MicroRNA-regulated network promotes pulmonary hypertension
MicroRNA-regulated network promotes pulmonary hypertension
Pulmonary hypertension is a complex disease that affects multiple vascular cell types, and mircoRNAs (miRNAs) have been implicated in the pathogenesis of this condition. In this episode, Stephen Chan discusses how his group used network theory to identify miRNA-130/301 as a regulator of a system of miRNAs that promote the development of pulmonary hypertension. Furthermore, inhibition of miR130/301 prevented the development on pulmonary hypertension in a hypoxic murine model. The results of this study support the use of network analysis for identifying complex miRNA-regulated pathways involved in disease manifestations.
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7.436 -> Stephen Chan: Hello, my name is Stephen Chan.
I'm an assistant professor of medicine at Harvard
12.72 -> Medical School at the Brigham and Women's Hospital
in Boston, Massachusetts. Today, I'm happy to be
18.48 -> discussing our laboratory's recent findings of
microRNAs that can act as systems-level regulators
24.88 -> in the pathogenesis of pulmonary hypertension,
or PH. As many of you know, PH refers to a group
31.76 -> of pulmonary vascular diseases that can cause
increased pulmonary pressure, right heart failure,
37.52 -> and often death, but the molecular origins of this
disease remain enigmatic. Over the past decade,
44.48 -> multitudes of newly identified molecules and
pathways have been implicated in PH, but it
50.88 -> has been challenging to understand the integrated
effects of all of these factors on overall disease
56.96 -> manifestation. microRNAs have been proposed
as important factors in this pathogenesis.
64.4 -> These are small, noncoding RNA molecules that
negatively regulate gene expression by binding
70.48 -> specific sequences in messenger RNA, in order
to cause translational repression and/or mRNA
76.64 -> degradation. Recently, we proposed that
microRNAs may serve as good candidates
82.56 -> that exert hierarchical regulation
of these complex molecular networks,
87.6 -> given their inherent pleiotrophy of repressing
several messenger transcripts simultaneously.
94.08 -> However, there are challenges of
studying such complex microRNA biology
98.64 -> using traditional scientific approaches, and
so we have attempted to address these obstacles
104 -> by the application of computational network theory
to hone our hypotheses. However, to date, relevant
111.04 -> high-throughput data in PH has been limited, and
analysis of systems-level regulation of microRNA
117.6 -> networks in general has consisted mostly of
computational theories without experimental data.
123.52 -> SC: So the central objective of this
study was to design a strategy combining
129.2 -> computational analysis of PH disease gene network
architecture with experimental validation that
136.32 -> accurately identifies microRNAs exerting
systems-level control of pulmonary hypertension.
142.96 -> To do so, we leveraged a simple concept:
that often microRNAs tend to regulate
148.16 -> multiple targets in the same functional pathway or
network. We first wanted to determine whether such
154 -> a network relevant to pulmonary hypertension could
be constructed from available molecular maps.
159.84 -> To do so, we curated 115 seed genes known to be
important in PH from the scientific literature.
167.2 -> We then mapped the functional interactions among
these genes using a consolidated set of databases
173.04 -> that represent all functional interactions among
the human transcriptome and proteome. We then
179.28 -> expanded the network to include genes that were
not mentioned in the PH-relevant literature but
184.64 -> were known to interact closely with a number of
our curated PH genes by our network analysis.
191.28 -> The end product was a single encapsulated
largest connected component carrying
195.92 -> 249 genes and over 2,000 interconnections.
SC: We then use this PH network as a platform,
203.36 -> coupled with a well-validated microRNA target
prediction algorithm, called target scan, in order
209.44 -> to identify those microRNAs that have the broadest
influence throughout the entire PH network.
215.84 -> To do so, we ranked microRNAs based not only
on the number of predicted targets they had
221.04 -> within the network but also how well distributed
those targets were throughout the network itself.
227.28 -> Based on this metric, we predicted
the microRNA-130 and -301 family
232.4 -> to be the most influential set of microRNAs in the
context of PH in this regard. This is a family of
239.84 -> 4 microRNAs that share the same seed sequence and
thus presumably regulate the same broad cohort
245.92 -> of PH-relevant target genes. We then performed
a similar set of analyses on the targets of the
252.56 -> miR-130 and -301 family as well as on their
closest interactors within the PH network,
258.48 -> in order to determine which of the microRNA family
targets and downstream pathways were the most
264.8 -> influential in disease. In this way, we uncovered
an intricate network of subordinate microRNA
271.44 -> activity spearheaded by the miR-130 target
PPAR-gamma, which can regulate miR-424 and -503
279.12 -> in pulmonary arterial endothelial cells as well as
miR-204 in pulmonary arterial smooth muscle cells.
286.08 -> SC: These findings suggested to us that the
miR-130/301 family serves as a regulator of
292.88 -> both of these pathways orchestrating a global
proliferative response throughout the vasculature,
298.48 -> ultimately culminating in pulmonary hypertension.
Importantly, this process of model building was
304.8 -> implemented entirely in silico, and while some
of these individual regulatory relationships
310.96 -> had been previously validated, the notion that
they are united by a single global regulatory
316.96 -> factor is a novel one and would have been
very difficult to uncover without the aid
321.52 -> of computational analyses such as these.
SC: We then wanted to determine and validate
327.36 -> this model experimentally. First, in cultured
pulmonary endothelial and smooth muscle cells,
333.68 -> we used a comprehensive set of gain of
function and loss, loss-of-function approaches
338.32 -> to manipulate miR-130 and -301, as well as
their downstream effectors, in order to prove
344.08 -> their pro-proliferative actions via regulation of
miR-424, -503, and miR-204. Second, we examined a
352.24 -> broad spectrum of disease models of PH spanning
seven different models in rodents and sheep, as
358.48 -> well as three different subtypes of human disease.
In all cases, we found a coordinated upregulation
364.72 -> of all miR-130/301 family members, particularly in
remodeled pulmonary vessels. Third, we identified
372.56 -> multiple triggers of PH as key regulators
of this microRNA family including hypoxia
378.72 -> inflammatory cytokines and a subset of factors
known to be genetically associated with human PH.
385.28 -> Finally, by pharmacologic manipulation of this
microRNA family in the pulmonary vasculature of
391.68 -> mice, we found miR-130 and -301 to be both
necessary and sufficient for hemodynamic
398.48 -> and histologic manifestations of PH in vivo.
SC: In conclusion, we believe that this is the
404.88 -> first description of a single microRNA family
regulating a hierarchy of subordinate microRNAs
411.44 -> with systems-level yet cell type–specific
effects in PH. We believe that deciphering
417.2 -> such systems-level relationships should guide
the development of more effective and perhaps
423.04 -> more potent clinical management strategies in
pulmonary hypertension. Perhaps more importantly,
428.8 -> our findings provide critical validation for
the evolving application of network theory
434.24 -> to the discovery of microRNA-based origins of
pulmonary hypertension, and we hope this work can
440.4 -> serve as a basis for the search in separate human
diseases for other microRNA master regulators
447.28 -> that are otherwise hidden in the architecture
of existing network databases. Thank you very
452.96 -> much for your interest, and on behalf of all of
the authors I hope you enjoy reading our work.
Source: https://www.youtube.com/watch?v=EFNIfZtrN-w