tauopathies a contemporary way to consider a set of neurodegenerative diseases based on their...

Tauopathies

A contemporary way to consider a set of neurodegenerative diseases based

on their molecular signature

John Growdon, M.D.

Neurofilament tangles are composed of paired helical filaments in AD, and straight filaments in conditions such as PSP.

Electron microscopy of neurofilament fibers, labeled by polyclonal anti-tau.

Tau Protein

• A microtubule associated protein largely localized to neuronal axons

• Important biological role in stabilizing microtubules and thereby aiding neuronal structure and axonal transport

• Hyperphosphorylation of tau at specific serine & threonine epitopes impairs it normal function; this process either leads to neuronal dysfunction & death, or is a marker of neuronal death.

Tauopathies: Clinical Diseases

• Alzheimer’s disease• Dementia pugilistica• Guam ALS/PD• Pick Disease• Argyrophilic grain

dementia• Nieman-Pick, type C• SSPE

• PSP• MSA• Corticobasoganglionic

degeneration• FTDP-17• Postencephalitic PD• Autosomal recessive

PD

History of LT born: 6/26/05 died: 11/16/87

1977: 72 y.o. woman with subtle onset of difficulty finding words in speaking.

1980: MGH examination. No focal neurologic signs. Speaking greatly impaired

with anomia & circumlocutions (pen=“something you write with”); intact

memory; no apraxia; preserved personality; independent ADLs. BDS = 2.

1982: worsening expressive language; sings better than she speaks. Recent onset

of apraxia. Stopped driving a car. Sweet personality. BDS = 12.

1983: expressive & receptive aphasia. Withdrawn personality with apathetic mood.

BDS = 16 .

1984: mute, but occasional non-verbal communication. No housework, but still

cares for personal hygiene.

ICD-10 Diagnostic Criteria for Pick’s Disease

1. Dementia.

2. Slow steady deterioration.

3. Two or more of the following:

a. Emotional blunting

b. Apathy or restlessness

c. Coarsening of social behavior

d. Aphasia

4. Relative preservation of memory & parietal-lobe functions.

Caregiver Report of Initial Symptoms in Pick Disease (PiD) and Alzheimer Disease (AD) Patients: Mean Prevalence (%)

Symptom PiD n=34 AD n=78

Memory 61.8 93.6 p<0.001

Speech 29.4 p<0.05 9.1

Use of objects 0.6 2.6

Socializing 2.9 2.6

Personality 53.3 p=0.07 14.1

Irritability/aggressiveness 11.8 3.9

Reasoning 5.9 6.5

Sense of direction 0.0 7.8

Vision 0.0 1.3

Mean Cognitive Test Scores (+/- SD) at Initial Examination for PiD, AD, and Normal Control Subject (NCS) Groups

Test PiD AD NCS

NYU Immediate Recall 3.1 (2.7) 2.5 (1.9) 8.4 (3.1)

NYU Delayed Recall 2.3 (3.1) 0.7 (1.3) 7.8 (3.2)

Geometric Figure Recall 4.0 (3.6) 2.2 (2.9) 7.2 (2.6)

Benton Visual Retention 9.2 (3.0) 8.3 (2.8) 11.9 (1.7)

Boston Naming 24.6 (9.7) 25.8 (9.1) 37.1 (5.0)

Stroop Color Naming 13.3 (10.1) 11.2 (7.6) 29.3 (10.9)

Luria Mental Rotation 8.1 (1.9) 6.0 (2.8) 8.3 (2.4)

Picture Arrangement 5.9 (4.3) 4.4 (3.1) 10.5 (5.1)

NCS scores were significantly superior to AD scores on all tests (p<0.05), and to PiD on all tests (p<0.05) on all tests except the Luria. PiD scores were significantly superior to AD scores on the NYU Delayed Recall and Luria tests (p<0.001).

Cognitive test scores over time: AD open circles; Pick black circles

As judged by global measures of dementia severity, PiD (black circles) progresses faster than AD (open circles).

Clinical Aspects: PcD vs. ADInitial Symptoms: Personality change & language impairments are more commonly reported in PcD; memory loss reported in both, but was more common in AD.

Cognitive Tests: PcD superior to AD in explicit memory & visuospatial functions. Over time, dementia worsened in both. PcD dclined more rapidly than AD on language tests and measures of global dementia severity.

Alzheimer’s disease is more prevalent than Pick’s disease

At the Massachusetts General Hospital between 1985 and 1996, 63% of the patients examined in the Memory Disorders Unit had a clinical diagnosis of AD. During the same period of time, only 2% of the patients had a clinical diagnosis of Pick’s disease.

Of autopsied cases (n=696), 52% had AD and 3% had Pick’s disease.

Six tau isoforms that are expressed in human brain: alternatively splicd exons 2,3 & 10 are shown in white; black bars indicate the microtubular-binding repeats.

Electrophoretic tau profiles distinguish AD from Pick’s disease (PiD).

Characteristic western immunoblots using phosphorylation-dependent monoclonal antibodies. In AD, all isoforms are phosphorylated; in PiD, only 3R isoforms.

MGH cases, courtesy of Andre Delacourte

Do defects in alternative exon 10 splicing of the tau gene underlie Pick disease?

• Missense mutations and splice variants of tau, many near exon 10, account for hereditary FTDP-17, a condition similar to Pick.

• Antibodies to exon 10 fail to immunostain Pick bodies.

• Mostly 3R tau (55 & 64 kD bands) in Pick.• Vulnerability to 3R tau, or altered 3R:4R ratio, in

frontal & temporal cortices may account for the regional distribution of degeneration in Pick.

Frontotemporal Lobar Degeneration

• Pick’s Disease

• Frontal Lobe Dementia +/- ALS

• Primary Progressive Aphasia

• Semantic Dementia

• FTD with Parkinsonism linked to chr. 17

• Corticobasalganglionic Degeneration

History of Mr. GSC born: 3/17/26 died: 1/27/95

1979: Insidious onset of difficulty arising from a chair.

1982: Hypophonia.

1985: Postural instability, with falling backward. Hip fracture.

1986: Difficulty focusing eyes and looking down when reading a page in a book.

1989: MGH Examination. Slow fractionated saccades; 3 mm vertical gaze. PD

stage 3 stigmata: akinesia, limb rigidity, en bloc turns. BDS = 2 (normal).

1991: Absent vertical saccades. Blepharospasms. Dsyphagia. Micrographia.

1992: Neck rigidity. Dysarthria. Requires assistance to stand; multiple falls with

fractured collarbone. Stage 4 PD.

1993: Eyes fixed…no volitional movement but intact oculocephalic reflex. Fell

with resultant skull fracture.

NINDS-SPSP Criteria for Dx PSP

• Gradually progressive disorder.

• Onset at age 40 years old or later.

• Either vertical supranuclear (up or down) gaze palsy or

• Both slowing of vertical saccades and prominent postural stability with falls in the first year on disease onset.

Supportive Criteria for Dx PSP

• Symmetric akinesia or rigidity.• Abnormal neck posture, especially retrocollis.• Poor or absent response of parkinsonism to

levodopa therapy.• Early dysphagia and dsyarthria.• Early onset of cognitive impairment, including at

least 2 of these: apathy, decreased verbal fluency, impaired abstract reasoning, & utilization behavior.

Memory is less affected in PSP than in classic dementing illnesses such as AD

Clinical Characteristics of PSP Patients and Separate Groups of Normal Control Subjects (NCS) Studied with Cognitive Tests & SPECT

Subjects Age, yrs. Duration, yrs. H&Y stage

PSP n=11 67.5 4.6 3.6

NCS- SPECT n=10 70.8 na na

NCS-Cognition n=16 66.5 na na

Cognitive Test Scores of PSP Patients and Normal Control Subjects

Cognitive Test PSP Control Subjects

Delayed Story Recall 5.8 (3.0) 8.3 (2.5)

Boston Naming 33.5 (2.3)** 38.2 (3.9)

Verbal Fluency “S” 4.1 (2.2)*** 18.8 (7.0)

Stroop 39.9 (23.7)*** 106.3 (9.0)

Raven’s Matrices 23.6 (5.2)*** 32.5 (3.3)

Picture Arrangement 4.0 (2.8)** 11.4 (4.5)

** = p<.01 ***= p<0.001

Thalam.

10181

Alzheimer

(1/1)

Alzheimer

(Wat)

(1/5)97 083

Gel 8-15 %Load: 20µL AD2 at 1/10 000e

Quantification of pathological tau proteins

:

.Cere

bellum

10186

Cortex

Temporal

10182

Cortex

Frontal

10179

Cortex

Frontal

10185

Cortex

Central

10177

Cortex

Occipital

10178

White

matter

10183

Cortex

Central

10184

Caudate

nucleus

10180

0

20

40

60

80

100

Wat

1/5

1018

2

1017

9

1018

5

1017

7

1018

4

1017

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1018

3

1018

0

1018

1

1018

6

Wat

1/1

6964

74

Tau doublet at 69 & 64kD that is characteristic of PSP

MGH case, courtesy of Andre Delacourte

74

64

60

In PSP, aggregated filaments are largely hyperphosphorylated tau 4R isoforms encoded by exon 10

The Search for Genetic Causes of PSP: 2004 Update

1. Hyperphosphorylated 4R tau in tangles

2. The tau gene A0 allele (a dinucleotide repeat in the intron following exon 10) is over represented in PSP.

3. The tau H1 haplotype has high sensitivity (98%) but only modest specificy as a marker for PSP

4. There are rare families with atypical PSP apparently caused by mutations in the tau gene.

5. Mutations in the tau gene have not been found in most sporadic PSP cases.

6. Some tau smoke, but no fire…more to follow!