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Objective/material and method: cryptic chromosomal imbalances contribute significantly to the etiology of multiple congenital anomalies with or without mental retardation (MCA/MR). Current approaches in prenatal diagnosis include targeted high resolution analyses by MLPA and some microarray platforms or a genomewide screening at maximal resolution using oligonucleotide or SNP arrays. The major disadvantages of the latter approach are cost and the inadvertent detection of copy number variation of unknown clinical significance. In this prospective work, fetal DNA samples from 66 fetuses who had pathological antenatal ultrasonography findings with normal karyotype and Multiprobe T-FISH results were tested using commercially available targeted MLPA probe-sets to compare the efficacy and the impact of MLPA testing at prenatal setting. Results: three submicroscopic deletions (3.66; 4.5%) were detected in the cohort. Two of them were de novo deletions, 18ptel and 7q11.23. The third finding was a 75 kb duplication at 18q, which was maternally inherited and probably a benign copy number variation unrelated to the pathological ultarsonography findings. Conclusion: the observed detection rate by MLPA testing can be considered within the expected range. Furthermore, benign copy number variation was identified with the targeted diagnostic approach as an unexpected finding. This study shows that MLPA is a practical and cost-effective technique to investigate submicroscobic chromosomal aberrations in fetuses., İstanbul Üniversitesi Araştırma Fonu

BACKGROUND Poikiloderma is defined as a chronic skin condition presenting with a combination of punctate atrophy, areas of depigmentation, hyperpigmentation and telangiectasia. In a variety of hereditary syndromes such as Rothmund-Thomson syndrome (RTS), Clericuzio-type poikiloderma with neutropenia (PN) and Dyskeratosis Congenita (DC), poikiloderma occurs as one of the main symptoms. Here, we report on genotype and phenotype data of a cohort of 44 index patients with RTS or related genodermatoses. METHODS DNA samples from 43 patients were screened for variants in the 21 exons of the RECQL4 gene using PCR, SSCP-PAGE analysis and/or Sanger sequencing. Patients with only one or no detectable mutation in the RECQL4 gene were additionally tested for variants in the 8 exons of the USB1 (C16orf57) gene by Sanger sequencing. The effect of novel variants was evaluated by phylogenic studies, single-nucleotide polymorphism (SNP) databases and in silico analyses. RESULTS We identified 23 different RECQL4 mutations including 10 novel and one homozygous novel USB1 (C16orf57) mutation in a patient with PN. Moreover, we describe 31 RECQL4 and 8 USB1 sequence variants, four of them being novel intronic RECQL4 sequence changes that may have some deleterious effects on splicing mechanisms and need further evaluation by transcript analyses. CONCLUSION The current study contributes to the improvement of genetic diagnostic strategies and interpretation in RTS and PN that is relevant in order to assess the patients' cancer risk, to avoid continuous and inconclusive clinical evaluations and to clarify the recurrence risk in the families. Additionally, it shows that the phenotype of more than 50% of the patients with suspected Rothmund-Thomson disease may be due to mutations in other genes raising the need for further extended genetic analyses.