SMPD1 and Prader-Willi syndrome: Five proteins, Brevican (BCAN), Neurocan (NCAN), Ephrin type-B receptor 6 (EPHB6), Sphingomyelin phosphodiesterase 1 (SMPD1), and Desmoglein 3 (DSG3), were upregulated in the serum of PWS subjects (Table 3 and Figure 2).