Mutation - Cftrscience

A Quick Guide to the
R117H
Mutation
CFTR
SCIENCE
© 2016 Vertex Pharmaceuticals Incorporated | VXR-HQ-02-00045a(1) | 03/2016
Loss of CFTR activity is the underlying cause of
cystic fibrosis (CF)1
Spectrum of Phenotypes Associated
With Total CFTR Activity1,2
•P
eople with 2 CFTR mutations
resulting in loss of CFTR activity
generally have a CF phenotype,
which may include1-3,6
100%
Clinical Phenotype
No CF Disease
–E
levated sweat chloride
(>60 mmol/L)
– Pancreatic insufficiency
Individuals with 2 normal alleles and CFTR mutation carriers
– CBAVD­a
– Lung function decline over time
Total CFTR
Activity
CFTR-related
Disorders
% of Normal
Clinical entities associated with CFTR dysfunction
that do not fulfill diagnostic criteria for CF, e.g., CBAVD,
acute recurrent or chronic pancreatitis and bronchiectasis
Some CFTR mutations
result in residual or
partial CFTR activity3-5
0%
Cystic Fibrosis
0%
Total CFTR
Activity
100%
–P
seudomonas aeruginosa
colonization
Some CFTR mutations
result in little to no
CFTR activity3-5
0%
100%
Typical phenotype: sinopulmonary disease, sweat
chloride >60 mmol/L,
insufficiency,
Totalpancreatic
CFTR
Activity
appearing early in life.
In some patients, progression
of disease is delayed or not all features are present
CBAVD, congenital bilateral absence of the vas deferens.
a
References: 1. Davis PB et al. Am J Respir Crit Care Med. 1996;154(5):1229-1256. 2. Rowe SM et al. Proc Am Thorac Soc. 2007;4(4):387-398.
3. Zielenski J. Respiration. 2000;67(2):117-133. 4. Sheppard DN et al. Nature. 1993;362(6416):160-164. 5. Welsh MJ, Smith AE. Cell. 1993;73(7):
1251-1254. 6. Castellani C et al. J Cyst Fibros. 2008;7(3):179-196.
2
Levels of CFTR activity affect survival in CF1
Survival Curves by CFTR Activity During a 10-Year Follow-Up
(1993-2002) of Patients From the US CFF Registrya
Survival Probability
1.00
0.75
n=1126
0.50
n=14,525
0.25
Residual CFTR activity (Class IV, V): R117H, R334W, R347P, 3849+10KbC–›T, 2789+5G–›A, A455E
Severely reduced CFTR activity (Class I, II, III): G542X, R553X, W1282X, R1162X, 621-IG–›T,
1717-1G–›A, 1078delT, 3659delC, I507del, N1303K, S549N, G85E, F508del, G551D, R560T
0.00
0
10
20
30
40
50
Risk Time (Age)
Adapted with permission from McKone EF et al. Chest. 2006;130(5):1441-1447.
These data represent population-based outcomes.1 Individual outcomes
in cystic fibrosis are variable.
aData are from a retrospective study of patients enrolled in the Cystic Fibrosis Foundation patient registry measuring risk of death over a 10-year observation period
from 1993 to 2002. Patients were grouped as having a high-risk or low-risk genotype based on the functional effects of their class of CFTR mutation on phenotype
and mortality. Patients having a Class I, II, or III mutation on both alleles were considered high-risk, while patients having at least 1 Class IV or V mutation were
categorized as low-risk. A total of 15,651 patients had a CFTR genotype of a known functional class; 14,525 (93%) had a high-risk CFTR genotype and 1126 (7%)
had a low-risk CFTR genotype.1
References: 1. McKone EF et al. Chest. 2006;130(5):1441-1447. 2. The World Bank. http://data.worldbank.org/indicator/SP.DYN.LE00.IN?page=2. Accessed
November 12, 2015. 3. MacKenzie T et al. Ann Int Med. 2014;161:233-241.
•L
ife expectancy in Western
countries (general population
born in 2000) is ~79 years2
•B
etween 1993 and 2002,
median survival for US patients
with genotypes associated with
little to no CFTR activity was
36.3 years (95% CI, 35.5 to
37.6 years), while median
survival for those having
genotypes associated with
residual CFTR activity was
50 years (95% CI, 47.1 to
55.9 years)1
– In this study, R117H was
considered only as a Class
IV CFTR mutation and
patients were part of the
residual CFTR activity group
•M
ore recent US data
(2000-2010) suggest median
survival across genotypes
continues to improve3
3
R117H is the most common residual function CFTR
mutation and the fifth most common CFTR mutation
in the world1,2
Prevalence of the R117H Mutation in Patients With
Cystic Fibrosis (% of Patients With at Least 1 Allele)
• In the CFTR2 global
database, ~2% of patients
with CF have at least 1
copy of the R117H
mutation2
Additional sources report
frequency of the R117H mutation
on CF alleles
US : 3%
3
Europe:
UK4: 4%
Ireland5: 4%
France6: 2%
Belgium7: 2%
Netherlands8: 2%
Germany9: 0.5%
Country
% of Alleles
Norway12
3%
Greece
1%
12
Aus10: 4%
New Zealand11: 2%
References: 1. Sheppard DN et al. Nature. 1993;362-3):160-164. 2. US CF Foundation, Johns Hopkins University, The Hospital for Sick Children. The Clinical and
Functional TRanslation of CFTR (CFTR2). http://www. cftr2.org. Accessed November 12, 2015. 3. Cystic Fibrosis Foundation. Cystic Fibrosis Foundation Patient Registry
2013 Annual Data Report. Bethesda, MD. © 2014; Cystic Fibrosis Foundation. 4. Cystic Fibrosis Trust. UK Cystic Fibrosis Registry Annual Data Report 2014. © 2015; Cystic
Fibrosis Trust; London, UK. 5. The Cystic Fibrosis Registry of Ireland. 2013 Annual Report. © CFRI, 2015; Dublin, Ireland. 6. French Cystic Fibrosis Registry. Annual Report
2013. © Vaincre la Mucoviscidose and Ined, 2015; Paris, France. 7. Belgisch Mucoviscidose Register – Registre Belge de la Mucoviscidose. The Belgian Cystic Fibrosis
Registry. Summary Report 2011. © 2014; Institute of Public Health (WIV-ISP), Brussels, Belgium. 8. Nederlandse Cystic Fibrosis Stichting. Dutch Cystic Fibrosis Patient
Registry. Report on the Year 2014. © 2015; NCFS: Baarn, Netherlands. 9. Mukoviszidose e.V. und Mukoviszidose Institut gemeinnützige Gesselschaft für Forschung und
Therapienntwicklung mbH. Beriichtsband Qualitätssicherung Mukoviszidose 2012. © 2013, Bonn, Germany. 10. Cystic Fibrosis Australia. Australian Cystic Fibrosis Data
Registry 2013–16th Annual Report. © 2015; Cystic Fibrosis Australia; Baulkham Hills NSW, Australia. 11. Cystic Fibrosis Association of New Zealand. PORT CFNZ National
Data Registry, 2014 Registry Report. Christchurch, New Zealand. 12. Bobadilla JL et al. Hum Mutat. 2002;19(2):575-606. 13. World Health Organization. The molecular genetic
epidemiology of cystic fibrosis: report of a joint meeting of WHO/ECFTN/ICF(M)A/ECFS; June 19, 2002; Genoa, Italy. © World Health Organization; 2004.
Austria13
0.7%
Canada
0.6%
13
Denmark13
0.5%
Switzerland13
0.5%
4
The R117H mutation results in reduced channelopening and conductance of the CFTR protein1-4
Illustrative Example of Class III Defect With Class IV Defect
CFTR Turnover
CFTR Function
CFTR
Trafficking
CFTR Trafficking
Posttranslational
modification
Immature CFTR
CFTR Processing
Translation
mRNA
CFTR Synthesis
• R
117H is a missense
mutation. R117H-protein
channels reach the apical
cell surface, but their
function is decreased1-4
– R
117H produces a
CFTR protein with
reduced channel-open
probability (or gating),
characteristic of a
Class III mutation
– R
117H also results in
decreased chloride
conductance, typical
of a Class IV mutation
mRNA
Transcription
DNA
References: 1. Welsh MJ, Smith AE. Cell. 1993;73(7):1251-1254. 2. Castellani C et al. J Cyst Fibros. 2008;7(3):179-196. 3. Zielenski J. Respiration. 2000;67(2):117-133.
4. Sheppard DN et al. Nature. 1993;362(3):160-164.
5
CF disease in patients with the R117H mutation is
influenced by the CFTR poly-T tract variant1-8
Intron 8 Poly-T Variant Length Affects Splice Efficiency
During R117H-CFTR Protein Synthesis1-3
Number
of thymidine
residues
TGmTTTTTTTTTAAACAG
TGmTTTTTTTAAACAG
TGmTTTTTAAACAG
Exon
CFTR gene
Intron 7
8
9T
7T
5T
Exon
Intron 8
9
Exon
Intron 9
Exons
7
8
9
10
Exons
10
7
8
10
Full-length CFTR mRNA
mRNA without exon 9
Normal CFTR protein
No CFTR protein
Longer poly-T length
More channels
More chloride transport
Shorter poly-T length
Fewer channels
Less chloride transport
• R
117H-5T: Causes the
greatest reduction of functional
CFTR at the apical cell surface.
Typically, 5T in cis with
R117H (i.e., on the same
allele) is associated with a CF
phenotype2-5,9,10
• R117H-7T: Less likely than
R117H-5T to result in CF,
however, individuals can
develop CF. Patients who have
7T in cis with R117H may still
need to be monitored for the
development of CF 5-10
• R117H-9T: Highly unlikely
to result in CF4,5
Adapted with permission from Claustres M. Reprod Biomed Online. 2005;10(1):14-41.
References: 1. Castellani C et al. J Cyst Fibros. 2008;7(3):179-196. 2. Claustres M. Reprod Biomed Online. 2005; 10(1):14-41. 3. Chu C-S et al. Nat Genet. 1993;3:151-156.
4. Kiesewetter S et al. Nat Genet. 1993;5:274-278. 5. Massie RJ et al. Eur Respir J. 2001;17(6):1195-2000. 6. O’Sullivan BP et al. Pediatrics. 2006;118(3):1260-1265.
7. Lording A et al. J Cyst Fibros. 2006;5:101-104. 8. Peckham D et al. J Cyst Fibros. 2006;5:63-65. 9. Zielenski J. Respiration. 2000;67(2):117-133. 10. US CF Foundation,
Johns Hopkins University, The Hospital for Sick Children. The Clinical and Functional TRanslation of CFTR (CFTR2). http://www.cftr2.org. Accessed November 12, 2015.
6
The R117H allele results in residual total
CFTR activity1-6
Total CFTR activity can be defined as total ion transport mediated by
CFTR protein channels at the cell surface, depending on CFTR protein
quantity and function.5
CFTR
Quantity
The R117H-7T allele
diminishes CFTR
protein quantity
less than the
R117H-5T allelle
x
x
CFTR Function
Channel-open
Probability
R117H allele
results in reduced
channel-open
probability
1
The R117H-5T allele
diminishes CFTR
protein quantity
more than the
R117H-7T allelle
Reduced
Synthesis
x
x
Conductance
R117H allele
results in reduced
conductance
2
Defective
Channel-open
Probability
(Class III)
=
Total
CFTR Activity
=
Residual
R117H-CFTR
Activity
3
Defective
Conductance
(Class IV)
References: 1. Castellani C et al. J Cyst Fibros. 2008;7(3):179-196. 2. Zielenski J. Respiration. 2000;67(2):117-133. 3. Welsh MJ, Smith AE. Cell. 1993;73(7):1251-1254.
4. Green DM et al. Respir Res. 2010;11:40. doi: 10.1186/1465-9921-11-140. 5. Sheppard DN et al. Nature. 1993;362(3):160-164. 6. Kiesewetter S et al. Nat Genet.
1993;5:274-279.
1
The 5T variant diminishes
CFTR protein quantity more
than the 7T variant…
2
…while R117H reduces
CFTR protein function
through reduced
channel-open probability
and conductance…
3
…resulting in reduced but
residual total CFTR activity
7
Both CFTR alleles play a role in determining phenotype
or disease severity1-7
100%
No CF Disease
Normal individuals and CF carriers
CFTR-related Disorder
Total
CFTR
Activity
Clinical entities associated with CFTR
dysfunction that do not fulfill diagnostic
criteria for CF
Cystic Fibrosis
•A
n R117H allele results
in residual CFTR activity.
The phenotype of a
particular patient is also
influenced by the mutation
on the other allele. The
R117H allele results
in variable phenotypes1-7
•R
117H typically results in
the indicated phenotypes
0%
Allele 1
Normal
Normal
Normal
Residual
Residual
Little
to None
Allele 2
Normal
Residual
Little
to None
Residual
Little
to None
Little
to None
Total CFTR Activity
Total CFTR Activity
Adapted from Zielenski J. Respiration.
2000;67(2):117-133.
References: 1. US CF Foundation, Johns Hopkins University, The Hospital for Sick Children. The Clinical and Functional TRanslation of CFTR (CFTR2).
http://www.cftr2.org. Accessed November 12, 2015. 2. deGracia J et al. Thorax. 2005;60(7):558-563. 3. Cystic Fibrosis Genotype-Phenotype Consortium. N Engl J Med.
1993;329(18):1308-1313. 4. Davis PB et al. Am J Respir Crit Care Med. 1996;154(5):1229-1256. 5. Castellani C et al. J Cyst Fibros. 2008;7(3):179-196.
6. Zielenski J. Respiration. 2000;67(2):117-133. 7. Massie RJH et al. Eur Respir J. 2001;17:1195-1200.
8
R117H in combination with another allele that
produces little to no CFTR activity can result in
CF symptoms that may emerge later in life1-6
CF Phenotype
CFTR Genotype
Modifier
Genes
Allele #1: R117H
Allele #2
Residual CFTR
Protein Activity
Little to No
CFTR Protein
Activity
Residual
Total
CFTR Activity
In patients registered in the CFTR2
database with an R117H mutation on
1 allele and a pancreatic insufficient
mutation on the second allele1
• Sweat chloride (average):
60 mmol/L
Environmental
Factors
• A range of pulmonary
phenotypes, including
classic CF, delayed onset
of pulmonary symptoms, or
no pulmonary symptoms6
• Pseudomonas colonization:
28% of patients
• Pancreatic insufficiency:
23% of patients
References: 1. US CF Foundation, Johns Hopkins University, The Hospital for Sick Children. The Clinical and Functional TRanslation of CFTR (CFTR2). http://www.cftr2.org. Accessed November 12, 2015. 2. deGracia J et al. Thorax. 2005;60(7):
558-563. 3. Cystic Fibrosis Genotype-Phenotype Consortium. N Engl J Med. 1993;329(18):1308-1313. 4. Davis PB et al. Am J Respir Crit Care Med. 1996;154(5):1229-1256. 5. Castellani C et al. J Cyst Fibros. 2008;7(3):179-196. 6. Massie RJH et al.
Eur Respir J. 2001;17:1195-2000.
9
Summary
• Loss of CFTR activity is the underlying cause of CF
• Levels of CFTR activity affect survival in CF
• R
117H is the most common residual function CFTR mutation
and the fifth most common CFTR mutation in the world
• The R117H mutation results in reduced channel-opening and
conductance of the CFTR protein
• C
F disease in patients with the R117H mutation is influenced
by the CFTR poly-T tract variant
• The R117H allele results in residual total CFTR activity
• Both CFTR alleles play a role in determining phenotype or
disease severity
• R
117H in combination with another allele that produces little to no
CFTR activity can result in CF symptoms that may emerge later in life
10