86 was critical for the regulation of chicken ccn2 expression (Mukudai et al. 2008). The destabilization effect of NPM on ccn2 mRNA is more specific and robust in chondrocytes that in other cell types, suggesting that other proteins are in fact actually responsible for the stability of the CCN2 mRNA. These results suggest that NPM may normally act to shuttle RNAs and ribosomal subunits to the cytosol, possibly by interacting with cis acting sequences on the 3′-UTRs of RNA. However, NPM presumably has additional functions, and can possibly act to by bring in additional protein to RNAs. To my knowledge, no study concerning the role of NPM in skeletal development has previously appeared in the literature; thus, the findings of Mukudai et al. (2008) appear to represent the first report of a novel NPM-mediated gene regulation system critical for proper chondrogenesis and endochondral ossification. The next goal of this laboratory is presumably to uncover the precise regulatory mechanism underlying the degradation of ccn2 mRNA mediated by the interaction among its 3’-UTR and NPM, including any other factor(s) that needs to be identified. Open Access This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which per- mits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. References Epstein E, Sela-Brown A, Ringel I, Kilav R, King SM, Benashski SE, Yisraeli JK, Silver J, Naveh-Many T (2000) Dynein light chain binding to a 3′-untranslated sequence mediates parathyroid A. Leask hormone mRNA association with microtubules. J Clin Invest 105:505–512. doi:10.1172/JCI8557 Grotendorst GR, Okochi H, Hayashi N (1996) A novel transforming growth factor beta response element controls the expression of the connective tissue growth factor gene. Cell Growth Differ 7:469–480 Holmes A, Abraham DJ, Sa S, Shiwen X, Black CM, Leask A (2001) CTGF and SMADs, maintenance of scleroderma phenotype is independent of SMAD signaling. J Biol Chem 276:10594– 10601. doi:10.1074/jbc.M010149200 Kondo S, Kubota S, Eguchi T, Hattori T, Nakanishi T, Sugahara T, Takigawa M (2000) Characterization of a mouse ctgf 3_-UTR segment that mediates repressive regulation of gene expression. Biochem Biophys Res Commun 278:119–124. doi:10.1006/ bbrc.2000.3780 Leask A, Abraham DJ (2006) All in the CCN family. J Cell Science 119:4803–4810 Leask A, Sa S, Holmes A, Shiwen X, Black CM, Abraham DJ (2001) The control of CTGF (ccn2) gene expression in normal and scleroderma fibroblasts. Mol Pathol 54:180–183. doi:10.1136/ mp.54.3.180 Macdonald PM, Struhl G (1988) cis-acting sequences responsible for anterior localization of bicoid mRNA in Drosophila embryos. Nature 336:595–598. doi:10.1038/336595a0 Macdonald PM, Kerr K, Smith JL, Leask A (1993) RNA regulatory element BLE1 directs the early steps of bicoid mRNA localiza- tion. Development 118:1233–1243 Maggi LB Jr, Kuchenruether M, Dadey DY, Schwope RM, Grisendi S, Townsend RR, Pandolfi PP, Weber JD (2008) Nucleophosmin serves as a rate-limiting nuclear export chaperone for the mammalian ribosome. Mol Cell Biol 28:7050–7065 Mukudai Y, Kubota S, Eguchi T, Kondo S, Nakao K, Takigawa M (2005) Regulation of chicken ccn2 gene by interaction between RNA cis element and putative trans-factor during differentiation of chondrocytes. J Biol Chem 280:3166–3177. doi:10.1074/jbc. M411632200 Mukudai Y, Kubota S, Kawaki H, Kondo S, Eguchi T, Sumiyoshi K, Ohgawara T, Shimo T, Takigawa M (2008) Posttranscriptional regulation of chicken ccn2 gene expression by nucleophosmin/ B23 during chondrocyte differentiation. Mol Cell Biol 28:6134– 6147. doi:10.1128/MCB.00495-08