Mitochondrial biology and genetics in diagnostic practice Flashcards
(32 cards)
What is mitochondrial genetics?
- H…………../Variation of the DNA that en………… mitochondria (especially ………………. DNA, mtDNA, but also …………. DNA, nDNA
Diagnostic service and g…………. counselling for individuals or families with, or at risk of, mitochondrial disease
What is mitochondrial genetics?
- Herability/Variation of the DNA that encode mitochondria (especially mitochondrial DNA, mtDNA, but also nuclear DNA, nDNA
Diagnostic service and genetic counselling for individuals or families with, or at risk of, mitochondrial disease
All the parts with in eukaryotic cell
- mic…………………
- ve……..
- cy…………
- rough en……………….. reticulum
- ribo…………..
- s…………. endoplasmic reticulum
- …………. membrane
- flag……………
- lys………..
- ## Go…. co……………..Parts of nucleus
- chro………
- nuclear en……………
nuclear p……… - nucl………….
All the parts with in eukaryotic cell
- microtubules
- vesicle
- cytosol
- rough endoplasmic reticulum
- ribosomes
- smooth endoplasmic reticulum
- plasms membrane
- flagellum
- lysosome
- ## Golgi complexParts of nucleus
- chromatin
- nuclear envelope
nuclear pore - nucleolus
Basic structure of mitochondria
- I…………… membrane
- o………….. membrane
- C…………..
- Ma……………
Basic structure of mitochondria
- Inner membrane
- outer membrane
- Cristae
- Matrix
Basic structure of mitochondria
- I……………. membrane
- o……….. membrane
- Cris……………
- Ma………
Basic structure of mitochondria
- Inner membrane
- outer membrane
- Cristae
- Matrix
Mitochondria
- fi………….
- f…………..
- mo……………
- B……………..
- Mi……………..
Mitochondria
- fission
- fusion
- movement
- Biogenesis
- Mitophagy
glycolysis
gl. ………..
- ………..
glucose 6 …………………….
………………….. 6 phosphate
- ATP
glyceraldehyde 3- ………………
2p + (2nad+>2NADH)
1,3 bi-phosph……………..
+2ATP
3-phosp…………….
3-phophoe…………….
+2ATP
pyruvate
glycolysis
glucose
- ATP
glucose 6 phosphate
fructose 6 phosphate
- ATP
glyceraldehyde 3- phosphate
2p + (2nad+>2NADH)
1,3 bi-phosphoglycerate
+2ATP
3-phosphoglycerate
3-phophoenolpyruvate
+2ATP
pyruvate
Processes linked to proton motive force
- Pr………… import
- ………. generation
- ………./…….. exchange
- ………….. generation
- …………. transport
- mito………… membrane pote………
- … transport
Processes linked to electron flow
- reactive ox………..species sign………
- nucle………. pools
- on………… c………metabolism
- NA……… generation
Processes linked to proton motive force
- Protein import
- ATP generation
- ATP/AFP exchange
- NADPH generation
- calcium transport
- mitochondrial membrane potential
- Pi transport
Processes linked to electron flow
- reactive oxygen species signalling
- nucleotide pools
- one carbon metabolism
- NADPH generation
How does mtDNA differ from nuclear DNA
mtDNA vs nDNA
- have a different ……………. code
- have d…………… chr…………arrangements and g…….. copy n………….
Have different i………….. patterns - Phe…………. expression
MtDNA genetics (like epigenetics) explains why nuclear DNA …………. ≠ phenotype
How does mtDNA differ from nuclear DNA
mtDNA vs nDNA
- have a different genetic code
- have different chromosomal arrangements and gene copy numbers
Have different inheritance patterns - Phenotypic expression
MtDNA genetics (like epigenetics) explains why nuclear DNA genotype ≠ phenotype
Different chromosome and gene copy numbers
nDNA
-…. chromosomes
…… pairs of autos……….. (non-sex)
……. pair of sex chromosomes (f is XX, M is XY)
2 Copies/ alleles of every gene one from Mum and one from Dad
mtDNA
- Multiple mitochondrial n………………..
- Multiple mtDNA copies, usually from mum
- Number is ………. type specific
Different chromosome and gene copy numbers
nDNA
-4 chromosomes
22 pairs of autosomes (non-sex)
1 pair of sex chromosomes (f is XX, M is XY)
2 Copies/ alleles of every gene one from Mum and one from Dad
mtDNA
- Multiple mitochondrial nucleoids
- Multiple mtDNA copies, usually from mum
- Number is cell type specific
Different inheritance patterns
nDNA
- ……………
mtDNA
- ………………
Different inheritance patterns
nDNA
- Mendelian
mtDNA
- Maternal
Mendelian genetic traits (nDNA)
- A………………… inheritance - encoded for by aut………………..
- …..-linked inheritance, e.g. haemophilia
- Rec………… disorder - both relevant alleles are non-functional for phe………, e.g. c…….. …………
- Dominant disorder - only 1 allele needs to be mut……… for phenotype, e.g. Huntington’s
- Homozy………./ Hetero………
Mendelian genetic traits (nDNA)
- Autosomal inheritance - encoded for by autosomes
- X-linked inheritance, e.g. haemophilia
- Recessive disorder - both relevant alleles are non-functional for phenotype, e.g. cystic fibrosis
- Dominant disorder - only 1 allele needs to be mutated for phenotype, e.g. Huntington’s
- Homozygosity/ Heterozygosity
Maternal Genetic Traits (mtDNA)
- Maternal inheritance - encoded for by ………….
Mutant mtDNA > 60% for ……………..
Heteroplasm/ Homoplasmy
- Mixture of DNA variants within a cell = ………….
- One type of mtDNA within a cell -= ……………..
Maternal Genetic Traits (mtDNA)
Maternal inheritance - encoded for by mtDNA
Mutant mtDNA >60% for phenotype
Heteroplasm/ Homoplasmy
- Mixture of DNA variants within a cell = heteroplasmy
- One type of mtDNA within a cell -= homoplasmy
Why maternal :
sperm DNA is di…………
sperm DNA is eli……………
Why maternal? Because sperm mtDNA is:
- Diluted
- Eliminated
Abnormal mtDNA Inheritance
(Non-uniparental)
Examples
- Paternal …………. tran…………..
- Donor cell mtDNA transmission following nuclear genome transfer techniques like so……… ce…….. nu……….. and 3 Pa………. ……..
Abnormal mtDNA Inheritance
(Non-uniparental)
Examples
- Paternal mtDNA transmission
- Donor cell mtDNA transmission following nuclear genome transfer techniques like somatic cell nuclear and 3 Parent IVF
Mechanisms
- Certain mtDNA sequences have a re………… advantage
- M……….. in nuclear genes that are involved in the elimination of “foreign” mi………… (lysosome/ autophagy pathways)
Combination of the two
Mechanism(s)?
Certain mtDNA sequences have a replicative advantage
Mutation in nuclear genes that are involved in the elimination of ‘foreign’ mitochondria (lysosome/ autophagy pathways)
Combination of the two
Maintenance of mtDNA/OXPHOS/mitochondria is highly dependent on nu………..-mito………….interactions
If they are disrupted e.g. through mutation of ………….. genes or ……….. genes encoding mtDNA transcription/replication factors or numerous other mitochondrial proteins you can get dysfunctional mitochondria and disease
Maintenance of mtDNA/OXPHOS/mitochondria is highly dependent on nuclear-mitochondrial interactions
If they are disrupted e.g. through mutation of mtDNA genes or nDNA genes encoding mtDNA transcription/replication factors or numerous other mitochondrial proteins you can get dysfunctional mitochondria and disease
Mutation in nDNA and mtDNA genes that affect the integrity of OXPHOS are associated with numerous diseases
- …….. disorders (inborn errors of metabolism)
- Neuro………………..
- Ag………..
- Me……………..
- C…………
Mutation in nDNA and mtDNA genes that affect the integrity of OXPHOS are associated with numerous diseases
- MRC disorders (inborn errors of metabolism
- Neurodegeneration
- Ageing
- Metabolic
- Cancer
MtDNA Genotype ≠ Phenotype
- M………..
- M……….. load (%heteroplasmy)
- A…….
- Envi………….
.
…….. mutant load is often required for a phenotypic affect to be observed
MtDNA Genotype ≠ Phenotype
Mutation
Mutant load (%heteroplasmy)
Tissue
Age environment
*> 60% mutant load is often required for a phenotypic affect to be observed
Why so many mutants in mtDNA
- little protection by h………. (although mtDNA - specific transcription factor …, TF….., is thought to play a histone - like role)
- Proximity to da. ……… rea…….. oxygen species produced by the OXPHOS system
- Lower proof reading ability of the mtDNA specific DNA polymerase (POLG)
Why so many mutants in mtDNA
- little protection by histones (although mtDNA - specific transcription factor A, TFAM, is thought to play a histone - like role)
- Proximity to damaging reactive oxygen species produced by the OXPHOS system
- Lower proof r……….. ability of the mtDNA specific DNA polym…….. (POLG)
Mitochondrial disease
- For the purposes of this seminar mitochondrial disease will represent only disorders of the mitochondrial respiratory chain (MRC) or mitoc……… elec……. transport chain
- In addition, defects in ATP synthase (complex …..) will also be included as a disorder of the MRX
Can be caused by m………… in nuclear DNA or mtDNA
Mitochondrial disease
- For the purposes of this seminar mitochondrial disease will represent only disorders of the mitochondrial respiratory chain (MRC) or mitochondrial electron transport chain
- In addition, defects in ATP synthase (complex V) will also be included as a disorder of the MRX
Can be caused by mutations in nuclear DNA or mtDNA
MRC disorders represent the most common group of inborn errors of metabolism
- Incidence of 1 in 50……
- MRC disorders are generally pro……… and multi-sys………
- Typically affected organs are those with high energy demands: Neur………. and neu………… presentations the commonest
MRC disorders represent the most common group of inborn errors of metabolism
- Incidence of 1 in 5000
- MRC disorders are generally progressive and multi-systemic
- Typically affected organs are those with high energy demands: Neuromuscular and neurological presentations the commonest
Complexity of genetics can lead to diverse clinical features:
- Any Sy........ - Any Org.... or T........... - Any Age of Prese............ - Any mode of in..........
Complexity of genetics can lead to diverse clinical features:
- Any Symptom - Any Organ or Tissue - Any Age of Presentation - Any mode of inheritance
Cli……….. Picture > B…………… > H…………. .> Mo……………. Bi…………, including genetics
Clinical Picture > Biochemistry > Histochemistry > Molecular Biology, including genetics
Diagnostic algorithm
Clinical presentation indicative of mitochondrial disease > …………. sample for biochemistry/genetic studies > …………… result/mutation or ….. evidence of an abnormality/mutation > Muscle ……….. for biochemistry, histology + further genetic studies
Diagnostic algorithm
Clinical presentation indicative of mitochondrial disease > Blood sample for biochemistry/genetic studies > Abnormal result/mutation or no evidence of an abnormality/mutation > Muscle biopsy for biochemistry, histology + further genetic studies
