Your observation raises many further questions as to the cause and mechanisms of giant sperm cells that are multinucleate.

First is the question of fusion, where much is understood about the fusion of oocyte and sperm at the moment of fertilisation, with the influence of fusogens. 'Fusion proteins' structurally similar to viral proteins have been identified in sperm cells, myoblasts and trophoblasts. In the case of oocytes, as opposed to sperm, giant binuclear oocytes occur with considerable frequency in human ovaries, but their ultimate fate recently been investigated as to if they can be fertilised. These multinuclear anomalies of morphology, cytogenetics and developmental potential of human giant oocytes are reported in patients undergoing assisted reproductive technologies. Most multinucleate giant oocytes are assumed lost, prematurely by atresia, before reaching ovulation. Some sperm are found to have fusion proteins, usually found in oocytes, and the aberrant expression of these may be the reason for giant multinucleate sperm cells during spermatogenesis.

Mutagenesis of the genome can occur during mitosis and meiosis during sperm development. Mendel's principle of independent assortment and exchange of genetic material is subject to many aberrant mechanisms causing spontaneous mutations, some of which could be fusogens, inhibtors of cell membrane fusion or factors affecting the mitotic cycle. Mutagenesis may affect inhibitory factors for fusion or insert fusogenic genes to the sperm genome.

A suggestion for investigation would be to genotype the giant cells and compare with ‘normal’ mononuclear cells, perhaps with an emphasis on known fusion genes, such as, Syncytins, F proteins, CD9 and fusexin or syncytin family members. There are examples of mechanisms of these processes in other species, such as, Caenorhabditis elegans. Fused cells can undergo dramatic changes in signaling and behavior and acquire new developmental fates.

Other examples of many cells known to fuse are macrophages, Langhans, Touton and Giant-cell arteritis. Reed–Sternberg cell, in lymphoma are the result of incomplete cytokinesis and re-fusion of small mononucleated Hodgkin cells lead to giant multinucleated Reed–Sternberg cells.

Also, the fusion of viruses’ envelope protein to host cell membranes is an area where some aspects are known and understood (HIVgp41 envelope glycoprotein).

Can knowledge be extrapolated from the mechanisms that form these cells, perhaps common fusogen proteins are involved? Or is there another mechanism involved, causing polyploidy is endomytosis or endoreduplication, understood as a variant form of the mitotic cell cycle?

An interesting paper describing abnormal mitoses in spermatogenesis was published in 1922, so this phenomenon has been observed and discussed for several decades as already stated. (Robert H. Bowen, Biological Bulletin, Vol. 43, No. 3 (Sep., 1922), pp. 184-202).

Hi Ludovic, are these normal or malignant tissues? Giant cells in metastatic tumors are now a hot topic.

Hi Steingrimur,

Fresh and cryopreserved prepubertal testicular tissues cultured were 'normal' tissues (not malignant). Histological evaluations were assessed after the extraction of testes and after cryopreservation procedures.

Do you have any informations / references on giant cells like these?

What methods were used? Also, what are the gold standard in this connection. Can you please add the reference of Method or its copy for reading. Thanks.

Hi Ludovic, the presence of giant cells in solid tumors was detected and described decades ago by histopathologists.

Unfortunately, these papers were overlooked. Only recently has interest in these cells been rekindled by their presence in new methods that capture circulating tumor cells (CTCs) based on size.

www.pnas.org/content/111/9/3514.short

Article Circulating Cancer Associated Macrophage-Like Cells Differen...

Your observation raises many further questions as to the cause and mechanisms of giant sperm cells that are multinucleate.

First is the question of fusion, where much is understood about the fusion of oocyte and sperm at the moment of fertilisation, with the influence of fusogens. 'Fusion proteins' structurally similar to viral proteins have been identified in sperm cells, myoblasts and trophoblasts. In the case of oocytes, as opposed to sperm, giant binuclear oocytes occur with considerable frequency in human ovaries, but their ultimate fate recently been investigated as to if they can be fertilised. These multinuclear anomalies of morphology, cytogenetics and developmental potential of human giant oocytes are reported in patients undergoing assisted reproductive technologies. Most multinucleate giant oocytes are assumed lost, prematurely by atresia, before reaching ovulation. Some sperm are found to have fusion proteins, usually found in oocytes, and the aberrant expression of these may be the reason for giant multinucleate sperm cells during spermatogenesis.

Mutagenesis of the genome can occur during mitosis and meiosis during sperm development. Mendel's principle of independent assortment and exchange of genetic material is subject to many aberrant mechanisms causing spontaneous mutations, some of which could be fusogens, inhibtors of cell membrane fusion or factors affecting the mitotic cycle. Mutagenesis may affect inhibitory factors for fusion or insert fusogenic genes to the sperm genome.

A suggestion for investigation would be to genotype the giant cells and compare with ‘normal’ mononuclear cells, perhaps with an emphasis on known fusion genes, such as, Syncytins, F proteins, CD9 and fusexin or syncytin family members. There are examples of mechanisms of these processes in other species, such as, Caenorhabditis elegans. Fused cells can undergo dramatic changes in signaling and behavior and acquire new developmental fates.

Other examples of many cells known to fuse are macrophages, Langhans, Touton and Giant-cell arteritis. Reed–Sternberg cell, in lymphoma are the result of incomplete cytokinesis and re-fusion of small mononucleated Hodgkin cells lead to giant multinucleated Reed–Sternberg cells.

Also, the fusion of viruses’ envelope protein to host cell membranes is an area where some aspects are known and understood (HIVgp41 envelope glycoprotein).

Can knowledge be extrapolated from the mechanisms that form these cells, perhaps common fusogen proteins are involved? Or is there another mechanism involved, causing polyploidy is endomytosis or endoreduplication, understood as a variant form of the mitotic cell cycle?

An interesting paper describing abnormal mitoses in spermatogenesis was published in 1922, so this phenomenon has been observed and discussed for several decades as already stated. (Robert H. Bowen, Biological Bulletin, Vol. 43, No. 3 (Sep., 1922), pp. 184-202).

Very Interesting and topical read. Thankful to the Houldsworth.

Khalid

As mentioned by Annwyne, mutations can affect the genome during mitosis or meiosis. Are there in human/mammals quantifications of the mutation rate during each mode of division (I know some data in yeast) ?

In answer to Herve's enquiry, I think that this paper may be useful.

Scally A. 2016 Mutation rates and the evolution of germline structure.

Phil. Trans. R. Soc. B 371 : 20150137. http://dx.doi.org/10.1098/rstb.2015.0137

Also,

Male Mutation Bias Is the Main Force Shaping Chromosomal Substitution Rates in Monotreme Mammals Vivian Link1, Diana Aguilar-G_omez2, Ciro Ram_ırez-Su_astegui2, Laurence D. Hurst3, and Diego Cortez2, Genome Biol. Evol. 9(9):2198–2210. doi:10.1093/gbe/evx155

According to the last paper, 'maternal gametes go through fewer genome replications than the paternal ones. This is because the maternal population of gametes has already been formed at birth of the future mother and maturation does not include further cell divisions besides meiosis (Chang et al. 1994; Drost and Lee 1995), whereas in males, by contrast, the formation of gametes (spermatogenesis) continues throughout adult life and necessitates a constant renewal of the initial spermatogenic cell (spermatogonia) pool through mitosis (Kanatsu-Shinohara and Shinohara 2013).'

Make sense and follow biological rule and logic.

agree with@Annwyne Houldsworth

regards

Thanks a lot for your replies (with a special thank to PhD @Annwyne Houldsworth).

I’m agreeing that these observations raises further questions as to the cause and mechanisms of giant sperm cells that are multinucleate. However, explanations about the fusion of oocyte and sperm at the moment of fertilisation seem off-topic due to the fact that the tissue presented in this Question is a testicular tissue. The presence and/or the defiition of those giant cells (Abnormal Pro-Metaphase or Metaphase Stages [orange arrows] or Variation in Meiotic Pachytene with the formation of Chiasmata) remain a mystery…

I already studied the presence of round spermatid nuclear alterations and DNA damages (with the formation of giant multinucleated cells) generated from spermatogonial stem cells during in vitro culture: https://www.researchgate.net/publication/308665082_Vitamin_A_prevents_round_spermatid_nuclear_damage_and_promotes_the_production_of_motile_sperm_during_in_vitro_maturation_of_vitrified_pre-pubertal_mouse_testicular_tissue

In addition, references like teams around Kanatsu-Shinohara and Shinohara go straight to the point of this topic. However, their studies don’t show any giant cells like these.

The hypothesis “independent assortment and exchange of genetic material is subject to many aberrant mechanisms causing spontaneous mutations, some of which could be fusogens, inhibtors of cell membrane fusion or factors affecting the mitotic cycle” could be a start point to study giant cells. Do you think these are fused cells? How to test this hypothesis on already paraffin fixed testicular explants (Bouin Solution and/or PFA4%)?

@Khalid Lone, the methodology of the in vitro culture protocol used in this study is similar of those used by our Team from 2015 (adapted from a 2011's publication of a japanese group). Please, feel free to take a look at my profile if you are still interested, these published articles were Full-Available in ResearchGate.

@Steingrimur Stefansson, the tissue is not malignant (and is murine).

@Herve Levesque, in vitro cultures controls of murine prepubertal testis were exempt of these alterations.

Dear Dr. Dumont,

Thanks for the answer. I would definitely look at the paper and methods. Thanks for sharing.

With regards.

Khalid lone

I'm not sure if this is any help but reading around this subject, one area of cell fusion research that has been well visited is the SYT–SSX fusion transcript (SYT–SSX1 and SYT–SSX2), fusion partners with SYT gene in t(X;18), and are related to the histologic and clinical characteristics in mutation. I just thought that it was an area worth suggesting.

This research is particularly associated with synovial sarcoma. A recurrent, tumour-specific translocation t(X;18)(p11.2;q11.2) and I know that this is a little off topic but may be helpful in contributing some laterally related knowledge, already investigated.

SSX1, SSX2, or infrequently SSX4, may also be involved on Xp11.2 germ cell mutation and a correlation between the location of the X chromosome breakpoint and the histologic subtype has been suggested.

Reverse Transcriptase-polymerise chain reaction (RT-PCR) can detect different SS18–SSX fusion genes, as well as the variants but fluorescence in situ hybridization (FISH) assay could distinguish between two most common fusion genes, SS18-SSX1 and SS18-SSX2 if RNA is not available. Interphase and metaphase cells can be compared, apparently and fusion gene status examined (http://ltd.aruplab.com/Tests/Pdf/230).

Translocation could occur during meiosis or mitosis between the X chromosome and chromosome 18, causing aberrant fusion.

SYT–SSX Gene Fusion as a Determinant of Morphology and Prognosis in Synovial Sarcoma. Akira Kawai, M.D., Ph.D., James Woodruff, M.D., John H. Healey, M.D., Murray F. Brennan, M.D., Cristina R. Antonescu, M.D., and Marc Ladanyi, M.D.

A novel FISH assay for SS18–SSX fusion type in synovial sarcoma

Cecilia Surace, Ioannis Panagopoulos, Eva Pålsson, Mariano Rocchi, Nils Mandahl & Fredrik Mertens

Detection of fusion gene in cell-free DNA of a gastric synovial sarcoma. Shinpei Ogino, Hirotaka Konishi, Daisuke Ichikawa, Junichi Hamada, Katsutoshi Shoda, Tomohiro Arita, Shuhei Komatsu, Atsushi Shiozaki, Kazuma Okamoto, Sanae Yamazaki, Satoru Yasukawa, Eiichi Konishi, and Eigo Otsuji