Mitochondrial disease 1 and 2

Question 1

Mitochondrial function

Answer 1

ATP production through ox phos, repirartory chain, regulation of molecules on inner and outer membrane (calcium), control of cystolic ca2+, MOMP crucial for apoptosis

Question 2

how many genes does the mitochondria encode for oxphos?

Answer 2

37 genes

Question 3

How do the nuclear encoded mito proteins get into mitocondria?

Answer 3

TIM and TOM

Question 4

What do we need to have mitochondrial biogenesis and what can we use to drive it?

Answer 4

Exercise drives coordinated
expression of 2 genomes and
mitochondrial biogenesis

Question 5

What is mitochondrial disease?

Answer 5

• Mutation in mito gene or nuclear gene encoding mito protein that affects organelle function
• Mito disease is multisystem disorder, affecting more than one type of cell/tissue
• Neuromuscular system has high energy needs, thus myopathy/neuropathy common features

Question 6

What does mitochondrial disease affect?

Answer 6

ns, eyes, heart, liver kidneys, skeletal muscle digestive tract, pancreas

Question 7

How common is mito disease?

Answer 7

1/5000 (15% mtDNA defects)

Question 8

what does inhertance look like for mito disease cause by mtDNA?

Answer 8

If mother is affected all kids have, if dad affected no kids are affected

Question 9

what does inheritance look like for mito disease cause by nDNA?

Answer 9

Mitochondrial diseases caused by nDNA mutations can be due to AR, AD, XAR

Question 10

Are there sporadic cases with mito diases?

Answer 10

Yes, increases with age

Question 11

What do we see with Gomori trichrome histochemical stain?

Answer 11

Ragged-red fibers caused by compensating for the dysfunction in mito so there is proliferation of subsarcolemmal
mitochondria (mito under sacrolemma)

Question 12

What does the Ragged-blue fiber show?

Answer 12

Succinate dehydrogenase (SDH) activity

Question 13

what does Normal cytochrome c oxidase (COX) histochemical staining show?

Answer 13

Normal cytochrome c oxidase (COX) histochemical staining highlighting
variability of mitochondrial enzyme activity in muscle biopsy (less COX = less mito activity/function)

Question 14

COX histo from CPEO patient shows?

Answer 14

COX histo from CPEO patient showing COX-deficient fibers, Mosaic pattern of COX activity highly suggestive of mtDNA disorder

Question 15

How does SDH play a role with decrease in COX and mito activity?

Answer 15

Increases to compensate

Question 16

Is it possible to have normal COX activity but abnormal mito proflieration?

Answer 16

Yes

Question 17

How is oxphos performed and how many are there?

Answer 17

OXPHOS performed by five large, multi-subunit supercomplexes (CI-CV) embedded in MIM

Question 18

What encodes for the complexes of the ETC for ox-phos to occur?

Answer 18

ETC complexes except complex II (SDH) (only nDNA) composed of subunits encoded by mtDNA & nDNA

Question 19

Describe mito DNA

Answer 19

• mtDNA is circular, contains
37 genes encoding 2 rRNAs,
22 tRNAs, & 13 OXPHOS
proteins
• mtDNA has ~10-fold
greater susceptibility for
spontaneous mutagenesis
versus nDNA
• Fewer DNABPs for
protection, coupled with
less robust DNA
maintenance & repair
systems

Question 20

What affects the severity of mito disease?

Answer 20

Severity of mitochondrial disease in child due to mtDNA mutation
depends on % mutant mtDNA inherited from mother in fertilized egg cell

Question 21

When all mtDNA molecules are identical?

Answer 21

homoplasmy

Question 22

When two or more mtDNA types are present?

Answer 22

heteroplasmy

Question 23

mtDNA mutations affect some but not all mtDNAs within cell?

Answer 23

heteroplasmy

Question 24

threshold effect?

Answer 24

Minimum % mutant mtDNAs required to cause overt disease = threshold effect

Question 25

What is the threshold?

Answer 25

impossible to establish universal disease threshold but generally considered ~80%

Question 26

Heteroplasmic mtDNA mutations cause mutations in respiratory chain when

Answer 26

Heteroplasmic mtDNA mutations only causes respiratory chain (OXPHOS)
dysfunction if present above certain minimal threshold level above 60%

Question 27

What is EPI-743?

Answer 27

Orally bioavailable synthetic CoQ10 analogue, 1,000-10,000 X more potent antioxidant

Question 28

How did EPI743 affect individuals with Leigh syndrome?

Answer 28

FDA Expanded Access open label 3 or 6 mo EPI-743 treatment slowed disease progression in kids 1-13 yrs old (x = 6.3) as assessed using various quality of life measurement instruments, taken orally 3 times a day

Question 29

Where are we know with EPI-743 RESEARCH?

Answer 29

Have not had a case study since 2017 where in Japan they had a patient living after 4 years

Question 30

what is Asexual healing: mtDNA replacement therapy

Answer 30

making a baby from 3 people, 3 sets of DNA

Question 31

Purpose of replacement therapy?

Answer 31

Mito genome replacement therapy to prevent next generation transmission of mtDNA mutations

Question 32

How does the replacement therapy work?

Answer 32

Transfer of nuclear genetic material from oocyte with mutant mtDNA to cytoplasm of donor enucleated oocyte with healthy mtDNA then Reconstructed oocyte fertilized & transplanted

Question 33

Transmito rhesus monkeys using replacement therapy showed:

Answer 33

Transmito rhesus monkeys display normal growth and

minimal % mtDNA heteroplasmy

Question 34

When was the first baby born used this technique?

Answer 34

2016: First baby born using “three parent” technique

Question 35

Asymptomatic carrier of Leigh syndrome (~30% mtDNA mutation load), with four undiagnosed pregnancy losses and deaths of two offspring (~95% load) as result of disease: what did they do?

Answer 35

Spindle transfer from patient’s metaphase II oocyte (~95% mutation load) into cytoplasm of enucleated donor oocyte (arrows indicate spindle), with intent to have male child

Question 36

What is a drawback with this technique? What did it cause in this case?

Answer 36

Might get some mito DNA still, Heteroplasmy level of maternal mito mutation in biopsied blastocyst = 6%; in son’s tissues
collected within 2 days of birth = ~2.5-9.5%

Question 37

10 patients with various mtDNA defects following 14 weeks cycle endurance training, what did they see?

Answer 37

improvements in quality of life, peak VO2, & mito function, but mutation load
increased in 6 patients

Question 38

So is endurance training effective for mito disease?

Answer 38

2 recent studies show similar training benefits, no rise in
mutations or muscle damage so yes Endurance training effective
and appears safe for MM (also resistance)