Cystic Fibrosis Flashcards
(119 cards)
1
Q
What is the leading impact to CF?
A
Abnormally thick mucus
* produced by malfunction in transporting salt ions (Cl-) across epithelial cells lining duct
2
Q
What are the clinical features affecting the RESPIRATORY system?
A
Frequent Coughing, Chronic Infections & Lung Damage
DUE TO:
* obstruction of bronchioles by mucus
* colonisation of bacteria (antibiotic-resistant strains)
* damage by inflammatory responses
3
Q
What are the clinical features affecting the REPRODUCTIVE system?
A
Infertility in males & SUB-infertility in females
DUE TO:
* blockage of vas deferens = leads to fibrosis or atrophy
* cervical mucus in females = barrier of passage of sperm
* females may be anovulatory
4
Q
What are the clinical features affecting the GASTROINTESTINAL system?
A
Poor Growth & Chronic Malabsorption
DUE TO:
- blockage of pancreatic ducts by mucus
- poor digestion of fats & proteins
5
Q
What chromosome is the CFTR gene on?
A
7
6
Q
What does the CFTR gene code for?
A
Ion channel protein & CFTR protein
ALSO:
* full transporter of four canonical domains === linked to single polypeptide chain
7
Q
What processes is the CFTR anion pore gating regulated by:
A
- cAMP-dependent (Protein Kinase A) phosphorylation
- ATP binding
8
Q
What are the domains of the CFTR protein?
A
4 Canonical Domains
* Membrane Spanning Domains (MSD - 1&2)
* Nucleotide Binding Domains (NBD - 1&2)
Regulatory Domain (R)
9
Q
What is the role of the NBDs?
A
- bind & hydrolyse ATP
- ATP binding → channel OPENS
- ATP hydrolysed → channel CLOSES
10
Q
What is the role of the MSDs?
A
- forms channel for passage of Cl-
11
Q
What is the role of the R domain?
A
- Phosphorylated by cAMP
- Phosphorylation leads to fine tuning of channel function
12
Q
How are the 4 Canonical Domains and R Domain linked?
A
They are linked into a single polypeptide chain
13
Q
How do interactions between the MSDs & NBDs occur?
A
Via coupling helices
14
Q
What do the channel opening & closing require in the CFTR molecule mechanism?
A
- Opening: Phosphorylation & Nucleotide (ATP) Binding
- Closing: Hydrolysis
15
Q
What is the 2-step activation process in CFTR molecular mechanism?
A
- PKA phosphorylation
- ATP binding
DETAILED:
1. R domain blocks channel but can disengage and allow channel to be turned on by PKA adding P group which acts as a temporary lock and allows channel to flow freely.
2. ATP binding occurs
3. Eventually, dephosphorylation of P occurs and blocks channel again & resets to allow ^^ again
16
Q
What is the gating cycle of the fully
phosphorylated CFTR channel?
A
-
Flow of Cl- ions = ATP-bound closed channels open to pre-hydrolytic open state
* ATP-induced dimerisation of NBD 1&2 = conformational changes in MSD 1&2 - Channel closure == ATP → ADP = NBD dimer disruption
17
Q
What happens to the NBD domains (NBD 1 & 2) in the presence of ATP?
Relates to the dimers
A
- NBD 1 & 2 combine head-to-tail forming dimers.
- Two ATP molecules are trapped between these dimers.
18
Q
What are the differences between NBD1 and NBD2?
A
- NBD1: head region has a “degenerate site” for ATP (weak binding, upper site 1)
- NBD2: tail region has a “catalytic site” for ATP (strong binding, lower site 2)
19
Q
Explain what the 2 ATP is used for in NBD1 & NBD2
A
- both ATP need to bind
THEN:
- ATP1 undergoes hydrolysis = proper gating
- ATP2 either remain bound (for rapid opening/closing) OR dissociate (so CFTR is more stably closed)
20
Q
How does the R domain affect the channel?
A
Interaction depends on phosphorylation state.
- dephosphorylated = wedges itself between the two halves of the channel = prevents NBD dimerisation & channel opening.
- phosphorylated = adopts a permissive state = allows the channel to function.
21
Q
What part of the CFTR protein interacts with other cellular proteins?
A
C-terminus
* acts like an anchor
22
Q
Why is the CFTR protein anchored to the cytoskeleton?
A
To be positioned near other proteins that influence its functions.
23
Q
List some of the functions influenced by proteins interacting with CFTR.
A
- Conductance (regulating flow of ions)
- Regulation of other channels (e.g., ENaC channel)
- Signal transduction (cellular communication)
- Localisation at apical plasma membrane (positioning)
24
Q
How does the CFTR function in NORMAL vs CF airways?
Lungs
A
Normal
* CFTR regulates movement of Cl- and Na+ ions.
* Balanced movement keeps airway surface liquid (ASL) hydrated
* Active transport: ENaC channels move Na+ into cells.
* Passive movement: Cl- follows Na+ out, maintaining hydration.
CF
* Defective CFTR disrupts ion regulation.
* Uninhibited ENaC causes excessive Na+ absorption.
* No functional CFTR for Cl- movement out of cells.
* ASL becomes depleted, hindering mucus clearance.
25
How does the CFTR function in NORMAL vs CF **sweat ducts**?
**Normal**
* Cl- ions, Na+ ions & water move into cell
* Sweat secreted in duct by gland
* Na+ & Cl- reabsorbed by duct cells before reaching skin surface
**CF**
* Cl- ions **unable** to enter cell == Na+ ions and water **remain** in sweat ducts
* resulting in **elevated Na+ & Cl- levels** in sweat
26
How does CFTR function in NORMAL vs CF **pancreas**?
**Normal**
* secretes bicarbonate
* bicarbonates moves into pancreatic duct
* mechanism: directly via CFTR & via bicarbonate chloride exchangers
**CF**
* absence of CFTR-dependent bicarbonate & Cl- secretion = **abnormal acidic & low volume secretions** = activation of proteolytic enzyme within gland
* == pancreatic inflammation & destruction
27
What are the CFTR gene **variant classes?**
**6 classes**
* **Class I:** **No** CFTR produced
* **Class II:** Defective **processing** - misfolds = trafficking defect
* **Class III:** Defective **regulation** - channel gate doesnt open properly
* **Class IV:** **Reduced ion conductance**-function of channel is faulty
* **Class V:** **reduced** CFTR production
* **Class VI:** accelerated turnover from the cell surface = **decreased CFTR stability**
28
What are the variant class-specific **therapies**?
* **Class I:** **Aminoglycoside antibiotics** = allows 'read through' of mRNA
* **Class II:** '**Correctors**' to improve processing
* **Class III:** '**Potentiators**' to activate protein
* **Class IV:** Flavonoid compounts = **augment** channel function == increase open probability
* **Class V:** splicing variants = increase levels of **correctly spliced RNA**
29
What is the **most common** CFTR gene variant?
F508del
30
What **class** of mutation is F508del?
**Class II** - possible *drug target*
* severe folding defect == premature **degradation** of most of translated protein in ER
* Located in **NBD 1**
* **Defective processing**
31
What is happening in F508del?
* **508 Phenylalanine deletion**
* 1 base from 507 Isoleucine and 2 bases from 508 Phenylalanine DELETED
32
What is the **inheritance pattern** of CF?
Autosomal recessive
33
What is the **carrier frequency** and the most affected **ethnicity**?
1 in 25 & northern Europe
34
What is the **incidence** of CF?
1 in 2500-3000 live births
35
What are the Heterozygote (carrier) **selective advantage**?
Protection against **diseases** - Cholera & Typhoid fever
36
Describe the CFTR **genotype-phenotype correlation**
**Limited** correlation - class of CFTR variant & phenotype
* Class **I,II,III** mutation = pancreatic **insufficiency** (strong correlation) & **more severe** lung disease
* Class **IV,V** mutation = pancretic **sufficiency** & **milder** lung disease
37
What is the **penetrance** of CF?
**Complete** penetrance for severe CF-causing variant = individuals carry these disease-causing variants on BOTH CFTR alleles == develop CF
**Incomplete** penetrance = certain combinations of underlying causativ CFTR variants
38
What is the **expressivity** of CF?
**Variable expressivity**
* phenotype associated with **disease-causing variant** = **differs** between individuals
* genetic & environmental modifiers contribute
39
What are the **genetic testing** for CF?
**Diagnostic testing**
* Confirmation of diagnosis in symptomatic individuals
**Cascade testing**
**Newborn screening**
**Population carrier screening**
40
What are the **special groups** of CFTR gene variants?
**Incompletely penetrant variants**
1. **PolyT tract** c.1210-12T[5_9] (intron**8**)
2. c.350G>A p.Arg117His (‘**R117H**’ in exon**4**)
* penetrance depends on polyT tract variant on same allele
41
State the **disease-causing** CFTR gene variant
On allelle 1 & 2 respectively.
**LP/P variant** (F508del) & **R117H & 5T**
42
For an individual with **F508del variant** on one allele and an **R117H variant** on the other, what **'_'T polymorphism** is more likely to **symptoms** of CF
**5T polymorphism**
* **maximises** effect of R117H = act as disease-causing variant
NOT 9T polymorphism since:
* minimises effect
43
Describe the **sweat test**
* measures **concentration of Cl excreted**
* pilocarpine iontophoresis induces sweating
* pilocarpine = parasympathomimetic == acts on cholinergic receptors
* Normal value: Cl<**40mmol/L** (<30 in infant)
* CF diagnosis: Cl>**60mmol/L**
44
Describe **Newborn screening**
* Identifies babies at risk of developing CF
* Allows early and pre-symptomatic therapy
1. RT test = heel prick onto blood spot cards (2-3 days old)
* **Elevated** IRT == **further** testing
2. Genetic testing using known common **LP/P gene variants** == only 12 common
* both = **CF**
* heterozygous = further testing = **sweat test**
* none = no CF
45
Describe **Cascade testing**
* Identification of **carriers** who are **relatives** of a **diagnosed** individual
* Information can be provided about reproductive risk
* only 12% opt-in
46
Describe **Population carrier screening**
* Identification of **carriers** in the **general population**
* Pre-conception carrier screening for reproductive purposes
47
Define **genetic modifiers** in term of CF?
* **influences phenotype**of CF BUT **cannot cause CF**
* e.g. can influence how severe CF symptoms are
48
Why is it important to **study genetic modifiers** of CF?
* identify **new targets** for therapies
* understanding of **genetic variability**
49
How to **identify genetic modifiers** of CF?
* **Linkage studies:** track gene/markers associated with specific phenotype in families with CF
* **Candidate gene association studies:** genes with known function relevant to CF features & correlate variations
* **Genome wide association studies:** examine DNA markers at many positions across genome
* **Transcriptomic, proteomic and metabolomic analyses** in human tissues and
animal models
50
What is the **Genome Wide Association Studies (GWAS)**?
1. Sequences **entire genome**
2. Looks for **Disease** associated SNPs & **Non-disease** associated SNPs
51
What are the **limitations** of GWAS?
* Needs a **large** sample size
* difficult to **replicate** studies for validation
52
What are the **genetic modifiers** in CF?
| Influences severity of the disease
**TFGB1**
* role in **regulating inflammation and tissue remodelling**
* genetic modifier of *lung disease* in CF
**MBL2**
* Encodes mannose binding lectin
* role in **innate immunity** (in lungs)
* important for P. aeruginosa immunity
* genetic modifier of *lung disease* in CF
53
What are the **environmental modifiers** in CF?
| Environmental factors associated with pooerer health outcomes
* Lower socio-economic status
* Exposure to tobacco smoke – active and passive
* Infectious exposures
* Disease self-management
* Female sex = poorer adherence to medical & dietary regimens that focus on high caloric intake to match
high metabolic demand associated with CF
* Access to healthcare
54
What is **meconium ileus**?
| To what degree is it affected by genes and environment
* **Blockage** in ileum of babies in utero by sticky, black faeces
* almost completely determined by **genes**
55
What is the **difference** between **conducting and respiratory zones**?
**Conducting**: mucosa lined, **no gas exchange**
**Respiratory**: simple squamous epithelium for **gas exchange**
56
What is the **acinus**?
**Gas exchange region** of the lung
Composed of:
* Respiratory bronchioles
* Alveolar ducts
* Alveolar sacs
* Alveoli
57
Describe the phases of **lung development**
1. **Embryonic:** lung bud appears, out pouching from foregut
2. **Pseudoglandular:** branching of airways up to terminal bronchioles
3. **Canalicular:** development of acinar region & type I and II pneumocytes
4. **Sacular / alveolar:**
* sacules form into alveolar ducts
* decrease in interstitial tissue, septation
* alveoli start to develop
| Septation = septa form between alveoli = forms more alveoli
58
What are the **functions** of the lungs?
* Gas exchange
* Defence
* Acid-base balance
* Metabolic
* Heat exchange
* Water balance
* Phonation
59
What are the lungs **defence** mechanism?
**Physical (airway)**
* Upper airway filter
* Reflexes= Sneeze & Cough
* Mucociliary escalator
**Cellular (alveolar)**
* Phagocytes e.g. alveolar macrophages
* Immunological
60
Describe the function of **Mucociliary Escalator**
* **ASL** present on cells in lumen
* Mucus produced by secretory cells inc. Goblet cells
61
Describe **gas exchange** in the lungs
* Takes place at the **level of alveoli**
* Alveoli filled with **air** upon inspiration
* Gas diffuses in solution across the single celled wall of the **alveolus** into the capillary
* **Basement membrane** between alveolus and capillary
62
What are the **parameters** used to measure lung function?
* Volume
* Flow = Volume/Time (of air)
* Pressure
63
Describe how **FEV** and **FVC** are measured
1. Maximal inspiration
2. Forced expiration until residual volume
First second: FEV
Until residual volume: FVC
64
When performing **Spirometry**, when is the **most air exhaled**?
First Second
65
What happens with **reversible intrathoracic airway obstruction**?
Air cant be exhaled as quickly
66
What are the **pulmonary complications** of CF?
* Poor lung function, progressive decline
* ↑ Cough and sputum production
* ↑ Dyspnoea
* Poor appetite
* Need for transplantation; death
* Respiratory failure
67
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What causes **lung disease & chronic airway infection** in CF?
CFTR Mutations/Dysfunction
68
What **cell types** in the **respiratory system** express **CFTR**?
* Serous cells of submucosal glands
* Alveolar epithelial type II cells
* Alveolar macrophages
* Neutrophils
69
Describe **Ion Transport** in **Normal Lung vs CF Lung**
**Normal Lung**
* CFTR coordinates **modulation of ASL** by
1. Na+ absorption Epithelial Na+ channel (ENaC)
2. Cl- secretion
**CF Lung**
* 2 functions of CFTR **lost**:
1. ENaC **not** inhibited = ↑ Sodium absorption (Water follows sodium)
2. Cl- ions **not** secreted = ↑ Na+, Cl-, and H2O absorption & ↓ ASL volume
70
What are the **consequences** of **reduced ASL volume**?
* Volume **depletion** of PCL = failure of ciliary beating
* **Decreased** lubrication = adherent mucous plaque
→ Promotes **chronic infection**
71
How does CFTR impact the **reduced pH of ASL** in CF?
**Lack of bicarbonate secretion** = reduced ASL = acidic
* CFTR normally = secrete bicarbonate
* CFTR in CF = bicarbonate reduced/absent & inhibits antimicrobial function
| CFTR is dysfunctional in CF
72
Describe **Anaerobic Millieu**
Thick mucus plaques adherent to epithelial surface & increased oxygen consumption by CF epithelia == **Anaerobic environment**
* Ideal environment for **growth of certain bacteria**
* *Pseudomonas* = converts to anaerobic biofilm mode of growth
73
What can **dysregulated immune pathways** in CF **cause**?
* ↑ activation of nuclear factorkappa B (NFᵏB)
* Abnormal lipid metabolism
* ↑ ROS production
* ER stress
* Defective interferon signaling
74
What are **Neutrophils antimicrobial function** & how do they **relate** to CF airways?
Neutrophils = **first & main inflammatory cell** found in CF airways
Antimicrobial functions:
* Generate reactive oxygen species
* Secrete proteases
* Phagocytosis
* NET formation
75
Describe the **pathology** of lung disease in CF
Infection, inflammation and obstruction of airways == Dilation and damage of airways
* Bronchiectasis = dilation of part of bronchial tree = caused by muscle and elastic tissue damage
76
What are the **treatments** of pulmonary complications in CF?
* Daily (x1-2) Airway clearance (chest physiotherapy)
* Mucolytics
* Antibiotics to treat infections
* Anti-inflammatory agents
77
How to **maintain** lung function?
* avoiding/aggressively treating infections
* perform airway clearance
78
What are the **clinical features** of a **high salt sweat** individials?
* **Hypoantrmic/Hypochloremic dehydration**
* Hypokalemic metabolic alkalosis = secondary to chronic salt loss = stimulates exchange of Na+ for H+ & K+
**Symptoms**:
* Headache/Irritability
* Muscle Cramps
* Nausea & Vomiting
* Fatigue
* Poor Concentration
79
Describe the **pathophysiology** of **Pancreatic Disease**
* CFTR == apical membrane of pancreatic ductal epithelial cell
* Regulation of **Chloride** secretion = reduced luminal liquid
* Regulation of **Bicarbonate** secretion = **acidic pH** of luminal liquid = also **key buffer** for pancreatic fluid
* **Viscous pancreatic** secretions = pancreatic duct obstruction
* **Premature activation** of **proteolytic enzyme** = inflammation & destruction of pancreas
80
What is the **management** of **pancreatic insufficiency**?
* **Nutrition**
* High **fat** (35-40%) & **protein** diet
* Improved growth ALSO improves lung function
* Pancreatic Enzyme Replacement Therapy (**PERT**)
* **Fat-soluble** vitamins = **A, D, E, K**
81
What causes **Pancreatitis**?
* Impaired **Bicarbonate**
* Impaired **control** of luminal pH = tissue damage
* **↓ luminal pH** = premature zymogen activation = pancreatitis
* PIP score = **Severity** of CFTR genotype = risk of pancreatitis
* CFTR **Mutation** = **non-CFTR modifiers** = pancreatitis in CF
82
What is the **management** of **Pancreatitis**?
**Acute** = supportive care
* **correction of fluid & electrolyte imbalance**
* Medicine = Analgesia
* Gut rest for 1-3 days
**Chronic**
* *Environmental Factors* = smoking, alcohol, hypertriglyceridemia
* *Medication* = antacids, PERT, analgesia
* *Surgery* = TPIAT
* Monitor for pancreatic cancer
83
What can the **pancreas (endocrine)** be impacted by?
* *Cystic Fibrosis Related Diabetes Mellitus (CFRDM)*
* Impaired & delayed **insulin secretion**
* = insulin **resistance**
* Lung function decline
* Treatment = insulin
84
What is the **pathogenesis** of CFLD (CF Liver Disease)?
* ↑ viscosity of bile
* Blocked intra-hepatic bile ducts
* ↑ risk in patients with alpha 1-antitrypsin Z-allele
85
What is the **clinical features** of CFLD (CF Liver Disease)?
* **Prolonged** neonatal jaundice
* Raised **liver enzymes** = commin in CF
* **Hepatic steatosis** = fatty liver
* **Cirrhosis & portal hypertension** = 3:1 M:F
* Hepatocellular failure = uncommon
* **Increased morbidity** = poor nutritional status & growth, worse pulmonary outcomes, CF-related diabetes
* **Malignancy-Hepatocellular carcinoma**
| Juandice = yellow discolourisation
86
How is CFLD **diagnosed**?
Requires two of:
1) Abnormal physical examination
* Hepatomegaly/splenomegaly
* Stigmata of chronic liver disease
2) Abnormal serum transaminases
* 3 consecutive occasions over a 12 month period
3) Ultrasound findings of CF related liver disease
4) Biopsy consistent with CF related liver disease
87
What is the **treatment** of CFLD?
* Optimise **nutritional status & pulmonary function**
* Monitor for **CF related diabetes**
* **Immunisations**: hepatitis A & B
* Ursodeoxycholic acid
* Monitor for **complications** of portal hypertension
* Monitor for **development** of synthetic liver failure
* Consideration of liver transplant
88
What is Meconium Ileus?
* Inspissated intraluminal meconium = causes bowel obstruction
89
What are the late complications of Meconium Ileus?
* ↑ DIOS risk
* Adhesive small bowel obstruction
90
What is the **Distal Intestinal Obstruction Syndrome (DIOS)**?
* Partial or complete bowel obstruction
Symptoms:
* Abdominal pain; crampy, RIF
* Constpiation
91
How can **Gastro-esophageal Reflux** (GERD) **worsen** lung disease in CF?
* Aspiration
* reflex bronchospasm
92
What is the role of a **CFTR modulator**?
* overcome basic CFTR defect
* **Restore** CFTR function
93
What is **protein rescue therapy**?
* depends on class of mutation
* uses drug to overcome dysfunctional protein
* e.g. Ivacaftor
94
Describe the **function** of **Ivacaftor**
* binds channel = allows it to function **properly** (i.e. keep channel open)
* **potentiator** = improves lung function in CF patients with class III mutation
95
What **class mutation** is **Ivacaftor** for?
&
What **gene mutation** is required to get Ivacaftor treatment?
**Class III mutation**
* dysregulated channel = gating defect
**Gene Mutation**
* Gly551Asp (**G551D**)
* impairs the ability of CFTR at the cell surface to open
96
What was used to identify Ivacaftor?
High Throughput Screening
97
What are the pros & cons of Ivacaftor?
**Pros**
* improvement in lung function
* increased weight
* increase in time to exacerbate
* decreased symptoms
* delayed exacerbation
* reduction in sweat chloride concentrations
**Cons**
* very expensive
98
Why was Ivacaftor significant?
* addresses underlying defect
* first CF therapeutic to do so
99
What were the outcome of short vs long term use of Ivacaftor?
**Short Term**
* Sustained improvements in **sweat Cl, FEV1, BMI & MCC**
**Long Term**
* Lung function **declined** over time
* Sustained improvements in
**sweat Cl, BMI and exacerbations**
100
What is Lumacaftor?
| Describe its function
* A **protein rescue therapy**
* A ‘**corrector**’: used for **Class II mutations**
**Function:**
* **increases** the amount of CFTR trafficked to the cell surface
101
Can Lumacaftor function well on its on? Explain why.
**No**
* requires **potentiator** (e.g. Ivacaftor)
* DUE TO: drug only gets mutated CFTR to surface = **doesnt functional optimally**
102
Describe the efficacy of Lumacaftor
| transport of CFTR
* **Lumacaftor** = CFTR transport is **15%** of wild type
* **Lumacaftor + Ivacaftor** = CFTR transport is **30%** of wild-type
103
# *MIGHT NOT BE IMPORTANT TO KNOW*
Describe the outcome of **Lumacaftor**-Ivacaftor (Orkambi)
* Mean change in **FEV1 of 2.6 to 4.0%**
* Exacerbation rate **↓ 39%**
* ↑ weight:**1.23 to 1.57kg**
104
# *MIGHT NOT BE IMPORTANT TO KNOW*
Describe the outcome of **Ezacaftor** + Ivacaftor (Symdeko™)
* Mean change in FEV1 of **4%**
* Exacerbation rate **↓ 35%**
* Improved CFQ-R of **5.1**
– Respiratory domain
* **no change** in BMI
105
# *MIGHT NOT BE IMPORTANT TO KNOW*
Describe the outcome of **Tezacaftor** +Ivacaftor (Symdeko™)
* Mean change in FEV1
– Symdeko **6.8%**
– Ivacaftor **4.7%**
* Improved CFQ-R of **11.1**
– Respiratory domain
* **↓ sweat Cl 9.5mmol/L**
* **no change** in BMI
* **No change** in exacerbation
106
# *MIGHT NOT BE IMPORTANT TO KNOW*
Describe the outcome of **Elexacaftor**-**Tezacaftor**-
Ivacaftor (TrikaftaTM)
* ↑ FEV1 of **14%**
* ↓ sweat Cl of **41.8mmol/L**
* Exacerbation rate **↓ 63%**
* CFQ-R RD score **↑ 20.2**
107
List the **future therapies** for CF Lung Disease
* Mutation specific therapies
* Novel symptomatic treatments
– Anti-infective
– Anti-inflammatory agents
– Mucolytics
* Genetic therapy
108
Outline the **phases of clinical trials**
**Phase I**
* Low doses on healthy volunteers
* progressively increase
**Phase II**
* 100-300 patients
* Examine effectiveness
– Dose
– Delivery method
– Dosing interval
* confirm safety
**Phase III**
* 1000+ patients
* Confirm previous findings
* Demonstrate safety & efficacy
* Determine best dosage
109
What are **nonsense mutations**?
* Ceases production of CFTR protein
* Class I
110
What are **therapies** for nonsense mutations?
* develop small molecules that can produce full-length functional protein
– facilitate **PTC read-through**
– **impede mRNA decay**
111
What are **PTC read-through agents**?
allows translation to continue despite PTC
112
What are **mRNA stabiisers**?
* **prevent breakdown** of mRNA
* since PTCs lead to shot lived mRNA due to nonsense mediated decay (NMD)
113
List the **genotype agnostic approaches**
| **Define** genotype agnostic approaches
* used **regardless** of an individuals **particular variation (genotype)**
* **restores** CFTR function
**Approaches**
* Targeting **alternative ion channels** to compensate for CFTR channel defect
* **Gene replacement therapy**
– DNA
– mRNA
* **Gene editing**
114
How is **targeting alternative ion channels** a genotype agnostic approach?
| Name the 2 channels
**Inhibits / activates** epithelial transporters
* ENaC (Sodium channel)
* TMEM16A (Calcium-gated chloride channel)
115
How is **RNA therapy** a genotype agnostic approach?
VX-522
* delivers **full-length copy** of CFTR mRNA to lung cells == using nanoparticles
* mRNA used to create functional protein
116
How is **gene therapy** a genotype agnostic approach?
* introduces normal copy of CFTR gene into cells of conducting airways
* Majority Phase I & II
117
What is **gene editing**?
| In regards to the genotype agnostic approach
* uses cells own DNA repair machinery
**CRISPR**
1. Enters cell nucleus
2. snips out mutated sequence
3. cell's DNA repair machinary = uses template = fix broken DNA
4. permanently corrects mutation
118
List the system in the body where CFTR protein is present in epithelial cells
| List 5
* Airways
* Sweat gland
* Pancreas
* Gastrointestinal tract
* Reproductive tract
119
What is **pulmozyme**?
* digests DNA released by neutrophils in mucus of lungs in CF patients
