This new model overexpresses truncated human alpha-synuclein in mice which progressively aggregates resulting in reduced dopamine levels and death of dopaminergic neurons, thereby closely replicating human PD. Impaired motor function is also observed.

Article Depopulation of dense α-synuclein aggregates is associated w...

There are numerous approaches to have an animal model of HD. As you wanted to be informed of previous literature, please check the following as useful ones:

https://www.sciencedirect.com/science/article/abs/pii/S0168952501026257

https://academic.oup.com/ilarjournal/article/48/4/356/644156

For transgenic rat model of HD:

https://academic.oup.com/hmg/article/12/6/617/573203

For PD models:

Article Animal Models of Parkinson’s Disease

Article Genetic Animal Models of Parkinson's Disease

Remember that animals have four paws/legs on the ground but humans only two. Therefore magnetic fields from remanent magnetism or magnetism in the lab however caused will vary in bodily absorption between man and animal. EMF levels in labs can be very high - are the labs shielded ? Reactive Oxygen Species from unpaired electrons are of very high significance in adverse effects.