Keratins

Question 1

Do keratins form hetero- or homo-dimers?

Answer 1

Heterodimers

Question 2

Which types of keratin (types 1 and 2) are:

a) acidic
b) basic-neutral

Answer 2

Type 1 keratins are acidic

Type 2 keratins are basic-neutral

Question 3

Which keratins are primarily expressed in basal keratinocytes in stratified epithelial of the skin and mucosae?

Answer 3

Keratins 5 and 14

Question 4

Which cells express keratin 7?

Answer 4

Apocrine glands and Merkel cells

Question 5

Where is keratin 15 expressed?

Answer 5

Basal epithelial cells and hair bulge (in stem cells)

Question 6

During epidermal differentiation, keratinocytes detach from the basal layer, migrate suprabasally and become post-mitotic. Which keratins are expressed as the cells migrate and keratins 5 and 14 are down regulated?

Answer 6

Keratins 1 and 10

Question 7

Which epidermal layers express keratin 2?

Answer 7

Upper stratum spinosum and stratum granulosum (marker of advance keratinocyte differentiation)

Question 8

Which keratin is found in the suprabasal cells of the follicular outer root sheath, hair follicle medulla, sebaceous gland, fetal epidermis and in nail bed and nail matrix epithelia?

Answer 8

Keratin 17

Question 9

What binds intermediate filaments to desmosomes?

Answer 9

Desmoplakin

Question 10

What binds intermediate filaments to hemidesmosomes?

Answer 10

• BPAG1e (bullous pemphigoid antigen-1 epithelial) also called BP230
• Plectin

Question 11

What does filaggrin do?

Answer 11

It gives strength and organisation to the cell by aggregating keratin filaments during collapse of keratinocytes and formation of the corneocyte during epidermal cornification.

Question 12

Where are keratin associated proteins predominantly expressed?

Answer 12

Hair follicles and other hard cornified structures like the claw

Question 13

In epidermolytic hyperkeratosis of Norfolk Terriers, there is a mutation of which keratin?

Answer 13

Keratin 10

Question 14

Basal epidermolysis bullosa simplex in Friesian-Jersey cattle is associated with a mutation near which keratin gene?

Answer 14

Keratin 5

Question 15

Chesapeake Bay retriever dogs that developed skin lesions consistent with ectodermal dysplasia skin fragility syndrome in humans had a mutation affecting which protein?

Answer 15

Plakophillin 1

Question 16

How many keratin tetramers (protofilaments) make up an intermediate filament?

Answer 16

8

Question 17

The cytoskeleton is formed of which three main filamentous polymer proteins?

Answer 17

Microfilaments
Intermediate filaments
Microtubules

Question 18

What type of strength do intermediate filaments give?

Answer 18

Intermediate filaments, including keratin filaments, are capable of stretching and elongating under stress and then recovering their shape without rupturing

Question 19

Hard keratins have higher _____ content in their terminal domains from increased cysteine that allows for additional di-sulfide bonds and covalent protein cross-linking.

Answer 19

Sulfur

Question 20

Which keratins are associated with the paw pad?

Answer 20

Keratin 6
Keratin 9
Keratin 16

Question 21

Canine epidermal Langerhans cells and some T-cells appear to also express which plakophilin?

Answer 21

PKP2

Question 22

What does this image, from a cow with EBS, show?

Answer 22

Aggregated eosinophilic globules of intermediate filaments