RYR1 and TTN: The challenge of giant genes implicated in Centronuclear Myopathy (CNM) Heinz Jungbluth MD PhD & Mathias Gautel MD PhD 1 Department of Paediatric Neurology, Neuromuscular Service, Evelina Children’s Hospital, London; 2 Randall Division for Cell and Molecular Biophysics, Muscle Signalling Section, and 3 Clinical Neuroscience Division, IoPPN, King’s College London ZNM Myotubular Trust European Family Conference, London, July 14 th , 2018
34
Embed
RYR1 and TTN: The challenge of giant genes implicated in … › wp-content › uploads › 2018 › … · RYR1 and TTN: The challenge of giant genes implicated in Centronuclear
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
RYR1 and TTN: The challenge of giant genes implicated in Centronuclear Myopathy (CNM)
Titin missense variants cause a wide variety of diseases
TMD/LGMD2J
Chauveau et al., HMG 2014
A recurrent, recessive TK mutation leading to myopathy: W34072R
Compound heterozygous, truncation after Z-disk (maternal), missense in kinase (paternal). No FH Cardiomyopathy, transplantation at age 3, skeletal myopathy.
New case (A. Ferreiro, Paris): Compound heterozygous, truncation in skeletal I-band (paternal), W34072R missense in kinase (maternal). No FH No cardiomyopathy, only skeletal myopathy.
W34072R is a recurrent, recessive pathogenic mutation in TK, a constitutively expressed domain.
With Ana Ferreiro, Carsten Bönnemann
A recessive TK mutation leading to myopathy: W34072R
Soluble, monomeric, no aggregation
Chauveau et al., HMG 2014
Computational models of TTN Fn3 domains are too inaccurate for mutation impact analysis
(iTasser)
Experimental structures and homology-based structural models required for accurate impact prediction
SG Tm: 54°C
WT Tm: 64°C
A63 WT (1.65Å)A63 SG (1.43Å)
A63 WT A63 SG
Ser Gly
Temperature (°C)
Rel
ativ
e Fl
uore
scen
ce
D zone C zoneI / A
1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 11A63
serine side chain forms H-bond with valine.
S14141G variant destabilises A63 domain
Common Titin missense variants are not destabilising
D zone C zoneI / A
1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 11A81 A110
RC:62°C
WT:62°C
WT:62°C
IV:63°C
A81 A110
Temperature (°C)
Rel
ativ
e Fl
uore
scen
ce
Temperature (°C)
TITINdb, a webtool to assess titinopathy-linked missense variants
Laddach, A., Gautel, M., and Fraternali, F., TITINdb-a computational tool to assess titin's role as a disease gene. Bioinformatics, 2017. 33(21): p. 3482-3485.
Tipping, K.W., P. van Oosten-Hawle, E.W. Hewitt, and S.E. Radford Trends Biochem Sci, 2015. 40: 719-27.
Conclusions
• TTN is the major scaffold of the sarcomere and a major gene for hereditary myopathies
• Recessive missense variants can become dominant in compound heterozygous settings when expressed with recessive truncating variants
• Discriminate bad from neutral and good?
• Truncating as well as destabilising missense variants frequent in “normal” population
• Accurate assessment of missense variants requires a rational assessment strategy including structural and functional data.
• Destabilising mutations can be recessive or dominant
• TITINdb designed to help with initial assessment of TTN missense variants
King’s College London Alexander AlexandrovichBirgit BrandmeierAtsushi FukuzawaAndrea GhisleniMark HoltKatharina JennichesAy Lin KhoEva MasierioRoksana NikoopourJing QiMartin ReesLuke SmithJessica Stuart
Anna LaddachFranca Fraternali
Mark Pfuhl
Stefano PernigoRoberto Steiner
Sergi Garcia-Manyes
King’s BHF Centre for Research Excellence
Göttingen UniversityJing QiKaomei Guan
Max-Planck-Institute DortmundStefan Raunser
Max-Perutz-Labs ViennaKristina Djinovic-Carugo
EMBL HamburgMatthias Wilmanns
Oxford UniversityKatja GehmlichHugh Watkins
University CologneMarcus Krüger
UKE HamburgLucie Carrier
UCL/Bart’s Luis LopesPetros SyrrisPerry Elliot
UCL ICH/GOSH Francesco Muntoni
Evelina London Children’s Hospital/ Tom Cullup, Heinz JungbluthGSTT Gerald Carr-White
West of Scotland Regional Genetics Glasgow Cheryl Longman
Université Paris Diderot-CNRS Claire ChauveauVirginie CarmignacAna Ferreiro
NIH Bethesda Carsten Bönnemann
University Helsinki Peter HackmanAnna ViholaBjarne Udd
Cologne University Hospital Sebahattin Cirhak
Göttingen University Hospital Elke HobbiebrunkenGabriele DekomienEkkehard Wilichowski
Radboud University Medical Centre Nicol VoermansNijmegen
Hôpital des Enfants Joël FlussGenève
Titin mutations in myopathies: open questions
• Why do truncating mutations mostly appear to be silent?
• Do missense mutations lead to phenotypic penetrance of truncating mutations, or vice versa?
• Do recessive missense mutations cause similar phenotypes in compound heterozygosity or homozygosity?
• What is the cellular fate of truncated titin? • What is the cellular fate of missense titin?
• Is perturbed protein homeostasis a common denominator?
• How does perturbed proteostasis impact on myocyte function?
Sarcomeric M-band links to protein quality control Disease implications
Fukuzawa et al., JCS 2008
Titin
Obsl1
Obscurin
Titin
Myomesin
Nbr1
Cullin-7
MURFs myospryn
SQSTM1
COP9
Calpain-3
TK mutations in HCM, specific myopathies
LGMD2A
LGMD2J, Salih myopathy
• Titin, a molecular ruler – blueprint to determine the length of myosin filaments,
the length of the I-band, and the thickness of the Z-disk
• Titin, a molecular spring – maintains myosin filaments centrally in the sarcomere – Ensures balanced forces between both halves of
sarcomere
• Titin, a “signal transducer” – Titin organises numerous cellular communication
pathways
Titin: a multitasking giant The biggest protein in the human body
myomesin
α-actinin
myosin filaments
M ZZ I IAA
NH2 COOHTitin
actin filaments
NH2
titin
COOH
The sarcomere and regulators of sarcomeric turnover