Broken skin barrier is a key driver of atopic eczema, and

Irwin McLean Centre for & Genetic Medicine Division of Molecular Medicine University of Dundee Scotland Skin – the largest organ The – a super-tough, self-renewing tissue

Stratum corneum

Epidermis

Dermis Skin barrier function Pathogens Allergens Irritants

Skin barrier Stratum corneum

H2O The gene 38: 337-342, March 2006

From …

38:441-446, April 2006

…to Atopic Eczema, Asthma etc

39:650-654, April 2007 Ichthyosis vulgaris

• Most common monogenic skin disorder • Dry, scaly skin, worse in winter/dry climate • Hyperlinearity of palms/soles; keratosis pilaris

• ~1% of the UK population have full form • >10% have a sub-clinical form

• Evidence for defect involving filaggrin – Biochemistry – Genetic mapping

• Large repetitive gene

• Difficult to sequence

• Many IV patients have eczema! Atopic

• (= “eczema”) • Affects >20% of children in developed nations • Incidence has increased in recent decades

• Often accompanied by other allergic diseases (atopic disease, ) – Eczema – Food (30%) – Asthma (50%) – Rhinitis (hay fever; 70%)

• “Atopic march”

• Healthcare burden US$ billlions Filaggrin protein

Profilaggrin 10-12 full filaggrin repeats N C

2x partial filaggrin repeats

S100 domain B domain Unique C-terminus Filaggrin - filament aggregating protein

Epidermal filaggrin staining

Keratin aggregation

Processed Filaggrin (37 kDa) Proteolysis

Profilaggrin (>400 kDa)

Keratin filaments “Natural moisturizing factor”

Epidermal filaggrin staining

Hygroscopic amino acids

Further proteolysis

Chemically modified filaggrin

Peptidyl arginine deiminases

Keratin aggregation Filaggrin – a multi-functional skin barrier protein

H2O RETENTION NMF pH UV PROTECTION Natural Moisturising Factor ANTI-MICROBIAL

BARRIER FORMATION

Filaggrin

INERT Profilaggrin FLG is a large, highly repetitive gene on 1q21.3

FLG gene

15 bp 153 bp 13 kb (or variant sizes of 14 kb or 15 kb)

FLG

Protein domains encoded

10-12 near-perfect 324 amino acid repeats 2 imperfect repeats Irvine, McLean,Aileen Leung Sandilands, NEJM Frances 2011 Smith, Toshifumi Nomura, Huijia Chen Irvine, McLean, Leung NEJM 2011 Alan Irvine, Irwin McLean, Donald Leung, NEJM (2011) Filaggrin function and inherited deficiency

“Normal” ~89% UK population

1x filaggrin mutation ~10% UK population

~8x risk eczema

2x filaggrin mutations ~1% UK population

~150x risk eczema 10 repeats 2x copies = 1.7x risk of AD

11 repeats

12 repeats2x copies = 0.6x risk of AD Filaggrin upregulation therapy Most filaggrin-related eczema patients carry a single null mutation

FLG

FLG Drug Discovery in Dundee

Cutaneous Drug Discovery Portfolio: CDDP Alan Mike Paul Irwin Fairlamb Ferguson Wyatt McLean

Target Discovery Validation Drug Lead Partnering selection

Potential Informatics Proof of Fully Industrial Clinically Drug Target and concept validated partners and useable functional Genetic/chemi molecular PPP partners therapeutics genomics cal/animal data model package Filaggrin expression in keratinocytes treated with chemical library

Robyn Hickerson, Pam Robertson Human filaggrin–luciferase transgenic mice

Xenogen IVIS 200 live animal imaging Luciferase IMF footpad Human filaggrin–luciferase transgenic mice

Untreated

Treated

Vehicle only Vehicle plus Compound Skin barrier function Pathogens Allergens Irritants

Skin barrier Stratum corneum

H2O Impaired skin barrier function Pathogens Allergens Irritants

Stratum corneum

H2O

Allergic immune response

Eczema Thanks Alan Irvine MD Thanks