[Gly-X-Y]n ‘R’ US READ Gelehrter et al. pages 143-150 SEE course web pages for related objectives and lecture notes

• Acquired/Multifactorial

– Aging

• Mendelian Inheritance

– Osteogenesis imperfecta (Type I Collagen)

– Ehlers-Danlos syndromes (Types I, II,III, V Collagens)

– Chondrodysplasias (Type II Collagen)

– Alport syndrome (Type IV Collagen)

– Stickler syndrome (Types II, XI Collagen)

– Schmid metaphyseal dysplasia (Type X Collagen)

– Dystrophic epidermolysis bullosa (Type VII Collagen)

Collagen DisordersCollagen Disorders

5

313336

5568 60 53 30s

R internal carotid dissection, cerebral infarct,R vertebral artery aneurysm, s/p repairAbdominal aorta aneurysm/chronic dissection, Aneurysm R common iliac

HTN Vertebral artery rupture 57, Aortic dissection 60,

Splenic Artery rupture,

Aortic dissection

32

1 4 5

Arterial rupture

Connective tissue proteins are synthesized in a tissue specific manner by a variety of specialized cells such as

fibroblasts, chondrocytes, osteoblasts.

Procollagen

Proelastin

What is collagen?• Major extracellular fibrous protein that provides

strength and structure to tissues by organizing the extracellular matrix via supramolecular assembly functions

• A ropelike structure made by intertwining three polypeptide chains into a triple helix

Fibrillar collagens have awesome tensile strength

Reticular collagens provide a meshwork of support

25 distinct collagen molecules vary by content of genetically distinct -chains

• Type I collagen: [1(I)]22(I) Heterotrimer two -1 chains (COLIA1 on chromosome 17) one -2 chain (COLIA2 on chromosome 7)

• Type III collagen: [1(III)]3

Homotrimer two -1 chains (COL3A1 on chromosome 2)

Skin contains Type I, III, V collagens and elastic fibers

Connective tissue surrounding blood vessels includes type III

collagen and elastic fibers

Connective tissue supporting

hollow organs including colon

contains Type III collagen

• Each polypeptide chain is wound in a left-handed helix • Three chains form a triple helix monomer• The helix is stabilized by hydrogen bonds in a right-handed helix.• Importantly, the third residue is glycine, as it can fit into the center of the helix.

[Gly-X-Y]n X: proline, lysineY: hydroxyproline, hydroxylysine.

disulfide bonds

The making of collagen…

Polypeptide chains are synthesized from ribosomes, signal peptides are removed and a series of post-translational modifications take place:

Intracellular modifications:• Hydroxylation of proline and lysines allows bonding to other molecules which

requires co-factors (i.e. vitamin C).• Glycosylation of hydroxylysine residues via galactosyl transferase, lysyl

hydroxylase, and glucosyl transferase controls fibrillar morphology.• The three chains align and disulfide bonds form to form triple helix.• Triple helix is packaged into a vesicle and secreted from the cell.

Extracellular modifications:• Calcium dependent N- and C-proteinases remove the propeptides • Procollagen molecules aggregate by a 1/4 staggering in respect to its neighbor and

are stabilized by covalent cross links.• A polymeric fibril is formed.• Fibril is arranged in different tissue specific ways

Type I collagen fibers

By EM (50,000 X), collagen appears as regular striated bundles in longitudinal

section and circles on cross section

Some collagens that form long structural fibrils

I. Skin, tendon, bone, dentin; a fetal form also exists Mutations cause osteogenesis imperfecta, procollagen cleavage mutations

cause EDSII. Cartilage, vitreous humor

Mutations cause abnormalities of skeleton and eye, Stickler syndromeIII. With type I in skin, also in muscles, blood vessels

Mutations cause Vascular EDSV. Fetal tissues, placenta, interstitial tissues, skin

Important for extracellular matrix assembly, mutations cause classic CClassic EDS

Type I collagen• 90% of our collagen is type I• two 1(I) chains (COL1A1 chr 17) and one 2(I) chains (COL1A2 chr 7))• Most abundant in: Bones, skin, tendons, cornea

300nm long 1.5nm in diameter

1(I) 2(I)

• COL1A1 and COL1A2 mutations cause Osteogenesis Imperfecta syndromes• Posttranslational modification defects cause rare Ehlers-Danlos syndromes

Type I collagen fibers

Type I collagen fibers arranged to provide structural integrity

OsteogenesisImperfecta

• Four major clinical sub-types (Sillence classification) vary in phenotypic characteristics and severity (I,IV,III,II)

• Highly penetrant, inter- and intra-familial variable expressivity

• Prognosis varies greatly depending on type

OI Type I (with or without DI)

• Most common form

• Type I collagen is decreased in amount, generally normal in structure

• Normal/near normal height

• Little or no bone deformity

• Blue/gray sclera

• Increased bruising

• Joint hypermobility

• Possible scoliosis

• Possible dentinogenesis imperfecta/opalescent dentin

• Conductive hearing loss in up to 50%

• Autosomal dominant

Osteogenesis Osteogenesis ImperfectaImperfecta

gray/blue scleragray/blue sclera

Opalescent dentin/Dentinogenesis

imperfecta

OI Type IV (with or without opalescent dentin)

• Osteoporosis and bone fragility without significantly blue/gray sclerae after birth or early onset deafness

• 25% have fractures at birth while in some cases fractures do not occur until later in life

• May be clinically confused with idiopathic juvenile• Short stature • Mild to moderate bone deformities• Scoliosis• Dentinogenesis imperfecta/opalescent dentin in some patients• Possible hearing loss, but not as common as in type I• Autosomal dominant

OI Type III• Significant fractures at

birth and/or infancy

• Marked short stature

• Severe kyphoscoliosis with progressive platyspondyly

• Severe long bone progressive deformities, often require wheelchair

• Decreased muscle mass in arms and legs

• Loose joints

• Whites of the eyes (sclera) have a blue, purple, or gray tint

• Brittle teeth

• Possible hearing loss

• Possible cardiopulmonary problems

• Most autosomal dominant,

• ? Autosomal recessive types

• ? Additional loci

OI Type II

• Most severe form with extreme bone fragility at birth– Continuous beaded ribs with

crumpled long bones– Crumpled long bones with

few rib fractures– Narrow, dysplastic beaded

ribs with poorly molded long bones and fractures

• Frequently lethal at or shortly after birth

• Numerous fractures

• Severe bone deformities

• Very small stature

• Underdeveloped lungs

• Abnormal brain neuropathology

• Diminished and structurally abnormal type I collagen

• Most cases autosomal dominant mutations with germline mosaicism

Skeletal dysplasia classified according to the region and type of bone involved

• Predominantly epiphyseal– Multiple epiphyseal dysplasia– Hereditary arthro-ophthalmopathy (Stickler syndrome)– Chondrodysplasia punctata

• Predominantly metaphyseal– Lethal short limb dwarfism– Achondroplasia– Metaphyseal chondrodysplasias

• Major involvement of the spine– Spondyloepiphyseal dysplasia ‘congenita’– SED (x-linked and others)– Pseudoachondroplasia– Kneist syndrome– Diastrophic dwarfism

• Predominant involvement of single sites– e.g. mesomelic dwarfism

• Abnormal bone density and/or modelling defects– e.g. sclerosing disorders of bone

From: Pope FM, Smith R. Color Atlas of Inherited Connective Tissue Disorders, Mosby-Wolfe, 1995

OI - Autosomal Dominant

• If a child inherits an altered collagen allele, the child will have the same type of OI as the parent

Parent with OI Unaffected Parent

Child with OI= Normal Gene

= altered Gene

degraded

okay

Normal typical Type I typical type II‘Protein suicide’

How is OI inherited when there is no family history of OI?

• 5-8% of families without a prior history of OI have multiple children with OI

• Due to “new” or “spontaneous” alteration occurs in the gonadal cells which give rise to multiple sperm or eggs.

• Germline or gonadal mosaicism - parent not affected by the condition, but mutation in certain percentage of his or her reproductive/germline cells

Clinical Testing• Diagnostic confirmation of type• Two available tests for OI

– Protein/Biochemical– DNA

• Prenatal diagnosis available using ultrasound (OI type II), amniocentesis or chorionic villus sampling.

How is OI treated?• Prevent/control symptoms, maximize mobility, and developing

optimal bone mass and muscle strength.– Physical therapy, exercise, maintain normal weight– Proper care of fractures– Activity guidance - avoid high risk of injury activities– Pain management– Surgical placement of metal rods in the bones to provide strength– Motility aids, such as wheelchairs and braces– Avoid smoking, excessive alcohol, steroids– Regular dental care

• Bisphosphates, calcium, and Vitamin D

Ehlers-Danlos Syndrome(s)Ehlers-Danlos Syndrome(s)

1 in 5,000 - 10,000 people both males and females all racial and ethnic backgrounds

•Skin: soft velvety; hyperextensible; fragile - tears or bruises easily; severe parchment paper scars; slow and poor wound healing; molluscoid pseudotumors over pressure areas, striae

•Joints: hypermobile/hyperextensible, loose/unstable; prone to dislocations and/or subluxations; pain; hyperextensible joints; early osteoarthritis; chronic, early onset, debilitating musculoskeletal pain, pes planus, scoliosis

•Other: mitral valve prolapse; blue sclerae, gum disease, organ and vascular fragility

•Classic Type (types I and II) AD - Type V and type ? collagen alterations

“Parchment paper” scars, joint hypermobility,skin hyperelasticity, bruising

•Hypermobility Type (type III) AD - Type ? collagen alterations

Joint hypermobility/extensibility, joint pain, premature arthritis

•Vascular Type (type IV) AD - Type III collagen alterations

Arterial/intestinal/uterine fragility or rupture, bruising, translucent skin •Kyphoscoliosis Type (type VI) AR - Lysyl hydroxylase deficiency

Scoliosis at birth, scleral fragility •Arthrochalasia Type (types VII A, VII B) AD - Type I collagen

alterations

Hypotonia, congenital hip dislocation

•Dermatosparaxis Type (type VII C) AR - Amino proteinase deficiency Severe skin fragility, doughy skin, blue sclerae, short stature, severe bruising

Six types of Ehlers-Danlos syndrome

• Autosomal Dominant

• Major Criteria

– Skin hyperextensibility

– Widened atrophic scars

– Joint hypermobility

• Minor Criteria– Smooth, velvety skin

– Molluscoid pseudotumors

– Subcutaneous spheroids

– Joint complications (eg. sprains, dislocations, subluxations, pes planus)

– Muscle hypotonia, gross motor delays

– Easy bruising

– Complications of fragile tissue (hiatal hernia, anal prolapse)

– Surgical complications (postoperative hernias)

– Positive family history

• Laboratory Diagnosis– Type V collagen abnormalities ( < 50%, most unknown)

– EM with ‘cauliflower’ fibrils

Diagnostic Criteria for Classic EDS (I and II) Diagnostic Criteria for Classic EDS (I and II)

• Autosomal Dominant

• Major Criteria

– Generalized joint hypermobility

– Skin hyperextensibility OR smooth, velvety skin (if atrophic scars are present, probably classic type)

• Minor Criteria

– Recurring joint dislocations (frequently shoulder, patella, and TMJ)

– Chronic joint/limb pain - often early onset and possibly debilitating

– Positive family history

• Laboratory Diagnosis

– None

• Distinguish from familial hypermobility (?)

Diagnostic Criteria for Hypermobility Type EDS Diagnostic Criteria for Hypermobility Type EDS

Hypermobility EDSHypermobility EDS

• Autosomal Dominant

• Major Criteria: Two major criteria - highly indicative of the diagnosis, One - be very suspicious especially if family history

– Thin, translucent skin

– Arterial/intestinal/uterine fragility or rupture

– Extensive bruising

– Characteristic facial appearance with decreased subcutaneous adipose tissue, particularly in face and limbs, often with big eyes, pinched nose

• Minor Criteria: One or more minor criteria with positive family history, be suspicious

– Acrogeria

– Hypermobility of small joints

– Tendon and muscle rupture

– Talipes equinovarus

– Early onset varicose veins

– Arteriovenous, carotid-cavernous sinus fistula

– Pneumothorax/pneumohemothorax

– Gingival recession

– Positive family history or vascular or organ rupture, sudden early death in relatives

• Laboratory Diagnosis: Type III collagen abnormalities in fibroblasts, COL3A1 mutation

Diagnostic Criteria for Vascular EDS Diagnostic Criteria for Vascular EDS

Compressed carotid artery by blood dissecting upward from a dissection.

Blood dissects along the media (asterisks).

*

Translucent skin

14

1732

31

90s

Unaffected

Probable EDS IV

EDS IV- Vascular typeConfirmed by DNA testing

Ruptured renal artery“Marfan disease”

Bilateral inguinal herniasEasy bruising

Soft, translucent skinIncreased bleeding

16 15

Ruptured thoracic artery

0 43

Vertebral aneurysmSpontaneous

pneumothoraxSigmoidal perforation

35

3

•Consists of 3 1(III) chains (COL3A1 on chr 2)•Thin collagen fibers created•Forms a loosely woven meshwork of reticular fibers

•Largely in: skin (with type I and type V collagens)blood vessels internal organs (e.g. smooth muscle layers GI

tract, uterus, bladder)

Type III Collagen

Vascular EDS Manifestations Vascular EDS Manifestations (Pepin et al, NEJM, 2000)(Pepin et al, NEJM, 2000)

• 220 patients, 199 relatives

• Mean age at ascertainment: 28.7

– Patients: 24.9 + 13 (M - 25.1, F - 24.7);

– Relatives: 33.3+15.6

• Family history present:

– Yes: 38.2 %

– No: 41.4%

• Age of first complication in index patients (n=136)

– 23.5+11.1 (M - 23.9, F - 22.8)

– 25% had significant complication before 20 years

– 80% had significant complications before 40 years

• Age at death ranged from 6 -73 years, median = 48

ArterialGINoneOrgan

Vascular EDS Manifestations Vascular EDS Manifestations (Pepin et al, NEJM, 2000)(Pepin et al, NEJM, 2000)

Type of first complication in index patients

ArterialOrganGI tractOther

Vascular EDS Manifestations Vascular EDS Manifestations (Pepin et al, NEJM, 2000)(Pepin et al, NEJM, 2000)

Causes of death (n =131)

Vascular EDS Manifestations Vascular EDS Manifestations (Pepin et al, NEJM, 2000)(Pepin et al, NEJM, 2000)

Cause of pregnancy related deaths in 12 of 81 women (167 live births)Maternal death rate 1 in 23 (11.5%)

Uterine rupture during labor

Arterial rupture in postpartum period

Arterial rupture at delivery

Treatment/Management of Vascular EDS

No specific therapies delay onset of complications.

No proven medical surveillance for complications of Vascular EDS.

The diagnosis should be established to provide genetic counseling, anticipatory guidance and education, and appropriate

management strategies for surgeries and pregnancies.

Defect in N-Proteinase Defect in N-Proteinase

• Autosomal recessive

• Major Criteria

– Severe skin fragility

– Sagging redundant skin

• Minor Criteria– Soft, doughy skin texture

– Easy bruising

– Premature rupture of fetal membranes

– Large hernias

• Laboratory diagnosis– Biochemical confirmation of procollagen N-terminal peptidase (N-proteinase) by

analysis of pN1(I) and pN2(I) in fibroblasts

– Determine level of N-proteinase activity

Diagnostic Criteria for Dermatosparaxis Type EDSDiagnostic Criteria for Dermatosparaxis Type EDS

Patient 1 Patient 2 Normal

Dermatosparaxis

•Classic Type (types I and II)Classic Type (types I and II)AD - Type V and type ? collagen alterations

•Vascular Type (type IV)Vascular Type (type IV) AD - Type III collagen alterations

•Dermatosparaxis Type (type VII C) Dermatosparaxis Type (type VII C) AR - Amino proteinase deficiency

Genetics of Ehlers-Danlos syndrome Genetics of Ehlers-Danlos syndrome

Treatment/Management of EDSJoint careSkin care Medications:

Pain medications (avoid excessive NSAIDS in vascular type)Ascorbic acid (vitamin C) 1 - 4 g/day in adults, 0.5 to 1.0 mg/day in children Consider risks/benefits of anticoagulation in vascular type

Medical and Surgical Care: Be sure all health care providers know about the diagnosis (medic alert tag)Obtain emergent care for any new onset of pain and/or neurological systems Proceed with caution - tissue fragility leads to tears, excessive bleedingManage hypertension, avoid constipation, carefully consider risks of

pregnancy Lifestyle:

Avoid contact sports and other high risk activitiesMaintain ideal body weight

•Collagen - main structural protein in bodyCollagen - main structural protein in body•Many genetically distinct types of collagenMany genetically distinct types of collagen

• all have triple helix structure all have triple helix structure • polypeptide chains with large (Gly -X-Y)n domainpolypeptide chains with large (Gly -X-Y)n domain• post translational modifications and extracellular processing critical post translational modifications and extracellular processing critical

•Type I collagen: Heterotrimer Type I collagen: Heterotrimer • abundant in skin, bones and ligaments. abundant in skin, bones and ligaments. • mutations in associated genes cause autosomal dominant OI mutations in associated genes cause autosomal dominant OI • point mutations in glycine can causing structural collagen abnormality point mutations in glycine can causing structural collagen abnormality can be more severe than haploinsufficincy (protien suicide)can be more severe than haploinsufficincy (protien suicide)• multiple severely affected children with normal parent can arise due to multiple severely affected children with normal parent can arise due to germline mosaicismgermline mosaicism

•Type III collagen: Homotrimer, Type III collagen: Homotrimer, • mutations in gene encoding tyope III collagen associated with Vascular mutations in gene encoding tyope III collagen associated with Vascular EDS (type IV EDS) characterized by vascular and tissue fragilityEDS (type IV EDS) characterized by vascular and tissue fragility

•Many types of EDS but classic EDS usually has skin and joint Many types of EDS but classic EDS usually has skin and joint manifestationsmanifestations

Collagen Disorders - Summary Collagen Disorders - Summary