Seeking patients with GTPCH, TH, and AADC for dystonia stem cell research project

Research Summary

The dystonias are a group of neurological disorders characterized by involuntary twisting or repetitive movements. The biological basis for the abnormal movements is not well understood, although there is good evidence for abnormal function of pathways in the brain including the basal ganglia, cerebellum and cerebral cortex. Exactly which of these pathways is most relevant for dystonia remains uncertain, and there is growing evidence that different types of dystonia may result from different kinds of problems in each of these pathways. It has been challenging to delineate how these pathways are affected in dystonia because it is not feasible to take a brain sample from a living patient to study the relevant neurons. A new technology has been developed that may help study neurons of different motor pathways.

This technology involves taking a small skin sample from patients with dystonia, growing living fibroblasts from the skin, and then converting the fibroblasts into stem cells for making neurons. Since these stem cells can be used to generate a variety of different types of neurons, it becomes possible to have an unlimited quantity of different types of neurons for many different types of studies. Since these cells are made from dystonia patients, they will contain the genetic defects responsible for the disorder. The goal of the current proposal is to develop a resource for the collection of skin samples for making fibroblast cultures for dystonia, to create stem cells from these fibroblasts to share with dystonia investigators, and to begin to examine the defects in these cells after they are converted into dopamine neurons.

Research Plan

Specific Aims. The aim of this project is exploit relatively recently developed technology for induced pluriopotent stem (iPS) cells from primary cells obtained from patients with different types of dystonia. These iPS cells can serve as a resource for many subsequent studies with direct relevance to dystonia.

Because of the enormous potential of these cells for future studies, the focus of this application is the development of resource to be shared among dystonia investigators rather than exploitation of the cells for short term experimental goals. The specific aims of this proposal are:

1. To create a shared resource for fibroblast cultures from different dystonia populations.
2. To create a shared resource of iPS cells from different dystonia populations.
3. To examine the ability of iPS cells to differentiate and function as dopamine neurons in vitro.

Background & significance. The dystonias are a group of neurological disorders characterized by involuntary twisting or repetitive movements.1 There are many different causes, both genetic and acquired. The pathogenesis of the abnormal movements is not well delineated, although there is good evidence for dysfunction of motor pathways involving the basal ganglia, cerebellum and cerebral cortex. Exactly which of these pathways is chiefly responsible for dystonia remains uncertain, and there is growing evidence that different subtypes of dystonia may result from different types insults to different pathways.2, 3 In addition to the possibility of different motor pathways being responsible for different types of dystonia, there also are differences among the dystonias at the genetic level.4

More than 40 different genes now are recognized to cause different forms of dystonia, including primary dystonias, dystonia-plus syndromes, and several developmental or degenerative disorders. The genes so far identified involve a wide array of cellular processes including nuclear envelope function, structural integrity of cells, cellular DNA and protein regulation, and multiple metabolic pathways.4 Etiological heterogeneity at both the motor systems and molecular levels means that an isolated focus on any single type of dystonia may provide idiosyncratic answers that are not broadly relevant for all other forms of dystonia. The etiological heterogeneity has led to growing interest in defining common motor and molecular pathways that may be shared by subgroups of dystonias.5, 6

This strategy requires investigating the consequences of different genetic insults in different regions of the nervous system, rather than a limited focus on a single gene or neural pathway. The dystonia research community would benefit considerably from the development of cellular models in which the influence of different genetic defects could be studied in different types of neural cells. So far, only a handful of such studies have been conducted, and most of these involve over-expression of a single transgene in neuroblastoma or non-neuronal cells.7-10 There are two main limitations of this strategy.

First, there is growing appreciation that transgene overexpression may be detrimental to cellular physiology Jinnah 3 independent of any gene defect.11, 12 Second, there is growing appreciation that the use of neuroblastoma and non-neural cells may not provide all the answers, since the biology of dystonia may involve specific gene-cell interactions. The recent development and refinement of induced pluripotent stem (iPS) cell technology provides a powerful solution to the need for cellular models for dystonia.13-15 This technology involves establishing primary fibroblast cultures from a skin biopsy taken from a patient harboring a known or presumed genetic defect, and then converting the fibroblasts into stem cells. Since these stem cells provide a renewable resource for generating a variety of different types of cells, they can provide an unlimited quantity of different types of neurons for many different types of studies.