[Gly-X-Y]n ‘R’ US

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

2. Collagen Disorders • 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)

3. 32 Aortic dissection 68 60 55 53 30s HTN Splenic Artery rupture, Vertebral artery rupture 57, Aortic dissection 60, 1 4 5 36 33 31 R internal carotid dissection, cerebral infarct, R vertebral artery aneurysm, s/p repair Abdominal aorta aneurysm/chronic dissection, Aneurysm R common iliac 5 Arterial rupture

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

5. 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

6. Fibrillar collagens have awesome tensile strength Reticular collagens provide a meshwork of support

7. 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)

8. Skin contains Type I, III, V collagens and elastic fibers Connective tissue supporting hollow organs including colon contains Type III collagen Connective tissue surrounding blood vessels includes type III collagen and elastic fibers

9. [Gly-X-Y]n X: proline, lysine Y: hydroxyproline, hydroxylysine. • 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.

11. disulfide bonds

15. 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

16. By EM (50,000 X), collagen appears as regular striated bundles in longitudinal section and circles on cross section Type I collagen fibers

17. 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 EDS II. Cartilage, vitreous humor Mutations cause abnormalities of skeleton and eye, Stickler syndrome III. With type I in skin, also in muscles, blood vessels Mutations cause Vascular EDS V. Fetal tissues, placenta, interstitial tissues, skin Important for extracellular matrix assembly, mutations cause classic C Classic EDS

18. 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

19. Type I collagen fibers arranged to provide structural integrity Type I collagen fibers

20. 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

21. 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 OI Type I (with or without DI)

22. Osteogenesis Imperfecta gray/blue sclera

23. Opalescent dentin/ Dentinogenesis imperfecta

24. 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 IV (with or without opalescent dentin)

26. 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 III

28. 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 OI Type II

30. 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

32. 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 OI - Autosomal Dominant = Normal Gene = altered Gene

33. ‘Protein suicide’ Normal typical Type I typical type II okay degraded

34. 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

35. 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.

36. 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 How is OI treated?

37. Ehlers-Danlos Syndrome(s) • 1 in 5,000 - 10,000 people • both males and females • all racial and ethnic backgrounds

38. 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

39. Six types of Ehlers-Danlos syndrome • 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

40. Diagnostic Criteria for Classic EDS (I and II) • 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

42. Diagnostic Criteria for Hypermobility Type EDS • 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 (?)

43. Hypermobility EDS

44. Diagnostic Criteria for Vascular 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

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

46. 31 90s Ruptured renal artery “Marfan disease” 35 32 0 43 17 Vertebral aneurysm Spontaneous pneumothorax Sigmoidal perforation Ruptured thoracic artery Unaffected Probable EDS IV EDS IV- Vascular type Confirmed by DNA testing 3 16 15 14 Bilateral inguinal hernias Easy bruising Soft, translucent skin Increased bleeding

47. Type III Collagen • Consists of 3 a1(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)

48. Vascular EDS Manifestations (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

49. Vascular EDS Manifestations (Pepin et al, NEJM, 2000) Type of first complication in index patients

50. Vascular EDS Manifestations (Pepin et al, NEJM, 2000) Causes of death (n =131)