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Dermatology
The Biology of the Basement Membrane
Built from Dermatology, 5th Edition
What’s inside
8 sections · 88 slides
Overview
- What this chapter covers
Basement membrane overview
What a basement membrane is, and why the skin needs one
- What a basement membrane is
- Functions of a basement membrane
- Two basement membranes in skin
- Four ultrastructural subregions of the epidermal basement membrane
- The four subregions, top to bottom
- Laminated model of the epidermal basement membrane
- The laminated model, in plain terms
Origin of the epidermal basement membrane
Two different cell types build this one structure together
- Built by two different cell types
- What each cell type contributes
Basal keratinocyte hemidesmosome proteins
The anchor plaques and integrins that hold skin cells to the membrane
- Plectin holds the hemidesmosome together
- Plectin's role, confirmed in mice
- Bullous pemphigoid antigen 1: found through disease
- What happens when BPAG1 is missing
- Bullous pemphigoid antigen 2 (type XVII collagen)
- BPAG2 exists in two forms
- BPAG2 assembles into a triple helix
- BPAG2 and autoimmune or inherited disease
- What integrins are
- How integrins bind their targets
- Inside-out and outside-in signaling
- Kindlin-1 loss causes Kindler EB
- Kindlin-1 loss in mouse skin
- Integrin alpha6beta4: the hemidesmosome's integrin
- When alpha6 or beta4 integrin is missing
- Non-hemidesmosomal integrins in keratinocytes
- Losing alpha3 integrin disrupts the basement membrane
- CD151: the tetraspan organizer
- How hemidesmosomes assemble around CD151
- Molecular interactions within the epidermal basement membrane
The lamina densa
Laminins, type IV collagen, nidogen, and proteoglycans forming the membrane's dense core
- Laminins: a family of matrix proteins
- Naming laminin isoforms
- Structure of laminin 111
- The three main epidermal laminins
- Laminin 332's disease importance
- Comparing four laminin isoforms
- Laminin isoforms: identity
- Laminin isoforms: processing and assembly
- Laminin isoforms: tissue distribution
- Laminin isoforms: interactions and functions
- Type IV collagen: unique to basement membranes
- Where the different type IV collagen chains sit
- The 'hockey stick' shape of type IV collagen
- Diseases from defective type IV collagen
- Type IV collagen fragments with their own biology
- Nidogen and perlecan binding in the lamina densa
- Nidogen links the lamina densa together
- Nidogen-2 and what's missing without nidogen
- Heparan sulfate proteoglycans: the 'bottle brush' molecules
- Perlecan: 'spot welding' the network together
Anchoring fibrils and the sublamina densa region
Type VII collagen ties the lamina densa down to the dermis
- Type VII collagen: unique to stratified epithelium
- Why anchoring fibril assembly matters
- Assembly of anchoring fibrils
- COL7A1: a large but compact gene
- Dominant dystrophic EB: a different mechanism
- Epidermolysis bullosa acquisita: the autoimmune version
- Microfibrils in the papillary dermis
Basement membrane remodeling
A living barrier that is constantly rebuilt
- The basement membrane is not static
- Enzymes that remodel the membrane
The epidermal basement membrane in bullous diseases
When these proteins are attacked by antibodies or missing from birth
- Two roads to the same result: blistering
- Proteins targeted in both autoimmune and inherited blistering disease
- Autoantigens and mutated proteins mapped to the epidermal basement membrane
- Classifying subepidermal immunobullous disease
- Well-characterized subepidermal immunobullous diseases
- Salt-split skin: a diagnostic trick
- Indirect immunofluorescence on salt-split skin
- Indirect immunofluorescence localization on salt-split skin
- Direct immunofluorescence: testing the patient's own skin
- Direct immunofluorescence localization on salt-split skin
- Cleavage plane in salt-split skin
- Studying EB deepened our understanding of the membrane
- EB subtypes, by where the skin splits
- How pathologists confirm the cleavage plane
- Representative forms of epidermolysis bullosa
- Representative forms of epidermolysis bullosa (continued)
- Confirming the missing protein directly
- Adhesion proteins by region: a reference map
- Representative adhesion proteins in the epidermal basement membrane
- Key takeaways
- References
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- Dermatology, 5th Edition (2-Volume Set)