zong-li; Sun, Li-bo (December 2017). "The Catsper channel and its roles in male fertility: a systematic review". Reproductive Biology and Endocrinology. 15 (1): 65. doi: 10.1186/s12958-017-0281-2 . PMC   5558725 . PMID   28810916.
  9. ↑ Simon, Luke; Lutton, Deborah; McManus, Joanne; Lewis, Sheena E.M. (February 2011). "Sperm DNA damage measured by the alkaline Comet assay as an independent predictor of male infertility and in vitro fertilization success". Fertility and Sterility. 95 (2): 652–657. doi: 10.1016/j.fertnstert.2010.08.019 . PMID   20864101.
  10. ↑ Belloc, Stephanie; Benkhalifa, Moncef; Cohen-Bacrie, Martine; Dalleac, Alain; Chahine, Hikmat; Amar, Edouard; Zini, Armand (May 2014). "Which isolated sperm abnormality is most related to sperm DNA damage in men presenting for infertility evaluation". Journal of Assisted Reproduction and Genetics. 31 (5): 527–532. doi:10.1007/s10815-014-0194-3. PMC   4016368 . PMID   24566945.
  11. ↑ Kumar, M.D., Naina; Singh, M.D., Amit K; Choudhari, M.D., Ajay R (August 2017). "Impact of age on semen parameters in male partners of infertile couples in a rural tertiary care center of central India: A cross-sectional study". International Journal of Reprodroductive Biomedicine. 15 (8): 497–502.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.