Nucleostemin and lens regeneration

Kobe, Japan -

It is known that in the newt, regeneration of differentiated cells occurs in response to various types of injury. It is also known that the gene for nucleostemin (NS) encodes a GTP-binding protein which is found in the nucleolus of stem cells and cancer cells at high concentrations. Accumulation of nucleostemin in the nucleolus of pigmented epithelial cells is also noted during lens development.

In a recent paper (Maki N et al. Rapid accumulation of nucleostemin in nucleolus during newt regeneration. Dev Dyn. 2007 Mar 15;236(4):spc1) lenectomy was performed in newts and expression of nucleostemin was examined. A marked upregulation of neucleostemin expression was detected in the regenerating pigmented epithelium.

This finding is very interesting since nucleostemin is involved in several functions essential to stem cells and regeneration. For example, it was reported that ablation of nucleostemin expression resulted in accelerated senescence (Zhu et al. Nucleostemin delays cellular senescence and negatively regulates TRF1 protein stability. Mol Cell Biol. 2006 Dec;26(24):9279-90). In the same paper it was demonstrated that nucleostemin accelerates degradation of TRF1, thus inhibiting telomere shortening.

Additionally, Sijin et al (The effect of knocking-down nucleostemin gene expression on the in vitro proliferation and in vivo tumorigenesis of HeLa cells. J Exp Clin Cancer Res. 2004 Sep;23(3):529-38) demonstrated that inhibition of nucleostemin expression resulted in the inhibition of cancer cell proliferation.

Accordingly, nucleostemin is an interesting gene whose function requires greater investigation.