Sofia Kitsiou-Tzeli

Origin of nondisjunction in trisomy 8 and trisomy 8 mosaicism.

Causes of chromosomal nondisjunction is one of the remaining unanswered questions in human genetics. In order to increase our understanding of the mechanisms underlying nondisjunction we have performed a molecular study on trisomy 8 and trisomy 8 mosaicism. We report the results on analyses of 26 probands (and parents) using 19 microsatellite DNA markers mapping along the length of chromosome 8. The 26 cases represented 20 live births, four spontaneous abortions, and two prenatal diagnoses (CVS). The results of the nondisjunction studies show that 20 cases (13 maternal, 7 paternal) were probably due to mitotic (postzygotic) duplication as reduction to homozygosity of all informative markers was observed and as no third allele was ever detected. Only two cases from spontaneous abortions were due to maternal meiotic nondisjunction. In four cases we were not able to detect the extra chromosome due to a low level of mosaicism. These results are in contrast to the common autosomal trisomies (including mosaics), where the majority of cases are due to errors in maternal meiosis.

Diagnostic exome sequencing to elucidate the genetic basis of likely recessive disorders in consanguineous families.

Rare, atypical, and undiagnosed autosomal‐recessive disorders frequently occur in the offspring of consanguineous couples. Current routine diagnostic genetic tests fail to establish a diagnosis in many cases. We employed exome sequencing to identify the underlying molecular defects in patients with unresolved but putatively autosomal‐recessive disorders in consanguineous families and postulated that the pathogenic variants would reside within homozygous regions. Fifty consanguineous families participated in the study, with a wide spectrum of clinical phenotypes suggestive of autosomal‐recessive inheritance, but with no definitive molecular diagnosis. DNA samples from the patient(s), unaffected sibling(s), and the parents were genotyped with a 720K SNP array. Exome sequencing and array CGH (comparative genomic hybridization) were then performed on one affected individual per family. High‐confidence pathogenic variants were found in homozygosity in known disease‐causing genes in 18 families (36%) (one by array CGH and 17 by exome sequencing), accounting for the clinical phenotype in whole or in part. In the remainder of the families, no causative variant in a known pathogenic gene was identified. Our study shows that exome sequencing, in addition to being a powerful diagnostic tool, promises to rapidly expand our knowledge of rare genetic Mendelian disorders and can be used to establish more detailed causative links between mutant genotypes and clinical phenotypes.

Survivin regulation by HER2 through NF-κB and c-myc in irradiated breast cancer cells

Radiotherapy is an important treatment modality against cancer resulting in apoptosis and inhibition of cell growth. Survivin is an important cancer biomarker conferring to tumour cells increased survival potential by inhibiting apoptosis. In the present study, we investigated the implication of breast cancer cells features, as hormone receptors and p53 status, in the radio‐resistance of breast cancer cells and in the regulation of survivin’s expression by nuclear factor (NF)‐κB and c‐myc. Six breast cancer cell lines Michigan Cancer Foundation (MCF‐7), MCF‐7/Human Epidermal Growth Factor Receptor (HER)2, M. D. Anderson – Metastatic Breast (MDA‐MB‐231), SK‐BR‐3, BT‐474 and Human Breast Lactating (HBL‐100) were irradiated and cell viability as well as cell cycle distribution were evaluated by 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay and flow cytometry, respectively. Survivin mRNA and protein levels were evaluated by real time PCR and Western blot analysis. Survivin and HER2 gene knockdown was performed with siRNA technology and investigation of transcription factors binding to survivin and c‐myc gene promoters was assessed by chromatin immunoprecipitation. Student’s t‐test and F‐statistics were used for statistical evaluation. Our results demonstrated that only HER2+ breast cancer cells up‐regulated survivin upon irradiation, whereas HER2 knockdown in HER2+ cells led to survivin’s down‐regulation. Survivin and especially HER2 knockdown abolished the observed G2/M cell cycle checkpoint and reduced the radio‐resistance of HER2 overexpressing breast cancer cells. Additionally, HER2 was found to regulate survivin’s expression through NF‐κB and c‐myc transcription factors. This study revealed the significance of HER2 in the radio‐resistance of HER2+ breast cancer cells through induction of transcription factors NF‐κB and c‐myc, leading to activation of survivin, a downstream target oncogene preventing apoptosis.

Acute acalculous cholecystitis in children with Epstein–Barr virus infection: a role for Gilbert's syndrome?

Acute acalculous cholecystitis (AAC) in association with acute Epstein-Barr virus (EBV) infection has rarely been described in childhood. In the literature, there are only four reported pediatric cases of AAC associated with isolated primary EBV infection. We present two cases (one new, one retrospectively reviewed) of children with Gilberts syndrome (GS) who presented with AAC during the course of primary EBV infection. Antibiotics were not used and AAC subsided gradually as the infection regressed. The co-occurrence of GS might have played a contributory role in the pathogenesis of AAC during acute EBV infection.

Influence of Interleukin 1α (IL-1α), IL-4, and IL-6 Polymorphisms on Genetic Susceptibility to Chronic Osteomyelitis

ABSTRACT The association between cytokine gene polymorphisms and chronic osteomyelitis was investigated in order to determine whether genetic variability in cytokine genes predisposes to osteomyelitis susceptibility. Significant genotypic and allelic associations were observed between interleukin 1α (IL-1α) −889-C/T, IL-4 −1098-G/T and −590-C/T, and IL-6 −174-G/C polymorphisms and osteomyelitis in the Greek population, pointing towards their potential involvement in osteomyelitis pathogenesis.

Gilbert syndrome as a predisposing factor for cholelithiasis risk in the Greek adult population.

We investigated the hypothesis that coinheritance of the common A(TA)(n)TAA promoter mutation at the UGT1A1 locus associated with Gilbert syndrome is a risk factor for gallstone formation in a homogeneous adult population, by conducting a case-control study that included 198 adult patients with cholelithiasis and 152 healthy controls both of Greek origin. Three genotypes were found: 7/7 (17.8% in controls and 23.3% in patients), 6/7 (33.5% in controls and 46.5% in patients), and normal homozygous 6/6 (48.7% in controls and 30.3% in patients). The Gilbert UGT1A1 genotypes 6/7 and 7/7 show significant association (odds ratio 2.225, 95% confidence interval 1.373-3.605, p=0.001, and odds ratio 2.101, 95% confidence interval 1.171-3.770, p=0.013, respectively) with cholelithiasis risk. This association supports the theory that genetic factors are responsible for a fraction of symptomatic gallstone disease; however, further studies are required in different ethnic groups to fully elucidate the involvement of Gilbert syndrome in gallstone disease.

Characterization of a prenatally assessed de novo supernumerary minute ring chromosome 20 in a phenotypically normal male

BackgroundThe heterogeneous group of small supernumerary marker chromosomes (sSMCs) presents serious counseling problems, especially if they are present de novo and diagnosed prenatally. The incidence has been estimated at 1 in 1000 prenatal samples. We present a case of mosaic sSMC diagnosed prenatally after amniocentesis. The sSMC was characterized by various molecular cytogenetic techniques and determined to be a r(20) chromosome. After genetic counseling, the parents decided to continue the pregnancy, and a boy with minor phenotypic variants was born after 39 weeks of pregnancy. The case is compared with four other cases of prenatally detected r(20) mosaicism.ResultsHere we describe a 3 months old male child with normal pre- and postnatal development and with a de novo ring supernumerary marker chromosome in amniocytes cultures. Using new fluorescence in situ hybridization (FISH) techniques, three distinguishable sSMCs (cryptic mosaicism), all derived from chromosome 20, were observed, including ring and minute chromosomes. This heterogeneity was impossible to detect by the conventional G-banding technique or conventional FISH technique that were used before the application of new FISH techniques (subcentromere-specific multicolor-FISH [subcenM-FISH]) and a probe, specific for the 20p12.2 band. The sSMC present in 25% of the cells was present as r(20)(::p12.2~12.3->q11.1::)[5]/r(20;20)(::p12.1->q11.1::q11.1 >p12.1::)[2]/min(20;20)(:p12.1->q11.1::q11.1->p12.1:)[1]. The final karyotype was 47,XY,+r(20)[25%]/46,XY[75%].ConclusionWe emphasize the importance of application of molecular cytogenetics in a prenatally diagnostic laboratory and description of more cases to enable a better genetic counseling and risk evaluation.

Maternal epigenetics and fetal and neonatal growth

Purpose of review The article provides an update on new insights of factors altering inherited maternal epigenome that ultimately affect fetal and neonatal growth. Recent findings A number of new publications have identified mechanisms through which maternal nutrition, environmental exposures such as stress and toxic substances altering expression of imprinted genes during pregnancy can influence fetal and neonatal phenotype and susceptibility to disease development later in life. The possible causes of metabolic syndrome by in-utero epigenetic alterations of genes involved in energy metabolism (PPAR&ggr; and PPAR&agr;), microRNAs, arginine methyltransferases, lysine demethylases, and histone deacetylaces have been elucidated. Moreover associations between methylation of key genes (NRC31, HSD11&bgr;1/2, GFI1) involved in the hypothalamic-pituitary-adrenal axis have been identified. Alcohol exposure during pregnancy was found to alter methylation patterns of several imprinted genes (H19, SLC22A18, SLC6A3, DRD4). Finally alterations in vulnerable epigenetic marks of imprinted genes such as H19/IGF2, during early stages of embryonic development result in intrauterine growth restriction. Summary All these investigations continue to provide new insights for improved clinical management of in-utero development.

Microduplication 3q13.2q13.31 identified in a male with dysmorphic features and multiple congenital anomalies

Constitutional microdeletions affecting 3q13.2q13.31 are rare and attempts for genotype–phenotype correlations have only recently been made in a cohort of 28 patients. The major phenotypic features of this rare syndrome are hypotonia, developmental delay, and facial anomalies. In this study, we report on a male infant with a novel reciprocal 3.671 Mb microduplication at the genomic region 3q13.2q13.31 associated with dysmorphic features and multiple congenital anomalies. The current patient was investigated by high‐resolution array comparative genomic hybridization (aCGH). This is the first report of a microduplication 3q13.2q13.31 that shares a lot of common clinical features with those carrying the microdeletion. The 3q13.2q13.31 duplicated region in our patient contains nine dosage sensitive genes, amongst them the genes ATG3, CCDC80, KIAA2018, NAA50, ZDHHC23, DRD3, ZBTB20, GAP43, LSAMP. As it is the case for many other well‐described reciprocal deletion/duplication syndromes, some have very different clinical features (Williams–Beuren deletion syndrome, WBS/WBS triplication) [Somerville et al. (2005); N Engl J Med 353:1694–1701], while others share similar phenotypic features (22q11.2 microdeletion/microduplication) [Portnoi (2009); Eur J Med Genet 52:88–93]. In conclusion, we describe the main phenotypic features of a possibly novel microduplication 3q13.2q13.31 syndrome. Additionally five of the dosage‐sensitive genes and BOC gene are suggested to be responsible for the main phenotypic features. Evaluation of multiple patients with the microduplication is needed for full delineation of this syndrome.

Genomic screening of ABCA4 and array CGH analysis underline the genetic variability of Greek patients with inherited retinal diseases.

Background Retinal dystrophies are a clinically and genetically heterogeneous group of disorders which affect more than two million people worldwide. The present study focused on the role of the ABCA4 gene in the pathogenesis of hereditary retinal dystrophies (autosomal recessive Stargardt disease, autosomal recessive cone-rod dystrophy, and autosomal recessive retinitis pigmentosa) in patients of Greek origin. Materials and methods Our cohort included 26 unrelated patients and their first degree healthy relatives. The ABCA4 mutation screening involved Sanger sequencing of all exons and flanking regions. Evaluation of novel variants included sequencing of control samples, family segregation analysis and characterization by in silico prediction tools. Twenty five patients were also screened for copy number variations by array-comparative genomic hybridization. Results Excluding known disease-causing mutations and polymorphisms, two novel variants were identified in coding and non-coding regions of ABCA4. Array-CGH analysis revealed two partial deletions of USH2A and MYO3A in two patients with nonsyndromic autosomal recessive retinitis pigmentosa. Conclusions The ABCA4 mutation spectrum in Greek patients differs from other populations. Bioinformatic tools, segregation analysis along with clinical data from the patients seemed to be crucial for the evaluation of genetic variants and particularly for the discrimination between causative and non-causative variants.