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Biochem Exam 4 > Collagen structure and function 2 > Flashcards

Collagen structure and function 2 Flashcards

1
Q

what happens when there is an issue with type I collagen?

A

osteogenesis imperfecta

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2
Q

mutations in what genes account for 90% of OI cases?

A

COL1A1 and COL1A2

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3
Q

how is OI inherited?

A

mostly autosomal dominant

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4
Q

is OI due to quantitative or qualitative abnormalities of collagen I?

A

both

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5
Q

what is the most common type of OI?

A

type I

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6
Q

what is type I OI?

A
  • bones predisposed to fracture (most occur before puberty)
  • normal stature/blue sclera
  • in most cases, “functional null” allele of COL1A1 or COL1A2 genes leads to no (or greatly reduced amounts) protein being produced from one allele
  • Other allele unaffected
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7
Q

can patients with type I OI still make normal collagen?

A

yes- still have one unaffected allele that makes reduced amounts of normal collagen

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8
Q

what trimers are formed in type I OI?

A

normal (encoded by normal allele)- but only half the amount of normal collagen produced
*quantitative deficiency

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9
Q

what is the most severe type of OI?

A

type II

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10
Q

what is type II OI?

A
  • Numerous fractures and severe bone deformity
  • Short stature
  • perinatal lethal
  • affects glycine residues that disrupts triple helical structure
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11
Q

can patients with type II OI still make normal collagen?

A

no
- Abnormal collagen molecules incorporated together with normal collagen into trimers, therefore few or no normal collagen trimers produced

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12
Q

what is type III OI?

A

progressive deforming type/ bones
fracture easily
-short stature, spinal curvature
-severe bone deformity
-blue sclera
*can be autosomal recessive

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13
Q

what is type IV OI?

A

severity intermediate
between types I/II
-mutations in COL1A2 and rarely COL1A1

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14
Q

why are many diseases with mutations in ECM proteins inherited in a dominant fashion?

A

bc mutant alleles mixed into normal ones make it hard to form the correct polymer

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15
Q

what is type V OI?

A

“mesh-like” bone histology/ calcification
-autosomal dominant but no mutations in collagen genes

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16
Q

what are the autosomal recessive types of OI?

A

types VI-XVI
*no mutations in type I collagen

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17
Q

mutations in CRTAP causes what?

A

defective 3-prolyl-hydroxylation which delays collagen folding

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18
Q

what results from a CRTAP null mutation?

A

severe lethal form of OI (similar to type II)

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19
Q

what are the three components of prolyl-3 hydroxylation complex?

A

CRTAP
cyclophilin B
prolyl-3-hydroxylase 1 (LEPRE1)

20
Q

what is caused by mutation in the prolyl-3 hydroxylation complex?

A

does not allow/delay collagen hydroxylation during biosynthesis
-can cause diseases like OI

21
Q

different proteins that act in the same pathway can produce diseases with what?

A

similar phenotypes

22
Q

what are the two kinds of mutations that can case OI?

A

-mutations in type 1 collagen genes
-mutations in genes encoding proteins involved in collagen post-translational modifications/regulation of collagen biosynthesis

23
Q

common orofacial manifestations of OI:

A

-brown/grey discoloration of teeth
-abnormalities of pulp chamber

24
Q

orofacial manifestation of severe forms of OI:

A

-triangular shaped face
-bossing of the forehead
-low set ears
-mid face deficiency/ malocclusions
-may have blue sclera

25
Q

what is a hereditary disease of dentin?

A

dentinogenesis imperfecta

26
Q

symptoms of dentinogenesis imperfecta

A

-Opalescent/brown teeth that wear easily
-bulbous crowns
-narrow roots
-Small/obliterated pulp chambers or enlarged pulp chambers
-frequent splitting of enamel from dentin under occlusal stress

27
Q

which type of dentinogenesis imperfecta occurs in families with OI and is due to mutations in COL1A1 or COL1A2?

A

type I

28
Q

which type of dentinogensis imperfecta occurs due to mutations in DSPP and is not associated with OI?

A

type II and type III

29
Q

implications for dental care for patients with OI

A
  • Teeth in OI patients more susceptible to wear/breakage and/or enamel fracturing from teeth
    *teeth can wear down to gingiva
  • Pulp chamber/root canals may be filled with dentin, so tooth may lose feeling.
  • For tooth extractions, extra support of jaw may be needed to avoid
    fracturing
30
Q

Early identification of OI condition/preventative interventions are important for what?

A

to minimize dental complications

31
Q

what is the common treatment for OI patients?

A

bisphosphonates

32
Q

what disease is associated with abnormal collagen biosynthesis due to nutritional deficiency in Vitamin C?

A

scurvy

33
Q

symptoms of scurvy

A

-lethargy
-bleeding gums/mucous membranes
-fragile blood vessels/petechial hemorrhage of skin
-loss of gingival and periodontal collagen fibers/anchoring fibers-loosening of teeth
-bone pain

34
Q

why does vitamin C matter in the biosynthesis of collagen?

A

required as a cofactor for hydroxylation

35
Q

what happens if hydroxylation of procollagen is prevented or it is unfolded?

A

retained in ER and/or degraded
-leads to collagen deficiency which causes inability to renew CT matrix

36
Q

what happens is something with type II collagen goes wrong?

A

chondrodysplasias

37
Q

types of chondrodysplasias

A

achondrogenesis type II/ hypochondrogenesis (ACGII-HCG)

38
Q

what is thought to cause AGCII-HCG?

A

involves replacement of glycine by a bulkier amino acid in triple helical region of a1(II) chain

39
Q

symptoms of ACGII-HCG

A

-die perinatally or in first weeks of life
-short, barrel-shaped trunk
-very short extremities
-large head, soft cranium
-flat face
-underossification of the axial skeleton.
-hypercellular epiphyseal cartilage
-poorly organized or absent growth plate
-diminished extracellular matrix
-thick, irregular collagen fibrils

40
Q

characteristics of Ehlers Danlos syndromes:

A

-Fragility of soft connective tissues
-Manifestations in skin, ligaments, joints, blood vessels, internal organs
-Clinical spectrum varies from mild skin + joint hyperlaxity to severe physical disability/life-threatening complications (ruptured arteries)
-Mild skeletal abnormalities (e.g. osteopenia)

41
Q

what disease is caused by mutations in genes encoding fibrillar collagens (types III and V)?

A

Ehlers Danlos syndrome

42
Q

what can be caused by problems with collagen IV?

A

kidney problems

43
Q

what is caused by problems with collagen VII?

A

epidermolysis bullosa
-can also have enamel defects

44
Q

what disease is caused by production of autoantibodies against non-collagenous domains of type IV collagen alpha 3 chain?

A

Goodpasture syndrome

45
Q

what is Goodpasture syndrome?

A

anti-glomerular basement antibody disease
rare autoimmune disease

46
Q

what are issues caused by Goodpasture syndrome?

A

-kidney filtration
-blood in urine
-burning sensation when urinating
-nephritis
-coughing up blood
-fatigue
-nausea

*can lead to acute renal failure

Biochem Exam 4 (11 decks)

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