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The Genetics of VHL Xia Wang, MD, PhD
VHL Alliance, 2017 Tampa, FL
The Genetics of VHL
Xia Wang MD PhD
Oct, 2017
• How human cells and tissue grow and die?
• Normal tissue growth is regulated by many genetic
factors
• Safe traffic is maintained by traffic lights and all
responsible drivers.
Proper tissue growth - controlled traffic
The Genetics of VHL Xia Wang, MD, PhD
VHL Alliance, 2017 Tampa, FL
Broken traffic light - predisposes to accident Additional traffic light malfunction -
Reckless driving – accident! When genetic factors are damaged
with time --
Tumor
CancerA
B
C
Mutated
A
B
C
Damaged
A
B
C
Defected
A
B
C
The Genetics of VHL Xia Wang, MD, PhD
VHL Alliance, 2017 Tampa, FL
van Asselt et al. Cilia 2013, 2:3 http://www.ciliajournal.com/content/2/1/3
• VHL is a tumor
suppressor
• VHL mutations
predispose to
tumors
• VHL affects 1 in
36,000 births
To understand genes…
• Genes are DNA molecules – genomic blueprints
• DNA RNA
• RNA Protein
• Proteins are the building blocks of our body
Each cell has the same set of genomic blueprints of
~20,000 genes that we are born with
Socratic.org Greatbigcanvas.com
DNA RNA Protein
VHL protein
The Genetics of VHL Xia Wang, MD, PhD
VHL Alliance, 2017 Tampa, FL
DNA genetic code, amino acid, and protein
www.bbc.co.uk Genome
Function of VHL protein:
control HIF1alpha
Normal oxygen levelLow oxygen level
Von Hippel–Lindau disease (VHL), modified from Wikipedia
VHL Tumors
Average age of onset Frequency in Patients, %
Hem
ang
iobla
sto
ma
Retina (Eye) 25 (0-68) 25-60
Cerebellum (Brain) 33 (9-78) 44-72
Brain stem 32 (12-46) 10-25
Spinal cord 33 (11-66) 13-50
Endolymphatic sac tumor 22 (12-50) 10-25
Renal cell carcinoma or cysts 39 (13-70) 25-75
Pheochromocytoma 27 (5-58) 10-25
Pancreatic Neuroendocrine Tumor (PNET)
36 (5-70) 11-17
Screening can find the tumor before it causes symptoms
Find the tumor early
Early intervention
Better outcomes
The Genetics of VHL Xia Wang, MD, PhD
VHL Alliance, 2017 Tampa, FL
Scre
en
ing
Re
co
mm
en
da
tion
s
VH
L A
llian
ce
Age Screening and Frequency
From Birth
Inform pediatrician of family history of VHL.
Pediatrician to look for signs of neurological disturbance, nystagmus, strabismus,
white pupil, and other signs which might indicate a referral to a retinal specialist.
Routine newborn hearing screening.
0-4
Annually
Pediatrician to look for signs of neurological disturbance, nystagmus, strabismus,
white pupil, and abnormalities in blood pressure, vision, or hearing
Eye/retinal examination with indirect ophthalmoscope by an ophthalmologist skilled
in diagnosis and management of retinal disease, especially for children known to
carry the VHL mutation.
5-15
Annually
Physical examination and neurological assessment by pediatrician informed about
VHL, with particular attention to blood pressure taken (taken both while lying and
standing), hearing Issues, neurological disturbance, nystagmus, strabismus, white
pupil, and other signs which might indicate a referral to a retinal specialist.
Eye/retinal examination with indirect ophthalmoscope by ophthalmologist informed
about VHL, using a dilated exam.
Test for fractionated metanephrines, especially normetanephrine in a “plasma free
metanephrine” blood test or in a 24-hour urine test.
Abdominal ultrasonography annually from 8 years or earlier if indicated.
Abdominal MRI or MIBG scan only if biochemical abnormalities found.
Every 2-3 years
Complete audiology assessment by an audiologist. Annually if any hearing loss,
tinnitus, or vertigo is found
In the case of repeated ear infections, MRI with contrast of the internal auditory canal
using thin slices, to check for a possible ELST.
Scre
en
ing
Re
co
mm
en
da
tion
s
VH
L A
llian
ce
Age Screening and Frequency
From Birth
Inform pediatrician of family history of VHL.
Pediatrician to look for signs of neurological disturbance, nystagmus, strabismus,
white pupil, and other signs which might indicate a referral to a retinal specialist.
Routine newborn hearing screening.
0-4
Annually
Pediatrician to look for signs of neurological disturbance, nystagmus, strabismus,
white pupil, and abnormalities in blood pressure, vision, or hearing
Eye/retinal examination with indirect ophthalmoscope by an ophthalmologist skilled
in diagnosis and management of retinal disease, especially for children known to
carry the VHL mutation.
5-15
Annually
Physical examination and neurological assessment by pediatrician informed about
VHL, with particular attention to blood pressure taken (taken both while lying and
standing), hearing Issues, neurological disturbance, nystagmus, strabismus, white
pupil, and other signs which might indicate a referral to a retinal specialist.
Eye/retinal examination with indirect ophthalmoscope by ophthalmologist informed
about VHL, using a dilated exam.
Test for fractionated metanephrines, especially normetanephrine in a “plasma free
metanephrine” blood test or in a 24-hour urine test.
Abdominal ultrasonography annually from 8 years or earlier if indicated.
Abdominal MRI or MIBG scan only if biochemical abnormalities found.
Every 2-3 years
Complete audiology assessment by an audiologist. Annually if any hearing loss,
tinnitus, or vertigo is found
In the case of repeated ear infections, MRI with contrast of the internal auditory canal
using thin slices, to check for a possible ELST.
Physical examination with vigilance about VHL tumors
Abdominal ultrasound to be started at age 8
16+
Annually
Eye/retinal examination with indirect ophthalmoscope by
ophthalmologist informed about VHL, using a dilated exam.
Quality ultrasound, and at least every other year MRI scan of
abdomen with and without contrast to assess kidneys, pancreas,
and adrenals, but not during pregnancy.
Physical examination by physician informed about VHL.
Test for fractionated metanephrines, especially normetanephrine
in “plasma free metanephrines” blood test or 24-hour urine test. Abdominal MRI or MIBG scan if biochemical abnormalities found.
Every 2-3 years
MRI scans should be ordered as no less than a 1.5T MRI with and
without contrast of brain, cervical, thoracic, and lumbar spine, with
thin cuts through the posterior fossa, and attention to inner
ear/petrous temporal bone to rule out both ELST and
hemangioblastomas of the neuraxis.
Audiology assessment by an audiologist.
Preg-nancy
Regular retinal checkup to anticipate potentially more rapid
progression of lesions.
Test for pheo early, mid, and again late pregnancy to ensure no
active pheo during pregnancy or especially labor and delivery.
During the 4th month of pregnancy, MRI—without contrast—to
check on any known lesions of the brain and spine. If known retinal,
brain, or spinal lesions, consider C-section.
Scre
en
ing
an
d e
arly
de
tectio
n
of tu
mors
Who to be screened?
• If a parent has VHL, how do we know which child will
be affected with VHL tumors?
The Genetics of VHL Xia Wang, MD, PhD
VHL Alliance, 2017 Tampa, FL
• 20% of the individuals affected with VHL did not inherit
it from the parents.
• The first case of VHL in the family is due to a new, i.e.
de novo mutation.
Who to be screened? VHL Inheritance Pattern – Autosomal Dominant
Von Hippel–Lindau disease (VHL), From Wikipedia
VHL Clinical Diagnostic Criteria
• Simplex case with two or more of the following:
–Two or more hemangioblastomas
–A single hemangioblastoma with multiple kidney or
pancreatic cysts
–Renal cell carcinoma
–Pheochromocytomas
–Endolymphatic sac tumors, papillary cystadenomas
of the epididymis or broad ligament, or
neuroendocrine tumors of the pancreas
VHL Clinical Diagnostic Criteria
• Simplex case with two or more of the following:
–Two or more hemangioblastomas
–A single hemangioblastoma with multiple kidney or
pancreatic cysts
–Renal cell carcinoma
–Pheochromocytomas
–Endolymphatic sac tumors, papillary cystadenomas
of the epididymis or broad ligament, or
neuroendocrine tumors of the pancreas
The Genetics of VHL Xia Wang, MD, PhD
VHL Alliance, 2017 Tampa, FL
VHL diagnosis based on VHL gene testing
VHL gene structure
Human genome -- 3,000,000,000 base pairs (bps)
VHL gene – 12,633 bps, 639 bps in exons, 213 amino
acids
VHL gene on the short arm of chromosome 3 Types of VHL gene changes
• Deletion of a segment of the chromosome
The Genetics of VHL Xia Wang, MD, PhD
VHL Alliance, 2017 Tampa, FL
• Base pair (DNA code) changes
• Deletion of a segment of the gene
Types of VHL gene changes
• The technology for genetic testing has changed
dramatically in the past 10 years.
Sanger sequencing reading the raw sequences of
VHL gene takes 3-4 days
Large deletions detection by Southern Blot takes
4-5 days
The Genetics of VHL Xia Wang, MD, PhD
VHL Alliance, 2017 Tampa, FL
Next-generation sequencing can detect single code
change, small/large deletions or duplications. It
takes 3 days to get the raw sequences of the entire
human genome!
Types of VHL variants
Classifications and Terms Meaning
Mutation
Pathological variant
Disease causing variant
Dysfunction
Loss of function
Benign variant
PolymorphismNormal function
Variant of uncertain significance
(VUS)Function unknown
VHL gene Variants on VHL gene
The Genetics of VHL Xia Wang, MD, PhD
VHL Alliance, 2017 Tampa, FL
Variants on VHL gene Interpretation of a variant is not always
straight forward J Genet Counsel (2015) 24:882–889, PMID 26323595
c.463+4C>T
VHL GRCh38
Chr3:10,146,640
Next gen
sequencing
???
significance
Affect
intron
splicing
In silico
prediction
model
RNA analysis
In test tubes
Confirmed
exon 2
skipping in
some RNA
products
One patient with
Hemangioblastoma
A 2nd degree
relative with Pheo
Current variant classification: c.463+4C>T
VUS (variant of uncertain significance)
• Blood or Skin cells To find the germline mutation
(mutation present at the beginning of life – a fertilized
egg)
• Tumor tissue May reveal the germline and/or the
somatic mutation (mutation occurred in later stage of
life)
Samples for Genetic Testing
The Genetics of VHL Xia Wang, MD, PhD
VHL Alliance, 2017 Tampa, FL
Genetic mutations lead to kidney cancer
(Renal cell carcinoma)
By Dr. Wong Ming Ho, Edmond, Urology, HK
An ethnic group in the mid-Volga region of Russia
Chuvash population
Chuvash population,
• A unique condition is known in Chuvash population
• It is caused by VHL gene mutations
• But it does not cause VHL tumors
Familial Erythrocytosis Type 2 (ECYT2) Familial Erythrocytosis Type 2 (ECYT2)
• Increased red blood cell production
• Increased levels of erythropoietin
• Normal oxygen affinity
• Thrombosis and/or hemorrhage
• Two copies of mutations on VHL, inherited in an
autosomal recessive fashion.
• No individuals with one copy of the mutation have
developed VHL-related tumors [Gordeuk et al 2004].
The Genetics of VHL Xia Wang, MD, PhD
VHL Alliance, 2017 Tampa, FL
• R200W (Chuvash)
• H191D
• Russell et al. (2011)
• R200W -- Not associated with tumors seen in VHL.
Familial Erythrocytosis Type 2 (ECYT2)