Genetic Engineering seminars

Developmental and epileptic encephalopathies (DEEs) are a broad spectrum of genetic epilepsies associated with impaired neurological development as a direct consequence of a genetic mutation, in addition to the effect of the frequent epileptic activity on brain. Compelling genetic studies indicate that heterozygous de novo mutations represent the most common underlying genetic mechanism, in accordance with the sporadic presentation of DEE. De novo mutations may exert a loss-of-function (LOF) on the protein by decrementing expression level and/or activity, leading to functional haploinsufficiency. These diseases share several features: severe and frequent refractory seizures, diffusely abnormal background activity on EEG, intellectual disability often profound, and severe consequences on global development. One of major causes of early onset DEE are de novo heterozygous mutations in syntaxin-binding-protein-1 gene STXBP1, which encodes a membrane trafficking protein playing critical role in vesicular docking and fusion. LOF STXBP1 mutations lead to a failure of neurotransmitter secretion from synaptic vesicles. Core clinical features of STXBP1 encephalopathy include early-onset epilepsy with hypsarrhythmic EEG, or burst-suppression pattern, or multifocal epileptiform activity. Seizures are often resistant to standard treatments and patients typically show intellectual disability, mostly severe to profound. Additional neurologic features may include autistic traits, movement disorders (dyskinesia, dystonia, tremor), axial hypotonia, and ataxia, indicating a broader neurologic impairment. Patients with severe neuro-cognitive features but without epilepsy have been reported. Recently, a new class of natural and synthetic non-coding RNAs have been identified, enabling upregulation of protein translation in a gene-specific way (SINEUPs), without any increase in mRNA of the target gene. SINEUPs are translational activators composed by a Binding Domain (BD) that overlaps, in antisense orientation, to the sense protein-coding mRNA, and determines target selection; and an Effector Domain (ED), that is essential for protein synthesis up regulation. SINEUPs have been shown to restore the physiological expression of a protein in case of haploinsufficiency, without driving excessive overexpression out of the physiological range. This technology brings many advantages, as it mainly acts on endogenous target mRNAs produced in situ by the wild-type allele; this action is limited to mRNA under physiological regulation, therefore no off-site effects can be expected in cells and tissues that do not express the target transcript; by acting only on a posttranscriptional level, SINEUPs do not trigger hereditable genome editing. After bioinformatic analysis of the promoter region of interest, we designed SINEUPs with 3 different BD for STXBP1. Human neurons from iPSCs were treated and STXBP1 levels showed a 1.5-fold increase compared to the Negative control. RNA levels of STXBP1 after the administration of SINEUPs remained stable as expected. These preliminary results proved the SINEUPs potential to specifically increase the protein levels without impacting on the genome. This is an extremely flexible approach to target many developmental and epileptic encephalopathies caused by haploinsufficiency, and therefore to address these diseases in a more tailored and radical way.

There are no effective disease-modifying therapies for neurodegenerative diseases such as Alzheimer’s, Parkinson’s, amyotrophic lateral sclerosis or Huntington’s disease. Huntington’s disease (HD) is a devastating autosomal dominantly inherited neurodegenerative disease and the world’s most common genetic dementia. I will present an overview of important approaches in development for targeting mutant HTT DNA and RNA (Tabrizi et al Neuron 2019), the cause of HD pathogenesis, and the translational pathway from bench to clinic for a HTT targeting antisense oligonucleotide (Tabrizi et al New England Journal of Medicine 2019, Tabrizi, Science 2020) which is now in phase 3 studies. In my talk I will also review some of the genetic approaches in development for other CNS diseases. I will talk a bit about my journey as a clinician scientist and share some of my learnings for young scientists on how to survive a career in science.

One of the major roadblocks to medical progress in the field of neurodegeneration is the absence of animal models that fully recapitulate features of the human diseases. Unprecedented opportunities to tackle this challenge are emerging e.g. from genome engineering and stem cell technologies, and there are intense efforts to develop models with a high translational value. Simultaneously, single-cell, multi-omics and optogenetics technologies now allow longitudinal, molecular and functional analysis of human disease processes in these models at high resolution. During this workshop, 12 experts will present recent progress in the field and discuss: - What are the most advanced disease models available to date? - Which aspects of the human disease do these accurately models, which ones do they fail to replicate? - How should models be validated? Against which reference, which standards? - What are currently the best methods to analyse these models? - What is the field still missing in terms of modelling, and of technologies to analyse disease models? CURE-ND stands for 'Catalysing a United Response in Europe to Neurodegenerative Diseases'. It is a new alliance between the German Center for Neurodegenerative Diseases (DZNE), the Paris Brain Institute (ICM), Mission Lucidity (ML, a partnership between imec, KU Leuven, UZ Leuven and VIB in Belgium) and the UK Dementia Research Institute (UK DRI). Together, these partners embrace a joint effort to accelerate the pace of scientific discovery and nurture breakthroughs in the field of neurodegenerative diseases. This Neurotechnology Workshop is the first in a series of joint events aiming at exchanging expertise, promoting scientific collaboration and building a strong community of neurodegeneration researchers in Europe and beyond.

One of the major challenges in developing therapeutics for the neurodegenerative disorders is the blood-brain barrier, limiting the availability of systemically administered therapies such as recombinant proteins or monoclonal antibodies from reaching the brain. Direct central nervous system (CNS) gene therapy using adeno-associated virus vectors expressing a therapeutic protein, monoclonal antibody or inhibiting RNA-coding sequences has two characteristics ideal for therapy of neurodegenerative disorders: circumventing the blood-brain barrier by directly expressing the therapy in the brain and the ability to provide persistent therapy with only a single administration. There are several critical parameters relevant to successful CNS gene therapy, including choice of vector, design of the gene to be expressed, delivery/route of administration, dose and anti-vector immune responses. The presentation will focus on these issues, the current status of clinical trials of gene therapy for neurodegeneration and specific challenges that will need to be overcome to ensure the success of these therapies.

Emmanuelle Charpentier and Jennifer Doudna explain the discovery and biochemical development of CRISPR-Cas9 as a programmable tool for modifying DNA. The scientific story begins with bacterial defence against invading genetic material and the role of tracrRNA in the CRISPR system. It proceeds through the reconstruction and simplification of the RNA-guided machinery and the demonstration that a chosen guide can direct DNA cleavage to a specified sequence. The lectures connect basic research on microbes and RNA with a method that transformed experimental genetics. They explain the molecular logic of the system and the possibilities it opened for studying gene function, engineering organisms and developing therapeutic approaches.

Human genes associated with brain-related diseases are being discovered at an accelerating pace. A major challenge is an identification of the mechanisms through which these genes act, and of potential therapeutic strategies. To elucidate such mechanisms in human cells, we established a CRISPR-based platform for genetic screening in human iPSC-derived neurons, astrocytes and microglia. Our approach relies on CRISPR interference (CRISPRi) and CRISPR activation (CRISPRa), in which a catalytically dead version of the bacterial Cas9 protein recruits transcriptional repressors or activators, respectively, to endogenous genes to control their expression, as directed by a small guide RNA (sgRNA). Complex libraries of sgRNAs enable us to conduct genome-wide or focused loss-of-function and gain-of-function screens. Such screens uncover molecular players for phenotypes based on survival, stress resistance, fluorescent phenotypes, high-content imaging and single-cell RNA-Seq. To uncover disease mechanisms and therapeutic targets, we are conducting genetic modifier screens for disease-relevant cellular phenotypes in patient-derived neurons and glia with familial mutations and isogenic controls. In a genome-wide screen, we have uncovered genes that modulate the formation of disease-associated aggregates of tau in neurons with a tauopathy-linked mutation (MAPT V337M). CRISPRi/a can also be used to model and functionally evaluate disease-associated changes in gene expression, such as those caused by eQTLs, haploinsufficiency, or disease states of brain cells. We will discuss an application to Alzheimer’s Disease-associated genes in microglia.