Figure 2.

a, SPG6 occurs in regions deleted in PWS and AS. SPG6 is mapped to chromosome 15q11, proximal to the imprinted PWS and AS domains, within a region containing four nonimprinted genes. These genes, including NIPA1, map within class I deletions in patients with PWS and AS but are intact in class II deletions (Chai et al. 2003 [in this issue]). BP = breakpoint hotspot; cen = centromere; tel = telomere. b, NIPA1 secondary structure analysis. Nine predicted transmembrane (TM) domains (Chai et al. 2003 [in this issue]) are shown. The NIPA1 T45R mutation occurs at the interface of TM1 and the first putative outside loop. c, Expression of NIPA1 by northern blot analysis. NIPA1 transcripts of 2.2 kb and 7.5 kb are found in all tissues but are greatly enriched in neuronal tissues. Probes were prepared from TA-cloned RT-PCR products of human NIPA1 (167 bp) and exons 2–3 of the control SNURF-SNRPN gene, were labeled with α-³²P-dCTP, and were hybridized in ExpressHyb (Clontech) at 65°C to northern blots (Clontech), according to the manufacturer’s protocol.