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Mutazioni primarie del mtDNA
Mutazioni primarie del mtDNA Massimo Zeviani IUSS, Medicina Mitocondriale Milano Istituto Nazionale Neurologico “C. Besta”
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mtDNA mutations Heteroplasmic mutations Homoplasmic mutations
Single-Nucleotide Polymorphisms
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Homoplasmic point mutation eg, LHON homoplasmic mother
mitochondrial bottleneck mitochondrial proliferation her oogonia Homoplasmic point mutation eg, LHON Mutation is necessary but not sufficient to produce the disease phenotype her offspring (usually) healthy (usually) sick
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the A1555G affects the aminoglycoside binding site of 12S rRNA
Secondary structure of decoding site of small ribosomal RNAs. The A site of E. coli 16 S rRNA oligonucleotide showing the DMS footprints, observed in the presence of the aminoglycosides neomycin and paromomycin, is marked with a dot (A). The corresponding region of S. cerevisiae mt-15S rRNA and human mt-12S rRNA is shown as the wild type version (B and E) and in the version containing the PR454 (C) and A1555G mutation (F), respectively.
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modifier loci/genes
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Sequence alignment of human Mto1p with its homologs
COX1 overlap
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Leber’s Hereditary Optic Neuropathy (LHON)
Leber, T. : Ueber hereditaere und congenital angelegte Sehnervenleiden. Graefes Arch. Ophthal. 17: , 1871.
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Homoplasmic point mutations
e.g. Leber’s Hereditary Optic Neuropathy 11778G->A blind healthy
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Homoplasmic point mutations
e.g. Leber’s Hereditary Optic Neuropathy 11778G->A mutant wt
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F V LUUR T P E LCUN SAGY H ND5 ND6 ND4 ND4L ND3 R COIII G ATPase6/8 K COII D SUCN COI A N C Y W ND2 I M Q ND1 16S 12S D-loop Cyt.b LHON/14484C 26% LHON/11778A 58% LHON/3460A 16%
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Hudson et al, Am J Hum Genet 2007
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Am J Hum Genet 2007
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Hudson et al, Am J Hum Genet 2007
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Homoplasmic mutations
SNHL/1555G LHON/14482G/A LHON/14485C LHON14495G LHON/14568T LHON/11778A LHON/3460A LHON/4171A LHON/10663C F V LUUR T P E LCUN SAGY H ND5 ND6 ND4 ND4L ND3 R COIII G ATPase6/8 K COII D SUCN COI A N C Y W ND2 I M Q ND1 16S 12S D-loop Cyt.b syndromic SNHL/7472insC aminoglycoside-induced SNHL/delT961 neonatal death- Leigh s./16427T SNHL/7445C SNHL/7510C SNHL/7511C MIHC/9997C MIHC/4300G Leigh s./9537insC Encephalopathy obesity/4290C hypertension hyperchol. hypoMg++/4291C
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Cytochrome c oxidase activity
Published online: 22 January 2002, doi: /ng819 volume 30 no. 2 pp 145 - 146 Multiple neonatal deaths due to a homoplasmic mitochondrial DNA mutation Robert McFarland1, Kim M. Clark1, Andrew A.M. Morris2, Robert W. Taylor1, Sheila Macphail3, Robert N. Lightowlers1 & Douglass M. Turnbull1 C1624T 230 bp 201 bp 154 bp 47 bp II-1 muscle II-1 blood I-2 blood III-6 buccal III-9 placenta control 1 blood undigested control 2 cardiac III-10 blood III-10muscle III-10cardiac Rsa I Digestion 21h pH Alive Leigh s. 85h 30h 26h 2h 12h Control mother Patient III-10 Heteroplasmic tRNA mutation Cytochrome c oxidase activity Skeletal muscle Cardiac mitochondria
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Activities in the living proband
Healthy Ataxia, dystonia, tetraparesis, optic atrophy, DM, obesity Same as older sister. Deceased at 16 yrs. Deceased at 1 yr. Necrotizing encephalopathy Activities in the living proband (fibroblasts) CI/CS CIV/CS 10 20 30 40 50 60 70 80 100 120 140 160 180 P C
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Respiratory Chain Activities
control complex I complex IV Respiratory Chain Activities in Cybrids nmol/min/mg protein p1 p2 p3 CI/CS CIV/CS 10 20 30 40 50 60 70 80 100 120 140 160 180 P1: mother P2, P3: patients I-2 II-2 C 2D-BNE on complex IV WT IV-1 WT II-1 ND5 COI ND4 cyt b ND2 ND1 COIII COII ATP6 ND6 ND3 ND4L ATP8 Mito-specific protein synthesis
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Familial hypomagnesemia, hypertension, and hypercholesterolemia
T4291C
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Increased penetrance of LHON mutations in haplogroups J and K
V LUUR T P E LCUN SAGY H ND5 ND6 ND4 ND4L ND3 R COIII G ATPase6/8 K COII D SUCN COI A N C Y W ND2 I M Q ND1 16S 12S D-loop Cyt.b LHON/14484C haplo J 100% LHON/11778A p .02 LHON/3460A haplo K p 2.3x10-3 haplo J-> cyt. b L236I haplo J1c-> cyt. b F18L haplo J2b-> cyt. b D171N cyt. b V356M haplo K-> cyt. b F18L
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mtDNA mutations Heteroplasmic mutations Homoplasmic mutations
Single-Nucleotide Polymorphisms
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mtDNA haplotypes F V LUUR T P E LCUN SAGY H ND5 ND6 ND4 ND4L ND3 R COIII G ATPase6/8 K COII D SUCN COI A N C Y W ND2 I M Q ND1 16S 12S D-loop Cyt.b What is the impact of mildly pathogenic mtDNA mutations or haplotypes? - haplogroup distribution during human migrations - haplogroup J vs. H in LHON - haplogroup H vs. T in asthenozoospermia - haplogroup K vs. H in Parkinson's Disease
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Gene products present in mammalian mitochondria
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Genetic classification of OXPHOS disease mutations
Defects of Mitochondrial DNA Protein synthesis genes (rRNAs, tRNAs) Protein-encoding OXPHOS subunit genes Large deletions Nuclear DNA mutations Genes encoding OXPHOS assembly factors Genes encoding factors affecting mtDNA maintenance Mitochondrial protein synthesis genes Genes encoding biosynthetic enzymes for lipids or cofactors Genes involved in mitochondrial biogenesis
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Chemiosomosis Chemiosmosis is the name given to the generation of ATP from a proton gradient. It occurs in all living things
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Chemiosomosis photosynthetic archaea
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Chemiosomosis purple proteobacteria
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Chemiosomosis mitochondria
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Chemiosomosis Chloroplasts
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