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

Acquired/MultifactorialAgingMendelian InheritanceOsteogenesis 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 Disorders

53133365568605330sR internal carotid dissection, cerebral infarct,R vertebral artery aneurysm, s/p repairAbdominal aorta aneurysm/chronic dissection, Aneurysm R common iliac

HTNVertebral artery rupture 57, Aortic dissection 60,Splenic Artery rupture,Aortic dissection 32145Arterial rupture

Connective tissue proteins are synthesized in a tissue specific manner by a variety of specialized cells such as fibroblasts, chondrocytes, osteoblasts. ProcollagenProelastin

What is collagen?Major extracellular fibrous protein that provides strength and structure to tissues by organizing the extracellular matrix via supramolecular assembly functionsA ropelike structure made by intertwining three polypeptide chains into a triple helix

Fibrillar collagens have awesome tensile strengthReticular collagens provide a meshwork of support

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

Type I collagen: [a1(I)]2a2(I) Heterotrimer two a-1 chains (COLIA1 on chromosome 17) one a-2 chain (COLIA2 on chromosome 7)

Type III collagen: [a1(III)]3 Homotrimer two a-1 chains (COL3A1 on chromosome 2)

Skin contains Type I, III, V collagens and elastic fibersConnective tissue surrounding blood vessels includes type III collagen and elastic fibersConnective 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 a1(I) chains (COL1A1 chr 17) and one a2(I) chains (COL1A2 chr 7)) Most abundant in: Bones, skin, tendons, cornea

300nm long 1.5nm in diameter

a1(I) a2(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

OsteogenesisImperfectaFour major clinical sub-types (Sillence classification) vary in phenotypic characteristics and severity (I,IV,III,II)Highly penetrant, inter- and intra-familial variable expressivityPrognosis varies greatly depending on type

OI Type I (with or without DI) Most common formType I collagen is decreased in amount, generally normal in structureNormal/near normal heightLittle or no bone deformityBlue/gray scleraIncreased bruisingJoint hypermobilityPossible scoliosis

Possible dentinogenesis imperfecta/opalescent dentinConductive hearing loss in up to 50%Autosomal dominant

Osteogenesis Imperfectagray/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 deafness25% have fractures at birth while in some cases fractures do not occur until later in lifeMay be clinically confused with idiopathic juvenileShort stature Mild to moderate bone deformitiesScoliosisDentinogenesis imperfecta/opalescent dentin in some patientsPossible hearing loss, but not as common as in type IAutosomal dominant

OI Type IIISignificant fractures at birth and/or infancyMarked short statureSevere kyphoscoliosis with progressive platyspondylySevere long bone progressive deformities, often require wheelchairDecreased muscle mass in arms and legsLoose jointsWhites of the eyes (sclera) have a blue, purple, or gray tintBrittle teethPossible hearing lossPossible cardiopulmonary problemsMost autosomal dominant, ? Autosomal recessive types? Additional loci

OI Type IIMost severe form with extreme bone fragility at birthContinuous beaded ribs with crumpled long bonesCrumpled long bones with few rib fracturesNarrow, dysplastic beaded ribs with poorly molded long bones and fracturesFrequently lethal at or shortly after birthNumerous fracturesSevere bone deformitiesVery small statureUnderdeveloped lungsAbnormal brain neuropathologyDiminished and structurally abnormal type I collagenMost cases autosomal dominant mutations with germline mosaicism

Skeletal dysplasia classified according to the region and type of bone involvedPredominantly epiphysealMultiple epiphyseal dysplasiaHereditary arthro-ophthalmopathy (Stickler syndrome)Chondrodysplasia punctataPredominantly metaphysealLethal short limb dwarfismAchondroplasiaMetaphyseal chondrodysplasiasMajor involvement of the spineSpondyloepiphyseal dysplasia congenitaSED (x-linked and others)PseudoachondroplasiaKneist syndromeDiastrophic dwarfismPredominant involvement of single sitese.g. mesomelic dwarfismAbnormal bone density and/or modelling defectse.g. sclerosing disorders of boneFrom: Pope FM, Smith R. Color Atlas of Inherited Connective Tissue Disorders, Mosby-Wolfe, 1995

OI - Autosomal DominantIf a child inherits an altered collagen allele, the child will have the same type of OI as the parent

Parent with OIUnaffected Parent

Child with OI= Normal Gene = altered Gene

degraded

okayNormal typical Type Itypical type IIProtein 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 OIDue 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 TestingDiagnostic confirmation of typeTwo available tests for OIProtein/BiochemicalDNA 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 weightProper care of fracturesActivity guidance - avoid high risk of injury activitiesPain managementSurgical placement of metal rods in the bones to provide strengthMotility aids, such as wheelchairs and bracesAvoid smoking, excessive alcohol, steroidsRegular dental careBisphosphates, calcium, and Vitamin D

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, striaeJoints: hypermobile/hyperextensible, loose/unstable; prone to dislocations and/or subluxations; pain; hyperextensible joints; early osteoarthritis; chronic, early onset, debilitating musculoskeletal pain, pes planus, scoliosisOther: mitral valve prolapse; blue sclerae, gum disease, organ and vascular fragility

Classic Type (types I and II) AD - Type V and type ? collagen alterationsParchment paper scars, joint hypermobility,skin hyperelasticity, bruisingHypermobility Type (type III) AD - Type ? collagen alterationsJoint hypermobility/extensibility, joint pain, premature arthritisVascular Type (type IV) AD - Type III collagen alterationsArterial/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 dislocationDermatosparaxis 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 DominantMajor CriteriaSkin hyperextensibilityWidened atrophic scarsJoint hypermobilityMinor CriteriaSmooth, velvety skinMolluscoid pseudotumorsSubcutaneous spheroidsJoint complications (eg. sprains, dislocations, subluxations, pes planus)Muscle hypotonia, gross motor delaysEasy bruisingComplications of fragile tissue (hiatal hernia, anal prolapse)Surgical complications (postoperative hernias)Positive family historyLaboratory DiagnosisType V collagen abnormalities ( < 50%, most unknown)EM with cauliflower fibrils

Diagnostic Criteria for Classic EDS (I and II)

Autosomal DominantMajor CriteriaGeneralized joint hypermobilitySkin hyperextensibility OR smooth, velvety skin (if atrophic scars are present, probably classic type)Minor CriteriaRecurring joint dislocations (frequently shoulder, patella, and TMJ)Chronic joint/limb pain - often early onset and possibly debilitatingPositive family historyLaboratory DiagnosisNoneDistinguish from familial hypermobility (?)

Diagnostic Criteria for Hypermobility Type EDS

Hypermobility EDS

Autosomal DominantMajor Criteria: Two major criteria - highly indicative of the diagnosis, One - be very suspicious especially if family historyThin, translucent skinArterial/intestinal/uterine fragility or ruptureExtensive bruisingCharacteristic facial appearance with decreased subcutaneous adipose tissue, particularly in face and limbs, often with big eyes, pinched noseMinor Criteria: One or more minor criteria with positive family history, be suspiciousAcrogeriaHypermobility of small jointsTendon and muscle ruptureTalipes equinovarusEarly onset varicose veinsArteriovenous, carotid-cavernous sinus fistulaPneumothorax/pneumohemothoraxGingival recessionPositive family history or vascular or organ rupture, sudden early death in relativesLaboratory Diagnosis: Type III collagen abnormalities in fibroblasts, COL3A1 mutation

Diagnostic Criteria for Vascular EDS

Compressed carotid artery by blood dissecting upward from a dissection. Blood dissects along the media (asterisks).* Translucent skin

1417323190sUnaffected

Probable EDS IV

EDS IV- Vascular typeConfirmed by DNA testing

Ruptured renal arteryMarfan diseaseBilateral inguinal herniasEasy bruisingSoft, translucent skinIncreased bleeding

1615Ruptured thoracic artery043 Vertebral aneurysmSpontaneous pneumothoraxSigmoidal perforation353

Consists of 3 a1(III) chains (COL3A1 on chr 2)Thin collagen fibers createdForms 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 (Pepin et al, NEJM, 2000)220 patients, 199 relativesMean age at ascertainment: 28.7Patients: 24.9 + 13 (M - 25.1, F - 24.7); Relatives: 33.3+15.6Family 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 years80% had significant complications before 40 yearsAge at death ranged from 6 -73 years, median = 48

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

Type of first complication in index patients

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

Causes of death (n =131)

Vascular EDS Manifestations (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 laborArterial rupture in postpartum periodArterial 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

Autosomal recessiveMajor CriteriaSevere skin fragilitySagging redundant skinMinor CriteriaSoft, doughy skin textureEasy bruisingPremature rupture of fetal membranesLarge herniasLaboratory diagnosisBiochemical confirmation of procollagen N-terminal peptidase (N-proteinase) by analysis of pNa1(I) and pNa2(I) in fibroblastsDetermine level of N-proteinase activity

Diagnostic Criteria for Dermatosparaxis Type EDS

Patient 1Patient 2Normal

Dermatosparaxis

Classic Type (types I and II)AD - Type V and type ? collagen alterationsVascular Type (type IV) AD - Type III collagen alterations Dermatosparaxis Type (type VII C) AR - Amino proteinase deficiency 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 typeMedical 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 bodyMany genetically distinct types of collagen all have triple helix structure polypeptide chains with large (Gly -X-Y)n domain post translational modifications and extracellular processing critical Type I collagen: Heterotrimer abundant in skin, bones and ligaments. mutations in associated genes cause autosomal dominant OI point mutations in glycine can causing structural collagen abnormality can be more severe than haploinsufficincy (protien suicide) multiple severely affected children with normal parent can arise due to germline mosaicismType III collagen: Homotrimer, mutations in gene encoding tyope III collagen associated with Vascular EDS (type IV EDS) characterized by vascular and tissue fragilityMany types of EDS but classic EDS usually has skin and joint manifestations Collagen Disorders - Summary