PM20D1 and Alzheimer disease: However, as the lack of expression of both PM20D1 and SLC41A1 is associated with a higher risk of AD, but only PM20D1 is upregulated by AD-related stressors and neuroprotective, this suggests that first, PM20D1 is the most relevant gene for AD within the analyzed loci, and second, that the increased levels of SLC41A1 in AD might be a mere consequence of the increased number of astrocytes.