M.Sc Thesis Van Dyk: Evaluating the involvement of mtDNA variants in patients diagnosed with M.E.

[Dolphin]

From: Dr. Marc-Alexander Fluks

Source: North-West University (South Africa)
Date: March 10 and June 8, 2016
URL: http://dspace.nwu.ac.za/handle/10394/17668
http://dspace.nwu.ac.za/bitstream/handle/10394/17668/Van_Dyk_HC_2016.pdf


Evaluating the involvement of mtDNA variants in patients diagnosed
with myalgic encephalomyelitis
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Hayley Christy Van Dyk
- Biochemistry, School of Physical and Chemical Sciences, Faculty
of Natural Sciences, North-West University, Building G6, Room 110,
Potchefstroom Campus, Potchefstroom 2531, South Africa


Abstract

In mitochondrial research, many investigators have examined the association between mitochondrial DNA (mtDNA) variants in rare as well as common complex diseases.

Previous studies at the CHM (NWU) detected three known pathogenic mtDNA variants (m.7497G>A, m.9185T>C and m.10197G>A) at low allele frequencies in a number of patients diagnosed with myalgic encephalomyelitis (ME).

Since no diagnostic examinations or conclusive treatments currently exist for ME, an association between ME and known pathogenic variants, or a cumulative effect of rare non-synonymous variants (pathogenicity score) on ME, could provide valuable insights into understanding the causes of ME.

Literature shows contradicting data regarding the role of mitochondrial dysfunction in ME, and while uncommon mtDNA deletions have been reported, the three known pathogenic mtDNA variants introduced here have not previously been observed in ME patients (but were later identified as sequencing artefacts in the duration of this study), nor has the combined effect of numerous rare non-synonymous variants on the mitochondrial bioenergetics of ME patients been assessed.

To do this, cytoplasmic hybrid (cybrid) cells were developed by fusing ρ0 (mtDNA-depleted) cells with healthy control and ME patient‟s blood platelets (containing solely mtDNA).

These cybrid cells were used for mitochondrial bioenergetic analyses, using a Seahorse XFe96 analyser, and for determination of the relative mtDNA copy number (RMCN), using real-time PCR. In addition, conditions for analysing selected cell lines (including the cybrids) using the Seahorse XFe96 analyser were optimized.

While no apparent bioenergetic irregularities were observed in ME patient cybrids compared to healthy controls, an increased pathogenicity score appeared to be associated with a decrease in ATP production and a decreased electron transport system (ETS) capacity in ME patients.

This new approach for investigating mtDNA variants and a common complex disease may provide new insights into the diagnostic and causative factors of ME.

Key words:
bioenergetics, myalgic encephalomyelitis, mtDNA variants, Seahorse XF analyser, mutational load hypothesis, haplogroups, mtDNA copy number.
copy number.

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(c) 2016 North-West University

 

[Valentijn]

Previous studies at the CHM (NWU) detected three known pathogenic mtDNA variants (m.7497G>A, m.9185T>C and m.10197G>A) at low allele frequencies in a number of patients diagnosed with myalgic encephalomyelitis (ME).

Of those three, only MTDNA 9185 is tested by 23andMe on the V3 and V4 chips. Its rsID is rs199476138, and it's on the ATP6 gene. The pathogenic allele is C, so T is the normal version. None of the 31 ME patients who I have matched with controls have the pathogenic version, nor do the controls.

It causes Leigh Disease, though the severity can vary immensely, even in members of the same family. It usually starts in early childhood, though sometimes not until adulthood, and can be triggered by energy-taxing events like infection or surgery.

More info is at https://en.wikipedia.org/wiki/Leigh_disease and https://omim.org/entry/516060#0008

 

[Sasha]

Nice to see that a PhD student is doing this kind of biomedical work on ME!

 

[snowathlete]

Of those three, only MTDNA 9185 is tested by 23andMe on the V3 and V4 chips. Its rsID is rs199476138, and it's on the ATP6 gene. The pathogenic allele is C, so T is the normal version. None of the 31 ME patients who I have matched with controls have the pathogenic version, nor do the controls.

It causes Leigh Disease, though the severity can vary immensely, even in members of the same family. It usually starts in early childhood, though sometimes not until adulthood, and can be triggered by energy-taxing events like infection or surgery.

More info is at https://en.wikipedia.org/wiki/Leigh_disease and https://omim.org/entry/516060#0008

I have the v3 chip but can't find rs199476138 in my raw data

 

[Valentijn]

I have the v3 chip but can't find rs199476138 in my raw data

Whoops. They've labeled it as i5002865