Genomic structure and mutational analysis of the human KIF1Bα gene located at 1p36.2 in neuroblastoma

KIF1a is a member of the kinesin superfamily proteins that are microtubule-dependent molecular motors involved in important intracellular functions such as organelle transport and cell division. We previously determined the structure of the human KIF1Bβ gene, which was found to be a homologue of the murine Kif1bβ, and demonstrated that the human KIF1Bβ is a causative gene of Charcot-Marie-Tooth disease type 2A although we did not prove that it is a tumor suppressor gene of neuroblastoma. Here, we identified another isoform of the human KIF1B gene, KIF1Bα. The KIF1Bα and KIF1Bβ are alternative splicing products of the KIF1B gene located on 1p36.2. The KIF1Bα is distinct from KIF1Bβ in the C-terminal cargo-binding domain; however, they have the same N-terminal motor domain. We found that the transcript of approximately 7.8 kb of KIF1Bα was expressed in several tissues, especially in skeletal muscle, by Northern blot analysis. To determine whether this gene is one of the candidate tumor suppressor genes for neuroblastoma (NB) or other pediatric solid tumors, we performed mutational screening of KIF1Bα in 25 NB, 9 rhabdomyosarcoma, 12 Ewing sarcoma and 24 other pediatric solid tumor cell lines. Using RT-PCR single-strand conformation polymorphism analysis and direct sequencing we detected a missense mutation (M807I) in 1 NB cell line (SK-N-SH), 3 silent mutations in 2 NB cell lines and 1 primitive neuroectodermal tumor cell line, respectively. RT-PCR analysis revealed that KIF1Bα was obviously expressed in almost all of the tumor cell lines examined except NB-1. Furthermore, real-time quantitative RT-PCR showed that there was no significant difference in KIF1Bα expression between 14 early-stage (stage I and II) and 14 advanced-stage (stage III and IV) NB fresh tumor specimens. These results suggest that KIF1Ba in addition to KIF1Bβ may not be a candidate tumor suppressor gene for NB.