SMPD1 and major depressive disorder: In order to identify mutations in the SMPD1 gene that potentially explain increased ASM activity associated with major depressive disorder [1] we performed a re-sequencing analysis of the six exons of SMPD1. This region includes a 1896 bp open reading frame that encodes a 631 amino acid protein according to NCBI Reference Sequence NM_000543.4.