Building of a diagnostic/prognostic database by high-throughput multiplexed assays for human ERG variant effects – CarDiag

For what concerns the methodological approaches, the project benefits from a high throughput automated patch clamp system fo the high throughput screening of hERG channel variants. This system allows for the recording of 384 cells per plate. We manage to record up to 4 variants simultaneously per plate. The other approaches require a tag for the followup of the channel trafficking and modeling softwares for the structural impact of the variants.

Right now, we have produced over 300 plasmids coding for the variants of the hERG channel. They have all been characterized at the functional level on the entirety of the biophysical parameters of the channel. In parallel, the structural impact of these variants has been studied allowing for the first time a correlation between structure and function. Also, for the loss of function of some variants, defects or not of the trafficking has been investigated.

We have accumulated the ECG recordings of about one third of the patients. we now develop a new algorithm of QTc prediction that is based on the biophysical properties of the hERG channel variant and that we can correlate with the QTc of the patient in order to perform a direct clinical link. In parallel a summary file will be created for each variant that will be web-accessible for any researcher or clinician.

Montnach J, Lorenzini M, Lesage A, Simon I, Nicolas S, Moreau E, Marionneau C, Baró I, De Waard M, Loussouarn G. Computer modeling of whole-cell voltage-clamp analyses to delineate guidelines for good practice of manual and automated patch-clamp. Scientific Reports 11, 3282 (2021). doi.org/10.1101/2020.04.27.062182

Oliveira-Mendes BBR, Feliciangeli S, Ménard M, Chatelain FC, Montnach J, Nicolas S, Ollivier B, Barc J, Baro I, Schott JJ, Probst V, Kyndt F, Denjoy I, Lesage F, Loussouarn G*, De Waard M*. A standardized hERG phenotyping pipeline to evaluate KCNH2 genetic variant pathogenicity. Clinical and Translational Medicine e609 (2021). * codirected. doi.org/10.1002/ctm2.609

Oliveira-Mendes B, Malak A, Montnach J, Ollivier B, Gibaud S, Feliciangeli S, Charpentier F, Lesage F, Loussouarn G, De Waard M*, Baro I*. Predicting hERG repolarization power at 37°C from recordings at room temperature. Clinical and Translational Medicine 13: e1266 (2023). doi.org/10.1002/ctm2.1266

Alameh M, Oliveira-Mendes B, Kyndt F, Rivron J, Denjoy I, Lesage F, Schott JJ, De Waard M*, Loussouarn G*. A need for exhaustive and standardized characterization of ion channels activity. The case of KV11.1. Frontiers in Physiology 14, 1132533 (2023). doi.org/10.3389/fphys.2023.1132533

Channelopathies induce severe heart rhythm or conduction disorders. Mutations of the KCNH2 gene, that encodes the human (h) ERG channel, is responsible for 30% of all cases of long QT syndrome. Besides, hERG is frequently responsible for off-target effects of several pharmacological agents. With the advent of Next Generation Sequencing, hundreds of new KCNH2 variants are accumulating in various databases, many being of unknown significance to clinicians which hampers the value of their diagnosis and the quality of patient management. Therefore, there is an urgent need to functionally characterize a large fraction of KCNH2 variants and provide access of this information to hospital clinicians. We assembled a consortium of clinicians, geneticists, biophysicists and computer bioscientists to build the largest web-accessible diagnostic/prognostic database of hERG-related channelopathies. To this end, we will take advantage of high-throughput techniques of channel variant phenotyping.