DEJ and Applied aspects.pptx

1. DERMOEPIDERMAL JUNCTION AND ITS APPLIED
ASPECTS
PRESENTED BY – DR.ADYASA BASA
JUNIOR RESIDENT
SCB MCH
MODERATED BY-DR.SIDDHARTHA DASH
ASSISTANT PROFESSOR
SCB MCH

2. INTRODUCTION
● The interface between lower part of epidermis and the top layer
of dermis is dermo-epidermal junction.
● It is a basement membrane zone which is recognised
histologically by positive staining with PAS.
● It is not visible in haematoxylin eosin stained section.

3. ● At dermo-epidermal junction, finger like upward
projections called the ‘dermal papilla’ and downward
projections into dermis called ‘epidermal rete ridges’
are seen.
● By transmission electron microscopy the laminated
model of the dermoepidermal juction is studied.

4. PAS staining showing the basement
membrane.
Electron microscopy shoeing ultra
structure of DEJ.

5. ORIGIN OF DEJ
Basal
keratinocyte
Plectin
BPAG1e
BPAG2
Integrin
CD151 tetraspan
Laminin 332 , 311
Dermal
fibroblast
Nidogen
Type IV collagen
Type VII collagen

6. FUNCTIONS OF DEJ
Dermo epidermal junction acts as:
● Substrate for attachment of cells.
● Template for tissue repair.
● Matrix for cell migration.
● Substrate to influence differentiation and morphogenesis.
● Permeability barrier for cells and macromolecules.

7. LAMINATED MODEL OF DEJ
● This model divides the DEJ ultrastructurally into 4 subregions:
I. The cytoskeleton,hemidesmosomal plaque and plasma
membrane of basal keratinocyte
II. Lamina lucida
III. Lamina densa
IV. Sublamina densa

10. HEMIDESMOSOMES
● Hemidesmosomes is the structure of 1st layer of BMZ.
● The number of hemidesmosomes is constant in each indivisual.
● Hemidesmosomes extend from intracellular component of basal
keratinocytes to lamina lucida in upper portion of dermal-
epidermal basement membrane.

11. ● The most cytoplasmic portion
is called the inner plaque .
● The portion of
hemidesmosome closely
attached with the basal
plasma membrane is called
the outer plaque.

12. ● The inner plaque is attached to the tonofilaments which
are composed of keratin 14 and keratin 5.
● The outer plaque is connected to anchoring filaments in
the lamina lucida.
● The hemidesmosomes consists of
 Transmembrane protein-integrin α6β4,BP180,CD151.
 Cytoplasmic protein - plectin and BPAG1.

14. ● Major components of hemidesmosomes are HD1(500),
HD2(230), HD3(200), HD4(180) and HD5(120).
● HD2 and HD4 bullous pemphigoid antigen 1 and 2 respectively.
● HD3 and HD5 corresponds to β4 and α6 integrins respectively.
● HD1 corresponds to plectin-intracytoplasmic adhesion molecule.

15. BPAG1
● It is a high molecular weight protein of plakin family of
cytoskeletal linkers which is localised to cytoplasmic
plaque of HD.
● It has a tripartite structure:
1)Amino terminal - globular domain:- cytoplasmic domain of BPAG2 and
β4 subunit of α6β4 integrin and ERBIN.
2)central coiled rod
3)carboxy terminal-intermediate filament binding domain.

16. ● Erbin protein interacts with transmembrane tyrosine kinase
receptor Erb-B2.
● There are many isoforms of BPAG1
○ BPAG1e present in skin.
○ BPAG1n present in neurons.
● Therefore mutation in BPAG1 also results in dystonia and
ataxia.

19. Plectins
● Intracellular protein present in cytoplasmic domain of
hemidesmosomes
● It stabilises BMZ by binding both intermediate filaments
and outer plaque components.

20. ● Carboxy terminus binds to
keratin intermediate
filaments.
● Amino terminal binds to the
cytoplasmic tail of β4 of α6β4
integrin.

22. BPAG2 (collagen XVII)
● Transmembrane protein of collagen family associated
with HD-anchoring filament complex.
● 2 divisions of this protein are:-
○ Intra cytoplsmic domain appears as globular head
○ Extra cytoplasmic domain as a central rod (coll 15) with flexible
tail.

23. ● The cytoplasmic domain of
BPAG2 associates with
BPAG1e, integrin subunit
β4 and plectin.
● The extra cellular domain
of binds to the integrin
subunit α6 and laminin
332.

24. Integrins
● These are heterodimeric transmembrane receptors that
promote cell-cell and cell-matrix interactions.
● These modulate cell adhesion,signal transduction,gene
expression,growth and other fundamental biologic
processes.
● The 2 types of integrins found in epidermal BMZ:
○ α6β4 :- laminin binding
○ α3β1:-collagen binding

25. ● Cytoplasmic domain of integrin interact with the actin
cytoskeleton.
● The extracellular domain forms the ligand binding site.
● In basal keratinocytes kindilin 1 and kindilin 2 form a part of
signalling complex of intergrins.
● Mutation in FERMT1 Gene encoding kindilin 1 are responsible
for KINDLER SYNDROME.

26. ● Autosomal recessive disease
characterized by
○ Trauma induced blistering
○ Photosensitivity
○ Poikiloderma
○ Mucosal involvement
○ Squamous cell carcinoma

27. ● Hemidesmosome associated integrin is α6β4.
● The cytoplsmic portion of β4 is associates with plectin.
● The distal carboxy terminal region binds to BPAG2.
● The proximal extra cellular domain of α6 binds to NC16A
donain of BPAG2.
● Cytoplasmic tail of β4 contains seqences required for
hemidesmosome assembly.

30. LAMINA LUCIDA
● Lamina lucida is electron lucent region of BMZ(20-
40nm)
● Lamina lucida connects hemidesmosomes above to
lamina densa below.
● The major constituents of lamina lucida are laminin 5 ,
α6β4 integrin and ecto domain of BP180.
● Spanning the lamina lucida and connecting lamina densa
to HD are the anchoring filaments.

32. Anchoring Filaments
● Anchoring filaments are thread like structures 3-4 nm in
diameter.
● Laminin 332 is the major component of these anchoring
filament;others being α6β4 integrin ,XVII collagen and laminin
311.
● They are derived from basal keratinocytes.

33. LAMININS
● Each laminin molecule
consists of 3 polypeptide
units,α, β and γ which forms
a cruciform structure with 3
short arms and 1 long arm.
● The major laminin in the
cutaneous basement
membrane zone is laminin
332.

34. ● Functions of laminins:
○ Interaction with hemidesmodomal components and type VII collagen
○ Cell attachment and spreading
○ Neurite outgrowth and cellular differentiation.
● Mutation in any of the three polypeptide subunit of laminin
332 results in junctional forms of EB.

35. LAMINA DENSA
● Lamina densa is the third layer of basement membrane
zone(40-60 nm).
.
● Lamina densa is connected to epidermis by anchoring
filaments and to dermis by anchoring fibrils.
● Type IV collagen is the major component of lamina
densa others being HSPGs and Nidogen.

37. TYPE IV COLLAGEN
● It is synthesized in rough endoplasmic reticulum and
secreted via golgi apparatus into basement membrane.
● Type 4 collagen molecule consists of 3 polypeptide
chains known as alpha α chains which assemble into
triple helical structure giving it a ‘hockey stick
appearance’

39. ● The composition of alpha chain varies with tissue
location of basement membrane zone.
● In cutaneous basement membrane zone, type 4 collagen
is made mainly of α1 and α2 chains.
● The individual collagen molecules in case of type 4
collagen form
○ dimers tetramers assembles in a lattice like structure
laterally in a complex hexagonal arrangement.

40. ● Such kind of arrangement allows BMZ to be highly flexible.

41. Immunofluoroscence staining of the dermis and the BMZ with an antibody for type IV collagen

42. Collagen fibrils showing a characteristic banding pattern after treatment and staining with uranyl acetate
and lead citrate for transmission electron microscopy.

43. HEPARAN SULPHATE PROTEOGLYCANS
● It is a diverse group of macromolecules that are ubiquitous
components of basement membranes.
● They consist of a core protein with covalently attached
heparan and sulphate chains in a ‘bottle brush’
configuration.
● Heparan sulphate proteoglycans are also found on the
surface of epithelial cells and mediate cell-matrix.
interactions.

44. ● The best characterised basement membrane HSPG is perlecan .
● Perlecan spot welds the laminin and collagen IV containing
networks together.
● The high sulphate content of HSPGs confer an overall negative
charge to basement membrane and thereby restricts their
permeability.

45. NIDOGENS
● Nidogen is a 150 kDa glycoprotein present in lamina
densa.
● It has 3 globular domains resembling a dumbell like
structure
○ G3 binds to laminin 311
○ G2 binds to collagen IV
● Nidogen laminin complexes bind to heparan sulfate
proteogylcan and stabilise the basement membrane.

48. SUBLAMINA DENSA
● Beneath the lamina densa, lies
the sublamina densa layer
composed of anchoring fibrils.
● Anchoring fibrils binds the
lamina densa to superficial
dermis.

49. ANCHORING FIBRILS
● Major component of anchoring fibril is type 7 collagen.
● Type VII collagen consists of three identical α chains.
● Amino terminus – NC1
● Carboxy terminus- NC2
● Type VII collagen molecules become organized into
anchoring fibrils through the formation of antiparallel
dimers linked through their carboxy‐terminal ends.

50. ● Globular NC1 domain binds the lamina densa at one end and
either loop back into lamina densa or connect to electron dense
elements in sublamina densa known as anchoring plaques.
● Anchoring plaques are portions of lamina densa that have
dropped out and fallen into sublamina densa region.
● The large amino‐terminal interact with type IV collagen and
laminin 332.

52. Anchoring fibrils.

53. DISORDERS OF DERMO-EPIDERMAL JUNCTION

54. Protein target Structural
target
Autoimmune
disease
Genetic disease
BPAG1e HD BP Recessive EB
simplex
Type XVII
Collagen
(BPAG2)
HD- Anchoring
filament complex
BP , PG ,
MMP,linear IgA
bullous
dermatosis
Junctional EB
Integrin subunit
β4
HD- Anchoring
filament complex
Occular MMP Junctional EB with
pyloric atresia
Laminin 332 Lamina lucida-
lamina densa
interface
Anti- epiligrin
MMP
Junctional
EB(often more
severe)
Type VII
collagen
Anchoring fibril EB
acqisita,Bullous
eruption of SLE
Dystrophic
EB(dominant and
Recessive)

55. TYPES OF ERIDERMOLYSIS BULLOSA
AND CAUSATIVE PROTEIN

56. Reference:-
● Kim B. Yancy. The Biology of Basement Membrane. In:Jean L. Bolognia, Julie V.
Schaffer, Lorenzo Cirroni, editor. Dermatology, fourth ed. China: Elsevir;2018 p.483-
493.
● John A.McGrath, Jouni Uttio. Structure and function of skin. In: Christopher E.M.
Griffiths,Jonathan Barker, Tanya Bleiker,Robert Calmer, Daniel Creamer. Rook’s
Textbook of Dermatology, ninth ed. West sussex:John Wiley and sons Ltd;2016.
p.2.1-2.48.
● Devinder Mohan Thappa, Deepti Konda. Structure and Function of Skin.In:
S.Sacchidanand, Chetan Obroi, Arun C.Inamdar. IADVL Textbook of Dermatology,
fourth ed. Mumbai: Bhelani Publishing House; 2022p.27-29.

57. THANK YOU.