Differential tissue specific expression of Kif23 alternative transcripts in mice with the human mutation causing congenital dyserythropoietic anemia type III.

Kinesin Family Member 23 (KIF23), a cell cycle regulator, has a key task in cytokinesis. KIF23 over-expression in cancer has been associated with tumor growth, progression, and poor prognosis, indicating a potential to be a cancer biomarker. A mutation in KIF23 (c.2747C > G, p.P916R) was shown to cause congenital dyserythropoietic anemia, type III (CDA III). To-date, fifteen KIF23 transcripts have been annotated, but their expression is poorly investigated. We hypothesized that tissue specific expression of a particular transcript can be critical for CDA III phenotype. In this study, we quantified expression of alternative Kif23 transcripts in a mouse model with human KIF23 mutation and investigated its association with a regulator of alternative splicing, serine/arginine-rich splicing factor 3 (Srsf3). We confirmed presence of an additional exon 8 in both human and mouse KIF23 transcripts. A transcript lacking exons 17 and 18 was ubiquitously expressed in mice while other isoforms were common in human tissues however in bone marrow of knock-in mice a transcript without exon 18 was prevalent as it was in bone marrow of a CDA III patient. We conclude that the possibility that the tissue specific expression of KIF23 alternative transcripts influence the CDA III phenotype cannot be neglected.

Mutation analysis and copy number alterations of KIF23 in non-small-cell lung cancer exhibiting KIF23 over-expression.

KIF23 was recently suggested to be a potential molecular target for the treatment of lung cancer. This proposal is based on elevated expression of KIF23 in several tumors affecting breast, lung, brain, and liver, and also on the presence of KIF23 mutations in melanoma and colorectal cancer. Recently, we identified a mutation in the KIF23 gene causing a rare hereditary form of dyserythropoietic anemia (CDA III) with predisposition to blood cancer. We suggested that KIF23 overexpression in tumors might be due to the presence of activating somatic mutations, and therefore, mutation screening of the KIF23 in 15 non-small-cell lung cancer (NSCLC) cases with elevated expression level of KIF23 was undertaken. Eight sequence variants were found in all samples. Furthermore, one variant was present in two cases, and one variant was case specific. Nine variants were previously reported while one variant lacks frequency information. Nine of ten cases available for single nucleotide polymorphism-array analysis demonstrated aberrant karyotypes with additional copy of entire chromosome 15. Thus, no activating somatic mutations in coding regions of the KIF23 were found. Furthermore, no mutations were detected in cell cycle genes homology region in KIF23 promoter responsible for p53-dependent repression of KIF23 expression. We showed that the elevated level of KIF23 could be due to additional copy of chromosome 15 demonstrated in 90% of NSCLC cases analyzed in this study. Considering the crucial role of KIF23 in the final step of mitosis, the gene is a potential molecular marker, and for better understanding of its role in cancer development, more tumors should be analyzed.

Congenital dyserythropoietic anemia type III (CDA III) is caused by a mutation in kinesin family member, KIF23.

Haplotype analysis and targeted next-generation resequencing allowed us to identify a mutation in the KIF23 gene and to show its association with an autosomal dominant form of congenital dyserythropoietic anemia type III (CDA III). The region at 15q23 where CDA III was mapped in a large Swedish family was targeted by array-based sequence capture in a female diagnosed with CDA III and her healthy sister. Prioritization of all detected sequence changes revealed 10 variants unique for the CDA III patient. Among those variants, a novel mutation c.2747C>G (p.P916R) was found in KIF23, which encodes mitotic kinesin-like protein 1 (MKLP1). This variant segregates with CDA III in the Swedish and American families but was not found in 356 control individuals. RNA expression of the 2 known splice isoforms of KIF23 as well as a novel one lacking the exons 17 and 18 was detected in a broad range of human tissues. RNA interference-based knock-down and rescue experiments demonstrated that the p.P916R mutation causes cytokinesis failure in HeLa cells, consistent with appearance of large multinucleated erythroblasts in CDA III patients. We conclude that CDA III is caused by a mutation in KIF23/MKLP1, a conserved mitotic kinesin crucial for cytokinesis.