Characterization of D630023F18Rik and its potential role in response of mouse neural progenitor cells to irradiation

The tumor suppressor protein p53 plays a central role in regulating various cellular responses such as the DNA damage response (DDR). p53 also plays an important role in brain development, however its candidate target genes have not been studied in much detail during this process. A study from 2015 identified several novel p53 targets that are activated after irradiation of the embryonic brain in mice. For a number of these target genes radiation induces different transcript isoforms in a p53-dependent manner. One of these target genes is D630023F18Rik, a brain-enriched gene which expresses besides
canonical long transcripts also short transcript variants that are induced by radiation via the binding of p53 to a p53 response element, in an alternative promoter. The expression of short and long transcripts is strongly induced during in vitro neuronal differentiation and in vivo brain development.
Thus, D630023F18Rik may be relevant to brain development and neuronal maturation and the short transcript variants possibly play a role in the DDR induced by ionizing radiation. Previous research also identified YWHAE and AHI1 as potential binding partners of D630023F18Rik on the basis of a genomewide
yeast-two hybrid screen. Therefore, the expression of the three proteins was investigated via western blotting in different possible experimental samples that could then be used for validation experiments. Experiments performed in this project revealed that YWHAE and different isoforms of D630023F18Rik are expressed in mouse neural progenitor cells (mNPCs) and in embryonic and
postnatal brain, whereas AHI1 could not be detected. Furthermore, in mNPCs the expression of D630023F18Rik is dependent on p53 as it was reduced in p53 knockout cells both at the mRNA and protein levels. The irradiation of wild-type, but not of p53 knockout mNPCs resulted in an increased expression of the exons that are part of the short transcript variants of D630023F18Rik suggesting that these short transcripts play a role in the DDR induced by radiation. Finally, we used siRNA-mediated knockdown and overexpression of D630023F18Rik to elucidate its role in mNPC proliferation via live cell imaging. The knockdown of D630023F18Rik resulted in a reduction in cell proliferation, whereas the overexpression of D630023F18Rik did not have an effect on the cell proliferation.