HDA Supported Research
For the Past two years, the HDA has had a scheme of competitive funding of research grants and PhD studentships.
In 1998:
Research grant to Drs. David Craufurd and Julie Snowden (Manchester) to study behavioural changes in HD.
Studentship to Dr Peggy Sholhourne (Glasgow) for Laura Kennedy to study a mouse model of HD, In 1999:
Research grant to Drs. Barbara Sahakian and Anne Rosser (Carnbridge) to provide support for neuropsychological monitoring and assessment of patients undergoing brain tissue transplantation.
Biological research in Huntington's Disease
1983 - found HD gene to be on chromosome 4
1993 - identified HD gene as one of unknown function containing abnormally expanded CAG repeat sequence,
The CAG repeat expansion makes a protein with an abnormally long sequence of one amino acid (glutamine) which prevents the protein working as it should.
Unlike some genetic diseases, where an abnormality means that the protein is just not eftective, or not present. in HD the abnormal protein has an effect - but an unwanted toxic one.
It is not known exactly what this eftct is. It may bind to other important proteins in the cell to stop them working, or it might clump together to form large deposits (Neuronal intranuclear inclusions = NII) that disrupt the normal workings of the cell.
Mouse Models Essential to this research has been the ability to produce "transgenic mice" that have an HD-like gene (Gill Bates).
These animals develop in 2-3 months the brain damage that takes decades to develop in humans. Although the pattern of cell death in the brain is not very similar to that in HD, the mechanisms of cell death may well be the same.
Peggy Shelbourne's work has been to develop a mouse model that better mimics HD. These animals live much longer and have more subtle problems with movement etc.
Cell culture models
It is also possible to introduce the HD gene into cells that can be grown in the laboratory. Although such models cannot demonstrate the problems that MD imposes on behaviour, they make it more easy to study the effects of the HD gene on the cell, and to investigate possible treatments. These can then be tested first in animal models.
The HD Protein (huntingtin) can be broken down by some enzymes (Caspases) that are involved in cell death. This results in fragments that more rapidly clump together and more rapidly kill the cell. Future drug treatment One approach to treatment might be to find drugs which block the breakdown of huntingtin - caspase inhibitors.
Other potential drug treatments
Glutamate receptor antagonists (blocking excitotoxicity) Antioxidants or free radical Scavengers Coenzyme Q etc etc
These are based mainly on what we understand to be the mechanisms of cell death in chemical rnodels of HD.
Treatment - Transplantation
Transplantation of embryonic brain tissue into the brain (striatum) in HD patients has been tried - results show that
* it can be done safely
* there may be some improvement in
psychological measures
Other sources of cells for transplantation:
* animal brain embryos
* human neuronal cells from carcinoma
cell-line
* genetically engineered cells
* neural stem cells
Genes make proteins. Proteins have many functions in the cell - they can be enzymes providing the energy for the cell's activities or involved in building the structure of the cell. They can be part of that structure, or be involved in moving other cellular components around to and from the outside of the cell. or from one part of the cell to another. It is this latter function transportation within the cell, with which the normal HD gene may be involved,
Everyone has two keys - most of us have one key that works which is enough, Each key comes from a different parent - and we'll copy each key to pass on a copy to our children, Only if both keys don't fit the lock do we have problems. (recessive)
But for some people, one key works while the other one, instead of just not fitting, breaks the lock, (dominant)