PM20D1 and obesity due to melanocortin 4 receptor deficiency: In addition, it has been shown that variants in the upstream region of the humanPM20D1 gene can modify methylation and transcription factor binding, which regulates the circulating levels of PM20D1; this has been proposed as a mechanism linking PM20D1 with obesity and neurodegenerative diseases (Benson et al. (Benson et al. 2019).