Transcript Slide 1

Stickler Syndrome Study at the
National Institutes of Health
Nazli McDonnell M.D., Ph.D.
Laboratory of Clinical Investigation
National Institute on Aging
National Institutes of Health
Baltimore, Maryland
Introduction
• Stickler Syndrome is an autosomal
dominant hereditary disorder that effects
the connective tissue
• 1 in 10,000 individuals in North America
(Hermann et al, 1975) are thought to have
Stickler Syndrome
• Stickler Syndrome may affect your eyes,
your hearing, your bones and joints
Intro cont.
• Known mutations that lead to Sticklers are
found on the Col2A1, Col11A1 and the
Col11A2 genes
• They are genes code for the collagens that
are found in your eyes, joints and bones
• Mutations on these genes account for
around 50% of the cases of Stickler
Syndrome. Other causes for Sticklers
syndrome are unknown at this time.
Manifestations
• Stickler Syndrome effects many parts of
the body.
• In the eyes, Stickler syndrome may cause
near-sightedness (myopia), vitreous
degeneration, retinal detachments and
retinal tearing, premature cataracts and
glaucoma
• People with Stickler Syndrome may be
born with cleft palates and/or bifid uvulas
Manifestations cont.
• The most noticeable manifestations of
Stickler are the facial manifestations.
People with Sticklers Syndrome often
have a flattened facial profile, flattened
and broadened nasal bridge and small
chins.
• Patients also have problems with high
frequency hearing loss and hypermobile
tympanic membranes
Diagnosis is often missed
• Stickler syndrome is among the most common
autosomal dominant connective tissue disorders
but is often unrecognized and therefore not
diagnosed by clinicians.
• Ten percent of patients with isolated cleft palate
and 12% with the Pierre-Robin sequence were
found to have undiagnosed Stickler syndrome in
one series [Kronwith et al., 1990; Sheffield et al.,
1987] The actual incidence is higher.
Background
• Collagens are the most common proteins
in the extracellular matrix
• Collagen Type II is abundant in the
vitreous of the eye, the spinal column,
cartridge, and inner ear
• Type II is also present in many tissues
during embryological development
• Collagen XI is found in association with
Collagen II.
The Collagens
• Collagens consists of three polypeptide chains which are
folded into a rod-like triple helical molecule
• Each of the constituent chains of the triple helix are
called alpha chains and are coiled in a left handed helix
with three amino acids per turn.
• The constituent amino acids are regularly arranged in
the order Gly-X-Y such that glycine, which is the smallest
of all amino acids, occupies the restricted space in which
the three helical chains come together.
• This arrangement is crucial for the stability of the
macromolecule.
Collagen structure
G
G
G
G
G
G
G
G
Top end view shows:
Secondary structure is a
collagen helix with pitch
of 3.0 residues per turn
GG
GG
GG
Side view shows:
Primary structure = (X-Y-gly)n
X,Y are often lysine or proline
G
G
G
GG
G
G
GG
Collagen Fibrils
Collagens and Stickler Syndrome
• Type 2 collagen is a homotrimer of three
COL2A1 gene products, whereas type 11
collagen is a heterotrimer containing one each of
the COL2A1, COL11A1, and COL11A2 gene
products.
• Both type 2 and 11 collagens are members of
the fibrillar collagens, which are primarily found
in cartilage, vitreous, and nucleus pulposus (soft,
gelatinous central portion of an intervertebral
disk).
The diagnostic criteria
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Orofacial Abnormalities (2 points maximum)
(2 points)
Cleft palate (open cleft, submucous cleft, or bifid uvula) (Major)
(1 point) Characteristic facies (malar hypoplasia, broad nasal bridge,
Micro/retrognathia)
Ocular Abnormalities (2 points maximum)
(2 points)
Characteristic vitreous changes or retinal abnormalities (lattice degeneration, retinal holes, or retinal
tear, retinal detachment) (Major)
Auditory Abnormalities (2 points maximum)
(2 points)
High frequency sensorineural hearing loss (Major)
Age < 20:
threshold  20 dB at 4-8 kHz
Age 20-40:
threshold  30 dB at 4-8 kHz
Age > 40:threshold  40 dB at 4-8 kHz
(1 point) Hypermobile tympanic membranes
Skeletal Abnormalities (2 points maximum)
(1 point) History of femoral head failure
(slipped epiphysis or Legg-Perthes like disease)
(1 point) Radiographically demonstrated osteoarthritis before age 40
(1 point) scoliosis, spondylolisthesis, or Scheuermann-like kyphotic deformity
Family History / Molecular Data
(1 point) Independently affected 1st degree relative in a pattern consistent with autosomal dominant inheritance or presence of
COL2A1, COL11A1, or
COL11A2 mutation associated with Stickler syndrome
Diagnosis requires: 5 or more points total up to 9 points
At least one 2-point major manifestation
Absence of features suggestive of a skeletal dysplasia (e.g. stature <5% centile)
Genotype/Phenotype Correlations
• Study involved 48 families suspected of
having Stickler Syndrome
• Consent was received from each
individual to allow the NIA to collect data
and genetic material from each patient
• Patients underwent a detailed clinical
genetics examination, dilated
ophthalmology exam, audiology and
otolaryngology evaluations
Materials and methods contd.
• In most cases, radiographs of the spine and hip
were available
• The enrollment and tests took place before the
development of the diagnostic criteria for Stickler
syndrome.
• Forty eight probands were selected from each
family for molecular genetic analysis
• Col2A1 and Col11A1 genes were amplified by
polymerase chain reaction (PCR) and were
screened for mutations
Results
• 23 mutations in Col2A1 and 4 mutations in
Col11A1 was found in our cohort of 48
probands.
• All persons included in the study had
orofacial features, while clefting of
palate/uvula showed intra and inter family
variability
• All persons also had ocular involvement in
the form of vitreous or retinal changes.
Types of Mutations
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STOP = 16
Splice Site = 8
Insertion = 1
Arg/Cys = 1
Other missense =1
Results contd.
• Hearing loss, premature osteoarthritis, and
skeletal involvement was common.
• Femoral head failure occurred in 3
families.
• Hip or knee pain needs to be taken very
seriously in children with Stickler
syndrome as it can be a manifestation of
femoral head failure.
Summary of Findings
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Facial features
Open Cleft
Submucus Cleft
Bifid Uvula
Vitreous Change
Retinal Change
Vitreous OR Retinal Change
High frequency sensory neural hearing loss
Hypermobile Tympanic Membranes
Femoral Head Failure
Premature Osteoarthritis
Skeletal Abnormalities
29/29
11/29
7/29
5/29
24/29
24/29
29/29
17/29
2/29
3/29
16/29
14/29
Discussion
• The mutation detection rate in this Stickler
Syndrome cohort was 56%
• All subjects with a mutation in Col2A1 or
Col11A1 met the recently published
Stickler Diagnostic Criteria
• The majority of the mutations detected
resulted in a splice site aberration (often
implicated in exon skipping) or a
premature termination codon.
Discussion Contd.
• The phenotype analysis revealed that
ocular involvement and craniofacial
dysmorphisms are core features of Stickler
syndrome.
• Comparison with a large pedigree without
a Col2A1/Col11A1 mutation in the proband
reveals that this family has a phenotype
indistinguishable from the subjects with
such mutations
Mutations in Stickler Syndrome
• All of the mutations found resulted in
haploinsufficiency (inadequate amount of
collagen, as opposed to abnormal collagen)
• Dominant negative mutations in Collagen II
result in the dwarfisms
• This opens the door to the possibility that
symptoms of Stickler syndrome may be treated
by a mechanism that increases collagen
production from the “good copy” of the gene.
Future directions
• The next project will be to study the genes
of the individuals who lack known
mutations.
• We are studying a candidate gene,
CSPG2, which has been implicated in a
family with Wagner syndrome which is a
disease that affects the eye very similarly
to Stickler syndrome.
Future Directions
• Tissues from patients with the known
mutations will be analyzed to learn more
about how the mutations effect the
workings of the collagen
• Phenotype analysis will continue to better
understand the syndrome
Enrollment of new patients
• We will start to enroll new patients soon
• Eye exam is now available for the study in
its new location in Baltimore, however we
are working on the details of transportation
of participants
• Hope to enroll 20 patients in 2008
Acknowledgements
Ben Griswold, Minna Männikko, Jeremy Wells, Marja Majava-Elo,
Joseph Tran, Katherine Mandel , Peter S. Rose, Howard P. Levy,Joie
Davis, Yvonne Szymko, Benjamin Rubin, Ekaterini Tsilou, Muriel
Kaiser, Andrew J. Griffith, Ruth Altshuler Liberfarb, Leena Ala-Kokko,
Clair A. Francomano
1 Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health
2 Department of Medical Biochemistry and Molecular Biology, University of Oulu
3 Department of Genetics, Massachusetts General Hospital
4 Clinical Research Branch, National Institute on Aging, National Institutes of Health
5 Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota
6 Department of Internal Medicine, Johns Hopkins University School of Medicine
7 National Human Genome Research Institute, National Institutes of Health
8 National Eye Institute, National Institutes of Health
9 National Institute on Deafness and Other Communication Disorders, National Institutes of Health
10Laboratory of Genetics, National Institute on Aging, National Institutes of Health
11Ursinus College, Collegeville, Pennsylvania