Inherited Disorders of Neuromuscular Transmission – from ...

Inherited Disorders of Neuromuscular Transmission –

from gene discovery to tailored treatments

IRDiRC conference, Dublin

Forward Look Session

April 17, 2013

Hanns LochmüllerInstitute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK

Hanns Lochmüller - Congenital Myasthenic Syndromes (CMS)

Clinical Criteria:� myasthenic syndrome: exercise induced muscle weakness� early onset of disease: birth / first years of life (< 2 years)� no response to immunosuppressive treatment� treatment with anticholinesterase drugs may lead to

improvement

CMS: Diagnostic Criteria


Neonatal:� poor suck and cry, choking spells, ventilatory failure, ptosis;

symptoms worsened by crying or activity

Infancy, childhood:� delayed motor milestones; seldom learn to run � cannot climb steps well; abnormal fatigability on exertion � cannot keep up with peers in sports� Ptosis; fixed or fluctuating ocular palsies� Spinal deformities, reduced muscle bulk

(Uehara and Desaki, in Salpeter, 1987; Ed.)

The neuromuscular junction - structure


Ca++ channel

ChAT deficiency

AChR

ColQ

Sodium channel, voltage-gated

laminin beta 2

agrin

axon

synaptic vesicle

acetylcholinesterase

potassium channel

AcetylCoA

Cholin

ACh

muscle

Lrp4

presynaptic

endplate-AChEdeficiency

ChAT CHAT

synaptic

10q11

COLQ 3p25

LAMB2 3p21 laminin

Kinetic changes of AChR/ endplate-AChRdeficiency

CHRNA1 2q24

rapsyn

CHRNB1CHRNDCHRNE

17p112q3317p13

agrin AGRN 1pter

postsynaptic

rapsyn (impaired clustern of AChR)

MuSK muscle-specific kinase

RAPSN 11p11

MUSK 9q31

Dok-7 downstream of kinase 7 DOK7 4p16

SCN4A 17q23Nav

GFPT1 GFPT1 2p13glutamine:fructose-6-phosphate amidotransferase

CHRNEno mutation

RAPSN

MUSK DOK7

CHRNA1

COLQ

CHRND

CHRNB1

CHAT

GFPT1


Identified genetic defects in a large CMS cohort(Munich, 1997-2011)

Most frequent !

CHRNE

CHRNE mutations leading to AChR deficiency: clinical clues

�Onset of disease: early infancy, typically within the first year of life

�Clinical symptoms: ptosis, fixed ophthalmoparesis, weakness of bulbar muscles, in general mild phenotype and benign course of disease

�Very rare: respiratory insufficiency, severe generalized weakness

�Anticholinesterase medication: clearly positive response to short-term and long-term treatment


CHRNEno mutation

RAPSN

MUSK DOK7

CHRNA1

COLQ

CHRND

CHRNB1

CHAT

GFPT1


LG-CMS represent a significant proportion of total CMS cases

� Onset usually in the first years of life, but late-onset is possible

� first symptom: limb girdle weakness(waddling; sometimes inward rotation of knee and feet)

� other frequent symptoms: ptosis, respiratory crisis (often with need for asisted ventilation)

� Mestinon ineffective for the long-term(sometimes worsening)

CMS with DOK7 mutations: clinical clues


LG-CMS with tubular aggregates – a distinct entity

�Limb girdle weakness�No ophthalmoplegia, no ptosis�Benefit from esterase inhibitors�No mutations in DOK7�Mutations in GFAT or DPAGT

Tubular aggregates


Zebrafish as animal model


Reduced number and size of AChR clusters after downregulation of Dok-7

Motor neurons mergeAChR

Non

-inje

cted

zDok

7MO

inje

cted

Neuromuscular junctions at 48 hpf


No

n-i

nje

cted

zDo

k7M

O in

ject

ed

AChR Slow muscle merge

Slow-twitch muscle fibre morphology is altered after downregulation of Dok-7

Slow-twitch muscle fibres and acetylcholine receptors at 48 hpf


DOK-7 knockdown in Zebrafish - summary

� Dok-7 deficient zebrafish have less and smaller

neuromuscular junctions and motility defects

� Dok-7 deficiency leads to misalignment of slow muscle

fibres. This is a previously unrecognised function of Dok-7

outside the NMJ

� This function is MuSK independent, as MuSK deficiency

causes a more severe loss of acetylcholine receptors, but

leaves slow muscle fibres intact

� Zebrafish are a good animal model for studying the

neuromuscular junction


Defect Gene Therapy

Cholin-Acetytransferase Deficiency CHAT AChEI, prophylactic usefor apnea prevention!

Endplate AChE Deficiency COLQ ephedrine? AVOID AChEI!

Receptor Deficiency CHRNA-E AChEI, 3,4 DiaminopyridineSlow Channel Syndrome CHRNA-E Fluoxetine, AVOID AChEI!Fast Channel Syndrome CHRNA-E AChEI, 3,4 DiaminopyridineRapsyn Defect RAPSN AChEI, prophylactic use?Sodium channel, voltage-gated SCN4A AChEI?? (1 family)MuSK (muscle-specific kinase) MUSK AChEI ?? (1 family)

Dok-7 (downstream of kinase 7) DOK7 ephedrine, albuterol/salbutamol?GFPT1/GFAT1 GFPT1 AChEI

CMS – Differential Therapy


Summary

�CMS are clinically very variable, genotype-phenotype correlations are difficult to establish. However, there are some clues pointing towards the underlying genetic defect


�Detection of the genetic defect is important for the selection of the appropriate drug therapy

�Clinical vigilance for neuromuscular transmission defects is key to accurately diagnose and treat patients with CMS

�Standard clinical trials may be difficult, but standardized follow-up of patients and international collaboration may help to improve standards of care and therapy

16|TREAT-NMDBioBank

Patient Registries

Care & Trial Site Registry

Outcome Measures

Standards ofDiagnosis &

CareTACT

Website & Communications

Joint Research for DMD

Standard Operating

Procedures

Three year

work plan

www.treat-nmd.eu

Action Plan

3 year plan

Milestone-driven approach

Maintains network

momentum & establish

new goals

Website &

Communication

Extensive website

250,000 annual page hits

70,000 visitors annually

Monthly newsletter sent

to 3,500 recipients

Proven communication

platform

Secretariat - Kate Bushby

Volker Straub

Funding – EC (operating grant)

TACT

TREAT-NMD Advisory

Committee for

Therapeutics,

Expert multidisciplinary

body

Independent and objective

guidance on advancing

new therapies for

neuromuscular diseases

Chair – Dominic Wells

Funding - US (Dept of Defense)

Joint research

Regular meetings to

consolidate efforts and

jointly tackle common

problems

Topics based on necessity,

hosting to be rotated

between partners

Leads - Eric Hoffman

Annemieke Aartsma-Rus

Filippo Buccella

Funding - COST

SOPs

Unified experimental

protocols improve the

comparability of studies

Drawn up by a group of

independent researchers

(listed in each protocol)

Approx 40 sops updated

regularly

EuroBioBank

Unique network of 18

members

Stores & distributes

440,000 quality DNA, cell

and tissue samples

Leads - Marina Mora

Lucia Monaco

Marco Crimi

Funding - Fondazione Telethon

Patient Registries

Standardized genetic &

clinical core data for trial

recruitment

Interface can vary

between countries whilst

still able to share core data

Ethical & governance best

practice

>10,000 DMD patients

across 30 countries

Leads - Jan Verschuuren

Hugh Dawkins

Funding - AFM & EC

(operating grant)

Care & Trial Site

Registry

Information about each

registered trial site kept in

one location for ease of

comparison

Addresses organisational

difficulties of identifying

appropriate sites when

setting up a trial

Coordinated by University

Medical Center Freiburg

Outcome measures

Tests to decide whether

treatment being tested in

a trial is having any effect

Vital to use the correct

outcome measure to

prove if a treatment works

Working to harmonise the

use of most appropriate

outcome measures for

different diseases

Lead - Eugenio Mercuri

Funding - Telethon & Parent

Organizations

Standards of

Diagnosis & Care

International consensus

publication recommended

standards of care

DMD-SMA-CMD-LGMD

Family guides

in 25 different languages

translations verified

Printed booklets or

download from

website

Leads - Thomas Sejersen

Kathy North

2007-2011EU funded Network

2012 onwardsAlliance funded

through multiple

streams with global

partners & membership

GovernanceChair – Hanns Lochmüller

Vice – Annemieke Aartsma-Rus

Executive Committee

Supported by academic advisory

board (“task force”) of NMD

leaders

Angela Abicht S BaumeisterV Mihaylova

Juliane Müller

Thank you to all sponsors, referringclinicians, patients

and families!


V Guergueltcheva

Marina DuslAmina Chaouch

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