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Dr. ed cooper kcnq2 Cure summit parent track learn more at kcnq2cure.org
1. An introduction to KCNQ2 mechanisms
and paths towards mechanism-based
therapy
Kristen Park, MD
Colorado Children’s
Univ. of Colorado Univ.
John Millichap, MD
Lurie Children’s
Northwestern Univ.
RIKEE collaborators
Ed Cooper, MD, PhD
Associate Professor
Neurology, Neuroscience,
Molecular & Human Genetics
BCM, Houston TX
NINDS
CURE,
Jack Pribaz
GSK
2. Disclosure
Grant from GSK for studies of Potiga combined
treatment with sodium channel blockers
Consultant for SciFluor, Inc.
3. To: Cooper, Edward C
Subject: KCNQ2
Dr. Cooper,
My wife and I saw the article regarding your research on KCNQ and had to reach out to
you. Our son was recently diagnosed with a mutation in the KCNQ2 gene. That diagnosis
has given us new hope and focus. For xxxx we had no diagnosis after xxxx of tests. He
experienced seizures his first day of life and is very developmentally delayed. The seizures
are now under control for the most part but his development and muscle tone are our
biggest concerns.
Our doctor says he is the only KCNQ2 patient they have. From all that we have heard, this
is a very rare condition. We are eager to hear what you think and to get involved with your
research anyway we can.
Please let me know how we can help one another, or anything else that we can do to get
closer to a cure. Thank you for your time and we look forward to hearing your thoughts.
Xxxxxxxxxx xxxxxxxxx
4. Genetics reports are more confusing to
patients and to us than we acknowledge
A change from C to T at
one position in the gene
A change from A to V in
the corresponding
position of the KCNQ2
protein
“KCNQ2 c.881C>T; p.A294V”
What does this mean? What are the limits of
current understanding? Are there a set of
explanations that can we can share generally?
5. Key background
1. The brain runs on
electricity, but...
salt molecules (ions) are the signal carriers
(not electrons)
2. Ion channels - the brain’s signaling “switches”,
are built according to a common plan, but come
in a many different varieties (~400 genes)
3. K-CN-Q-2
2nd member of the “Q subfamily of K channels”
Subfamily of potassium channels “Q” (KCNA, B, C....)
Short for “channel”
Chemical symbol for potassium
6. Understanding “genes”
We have many
genes
Each cell uses a
subset of those
genes tailored to
its own function
Each gene’s “recipe”
is written in a long
string (of DNA)
Genome is like a
vast recipe collection
Different recipes for
breakfast, dinner,
seasons, special
occasion
That’s where the
numbers come from
7. The cell converts (reads) the DNA string to a
protein string
1 2 3 4 5 6 7 8 9 DNA position
. . . ~2600 in KCNQ2
1 2 3 “codon” position
1 2 3 Protein position
Amino acids
. . . ~872 in KCNQ2
Start
8. Proteins are the molecular machines for
most of the body’s functions
How can long strings be made into machines?
• Amino acids are different from each other:
– “Oily” vs. “watery”
– Positive vs. negative
– Big vs. small
10. Amino acids have different sizes....
(and packing matters)
oily
-
4
2
1
The 3-dimensional shape (and
moving parts) of each protein
are built from the folded amino
acid chain
3
5
6 7
8
9
10
11
12
11. “anatomy of an ion channel” – e.g., KCNQ2!
......872 x 4 =
3488 beads
per KCNQ2
channel!!!
watery amino acids face
outside of cell
oily amino acids face
the cell membrane (it’s oily)
watery amino acids face
watery inside of cell
1. It’s buried in the oily cell membrane, so
oily amino acids make
up the interior of the protein
(mostly)
12. “anatomy of an ion channel”
......872
2. add a hole in the middle, filled with water (the ion pore)
watery amino acids
oily amino acids
watery amino acids
oily amino acids
buried within the
protein
pore facing amino acids are watery
13. “anatomy of an ion channel”
......872
3. add a “gate” (a “moving part”)
outside
inside
+
closed
+
open
sensor
gate
_
_
14. Why do some KCNQ2 variants cause mild,
but others cause severe disease?
Severe variants are “substitutions” that replace one
amino acid with another of different chemical properties.
The change results in a “packing problem” or a “folding
problem”
Due to location within the channel, some mutation of
this type can allow one subunit to poison the function of
up to 3 normal subunits, resulting in up to 16-fold
(92.5%), but not complete, loss of channel activity.
15. The first few encephalopathy mutations suggested
a mechanism: 3 functional “Achilles’ heels”
Weckhuysen... Berkovic , Scheffer, de Jonghe, 2012; Millichap and Cooper, 2012
19. Variant type 3: can’t reach cell surface
Millichap and Cooper 2012
Inside
surface
membrane
X
calmodulin
20. One copy of a missense mutation can lead to
mild transient neonatal epilepsy (BFNS), and
reduces channel activity – but only slightly
0.75
current, fraction of
control
Schroeder (1998)
Nature 396, 687
0 0.5 1
wt Q2 + wt Q3
wt Q3 + ½Q2
Q3 +
½Q2 + ½Q2 mut
Chrom 20 Chrom 8
Q3
Q2
21. How one copy of some KCNQ2 variants
cause more severe loss of activity
Channels formed by 4
KCNQ2 subunits,
50% mutant
Channels formed by 2
KCNQ2 subunits, 50% mutant
and 2 KCNQ3 subunits
1 : 4 : 6 : 4 :1 1 : 2 : 1
22. Basic studies provide a rationale for KCNQ
opener drug treatment (1)
1. Neurons use very little of the KCNQ channel’s maximal
capacity
1% maximal KCNQ
1 msec activity
Battefeld et al., 2014
23. Rationale for drug treatment (2)
2. when channel gates are maximally opened by strong
membrane depolarization (without drug treatment), they
are still closed most of the time
single channel recording Li and Shapiro Journal of Neuroscience
2004
24. Rationale for drug treatment (summary)
1. Without drugs, the maximal channel opening possible
experimentally is only 10% (KCNQ2) to 30% (KCNQ2/3).
2. Neuron can only open channel 3-10% of that maximum,
because nerve signals are short in duration.
3. Therefore, channel is only “used” at .3 to 3% of maximal
capacity
4. With a powerful enough drug, should be able to increase
activity considerably
5. 8 fold difference between worst possible suppression
and a mild, transient syndrome: BFNS.
25. Challenges to implementing drug treatment
1. Currently available drug (Potiga) is relatively
low potency, low selectivity for KCNQ2/3, has
known side effects. Max clinical dose is about
1/10 what is used in the lab
2. Introducing new drugs is difficult and
expensive, especially for children.
3. Diagnosis is often delayed.
Solutions: our energy, skills, and dedication to the
task...
26. Intro to KCNQ2: conclusions
1. KCNQ2 is a needed molecule for preventing
seizures and promoting early brain
development; severity of related illnesses
appears to relate to degree of deficiency
2. KCNQ2 deficiency is never complete and drug
therapy is a strategy to augment activity of the
remaining normal channels
3. A large number of KCNQ opener drugs are
known but clinical development so far is limited
4. Many questions and challenges remain for
current research
27. Acknowledgements
BCM/TCH
Mingxuan Xu, Bao Tran, Li Li, Zhigang Ji
RIKEE Network
Lionel Carment, Universite de Montreal Marc Patterson, Mayo
Eric Marsh, Xilma Ortiz-Gonzalez, Emily Robbins Children’s Hospital of Philadelphia
Bruria Ben Ze’ev Tel Aviv Molly Tracy Hasbro Children’s, Brown Univ.
Tammy Tsuchida, Phil Pearl (now BCH), Children’s National (DC)
John Millichap, Lurie Children’s (Northwestern U.)
Kristen Park, Paul Levisohn, Colorado Children’s (Aurora, CO)
Brenda Porter, Packard Children’s (Stanford)
UPENN
Zongming Pan Steve Scherer Amy Brooks-Kayal
Tingching Kao Steve Cranstoun Yogi Raol
Other Collaborations
Van Bennett (Duke) Jurgen Schwarz (Hamburg) Hugh Bostock (UCL) Ryuji Kaji
(Tokushima) Yasushi Okamura, Atsuo Nishino (NIPS) Maarten Kole (Amsterdam,
NIN) David Brown (UCL), Mala Shah (UCL)
Funders: NINDS, Miles Family Fund, AES/EF, Jack Pribaz Foundation, CURE
