Genotypic and Phenotypic Examination of Disease Pathogenesis in C9orf72 FTD
Abstract
Frontotemporal dementia (FTD) is one of the major causes of dementia in adults under the age of 65, affecting neurons in the frontal and temporal cortices of patients, which leads to clinical abnormalities in behavior, language, and personality. FTD still remains a poorly understood disease, especially in regards to its underlying cellular and molecular mechanisms thought to trigger disease manifestation and progression. FTD presents as an extremely heterogeneous disease in regards to patient-specific symptoms, genetics, and pathological markers identified in postmortem brain tissue. To better understand this disease, we will focus our studies on one of the most prevalent subsets of FTD patients, those carrying a mutation in the C9orf72 gene (C9 FTD). To gain more knowledge about how mutations in C9orf72 lead to FTD, we will generate a genetic signature profile of postmortem patient tissues specifically affected in FTD patients – the frontal cortex. We will use a novel technology that will allow us to obtain a genetic profile of each individual cell type present in this brain region. While FTD leads to the degeneration of neurons, it is suggested that other cell types in the brain equally contribute to the disease manifestation and progression. Using an approach called “single cell RNA sequencing,” we will be able to isolate these different cell types from the frontal cortex and look at the genetic make-up of each individual cell. By comparing those genetic profiles obtained from C9 FTD patients to those obtained from healthy control subjects, we can identify genes that are regulated differently, which are therefore likely to contribute to the disease pathogenesis. In addition to the analysis of postmortem tissue, we will generate and culture live human neurons from C9 FTD patients using yet another novel technology called induced pluripotent stem cells or iPSCs. To obtain iPSCs from C9 FTD patients, blood or skin fibroblasts from a patient will be converted into an iPSC, which can then be transformed into a neuron. These neurons, so-called cortical neurons, grow in vitro and resemble the neurons present in the frontal cortex of humans. iPSC-cortical neurons from C9 FTD patients will then be analyzed for their genetic signature profile similarly to what is proposed for the postmortem frontal cortex brain tissue and compared to those findings. In addition, we will study neuronal function in these living neurons, for example, neuronal electrical activities. Electrical firing of neurons is required for normal neuronal function, such as transmission of information from one neuron to another, and deficiencies in these electrical properties are indicative of neuronal degeneration. By comparing C9 FTD cortical neurons to cortical neurons obtained from healthy control subjects, we will identify specific cellular phenotypes that are only present in the diseased cells and are therefore likely to contribute to disease progression. Finally, after analyzing the genetic signature profiles from postmortem tissue and individual patient-derived cells, we will select candidate genes that we hypothesize play a significant role in C9 FTD disease pathogenesis. To test whether these genes will affect the behavioral cognitive phenotypes of C9 FTD patients, we will use a Drosophila (fruit fly) model of C9 FTD and use genetics to identify which of these candidate genes contribute to disease in vivo dementia model. Specifically, we will genetically manipulate flies to test whether specific gene mutations will affect the cognitive behavior of flies that have mutations in the C9orf72 gene similar to C9 FTD patients. Those genes that either ameliorate or exacerbate the behavior of C9 flies will then be re-examined in the patient-derived iPSC cortical neurons and the patient postmortem tissue to validate findings from flies with humans as we have successfully done in the past for ALS (amyotrophic lateral sclerosis). The data obt
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 16, 2019
- Source ID
- W81XWH1910276
Entities
People
- Rita Sattler
Organizations
- United States Army