IGFBP2 and Prader-Willi syndrome: Furthermore, Bittel et al. [6] reported that the amount of mRNA isolated from lymphoblastoid cell lines established from individuals with PWS for the four genes (i.e., NIPA1, NIPA2, CYFIP1, TUBGCP5) found in the genomic area between BP1 and BP2 in the 15q11.2 chromosome band explained between 24% to 99% of the phenotypic variability in behavioral and academic measures.