Homo sapiens C/D box snoRNA HBII-13: this snoRNA was first cloned in the mouse by Cavaillé et al. (2000), and found to be brain-specific. HBII-13 is predominantly expressed in the brain, and, to a lesser extent, in muscle, lung and kidney. As HBII-85 and HBII-52, HBI-13 was not expressed in the brain of a patient with a paternal 15q11-q13 deletion (Prader-Willi syndrome), but was normally expressed when the deletion is maternally inherited (Angelman syndrome). HBII-13 (as well as HBII-436, HBII-437, HBII-438A/B and the two clusters of HBII-85, HBII-52 snoRNAs) is encoded in an intron of the large (460kb), paternally expressed, transcription unit (SNURF-SNRNP-UBE3A AS), that is antisense to the maternally expressed UBE3A gene (Runt et al., 2001). This snoRNA has no identified RNA target.