Research article

Overexpression of the human MNB/DYRK1A gene induces formation of multinucleate cells through overduplication of the centrosome

Eishi Funakoshi¹ , Takamitsu Hori¹ , Tokuko Haraguchi^2,3 , Yasushi Hiraoka^2,3 , Jun Kudoh⁴ , Nobuyoshi Shimizu⁴ and Fumiaki Ito¹

¹Department of Biochemistry, Faculty of Pharmaceutical Sciences, Setsunan University, Osaka 573-0101, Japan

²Kansai Advanced Research Center, Communications Research Laboratory, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe 651-2492, Japan

³Department of Biology, Graduate School of Science, Osaka University, 1-16 Machikaneyama, Osaka 560-0043, Japan

⁴Department of Molecular Biology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan

author email corresponding author email

BMC Cell Biology 2003, 4:12doi:10.1186/1471-2121-4-12

Published:	10 September 2003

Abstract

Background

Previously we cloned the human MNB/DYRK1A gene from the "Down syndrome critical region" on chromosome 21. This gene encodes a dual specificity protein kinase that catalyzes its autophosphorylation on serine/threonine and tyrosine residues. But, the functions of the MNB/DYRK1A gene in cellular processes are unknown.

Results

In this study, we examined HeLa cells transfected with cDNA encoding a green fluorescent protein (GFP)-MNB/DYRK1A fusion protein and found 2 patterns of expression: In one group of transfected cells, GFP-MNB/DYRK1A was localized as dots within the nucleus; and in the other group, it was overexpressed and had accumulated all over the nucleus. In the cells overexpressing GFP-MNB/DYRK1A, multinucleation was clearly observed; whereas in those with the nuclear dots, such aberrant nuclei were not found. Furthermore, in the latter cells, essential processes such as mitosis and cytokinesis occurred normally. Multinucleation was dependent on the kinase activity of MNB/DYRK1A, because it was not observed in cells overexpressing kinase activity-negative mutants, GFP-MNB/DYRK1A (K179R) and GFP-MNB/DYRK1A (Y310F/Y312F). Immunostaining of GFP-MNB/DYRK1A-overexpressing cells with specific antibodies against α- and γ-tubulin revealed that multiple copies of centrosomes and aberrant multipolar spindles were generated in these cells.

Conclusions

These results indicate that overexpression of MNB/DYRK1A induces multinucleation in HeLa cells through overduplication of the centrosome during interphase and production of aberrant spindles and missegregation of chromosomes during mitosis.