Genomic structure and mutational analysis of the human KIF1B gene which ishomozygously deleted in neuroblastoma at chromosome 1p36.2

In order to clone candidate tumor suppressor genes whose loss contributes t o the pathogenesis of neuroblastoma (NB), we performed polymerase chain rea ction (PCR) screening using a high-density sequence tagged site-content map within a commonly deleted region (chromosome band 1p36) in 24 NB cell line s. We found a similar to 480 kb homozygously deleted region at chromosome b and 1p36.2 in one of the 24 NB cell lines, NB-1, and cloned the human homol ogue (KIF1B-beta) of the mouse-Kif1B-beta gene in this region. The KIF1B-be ta gene had at least 47 exons, all of which had a classic exon-intron bound ary structure. Mouse Kif1B is a microtubule-based putative anterograde moto r protein for the transport of mitochondria in neural cells. We performed m utational analysis of the KIF1B-beta gene in 23 cell lines using 46 sets of primers and also an allelic imbalance (Al) analysis of KIF1B-beta in 50 fr esh NB samples. A missense mutation at codon 1554, GTG (Gly) to ATG (Met), silent mutations at codon 409 (ACG to ACA) and codon 1721 (ACC to ACT), and polymorphisms at codon 170, GAT (Asp) to GAA (Glu), and at codon 1087, TAT (Tyr), to TGT (Cys), were all identified, although their functional signif icances remain to be determined. The Al for KIF1B-beta was slightly higher (38%) than those for the other two markers (D1S244, D1S1350) (35 and 32%) w ithin the commonly deleted region (1p36). Reverse transcriptase-PCR analysi s of the KIF-IB-fl gene revealed obvious expression in all NB cell lines ex cept NB-1, although decreased expression of the KIF1B-beta gene was found i n a subset of early- and advanced-stage NBs. These results suggest that the KIF1B-beta gene may not be a candidate for tumor suppressor gene of NB.