This Expression of Concern relates to J. Cell Sci. (2009) 122, 1091-1099 (doi:10.1242/jcs.039644).

Journal of Cell Science was informed that part of the 4.1G U2 blot in Fig. 1B is duplicated in the 4.1G U1 panel above. As the corresponding author, Xiuli An, was unable to locate the original data, the journal is unable to determine whether the results and conclusions reported in the paper are compromised. Therefore, the journal is publishing this Expression of Concern to make readers aware of the issues with the western blots shown in Fig. 1B.

The authors apologise to readers for any inconvenience caused.