Neurodegenerative Disease:Neurodegenerative Disease:Too much of a bad thing, kills youToo much of a bad thing, kills you

John Hardy Ph.D. NIA

Pathology of Diseases

• Alzheimer’s disease: plaques (Aβ), tangles (tau) and often, Lewy bodies (α-synuclein).

• Prion disease: often PrP plaques; sometimes tangles; sometimes Lewy bodies.

• FTDP-17/Pick’s disease: tangles or Pick bodies (3-repeat tau).

• Progressive Supranuclear Palsy and Corticobasal Degeneration (tangles).

• Parkinson’s disease/Lewy body dementia: Lewy bodies.

A Prescient Suggestion

Alzheimer’s Disease

• Primary Deposited Protein is Aβ• Genes for Mendelian Forms are

– APP: precursor of Aβ– Presenilin 1 and 2: enzymes catalysing

production of Aβ from APP• Tangle (tau) and Lewy Bodies (α-

synuclein) are Secondary Pathologies.

Exon 9Exon 8

Cytosol

Lumen

PS1

I T VL A

L IW N FV V

M I S

Y

VD

A

Y

VN

K G

HW

G

IG

Exon 5Exon 4

Exon 3Exon 4

HK

AG

YK

IK

SV

S

D

R

YT

K

GQ

YL113 I

114

F

T

PFL

VT L

MV

V A T

VC

V

V

V

I M

PS1-NTF

LT

L E E D EEDEEVVQ

Q

Q

NS

R

G

RP

NS GLP PEHGLSR

RS L N

SE

HD

M

TV NRSQ29

DNRE N30

AN

Q

S QY FLP PT AE LM1

RD

EQ

NH

Exon 7Exon 8

R

P

M

L

CP

TWL I

VS

Y

AI

VVL

258

AL

AL V

D257

KG

L P EW

T

R

EL

V AQ

EN

E

AL S

290LT

F

P

V

WL

M VN

E

MT291I

YS

A

GDP

EA

QRVR

SKNY SKExon 9Exon10 E

NA

V

R

Q

ES

DT

EA

ND

DG

GS E

FWE

ES319

T320

Exon11Exon12

N

IV AI

LI G

LC

T L LLI

F411

AL

A C410

L

DW

G

TT

F

KK

A

AL

I

P

LP

SI

TF

F

GL

V

YF

AT

D

PS1-CTF

YL

VQ

PF

MD

A

QL

F

FQ

Y

H

I467

Exon11Exon10V

LKL GF I F

VYV

R377

D

G

G

L

G378

S

K

SAA

AS

T

R

S

T

E E

LEQV

AA

SE

P

E A Q R D HSL G P

DP

E

LAG

ISS

RS

H

Exon 6Exon 5

Exon 7Exon 6

V

KT

F

LG183

E184

AII

SL

LF FF I Y

H

L

FS

SL

W

L

YK160

IV161

V

LIS

HL

QR

A

G

T

TD

TFE

P

E

A

L

A

SV

VI

I

VI

L VV

NM

IM T

L

RC

KY

YR

P

LY AL

QIM I S

LA

VI

L

KY

Q

F

AL M

Exon 16Exon 17

KSN

K

Q

D

GV

Y

FF A E

HH V

F

G S DR

V

HE

A EK

K

M

APP

LM

IT

TA I V VG G VLMG I

V

I A G

V

L

VI

β secretase

α secretase

APP-NTF ...

...APP-CTF

ESIEETK D

VL

γ secretase

VM

293

Presenilinase

292

D257

D385

Exon 9Exon 8

APP-CTF

γ secretase

Presenilinase

CP

W

SY

IL

A VD

R

QE

NE

AL S

LT

F

P

V

WL

M VN

E

MTIYS

A

GDP

EA

VLF

YD

L

G

S

E E

DP

E

LAG

ISS

K

L MIT

TA I V VG G VLMG I

V

I A G

V

L

VI

...

293

292

257

385

GV

Q

April 1999

Membrane

APP wild-type

αβ

Membrane

APP 670/1 Mutation

αβ

3 kD fragment(p3)

Mainly Aβ40

Released intoextracellular fluid

αSecretases

γ

β

γ

Less3 kD fragment

(p3)

Released intoextracellular fluid

Moretotal Aβ

Deposited

β

γ

+αSecretases

γ

Membrane

APP 717 Mutations

αβ

Membrane

APP 692 Mutation

αβ

Released intoextracellular fluid

More Aβ42

Deposited

3 kD fragment(p3)

β

γ

PRESENILIN MUTATIONS HAVE SAME

EFFECT

α

γ

Released intoextracellular fluid

Moretotal Aβ

Deposited

3 kD fragment(p3)

βαSecretases

γ γ

-

APP Probably a Locus for “Sporadic” Alzheimer’s Disease

July 1999

Oct. 2001

Conclusion on Alzheimer’s Disease

• Overexpression of APP in Down syndrome causes disease.

• Overproduction of Aβ42 because of APP or presenilin mutations causes disease in a mendelian fashion.

• Genetic variability in ‘normal’ APP expression contributes to disease risk.– (not clear whether variability in presenilin expression

also contributes).

Prion Diseases

• Primary protein deposit is PrPSc: sometimes as plaques, more often much more subtle.

• Hereditary (caused by prion gene mutations).• Sporadic (of unknown cause)• Infectious (iatrogenic, cannibalistic or infectious)• Tangle (tau) and Lewy Bodies (α-synuclein) can

be Secondary Pathologies.

The First Family with a Prion Mutation

Prion Disease Conclusions• Mutations in prion gene cause mendelian disease.• Homozygosity at codon 129 prediposes to infectious disease: whether

it is MM or VV depends on the sequence of the infecting prion.• Homozygosity of either allele predisposes to sporadic CJD.• Particular promoters, presumably high expressing ones, also

predispose to sporadic CJD.• But the promoter association does not hold up for infectious disease.• Thus, the mechanism of initiation of infectious disease is different

from that of sporadic disease (the former is not concentration dependent but the latter is?)

Disease with only Tau Pathology

• FTDP-17 (previously, many families would have been called Pick’s disease): mendelian disease with variable pathology: tangles, Pick bodies or wispy tau filaments.

• Progressive Supranuclear Palsy, Corticobasal degeneration, Argyrophilic Grain Disease

• Parkinson’s Dementia Complex of Guam• Many other rare diseases including von

Economo’s disease and subacute sclerosing panencephalitis.

The microtubule associated protein tau

1 2 3-1 4 4A 5 6 7 8 9 10 11 12 13 14

Tau gene

Tau 3 repeat protein isoforms

Tau 4 repeat protein isoforms

352

1 2 3-1 4 4A 5 6 7 8 9 10 11 12 13 14

Tau gene

3812+

1 2 3-1 4 4A 5 6 7 8 9 10 11 12 13 14

Tau gene

4102+ 3+

1 2 3-1 4 4A 5 6 7 8 9 10 11 12 13 14

Tau gene

38310+

1 2 3-1 4 4A 5 6 7 8 9 10 11 12 13 14

Tau gene

4122+ 10+

1 2 3-1 4 4A 5 6 7 8 9 10 11 12 13 14

Tau gene

4412+ 3+ 10+

June 1998

June 1998

Tau Exon 10 3’ splice site mutations increase U1 snRNP binding and splicing of Exon 10

G-U-C-C-A-U-U-C-A-U-A

U1 snRNP

Splicesite

Exon 10

U

ACU

C

GA U

G

GUG

C

CAA

ACC

GU

AC

U

U (+16)

G (+13)U (+14)

(+3) A

(-2) A

U (+12)x

x

xxx

x

U1 snRNP

G-U-C-C-A-U-U-C-A-U-A

-C-A-G-U-G-U-G-A-G-U-A-C-C-U-U-C-A-C-A-C-G-U-Exon 10A A U G UU

Evolution of Human tau haplotypes (no recombination between H1/H2)

H1 H29iiiG

(+)Multiple independent mutagenic events (9iii)

1 2 3 9i 9ii 11 13 1 2 3 9i 9iia3

13A11

C9iiiG

(-)

A C A A T a0 G T G T G G C

Slippage of a0 to a1/a2

H1 (9iii)

a09iiiA

1 2 3 9i 9ii 11 13 Slippage of a3 to a4A C A A T G T

(+) H2 (a4)

a1/a2 G119ii

iG

(+)

H1 (a1/a0)1 2 3 9i 9ii 13 1 2 3 9i 9ii

a49iiiG

(-)

11 13A C A A T T G T G G C A C

(+)/(-) indicates location of intronic deletion 5’ of E10

April 1999

Worldwide Distribution of Tau Haplotype

Results

• LD extends almost the same distance in all populations (1.6Mb)

• Some breakdown at the teleomeric edge

Inversion

Haplotype dating

• Inversion/LD block implies distinct evolutions for each haplotype because there is suppressed recombination between the two haplotype clades

• Performed 2 analyses to determine the evolutionary distance between H1 and H2

Comparison of chimp and human sequence

• neither haplotype is the founder of the other, since chimp at some level resembles either haplotype

• H1/H2 diverged from ~3 million years ago (also DeCode and Antwerp data)

GAGrs752141461242

CTCrs946841457408

TCCrs73396641445400

-++ins/del941442488GAGsthQ7R41432502

GAGrs105255341429726ATTrs75451241411483

GAGrs221739441409284GCCrs76705841354620

GTCrs388579641336326AGGrs156031041334330

TCCrs186432541333623AGArs205579441307507

CTCrs107883041301910H2H1ChimpdbSNP IDPosition

Slippage of dinucleotide repeat markers

868 (21,700)62%24044475319Tau Hap 7243 (6,075)87%49644439826Tau Hap 6267 (6,675)86%25844423308Tau Hap 5542 (13,550)74%18345289761Tau Hap 3513 (12,825)75%18244752820Tau Hap 2

Predicted Age in Generations

(Years)

Major allele

frequency

Major Allele Size

LocationMarker name

• Assuming that H2 is a single founder event and an average of 25generations for each slippage event, typed 13 CEPH H2 homozygotes with microsatellite markers mapping to the region.

• The age of H2 in H. sapiens is ~10,000-30,000 years based on distribution and slippage.

H2 has been re-introduced once exclusively into European H. sapiens populations

• Contradictory evolutionary evidence:– H1 and H2 diverged ~ 3M years ago– Yet, based on slippage analysis H2 is a recent

haplotype within H. sapiens (10-30K years ago)

• Further evidence:– H2 haplotype has reduced diversity compared with H1– H2 distribution reflects the spread of European

populations and is not seen within Asian and most African chromosomes

H1, not H2 is Inverted!

Model of the evolution of the MAPT locus

Ancestral -6M years

Chimp

H2 clade?

-3M yearsInversion

H1 clade

-0.03M yearsSingle form of H2 into H. sapiens

H. Sapiens H2 haplotype

Tagging SNPs Selection

• 25 SNPs spanning the entire locus were selected from the CEPH database (www.hapmap.org)

• Using the program Tagit (popgen.biol.ucl.ac.uk/software) 5 SNPs were identified that captured the haplotype diversity of the MAPT locus

More Complex than Just H1/H2

Dissecting H1 further…

Associations with PSP… and AD

(321)0.000006

(360)0.006

(272)(n) ‘p’

564855Others

24149H1c

141513H1b

62323H2a

PSPAlzheimer Disease

Controls

MAPT and meta-analysishttp://www.alzforum.org/res/com/gen/alzgene/default.asp

Primary Tauopathies• Mutations in the opening reading frame or in the exon 10

splice area cause mendelian tau disease (FTDP-17): the precise tau pathology is largely dependent on the mutation.

• Sporadic tangle diseases, PSP and CBD are predisposed to by the tau H1 haplotype.

• Weaker association of same haplotypes with Alzheimer’s disease.

• Other sporadic tangle diseases are either not assessed (too rare) or occur in populations without an H2 allele (Guam).

• Not clear whether haplotype association reflects differences in splicing or in expression (though overexpressing mice get tangles).

Diseases with only Lewy Bodies

• Parkinson’s disease• Lewy body dementia

June 1997

Aug. 2001

Iowa Kindred Structure

Laboratory of Neurogenetics, National Institute on Aging

Laboratory of Neurogenetics, National Institute on Aging

Diffuse α-synuclein pathologies in male patient: abnormal neuronal and glial inclusions and processes

Globus pallidus

Substantia nigra

Hippocampus

Chromosomal Spreads (FISH)

Laboratory of Neurogenetics, National Institute on Aging

Lewy Bodies Disease Conclusions

• Mutations in α-synuclein can cause either mendelian Parkinson’s disease or Lewy Body dementia, sometimes both in the same family.

• Triplication (overall doubling) of the α-synuclein locus causes disease onset in the 30’s (duplication of the locus, causes disease in the 50’s)

• Genetic variability in the normal promoter contributes to risk of sporadic disease with high expression promoters being more prone to disease.

Overall Conclusions• Analysis of autosomal dominant forms of neurodegenerative diseases

in which there is pathological deposition reveal that the causative locus encodes the protein which is deposited (most cases) or the enzymes responsible for the liberation of the deposited peptide (presenilins).

• Normal genetic variability at these same loci contribute to the risk of sporadic forms of these diseases: most likely, high expressors are predisposed to disease.

• Predictions and Implications– Deposition is clearly important.– SOD and sporadic ALS?– Genetic variability in degradation may also contribute to risk?

Whole Genome Study For AD (presently underpowered ~180 cases and controls)

Loss of Heterozygosity (10% North American Controls Show Evidence for

Consanguinity

Sample Whole Genome DataChromosome 5 Control Male of 65 years