Milano

www.mitopedia.org

Istituto Nazionale Neurologico “C. Besta”

Mutazioni primarie del mtDNAMassimo Zeviani

IUSS, Medicina Mitocondriale

mtDNA mutations

•Heteroplasmic mutations

•Homoplasmic mutations

•Single-Nucleotide Polymorphisms

homoplasmic mother

her offspring

(usually) healthy (usually) sick

Mutation is necessary but not sufficient to produce the disease phenotype

Homoplasmicpoint mutationeg, LHON

mitochondrial bottleneck

mitochondrialproliferation

her oogonia

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.

modifier loci/genes

Sequence alignment of human Mto1p with its homologs

MTO1 COX1 overlap

Leber’s Hereditary Optic Neuropathy (LHON)

Leber, T. : Ueber hereditaere und congenital angelegte Sehnervenleiden. Graefes Arch. Ophthal. 17: 249-291, 1871.

Homoplasmic point mutations Homoplasmic point mutations e.g. Leber’s Hereditary Optic Neuropathy 11778G->Ae.g. Leber’s Hereditary Optic Neuropathy 11778G->A

blindhealthy

mutantwt

Homoplasmic point mutations Homoplasmic point mutations e.g. Leber’s Hereditary Optic Neuropathy 11778G->Ae.g. Leber’s Hereditary Optic Neuropathy 11778G->A

F

V

LUUR

T

PE

LCUN

SAGY

H

ND5ND6

ND4

ND4L

ND3R

COIII

G

ATPase6/8KCOIID

SUCN

COI

A NC Y

W

ND2

IM

Q

ND1

16S

12S

D-loop Cyt.b

LHON/14484C26%

LHON/11778A58%

LHON/3460A16%

Hudson et al, Am J Hum Genet 2007

Am J Hum Genet 2007

Hudson et al, Am J Hum Genet 2007

F

V

LUUR

T

PE

LCUN

SAGY

H

ND5ND6

ND4

ND4L

ND3R

COIII

G

ATPase6/8KCOIID

SUCN

COI

A NC Y

W

ND2

IM

Q

ND1

16S

12S

D-loop Cyt.b

SNHL/1555G

LHON/14482G/ALHON/14485CLHON14495GLHON/14568T

LHON/11778A

LHON/3460ALHON/4171A

LHON/10663C

Homoplasmic mutations

syndromic SNHL/7472insC

aminoglycoside-induced SNHL/delT961

neonatal death-Leigh s./16427T

SNHL/7445CSNHL/7510CSNHL/7511C

MIHC/9997CMIHC/4300G

Leigh s./9537insC

Encephalopathyobesity/4290C

hypertensionhyperchol.hypoMg++/4291C

Published online: 22 January 2002, doi:10.1038/ng819volume 30 no. 2 pp 145 - 146

Multiple neonatal deaths due to a homoplasmic mitochondrial DNA mutationRobert 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

mu

scle

II-1

blo

od

I-2

blo

od

III-

6 b

ucc

al

III-

9 p

lace

nta

cont

rol 1

blo

od

un

dig

est

ed

cont

rol 2

ca

rdia

c

III-

10 b

lood

III-

10m

uscl

e

III-

10ca

rdia

c

un

dig

est

ed

Rsa I Digestion

21h

pH

Alive

Leigh s.

85h

pH

30h

pH

26h

pH

2h

pH

12h

pH

Control

mother Patient III-10

HeteroplasmictRNA mutation

Cytochrome c oxidase activitySkeletal muscle Cardiac mitochondria

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/CS0

10

20

30

40

50

60

70

80

0

20

40

60

80

100

120

140

160

180

PP

CC

controlcomplex Icomplex IV

Respiratory Chain Activities in Cybrids

nm

ol/

min

/mg

pro

tein

p1 p2 p3 p1 p2 p3

CI/CS CIV/CS

0

10

20

30

40

50

60

70

80

0

20

40

60

80

100

120

140

160

180

P1: motherP2, P3: patients

I-2

II-2

C

2D-BNE on complex IV

WT

IV-1

WT II-1

ND5COIND4cyt bND2ND1COIIICOII

ATP6

ND6

ND3

ND4L

ATP8

Mito-specific protein synthesis

T4291C

Familial hypomagnesemia, hypertension, and hypercholesterolemia

F

V

LUUR

T

PE

LCUN

SAGY

H

ND5ND6

ND4

ND4L

ND3R

COIII

G

ATPase6/8KCOIID

SUCN

COI

A NC Y

W

ND2

IM

Q

ND1

16S

12S

D-loop Cyt.b

LHON/14484Chaplo J100%

LHON/11778Ahaplo J

p .02

LHON/3460Ahaplo K

p 2.3x10-3

haplo J-> cyt. b L236Ihaplo J1c-> cyt. b F18Lhaplo J2b-> cyt. b D171N

cyt. b V356M

haplo K-> cyt. b F18L

Increased penetrance of LHON mutations in Increased penetrance of LHON mutations in haplogroups J and Khaplogroups J and K

mtDNA mutations

•Heteroplasmic mutations

•Homoplasmic mutations

•Single-Nucleotide Polymorphisms

F

V

LUUR

T

PE

LCUN

SAGY

H

ND5ND6

ND4

ND4L

ND3R

COIII

G

ATPase6/8KCOIID

SUCN

COI

A NC Y

W

ND2

IM

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

mtDNA haplotypes

Gene products present in mammalian mitochondria

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

• Protein-encoding OXPHOS subunit genes• 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

Chemiosomosis

• photosynthetic archaea

Chemiosomosis

• purple proteobacteria

Chemiosomosis

• mitochondria

Chemiosomosis

• Chloroplasts