DNA repair after ionizing radiation.

<p>The remaining DNA damage after irradiation of isolated peripheral mouse lymphocytes with 1 Gy (¹³⁷Cs) is given. 77–95 cells of each mouse were counted manually for remaining γH2AX foci 6 hrs after irradiation. It is obvious that the heterozygous mutant show significantly more foci than the wild types indicating that the repair of DNA double-strand breaks in the mutants is not as efficient as in the wild types (p = 0.006602). The columns represent the means of foci per nucleus from 3 males of each phenotype; bars indicate the standard error of the mean (SEM).</p

Immuno-histochemistry ERCC2 expression.

<p>Using antibodies against ERCC2 and Alexa488 (green) as secondary antibody, we demonstrate that ERCC2 is expressed weakly in the ocular lens around birth; expression is increasing from P7 onward. Cell nuclei are counterstained by DAPI (blue). ERCC2 is mainly expressed in the cytosol.</p

Sequence analysis of <i>Ercc2</i> gene.

<p>Schematic drawing of the mouse <i>Ercc2</i> gene (ENSEMBL); the red arrow points to the site of the mutation in exon 23. Sanger sequencing confirmed the exome sequencing data (c.2209T->C; red arrows); the frame of the sequence trace is indicated by placing a bar over the mutant codon. The changes in the amino acid sequence (Ser737Pro) are given below; the underlined DNA sequence demonstrates the new <i>Mwo</i>I restriction site in the mutants.</p

<i>RCO015</i> mutants and identification of the underlying mutation.

<p>a) A heterozygous (left) and homozygous (middle) <i>RCO015</i> mutant mouse at the age of 9 months compared to a wild type (right). The homozygous mutants are smaller and have rough hair and small eyes. b) Haplotype analysis defines the critical interval between the markers <i>116J6</i>.<i>1</i> and <i>D7Mit294</i> at mouse chromosome 7.</p

Histology.

<p>Histological sections from embryonic day 17.5 (E.17.5) till postnatal day 14 (P14) are given in an overview (left panel) and in a higher magnification of the anterior/equatorial region in the right panel of wild types, heterozygous and homozygous mutants. Cataract formation starts after birth in the homozygous mutants only. The first signs are vacuoles in the posterior cortical region of newborn mice (P1, red arrows), which are compressed later by the growing lens (P7, red arrow). Finally, they give rise to the sharp boundaries in the cortical region (P14, red arrow) being observed in the isolated lenses (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125304#pone.0125304.g002" target="_blank">Fig 2A</a>). The bars indicate the magnification of the individual figures; the lenses of the homozygous mutants are shown in an even higher magnification than the heterozygotes to demonstrate the pathological processes in more detail.</p

Primers for PCR.

<p>Primers for PCR.</p

Cataracts in <i>RCO015</i> mutant mice at the age of 5 weeks.

<p>a) Lenses of wild types, hetero- and homozygous <i>RCO015</i> mutants are prepared and photographed. The lenses of wild types are completely clear; the lenses of heterozygous mutants demonstrate opacities at the capsule, and in the homozygous mutants clear boundaries in the cortical areas are observed in addition to the nuclear opacity. The lenses of homozygous mutants are smaller (bar: 500 μm). b) Scheimpflug imaging of the same lenses as shown in a) demonstrates the clear lenses in wild types and heterozygotes; the opacity in the nuclear region of homozygous mutants is clearly visible above the slightly opaque background of the entire lens. c) The quantitative data of the lens density of the Scheimpflug images are given in a box-and-whisker plot; the whiskers give the 1^st and 3^rd quartiles, and the bar in the middle of the box indicates the median of the lens density.</p

Age-dependent differences in DNA damage after in vitro CT exposure

<p><b>Purpose:</b> Age dependent radiation sensitivity for DNA damage after in vitro blood exposure by computer tomography (CT) was investigated.</p> <p><b>Materials and methods:</b> Radiation biomarkers (dicentrics and gammaH2AX) in blood samples of newborns, children under five years and adults after sham exposure (0 mGy), low-dose (41 mGy) and high-dose (978 mGy) in vitro CT exposure were analyzed.</p> <p><b>Results:</b> Significantly higher levels of dicentric induction were found for the single and combined newborns/children group compared to adults, by a factor of 1.48 (95% CI 1.30–1.68), after exposure to 978 mGy. Although a significant dose response for damage induction and dose-dependent repair was found, the gammaH2AX assay did not show an age-dependent increase in DNA damage in newborns/children compared to adults. This was the case for the gammaH2AX levels after repair time intervals of 30 minutes and 24 hours, after correcting for the underlying background damage. For the low dose of 41 mGy, the power of the dicentric assay was also not sufficient to detect an age-dependent effect in the sample size investigated.</p> <p><b>Conclusion:</b> A 1.5-fold increased level of dicentric aberrations is detected in newborns and children under five years after 1 Gy radiation exposure.</p