Lerche Lab

With the BMBF-funded Treat-ION consortium on Neurological Ion Channel and Transporter Disorders we focus on therapeutic studies in cellular, animal and human models, which are complemented by in silico searches for new treatments, better predictions for the functional consequences of mutations for therapeutic purposes and cellular drug screens. The use of approved and available ‘repurposed’ drugs such as 4-aminopyridine is a a specific goal to enable precision treatment. Our findings are directly delivered to patients through molecular therapeutic boards attached to the German academy of rare neurological diseases (DASNE) and the centers for rare diseases (ZSEs) in Baden-Württemberg and through a structured process for drug repurposing. Functional implications of selected mutations are examined in neuronal expression systems, such as transfected murine primary neurons, in utero electroporated neurons and genetically altered animal models carrying a human mutation (so-called “humanized mouse models”). The advantage of both in utero electroporated neurons and gene-targeted mouse models is that altered channels can be studied in their natural environment and additionally, the consequences on intrinsic neuronal properties and network activity can be studied using single cell patch clamp, extracellular recording or multielectrode array (MEA) techniques. We perform 256 electrode MEA recordings and high-resolution electrical imaging (CMOS with 4000 electrodes) to analyze single cell compartments and neuronal network activity in brain slices of transgenic animals and study network dysfunction of our mouse models in vivo together with O. Garaschuk (Inst. Neurophysiology) using Ca²⁺ imaging in the frame of the DFG Research Unit. To gain insight into the exact mechanisms as to how epilepsy develops as a consequence of a genetic defect, we investigate brain region- and time-specific RNA expression using single cell RNA sequencing in distinct neuronal subpopulations in mouse models.

Since human brain tissue is a limited resource in neuroscience research, we are additionally generating neurons from induced pluripotent stem cells (iPSCs). These represent an attractive, albeit simplified, alternative of a human model system to study diseases of the nervous system.

By reprogramming patient-specific fibroblasts into pluripotent stem cells and subsequently overexpressing specific transcription factors, we can specifically generate excitatory and inhibitory cortical neurons. In subsequent functional studies, the disease mechanism of individual patients can be investigated taking into account their unique genetic background. We investigate network activity using a multiwell-MEA system as well as single cell activity by patch clamp measurements. By this, we were already able to show that developmental electrophysiological activity patterns in iPSC-derived neurons are comparable to those in humans and animals (Rosa et al., Stem Cell Rep 2020). Current projects include electrophysiological analysis of patient-specific iPSC neurons carrying pathological mutations in genes encoding ion channels (KCNA2, KCNH1) or synaptic proteins (STX1B).

As another human model system, we are using human slice cultures which can be maintained for up to four weeks with good neurophysiological properties when human cerebrospinal fluid (CSF) is used as culture medium. The use of ex vivo brain slices derived from adult human neurosurgical-resected tissue allows to probe electrophysiological properties at single cell and network level (Schwarz et al., Sci Rep 2017). We demonstrated robust preservation of neuronal cytoarchitecture and electrophysiological properties of human pyramidal neurons. Further experiments delineate the optimal conditions for efficient viral transduction of cultures, enabling ‘high throughput’ fluorescence-mediated 3D reconstruction of genetically targeted neurons, and demonstrate feasibility of long term live cell imaging of human cells in vitro.