Lecture 50: Molecular Mechanism in Inherited Disorders

Question 1

Cystic Fibrosis

Answer 1

• AR
• Mutation in CFTR –> can’t regulate/transport cl-
• ATP binding cassette (ABC) Transporter
• Allelic heterogenity

Symptoms:

• Fat in feces (Steatorrhea)
• Decline in growth
• Bronchitis infection (lung issues)
• Serum albumin levels low = malnourished
• Salty sweat –> high chloride on skin bc problems w CFTR reabsorbing NaCl
• Infertility (no vas deferens = CBAVD)

Treatment:
-Enzyme replacement for malnourishment

Question 2

Pancreas in cystic fibrosis

Answer 2

• Exocrine insufficiency
• Loss of CFTR = thicker secretions = duct obstructions/tissue destruction
• Deficiency of pancreatic enzymes –>lipase, trypsin, chymotrypsin

Results:

• fat in feces –> deficiency of vitamins
• Malnourished/growth delay

Question 3

Respiratory in cystic

Answer 3

• Mutant CFTR doesn’t transport Cl- airway into lumen
• Thickened and viscid mucus secretions = bacterial infections
• Respiratory infections = mortality and morbitity

Question 4

Diagnosis of CF

Answer 4

1) Sweat Chloride Test
- Uses pilocarpine, electrodes stim sweat glands, sweat measured

2) Molecular Diagnostic Test
- Aso test (carriers = hererozygous, children = homo)

Question 5

Diagnosis of CF

Answer 5

1) Sweat Chloride Test
- Uses pilocarpine, electrodes stim sweat glands, sweat measured

2) Molecular Diagnostic Test
- ASO test (carriers = hererozygous, children = homo)

Question 6

Sickle Cell Anemia

Answer 6

• AR
• Low Hemoglobin
• Rise in bilirubin–> Jaundice

Symptoms:

• Distorted RBCs (Can create block in arteries)
• Hemolytic anemia (RBC die quicker)
• Splenomegaly
• Jaundice (yellow eyes, liver can’t break down toxins)
• Silent stroked

Question 7

Molecular change in sickle cell

Answer 7

• Pt mutation in B-globin = low hemoglobin
• Glutamic acid –> valine (Acidic changed to hydrophobic = missense)
• Glutamic acid on exterior of hemoglobin
• Valine created hydrophobic pocket on exterior of hemoglobin
• HbS aggregates to forms long filaments = distorted RBC

Question 8

Molecular Testing sickle cell

Answer 8

1) Hemoglobin electrophoresis:
- HBA (glutamate) moves faster than HbS (valine)
- Anode = +

2) ASO:
- Special probe for HbS
- Heterozygous carriers and homo affected

3) RFLP test:
-Detects for sickle cell disease and carriers
-Mutation = loss of restriction site on B-globin gene = larger fragment made
-Size HbS > HbA
(HbS = moves slower)

Question 9

Duchenne Muscular Dystrophy and Becker Muscular Dystrophy

Similarities/diffs

Answer 9

Both:

• Dystrophin gene mutation
• X-linked recessive disorder = more males affected

DMD:

• FRAMESHIFT MUTATION= abolishes translation of dystrophin protein
• ABSENCE of functional dystrophin or less amounts of it
• Low reproductive fitness

BMD:

• MUTATION IN FRAME
• ABNORMAL dystrophin or less amounts of it
• Earlier onset (Children)
• Milder
• Normal reproductive fitness

Question 10

Symptoms of Duhennes Muscular Dystrophy (DMD)

Answer 10

• Pseudohypertrophy of calf

- Gowers manuever (Hard to and weird way to get up)

Question 11

Dystrophin gene and protein w/ DMD

Answer 11

-Mutation hotspot –> smooth, cardiac, skeletal muscle, brain

Function of Dystrophin:
-Anchors cytoskeleton (actin) of muscle cells to ECM (Basal lamina) = stabilizes plasma membrane proteins of the muscle cell to withstand stress during muscle contraction

-DMD peeps aint got this working properly

Question 12

Molecular testing and DMD/BMD

Western Blot

Immunostaining

add more

Answer 12

Western Blot:

• Can view BMD in frame deletion
• Cannot view DMD frame shift deletion

Immunostaining:

• Reduced quantity of dystrophin in BMD (less pronounced lines)
• Complete absence of dystrophin in DMD (But connective tissue between myocytes increases)
• Creatine Kinase (MM) levels = elevated for muscular dystrophy pt’s (Usually females have higher levels)
• Some heterozygous females have asymmetric x-inactivation