NPAP1 and Prader-Willi syndrome: The Nuclear Pore Associated Protein 1 (NPAP1), formerly known as Chromosome 15 Open Reading Frame 2 (C15orf2), is an intronless gene that is biallelically expressed in adult testis and monoallelically expressed in fetal brain, including the hypothalamus which is related to several endocrine features of PWS (106, 111).