APP and Parkinson disease: In analyzing differential expression between the human and siamang PFC, we note that similar trends for enrichment are also found, such as ‘Neural Growth and Development’ and ‘Metabolic Processes,’ and ‘Gene Regulation.’ Of interest, under the category of ‘Positive Regulation of Transcription by RNA polymerase II’ we find several genes that appear to be upregulated in humans compared to siamang: APP (amyloid precursor protein, related to plaque formation in Alzheimer’s disease) as well as PRKN (found to be causal in Parkinson’s disease) (Funayama et al., 2023).