November 22, 2023 | Jerry Bergman

More Details on Sperm Design Published

Yet more experimental research documents
intelligent design of sperm cells

 

by Jerry Bergman, PhD

Part II: Sperm Design vs Evolution

To fully detail what is known about the once-thought simple cell called ‘sperm’ would require a book the size of a door stop.

One recent example is a six-volume set of almost 4,000 pages covering sperm and related areas.[1] On the subject of sperm competition for fertilization alone, a 354-page book has been published.[2] In addition to my last post,[3] other new research has added even more evidence of design of sperm.

Ed. comment: Every sexually reproducing organism, whether a plant, butterfly, dinosaur, turtle, bird or lion, required the union of two gametes: a sperm (“seed”) with an egg. Sperm cells are of particular interest because they have to move toward the egg. Sperm cells in flowering plants grow pollen tubes that extend down to the ovules. Most animal sperm cells are equipped with whip-like flagella to swim to the egg. As Dr Bergman explained in his previous article, animal sperm cells—though among the smallest of eukaryotic cells—are far more complex than previously thought. This three-part series evaluates recently-published research detailing the complexity.

Chemotaxis

One recent analysis further detailed how sperm reaches the egg without getting lost in its precarious journey. The key is chemo-attractants, chemical signals released by the egg that not only direct the sperm’s path, but also activate the previous passive sperm. These signals are sent by the egg and bind to receptors on the sperm’s surface.

A diagram of the activation of sperm from dormant to activated as shown in the second illustration. From David Drew. “Sperm’s secret voltage switch: Scientists unlock the mystery of motility,” 25 Oct 2023.

The binding triggers a series of events that begins with sperm’s movement swimming towards the egg.[4] Furthermore, metazoan (tissue- and organ-based organism) sperm mobility is “directed by a highly conserved signaling cascade in which sperm motility is stimulated by the pH-dependent activation of the cAMP-producing enzyme sAC.” One critical player is the protein “SLC9C1.”[5] This protein is part of a

highly sophisticated exchange system. It swaps protons from inside the cell for sodium ions from the outside, temporarily creating a less acidic environment within the sperm. This change in the internal environment triggers increased sperm motility… The activation of SLC9C1 is driven by a change in voltage that occurs when chemo-attractants attach to the sperm. To accomplish this, SLC9C1 uses a unique feature called a voltage-sensing domain (VSD). Typically, VSD domains are associated with voltage-gated ion channels. But in the case of SLC9C1, it’s something truly exceptional in the realm of transporters… The VSD domain responds to the change in voltage by pushing its rod like S4 helix inwards. This clears the way for ion exchange by SLC9C1, ultimately initiating sperm motility.”[6]

Illustration from Yew, Hyunku, et al. “Structure and electromechanical coupling of a voltage-gated Na+/H+ exchanger.” Nature 623:193–201, 25 October 2023.

Professor Drew adds that

Transporters work very differently than channels and, as such, the VSD is coupled to the sperm protein in a way that we have just never seen before, or even imagined. It’s exciting to see how nature has done this and perhaps, in the future, we can learn from this to make synthetic proteins that can be turned-on by voltage or develop novel male contraceptives that work by blocking this protein.[7]

A diagram of the activation of sperm from dormant to activated as shown in the second illustration. From David Drew. “Sperm’s secret voltage switch: Scientists unlock the mystery of motility.” https://www.su.se/english/news/sperm-s-secret-voltage-switch-scientists-unlock-the-mystery-of-motility-1.685891, 25 October 2023.

Analysis of the SLC9C1 System

The SLC9C1 system is an excellent example of both excellent design and irreducible complexity. The system is described as “highly conserved” in all metazoan life-forms. Metazoan life-forms include all animals composed of cells differentiated into tissues and organs, plus (in most cases) a digestive cavity lined with specialized cells. It included all animals that reproduce sexually, including insects, birds, fish, amphibians, reptiles, mammals and primates, including humans).

Evolutionarily “conserved” means that the same design of the protein exists in all metazoans from the most-primitive to the most-advanced, in the latter case namely humans. The same design exists usually because this design is the only, or the most-effective design possible, given size and other constraints. In other words, it is both well-designed and irreducibly complex. As is obvious from the quotes by Professor Drew, it is a very complex system involving a voltage-sensing domain that “is coupled to the sperm protein in a way that we have just never seen before, or even imagined.”[8]

This well-designed and irreducibly complex system, the researchers claim, evolved (by chance?) and, as Drew exclaims, it is “exciting to see how nature has” created this. His statement is not an explanation of its origins because reproduction cannot occur in metazoans until this system has evolved, a subject he hand waves away by describing it as “how nature has” created it. No evidence of evolution was admitted because the SLC9C1 system was described in the most-primitive animal as the same in the most-advanced life-forms. A diagram of the system (shown below), as published in the Nature article, illustrates the complexity of the SLC9C1 system:

Mitochondrial Streamlining

Yet another complex system used to maximize the efficiency of sperm travel by removing both dysfunctional and excess mitochondria in the sperm. The previously described mechanism expels excess healthy mitochondria in membrane-bound structures called mitophers.[9]  The research on the roundworm Caenorhabditis elegans indicated that this fine-tuning exists in all sexually reproducing metazoan life-forms. This free-living transparent nematode is a favorite research organism for many reasons. These include the fact that many C. elegans genes have functional counterparts in humans which makes it an extremely useful model for human diseases.

Another research program involved further understanding the process of mitochondrial export into the extracellular space. This process is a fundamental cellular mechanism involved in diverse physiological activities including discarding damaged mitochondria.[10] Called mitopherogenesis, it is a form of mitochondria-specific exocytosis, a process by which the contents of a cell vacuole are released to the cell exterior through a fusion of the vacuole membrane with the cell membrane. This process regulates sperm mitochondrial quantity and fertility. This is yet another example of a well-designed irreducibly complex system that is ‘evolutionarily conserved’.

Exocytosis. At the bottom, a vesicle encloses the mitochondria that will be expelled. The vesicle then unites with the cell membrane wall, opens up, and expels the material picked up from inside the cell into the extracellular fluid. Lastly, the vesicle membrane then becomes part of the cell membrane. From Wikimedia Commons.

Summary

The three new mechanisms detailed in this review further support the conclusion that the so-called ‘simple’ sperm cells are far more complex than assumed only a few years ago. These discoveries also eloquently illustrate well-designed, irreducibly complex systems that are evolutionarily conserved. These systems, as far as is known, are employed in all metazoan life-forms and document stasis, the situation in which evolutionary traits persist for long periods without change, contrary to the expectations of evolutionary theory.

References

[1] Skinner, Michael K. Encyclopedia of Reproduction, 2nd edition. Academic Press, Cambridge, MA, 13 August 2018,

[2] Baker, Robin, and Mark Bellis. Human Sperm Competition. OverDrive Publisher, Cleveland, OH, 2014.

[3] Bergman, Jerry. “Intricate Design Found in Sperm Cells. Research is proving that a supposed simple cell is far more complex than once thought.” https://crev.info/2023/11/intricate-design-found-in-sperm-cells/, 2023.

[4] Yew, Hyunku, et al. “Structure and electromechanical coupling of a voltage-gated Na+/H+ exchanger.” Nature 623:193–201, 25 October 2023.

[5] Drew, David. “Sperm’s secret voltage switch: Scientists unlock the mystery of motility.”

https://www.su.se/english/news/sperm-s-secret-voltage-switch-scientists-unlock-the-mystery-of-motility-1.685891, 25 October 2023.

[6] Drew, 2023; emphasis added.

[7] Drew, 2023; emphasis added.

[8] Drew,  2023.

[9] Shakes, Diane. “Sperm bud mitochondria to adjust the numbers.” Nature Cell Biology 25:1564–1565, https://www.nature.com/articles/s41556-023-01255-0Shakes, 9 November 2023.,

[10] Liu, Pang, et al. “Mitopherogenesis, a form of mitochondria-specific exocytosis, regulates sperm mitochondrial quantity and fertility.” Nature Cell Biology 25(11):1625–1636, November 2023.


Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,300 publications in 12 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,800 college libraries in 27 countries. So far over 80,000 copies of the 60 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.

(Visited 247 times, 1 visits today)

Leave a Reply