Genome-wide Epistasis for cardiovascular severity in Marfan Study

Marfan syndrome is an autosomal dominant connective tissue disorder with
pleiotropic manifestations in the ocular, skeletal and cardiovascular systems.
Morbidity and mortality are mostly determined by aortic root aneurysm leading
to dissection and rupture. Although mutations in FBN1, the gene coding for the
extracellular matrix protein fibrillin-1, are the well-established genetic
cause of this condition, there is a very poor correlation between the nature or
location of the causal FBN1 mutation and the phenotypical outcome. Indeed, wide
intra- and interfamilial phenotypical variability is observed. So, even with an
identical primary FBN1 mutation in all family members, the clinical spectrum
varies widely, from completely asymptomatic to sudden death due to aortic
dissection at a young age. The precise mechanisms underlying this variability
remain largely elusive. Consequently, a better understanding of the functional
effects of the primary FBN1 mutation is highly needed and the identification of
genetic variation that modifies these effects is becoming increasingly
important. In this project, different innovative strategies have been carefully
selected to discover mother nature*s own modifying capabilities with respect to
Marfan syndrome aortopathy. The identification of genetic modifiers will
advance the knowledge on the pathomechanisms of aortopathy beyond the current
understanding, it will allow to individualize current treatment protocols to
deliver true precision medicine and will offer promising new leads to novel
therapeutic strategies.
The impact of modifier discovery on therapy development has already been shown
in diseases such as Alzheimer*s disease and spinal muscular atrophy

Identification of possible genetic modifiers, that will advance the knowledge
on the pathomechanisms of aortopathy.
Hopefully this will offer promising new leads to novel therapeutic that will
allow to individualize current treatment protocols to deliver true precision
medicine.

Objectives:
- Assembly of clinical data for carriers of selected FBN1 variants
- Molecular characterization of the assembled cohort
- Assembly of genomic data of selected Marfan syndrome individuals and families
- Omics integration for modifier identification in the extreme ends of the
cohort with selected FBN1 mutations
- Functional validation of the identified modifiers
- Replication of the identified modifiers in a large Marfan syndrome cohort

The patient will be informed by their physician about the study. If the patient
would like to participate he/she will be invited for a consultation. At the
consultation the physician will inform the patient about the study before
participation. He will ask the patient to complete the informed consent .
The physician will complete the clinical form with the patient. If the patient
agrees, a blood sample will be taken.

From the blood samples the DNA will be extracted in the laboratory of the
Medical Genetic Department at the University Hospital of Antwerp. A gene panel
for thoracic aortic dilatation and/or disscetion (TAAD) will be sequenced and
modifier genes from preliminary data- will be cross-vaildated.
Whole Genome Sequencing (WGS) on blood-derived gDNA of the 25% most (P75-P100)
and 25% least (P0-P25) severely affected patients will be performed .

In the second phase of the study a selection of the patients that are on the 5%
"extreme" ends of the phenotypical spectrum will be made, based on their
medical cardiovascular history (z-Score, timing of surgery and expert
curation).Of these patients iPSC - VSMCs (induced pluripotent stem cell -
vascular smooth muscle cells) will be generated to integrate transcriptomic
data with the previously obtained genomic data.

Once candidate modifier genes (and hence candidate modifier variants) have been
identified, their modifying capacity will be functionally checked in relevant
cell- or animal models. Further evidence for a modifying role of the most
interesting candidate genes will be obtained by performing targeted
re-sequencing of these genes* coding and regulatory sequences in, again, the
25% most and least severely cardiovascular affected MFS cases of a large
replication cohort consisting of more than 3000 clinically and molecularly
(FBN1 mutation-positive) characterized index patients.

This study may be deemed to be group-related because it could not be conducted
without the participation of the identified patients. The risks associated with
participation, can be considered negligible and the burden can be considered
minimal because it is a non-intervention study. Only marfan patients with the
mentioned FBN1-mutations can be included because they are the population of
interest. The patient may benefit in the future directly themselves from the
study. Patients also will contribute in gaining more knowledge for health care
professionals about Marfan syndrome.
If any unexpected medical information will be discovered (e.g.other mutations
with a known health risk) the patient will be informed by a geneticist (who has
the experience to bring this information) about the findings if he/she has
agreed to this information on the PIFICF.