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Sarah - Structure > Cornification and the epidermis > Flashcards

Cornification and the epidermis Flashcards

1
Q

Non-living corneocytes form through programmed cell death of viable keratinocytes of which layer?

A

Stratum granulosum (SG1) layer

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2
Q

What are the key cellular changes that occur when a keratinocyte becomes a corneocyte?

A

1) cell flattening
2) organelle loss
3) cytoskeletal compaction
4) cornified envelope formation
5) structural protein cross-linking

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3
Q

What size are corneocytes?

A

1um thick, 30-40um in diameter

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4
Q

The keratin intermediate filament network is collapsed and compacted by which protein?

A

Filaggrin

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5
Q

A cornified envelope forms by deposition of a dense layer of mixed proteins just below the plasma membrane and stabilises the cell periphery. Name four cornified envelope proteins.

A

Envoplakin, periplakin, loricrin, involucrin, small proline rich proteins, filaggrin, and others

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6
Q

What do transglutaminases do in the corneocyte?

A

Provide strength through covalently cross-linking keratin intermediate filaments, cornified envelope proteins and adhesion complexes.

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7
Q

Activation of caspase-14, autophagy and transglutaminase activity are key biochemical features of which process?

A

Programmed keratinocyte death

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8
Q

Where are the proteins needed for keratinocyte cell death stored?

A

In keratohyaline granules

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9
Q

Ichthyosis in JRTs is associated with a mutation in which gene?

A

TGM1 (transglutaminase 1) - insertion

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10
Q

A mutation in the KRT10 gene is associated with hyperkeratosis in which breed of dog?

A

Norfolk Terriers

SNP (splicing)

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11
Q

There is a mutation in which gene in the Dogue de Bordeaux with footpad hyperkeratotis?

A

KRT16 (complex rearrangement)

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12
Q

Hereditary footpad hyperkeratosis in the Kromfohrländer and Irish Terrier breeds is associated with a mutation of which gene?

A

FAM83G (missense)

Also reported in Bedlington terriers!

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13
Q

Which organelle do lamellar bodies come from?

A

Endoplasmic reticulum

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14
Q

Which protein anchors long fatty acid chains of omega-(acylated)-OH-ceramides, derived predominately from linoleic acid, to involucrin of the cornified envelope?

A

Transglutaminases

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15
Q

What role does cholesterol play in the stratum corneum?

A

It contributes to fluidity and flexibility to membranes and lipid lamellae and it also plays key role in promoting desquamation.

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16
Q

In disease, alterations in lipid metabolism can lead to depleted intercellular lipids and…

A

Build up of toxic lipid metabolites

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17
Q

What do corneodesmosomes bind?

A

Extracellular cadherins, desmoglein-1 and desmocollin-1, of desmosomes

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18
Q

A mutation in PNPLA1 (patatin-like phospholipase domain-containing protein 1) is associated with ichthyosis in which dog breed?

A

Golden Retrievers (insertion-deletion)

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19
Q

The proteases kelikrien-5, 7 and 14 and others, progressively cleave which proteins?

A

Corneodesmosin and then desmoglein-1 and desmocollin-1 in corneodesomosomes.

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20
Q

Naked foal syndrome in Akhal-Teke horses is associated with a mutation of which gene?

A

ST14 (suppressor of tumorigenicity 14 gene, Matriptase)

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21
Q

In Cocker Spaniels with primary seborrhea, what is the epidermal turnover time?

A

8 days

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22
Q

Primary seborrhea has been recognised in which breeds of cat?

A

Persians, Himalayans and Exotic SH

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23
Q

What is the epidermal renewal time in dogs with icthyosis?

A

3.6 days

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24
Q

In Golden Retrievers with icthyosis, which epidermal structure is retained?

A

Corneodesmosomes

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25
Q

Which part of the body is affected in Schnauzer comedo syndrome?

A

Dorsum

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26
Q

In epidermolysis bullosa simplex, clefting and blisters occur at which layer?

A

Basal layer of the epidermis

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27
Q

In Junctional epidermolysis bullosa, clefting and blisters occur at which layer?

A

Lamina lucida

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28
Q

In Dystrophic epidermolysis bullosa, clefting and blisters occur at which layer?

A

Within or below the lamina densa

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29
Q

Which breeds, other than Rough Collies and Shetland Sheepdogs, has familial dermatomyositis been reported in?

A

Beauceron Shepherd, Belgian Tervurens, Portugese Water Dogs

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30
Q

Medullary trichomalacia typically affects which breed?

A

German Shepherds

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31
Q

In black hair follicle dysplasia, at what age does near-total alopecia occur by?

A

6-9 months

32
Q

What do you find on histopath with pattern baldness?

A

Minaturisation of hair follicles with normal adnexal structures

33
Q

Which breed is typically affected by follicular lipidosis?

A

Rottweilers

34
Q

Which presenting sign of follicular lipidosis is pathognomic?

A

Hair loss restricted to the mahogany points of the face and feet

35
Q

Acanthosis nigricans affects which breed and which body site?

A

Dachshunds, the axillae

36
Q

What are the four layers of the basement membrane?

A
  1. Basal cell plasma membrane
  2. Lamina lucida
  3. Lamina densa
  4. Sublamina densa
37
Q

Name two omega-3 fatty acids

A 
Docosahexaenoic acid (DHA) and eicosapentaenoic
acid (EPA)
38
Q

Name an omega-6 fatty acid

A

Gamma-linolenic acid (GLA)

39
Q

Which fatty acids tend to form pro-inflammatory mediators (such as PGE2, leukotriene B4)

A

Omega-6

40
Q

Which proteins make up the inner plaque of a hemidesmosome?

A

HD1/plectin

BP230

41
Q

Which proteins make up the outer plaque of a hemidesmosome?

A

alpha-6-beta-4-intergrin

BP180

42
Q

The lamina lucida is formed by the plasma membrane, the sub-basal dense plate and the anchoring filaments composed of which proteins?

A

BP180 (aka collagen XVII)

laminin 332

43
Q

The lamina densa is mainly composed of which collagen?

A

Collagen IV

44
Q

Beneath the lamina densa are the anchoring fibrils - cross banded structures composed of which collagen?

A

Collagen VII

45
Q

In which species is cytolysis of basal cells seen in epidermolysis bullosa simplex?

A

Cattle

No cytolysis in dogs and buffalo

46
Q

In which species are oral ulcers not seen with epidermolysis bullosa simplex?
Cattle
Dogs
Buffalo

A

Buffalo

47
Q

A missense mutation in which keratin has been identified in cattle as a cause of EBS?

A

Keratin 5

48
Q

In animals, is junctional epidermolysis bullosa an autosomal dominant or recessive trait?

A

Autosomal recessive

49
Q

In dogs, junctional epidermolysis bullosa has been associated with mutations of which gene?

A

LAMA3 (laminin 332) - German pointer

LAMB3 (laminin 332) - Australian shepherd

50
Q

Dystrophic epidermolysis bullosa is associated with mutations in which gene?

A

COL7AI (codes for type VII collagen - anchoring fibrils)

51
Q

As the nucleus and intracellular organelles undergo proteolysis, ________ (found in keratohyalin granules) in the granular cell layer is dephosphorylated into ______.

A

Profillagrin

Filaggrin

52
Q

__________ mediate calcium-dependent cross-linking of small peptides to replace the plasma membrane of the keratinocyte with a tough protein layer (corneocyte envelope).

A

Transglutaminases

53
Q

Lamellar bodies are formed in the stratum _______

A

Spinosum

54
Q

The lipid in the stratum corneum is an equimolar mix of ________, long-chain fatty acids and ________.

A

Cholesterol

Ceramides

55
Q

In horses, junctional epidermolysis bullosa has been associated with mutations of which genes?

A

LAMA3 and LAMC2 (laminin 332)

56
Q

In sheep, junctional epidermolysis bullosa has been associated with mutations of which gene?

A

LAMC2 (laminin 332)

57
Q

A mutation in which gene has been identified in dogs as a cause of EBS?

A

PKP1 (plakophilin 1)

58
Q

What happens to filaggrin in the upper stratum corneum?

A

It is deaminated and totally degraded by several proteases in the upper SC to release its constitutive amino acids [part of the ‘natural moisturizing factor’(NMF)] which contributes to epidermal hydration and barrier function.

59
Q

Where do you find profilaggrin?

A

In keratohyalin granules of the stratum granulosum cells

60
Q

The cornified envelope of the corneocyte is a 15 nm-thick layer of keratin fibres, cross-linked proteins and ceramides that replaces the plasma membrane. Cornified envelope assembly is triggered by a rise of intracellular what?

A

Calcium ion concentration in the stratum granulosum

61
Q

In the study by Ardesjo-Lundgren et al., evaluating the role of PKP2 in CAD, were PKP2 expression levels different in GSD with and without AD?

A

No difference in PKP2 abundance between CAD cases and controls was observed.

Found the novel finding of PKP2 expression in dendritic cells and T cells in dog skin.

62
Q

Hereditary nasal parakeratosis in Labrador retrievers is attributed to a mutation in which gene? A different mutation in the same gene has been found in Greyhounds.

A

SUV39H2 (deletion)

It alters epidermal differentiation, interrupts corneocyte nucleophagy and induces parakeratosis

63
Q

What is the composition of the intercellular lipids?

A

Approximately 50% ceramides, 25% cholesterols and 10 to 15% fatty acids

64
Q

The cornified lipid envelope replaces the corneocyte plasma membrane with long fatty acid chains of omega-(acylated)-OH-ceramides, derived predominately from linoleic acid, that are covalently anchored to _______ of the cornified envelope by ____________

A

Involucrin

Transglutaminases

65
Q

What role do the proteases kelikrien-5, 7 and 14 have in desquamation?

A

Progressively cleave corneodesmosin and then cleave desmoglein-1 and desmocollin-1 in corneodesomosomes

66
Q

What role does caspase-14 have in desquamation?

A

It processes profilaggrin to filaggrin and then to free amino acids (natural moisturizing factors)

67
Q

EM image of the stratum corneum, what are the arrows pointing at?

A

Top: corneocyte
Bottom left: intercellular lipids
Bottom middle: cell junctions
Bottom right: enzyme network

68
Q

Lethal acrodermatitis in Bull terriers is associated with a mutation in which gene?

A

MKLN1

69
Q

As well as PNPLA1, which other gene mutation has been identified on golden retrievers with ichthyosis?

A

ABHD5 (deletion)

70
Q

A mutation in NSDHL is associated with which disease in dogs?

A

Verrucous epidermal keratinocytic nevi in Labrador and Chihuahua
(deletion) X semi dominant

71
Q

A mutation in DSG1 is associated with which disease in dogs?

A

Footpad hyperkeratosis and allergies in a Rottweiler

(deletion) - AR/autosomal semi-dominant

72
Q

A mutation in SLC27A4 is associated with which disease in dogs?

A

Ichthyosis in Great Danes

SNP, splicing

73
Q

A mutation in KRT1 is associated with which disease in dogs?

A

Ichthyosis in Shar-Pei

74
Q

Which types of ichthyosis in dogs do not have autosomal recessive inheritance?

A

ASPRV1 - GSD - AD

KRT1 - Shar-Pei - AD

75
Q

Which of these gene mutations associated with cornification disorders are not autosomal recessive in inheritance?
Footpad HK DSG1
Footpad HK FAM83G
Footpad HK KRT16
Nasal paraK SUV39H2
Verrucous epidermal keratinocytic nevi NSDHL

A

Footpad HK DSG1 = AR/autosomal semi-dominant

Verrucous epidermal keratinocytic nevi NSDHL = X semi-dominant

Sarah - Structure (5 decks)

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