I personally think it is always a mistake to try to define mitochondria in numbers, as they are constantly undergoing fission and fusion so the true 'number' of independent mitochondria is constantly changing, in all cells. It is better to define mitochondria within a specific cell type in terms of their specific function (e.g. amount of ATP generation, redox potential, etc).

Theoretically "0". That is why mitochondrial DNA related diseases only come from mother. But, personally, I believe anything can happen in biology.

Hi Ru,

Dont you think the sperm cells require mitochondria (or rather ATP) to reach the egg ? As far as i know it does have mitochondria in the central filamentous core of the mid piece.

I agree with you Mr. Murugappan,... but I wonder of there is a number known, or estimate or approximate... because I could not find any information sources on the internet.

Based on this source ,a mature mammalian sperm cell contains 22 - 75 mitochondria .Here is the source http://humrep.oxfordjournals.org/content/18/3/550.full

Sperm cells have mitochondria at the base of their flagella which do not fuse with an egg upon fertilization.

Thank you very much !

Mitochondria are a vital component of sperm physiology and are specifically concentrated in the mid-piece to provide energy for active tail movements.

They are vital because this is sperm which has to move towards the egg, and mitochondria will provide ATP to fuel this movement.

In a human sperm, mitochondrial activity also is one of the factors determining the half-life of sperm.

Regarding their non-transmission to offsprings, its only the genetic material and the centriole which are provided by the sperm. Mitochondria are disintegrated if they get a chance to enter egg cytoplasm. So paternal mitochondrial contributions are extremely rare, if at all.

See Gilbert's Developmental Biology for more details.

Hmm, It makes sense. Yes, I recall there are mitochondria in the tail portion of healthy sperm but the mitochondria will not get into the fertilized egg. I might make a mistake in answering the question.

No problem Ru-Jeng, I thank you for having the possibility of having talks here... I only was interested in their number...

I personally think it is always a mistake to try to define mitochondria in numbers, as they are constantly undergoing fission and fusion so the true 'number' of independent mitochondria is constantly changing, in all cells. It is better to define mitochondria within a specific cell type in terms of their specific function (e.g. amount of ATP generation, redox potential, etc).

Count youself, don't mix them with nucleus.

Agree whit Joseph. At least one big mitochondria (a rather strange thing) . This is important when you are thinking about a propper definition for the organelle. Remember the fussion and fission proccess are a consequense of cell physiology (sperm innthis specific case).

Just.womdering has anyone measured mitochondrial DNA in sperm?

You can use citrate synthase and mitochondrial DNA to estimate the number of mitochondria

Thank you Antonio. Can you guide me a little more what exactly would be the procedure in order to estimate the number of mitochondria inside a cell ?

Citrate Synthase activity assays which are done spectrophotometrically are traditionally used to determine differences in total mitochondrial amount between different treatment groups. The assay is based on the principle that oxaloacetate and acetyl CoA will form Citrate and CoASH. The CoASH will then react with dinitrobenzoic acid (DTNB) to form a Co-DTNB complex which can be measured kinetically. Epitomics has an antibody against citrate synthase that works really nice as well so you can have a western blot to correlate with the activity assay.

If you are interested in mitochondrial number per se, I would recommend electron microscopy, but remember that the mitochondrial network is a dynamic process in which the mitochondrial network is undergoing fission, fussion and mitophagy so you will only get a snap shot of the entire picture.

Thank you Michelle. I'll keep that in mind.

From:

Biol Reprod. 2014 Sep 10. Tian et al. Association of DNA Methylation and Mitochondrial DNA Copy Number with Human Semen Quality.

http://www.biolreprod.org/content/early/2014/09/08/biolreprod.114.122465.long

In order to produce normal sperm, the process of spermatogenesis is complex, including

gradual mitochondrial DNA (mtDNA) elimination and dramatic epigenetic modifications ...

In mammals; matured sperm contain only a few mtDNA copies (some 10 to 100) ...

Human individual sperm contain ≈10 copies [8,29]

However, mtDNA copy numbers are dramatically higher in poor-quality and abnormal sperm than in the most motile and fertilizing examples [8].

Thus, sufficient mtDNA copy elimination during spermiogenesis is critical for sperm maturation and

mtDNA copy number may indicate genomic quality.

There are 2-10 copies of mtDNA per mitochondrion.

:)

Very good paper. Thank you Marika.

It is worth mentioning that sperm and oocytes are the cells were each mitochondria carry one mtDNA copy. This is somehow different than other, somatic cells, where You can find multiple copies of mtDNA within one organelle depending of energy provision in specific tissue. If therefore as claimed in papers one sperm possess around 20 mtDNA copies You can not conclude that there are 2-10 mtDNA copies per mitochondrium since you will find only few of them in mature sperm. In fact there are 10-80 mitochondria in sperm depending on species and sperm quality

I agree with Joseph above. Constant fission and fusion makes it difficult to answer the question "how many", and even if some estimate could be done with imaging techniques this is a snapshot from a constantly changing network.

interesting work, why sperm to have so many copies of mt DNA is still debatable.