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Abstract Background Environmental risk factors have been shown to alter DNA copy number variations (CNVs). Recently, CNVs have been described to arise after low-dose ionizing radiation in vitro and in vivo. Development of cost- and size-effective laser-driven electron accelerators (LDEAs), capable to deliver high energy beams in pico- or femtosecond durations requires examination of their biological effects. Here we studied in vitro impact of LDEAs radiation on known CNV hotspots in human peripheral blood lymphocytes on single cell level. Results Here CNVs in chromosomal regions 1p31.1, 7q11.22, 9q21.3, 10q21.1 and 16q23.1 earlier reported to be sensitive to ionizing radiation were analyzed using molecular cytogenetics. Irradiation of cells with 0.5, 1.5 and 3.0 Gy significantly increased signal intensities in all analyzed chromosomal regions compared to controls. The latter is suggested to be due to radiation-induced duplication or amplification of CNV stretches. As significantly lower gains in mean fluorescence intensities were observed only for chromosomal locus 1p31.1 (after irradiation with 3.0 Gy variant sensitivites of different loci to LDEA is suggested. Negative correlation was found between fluorescence intensities and chromosome size (r = − 0.783, p

Abstract Background Copy number variants (CNVs) are the genetic bases for microdeletion/ microduplication syndromes (MMSs). Couples with an affected child and desire to have further children are routinely tested for a potential parental origin of a specific CNV either by molecular karyotyping or by two color fluorescence in situ hybridization (FISH), yet. In the latter case a critical region probe (CRP) is combined with a control probe for identification of the chromosome in question. However, CNVs can arise also due to other reasons, like a recombination-event based on a submicroscopic, cryptic inversion in one of the parents. Results Seventy-four patients with different MMSs and overall 81 CNVs were studied here by a novel three color FISH approach. The way how three locus-specific probes are selected (one is the CRP and two are flanking it in a distance of 5-10 Mb) enables to detect or exclude two possible parental conditions as origins of the CNV seen in the index: (i) direct parental origin of the CNV (deletion or duplication) or (ii) a parental cryptic inversion. Thus, for overall 51/81 CNVs (63%) a parental origin could be determined. 36/51 (70.5%) inherited the CNV directly from one of the parents, but 15/51 (29.5%) were due to an exclusively by three color FISH detectable parental inversion. A 2:1 ratio of maternal versus paternal inheritance was found. Also almost two times more male than female were among the index patients. Conclusion The new, here suggested three color FISH approach is suited for more comprehensive parental studies of patients with MMS. The detection rate for parental origin was increased by 140% in this study. Still, for 30/81 cases (37%) no reason for the ‘de novo’ MMS in the affected index patient could be found by the here suggested FISH-probe set.