1 - 6 March
Biophysical Society 63rd Annual Meeting 2019
As always at Biophysics we have a lot of activities going on. Please see below.
Friday, 1st March
Ion Channel Satellite Meeting
Sophion will be co-hosting the recurring satellite meeting, Drug Discovery for Ion Channels. Read more about the meeting here.
Saturday, 2nd March
Monday, 4th March
01:45 PM – Poster presentation:
Title: IPSC-derived motor neurons on the automated patch clamp platforms Qube and QPatch
Poster presenter: Application scientist Kadla Rosholm
Location: Exhibit Hall A-E – Poster board No.: B332
Human induced pluripotent stem cells (hiPSCs) can be differentiated into multiple cell types, including neurons and cardiomyocytes. This gives rise to a novel way of establishing human disease models, which in turn can be used for drug development in vitro. Ion channels represent highly attractive therapeutic targets in the nervous and the cardiovascular system, rendering electrophysiological studies of hiPSCs important for their usage in drug discovery. However, such studies have traditionally been limited by the labor-intensive and low-throughput nature of patch-clamp electrophysiology. Here we use our automated patch clamp systems Qube 384 and QPatch 48 in order to increase throughput and reduce timelines.
Our observations include channel expression versus time in culture, the pharmacological dissection of endogenous ion channels (e.g. Nav and Kv), identification of ligand-gated receptors, and recordings of action potentials using the current clamp feature. Also, we show the electrophysiology of a spinal muscular atrophy (SMA) and an amyotrophic lateral sclerosis (ALS) model. The disease model for SMA was derived by mutations in the SMN1 gene and shows enhanced sodium channel activity but no shift in the normalized current-voltage relationship. ALS was here mimicked by a single point mutation in the superoxide dismutase 1 protein (SOD1), D90A, which had previously been identified in recessive, dominant and seemingly sporadic pedigrees. Cells carrying this point mutation displayed larger sodium currents, which eventually led to neurofilament aggregation, neurite degeneration and other phenotypes. We could confirm that the electrophysiological effect could be reversed by point mutation to D90D.
Our measurements validate the feasibility of measuring hiPSC ion channel currents using the APC platforms Qube and QPatch. Altogether, these results can facilitate evaluating the use of hiPSC for early drug development and in extension personal medicine.
Tuesday, 5th March
9:30-11:00 AM – Sophion will be hosting a mini ion channel symposium in Room A at Baltimore conference center titled:
Electrophysiological characterization using automated patch clamp (QPatch and Qube) of hiPSC-derived neurological disease models, new automated patch clamp ion channel assays for CiPA cardiac safety testing (dynamic hERG and LQT3 late NaV1.5) and NaV1.7 drug discovery.
- Marc Rogers (Metrion Bioscience): Milnes and late Nav1.5 for cardiac safety,
- Bryan Moyer (Amgen): HTS drug discovery,
- Kadla Rosholm (Sophion): hIPS neuronal disease models
- Sarah Williams (Charles River): Adaptive online V½ estimation.
01:45 PM – Poster presentation:
Title: Biophysical and pharmacological profiling of multiple voltage-gated sodium channel subtypes on QPatch II
Poster presenter: Application scientist Daniel Sauter
Location: Exhibit Hall A-E – Poster board No.: B285
Voltage-gated sodium channels (VGSC) are responsible for the initiation and propagation of action potentials in excitable cells. VGSC have been identified as excellent drug targets for treatment of pain, epilepsy and to other neurological disorders. Early compounds, however, were developed using empirical approaches. The identification of the molecular identity of VGSC in combination with technological advances, such as the automated patch clamp technique, provide the basis for a rational design of subtype-selective compounds.
To date, 9 functional mammalian isoforms (NaV1.1–1.9) have been described in the literature. The various subtypes differ in their expression pattern and exhibit distinct biophysical and pharmacological profiles. All have in common that they produce a transient inward current in response to membrane depolarization. During this process, the VGSC transitions from a closed to an open into an inactivated state. Interestingly, inhibitor compounds often exhibit different pharmacological profiles dependent upon the ion channel conformational state.
In the present study, the second generation QPatch (QPatch II; Sophion Bioscience) was used in combination with adaptive voltage protocols to investigate state-dependent inhibition of tetrodotoxin (TTX) and tetracaine on 8 different VGSC subtypes (NaV1.1-8). A first step was to determine the half-inactivation potential V½(inactivation) for each individual cell. This value was then used during the next steps as preconditioning pulse. Such an adaptive protocol allowed to determine IC50 values for both the closed and the inactivated state and reduce heterogeneity of the cells. Both IC50 values and biophysical parameters of the different subtypes align well with literature values.