Chromosomal instability in patients with Fanconi anemia from Serbia.

BACKGROUND/AIM: Fanconi anemia (FA) is a rare hereditary disease in a heterogeneous group of syndromes, so-called chromosome breakage disorders. Specific hypersensitivity of its cells to chemical agents, such as diepoxybutane (DEB), was used as a part of screening among patients with clinical suspicion of FA. The aim of this study was to determine chromosomal instability in patients with FA symptoms in Serbia. METHODS: A total of 70 patients with phenotypic symptoms of FA, diagnosed at the Mother and Child Health Care Institute of Serbia "Dr Vukan Cupic, Belgrade and University Children's Hospital, Belgrade from February 2004 to September 2011, were included in this study. Cytogenetic instability analysis was performed on untreated and DEB-treated 72 h-cultures of peripheral blood. RESULTS: Ten patients in the group of 70 suspected of FA, showed increased DEB induced chromosome breakage and were classified into the FA group. The range of DEB induced aberrant cells percentages in the FA group was from 32% to 82%. DEB sensitivity of 58 tested patients were bellow FA values (range: 0-6%) (non-FA group), with no overlapping. The remaining two patients showed borderline sensitivity (borderline FA group - FA*), comparing to the healthy controls. CONCLUSION: This study revealed 10 patients with FA on the basis of cytogenetic analysis of DEB induced chromosome aberrations. Our results are in consistency with those from the literature. Early and precise diagnosis of FA is very important in further treatment of these patients, considering its cancer prone and lethal effects.

Radiation-induced mitotic catastrophe in FANCD2 primary fibroblasts.

PURPOSE: As the Fanconi anemia (FA) pathway is required for appropriate cell cycle progression through mitosis and the completion of cell division, the aim of the present study was to determine the destiny of FA cells after irradiation in vitro and to elucidate any difference in radiosensitivity between FA and control cells. MATERIALS AND METHODS: Analyses of phosphorylated histone H2AX (γ-H2AX) foci, micronuclei formation and cell cycle analysis were performed in unirradiated (0 min) and irradiated primary FA fibroblasts and in a control group at different post-irradiation times (30 min, 2 h, 5 h and 24 h). RESULTS: The accumulation of γ-H2AX foci in irradiated FA fibroblasts was observed. At 24 h post-irradiation, 57% of FA cells were γ-H2AX foci-positive, significantly higher than in the control (p < 0.01). The cell cycle analysis has shown the transient G2/M arrest in irradiated FA fibroblasts. The portion of cells in the G2/M phase showed initial increase at 30 min post-irradiation and afterwards decreased over time reaching the pretreatment level 24 h after irradiation. Irradiated FA fibroblasts progressed to abnormal mitosis, as is shown by the production of cells with different nuclear morphologies from binucleated to multinucleated surrounded with micronuclei, and also by a high percentage of foci-positive micronuclei. The majority of radiation-induced micronuclei were γ-H2AX foci-positive, indicating that radiation-induced micronuclei contain fragments of damaged chromosomes. In contrast, in the control group, most of the micronuclei were classified as γ-H2AX foci-negative, which indicates that cells with unrepaired damage were blocked before entering mitosis. CONCLUSION: The results clearly indicate that mitotic catastrophe might be an important cell-death mechanism involved in the response of FA fibroblasts to ionizing radiation.

Ten years of experience in molecular prenatal diagnosis and carrier testing for spinal muscular atrophy among families from Serbia.

OBJECTIVE: To describe 10 years of experience of prenatal analysis of spinal muscular atrophy (SMA). METHODS: Data were retrospectively evaluated from prenatal analysis and carrier screening among parents and close relatives between January 2003 and December 2012. Screening was done before the parents were offered prenatal diagnosis. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) were used to detect the most frequent homozygous deletions in the SMN1 gene in fetal samples. A commercial MLPA kit (SALSA P060) was used to analyze SMN1 copy number for carrier status determination among healthy individuals. Bayesian calculation was used to accurately assess the risk of having a child affected with SMA. RESULTS: During the study period, 66 fetal samples from 44 Serbian families were analyzed, and 13 (19.7%) showed a homozygous deletion in the SMN1 gene. Among 28 healthy individuals, carrier status was confirmed for 16 (57.1%). For 7 couples, quantitative analyses and Bayesian calculation reduced the final risk of having a child with SMA from 1 in 200 to 1 in 2448. CONCLUSION: Owing to disease severity and lack of a curative treatment, prenatal diagnosis of SMA is the best way to prevent recurrence. Carrier detection allows accurate risk assessment and appropriate genetic counseling for all family members.

Complex small supernumerary marker chromosomes - an update.

BACKGROUND: Complex small supernumerary marker chromosomes (sSMC) constitute one of the smallest subgroups of sSMC in general. Complex sSMC consist of chromosomal material derived from more than one chromosome; the best known representative of this group is the derivative chromosome 22 {der(22)t(11;22)} or Emanuel syndrome. In 2008 we speculated that complex sSMC could be part of an underestimated entity. RESULTS: Here, the overall yet reported 412 complex sSMC are summarized. They constitute 8.4% of all yet in detail characterized sSMC cases. The majority of the complex sSMC is contributed by patients suffering from Emanuel syndrome (82%). Besides there are a der(22)t(8;22)(q24.1;q11.1) and a der(13)t(13;18)(q11;p11.21) or der(21)t(18;21)(p11.21;q11.1) = der(13 or 21)t(13 or 21;18) syndrome. The latter two represent another 2.6% and 2.2% of the complex sSMC-cases, respectively. The large majority of complex sSMC has a centric minute shape and derives from an acrocentric chromosome. Nonetheless, complex sSMC can involve material from each chromosomal origin. Most complex sSMC are inherited form a balanced translocation in one parent and are non-mosaic. Interestingly, there are hot spots for the chromosomal breakpoints involved. CONCLUSIONS: Complex sSMC need to be considered in diagnostics, especially in non-mosaic, centric minute shaped sSMC. As yet three complex-sSMC-associated syndromes are identified. As recurrent breakpoints in the complex sSMC were characterized, it is to be expected that more syndromes are identified in this subgroup of sSMC. Overall, complex sSMC emphasize once more the importance of detailed cytogenetic analyses, especially in patients with idiopathic mental retardation.

Combined NGS approaches identify mutations in the intraflagellar transport gene IFT140 in skeletal ciliopathies with early progressive kidney Disease.

Ciliopathies are genetically heterogeneous disorders characterized by variable expressivity and overlaps between different disease entities. This is exemplified by the short rib-polydactyly syndromes, Jeune, Sensenbrenner, and Mainzer-Saldino chondrodysplasia syndromes. These three syndromes are frequently caused by mutations in intraflagellar transport (IFT) genes affecting the primary cilia, which play a crucial role in skeletal and chondral development. Here, we identified mutations in IFT140, an IFT complex A gene, in five Jeune asphyxiating thoracic dystrophy (JATD) and two Mainzer-Saldino syndrome (MSS) families, by screening a cohort of 66 JATD/MSS patients using whole exome sequencing and targeted resequencing of a customized ciliopathy gene panel. We also found an enrichment of rare IFT140 alleles in JATD compared with nonciliopathy diseases, implying putative modifier effects for certain alleles. IFT140 patients presented with mild chest narrowing, but all had end-stage renal failure under 13 years of age and retinal dystrophy when examined for ocular dysfunction. This is consistent with the severe cystic phenotype of Ift140 conditional knockout mice, and the higher level of Ift140 expression in kidney and retina compared with the skeleton at E15.5 in the mouse. IFT140 is therefore a major cause of cono-renal syndromes (JATD and MSS). The present study strengthens the rationale for IFT140 screening in skeletal ciliopathy spectrum patients that have kidney disease and/or retinal dystrophy.

Newborn screening for cystic fibrosis in Serbia: a pilot study.

BACKGROUND: We performed a pilot study of neonatal screening for cystic fibrosis (CF) in order to introduce it to the national screening program in Serbia. METHODS: Immunoreactive trypsinogen (IRT) concentrations were analyzed in dried blood spot samples. Patients were recalled for repeated measurements in case of high IRT levels. Persisting high IRT levels resulted in DNA testing for the 29 most common mutations in the CF transmembrane regulator (CFTR) gene (IRT/IRT/DNA method). Sweat chloride measurements and clinical assessment were further performed for newly diagnosed patients. RESULTS: Of 1000 samples, three were initially positive and were further analyzed for the presence of the most common CFTR mutations in the Serbian population. DNA analysis revealed two patients being homozygous for F508del mutation. One sample was false positive, as the genetic test proved to be negative and associated with normal sweat chloride concentration and unremarkable clinical presentation. CONCLUSIONS: The results of our pilot study justified the expanding of the routine neonatal screening program in Serbia with CF. Data could be used in future in order to obtain accurate incidence of CF and carrier prevalence in our country.

Dysfunctional telomeres in primary cells from Fanconi anemia FANCD2 patients.

BACKGROUND: Fanconi anemia (FA) is characterized by sensitivity to DNA cross-linking agents, mild cellular, and marked clinical radio sensitivity. In this study we investigated telomeric abnormalities of non-immortalized primary cells (lymphocytes and fibroblasts) derived from FA patients of the FA-D2 complementation group, which provides a more accurate physiological assessment than is possible with transformed cells or animal models. RESULTS: We analyzed telomere length, telomere dysfunction-induced foci (TIFs), sister chromatid exchanges (SCE), telomere sister chromatid exchanges (T-SCE), apoptosis and expression of shelterin components TRF1 and TRF2. FANCD2 lymphocytes exhibited multiple types of telomeric abnormalities, including premature telomere shortening, increase in telomeric recombination and aberrant telomeric structures ranging from fragile to long-string extended telomeres. The baseline incidence of SCE in FANCD2 lymphocytes was reduced when compared to control, but in response to diepoxybutane (DEB) the 2-fold higher rate of SCE was observed. In contrast, control lymphocytes showed decreased SCE incidence in response to DEB treatment. FANCD2 fibroblasts revealed a high percentage of TIFs, decreased expression of TRF1 and invariable expression of TRF2. The percentage of TIFs inversely correlated with telomere length, emphasizing that telomere shortening is the major reason for the loss of telomere capping function. Upon irradiation, a significant decrease of TIFs was observed at all recovery times. Surprisingly, a considerable percentage of TIF positive cells disappeared at the same time when incidence of γ-H2AX foci was maximal. Both FANCD2 leucocytes and fibroblasts appeared to die spontaneously at higher rate than control. This trend was more evident upon irradiation; the percentage of leucocytes underwent apoptosis was 2.59- fold higher than that in control, while fibroblasts exhibited a 2- h delay before entering apoptosis. CONCLUSION: The results of our study showed that primary cells originating from FA-D2 patients display shorten telomeres, elevated incidence of T-SCEs and high frequency of TIFs. Disappearance of TIFs in early response to irradiation represent distinctive feature of FANCD2 cells that should be examined further.

Monitoring of pediatric patients with malignant hematological diseases after allogeneic HSCT: Serbian experience.

We describe the implementation of short tandem repeats-polymerase chain reaction (STR-PCR) chimerism analyses coupled with reverse transcription PCR detection of recurrent translocations characteristic for childhood leukemia in monitoring of patients after allogeneic hematopoietic stem cell transplantation in Serbia and the first clinical results thereof. Chimerism and minimal residual disease were regularly analyzed from blood and marrow samples of 26 pediatric patients taken after stem cell transplantation with a median follow-up of 17.6 months. Our results demonstrate that STR-based chimerism monitoring is sufficient in establishing the origin of engrafted cells after transplantation and in detecting graft rejection, but more specific and more sensitive method is necessary for identifying patients with threatening leukemia relapse.

Lower incidence of deletions in the survival of motor neuron gene and the neuronal apoptosis inhibitory protein gene in children with spinal muscular atrophy from Serbia.

Spinal muscular atrophy (SMA) is the second most frequent autosomal recessive disease characterized by degeneration of the anterior horn cells of the spinal cord, leading to muscular atrophy. SMA is classified into three types according to disease severity and age-onset: severe (type I), intermediate (type II) and mild (type III). Deletions in the survival motor neuron (SMN) gene, located in the chromosome region 5q11.2- 5q13.3, are major determinants of SMA phenotype. Extended deletions that include the neuronal apoptosis inhibitory protein (NAIP) gene may correlate with the severtity of SMA. SMN gene is present in two highly homologous copies, SMN1 and SMN2, but only deletions of the SMN1 gene (exons 7 and 8 or exon 7) are responsible for clinical manifestations of SMA. Here, we present the deletion profiling of SMN1 and NAIP genes in 89 children with SMA from Serbia: 52 patients with type I, 26 with type II, and 11 with type III. The homozygous deletion of the SMN1 gene was confirmed in 72 of 89 (81%) patients, being the most frequent in SMA type I (48/52): 68 patients (94.4%) with deletion of exons 7 and 8 and 4 patients (5.6%) with deletion of exon 7. The extended deletion including the NAIP gene was detected in 18 of 89 (20.2%) patients, mostly affected with type I. This study has revealed the lower incidence of deletions in the SMN1 and NAIP genes in families with SMA in Serbia and will provide important information for genetic counselling in these families.

Gender-related differences in the oxidant state of cells in Fanconi anemia heterozygotes.

Abstract Fanconi anemia (FA) is a rare cancer-prone genetic disorder characterized by progressive bone marrow failure, chromosomal instability and redox abnormalities. There is much biochemical and genetic data, which strongly suggest that FA cells experience increased oxidative stress. The present study was designed to elucidate if differences in oxidant state exist between control, idiopathic bone marrow failure (idBMF) and FA cells, and to analyze oxidant state of cells in FA heterozygous carriers as well. The results of the present study confirm an in vivo prooxidant state of FA cells and clearly indicate that FA patients can be distinguished from idBMF patients based on the oxidant state of cells. Female carriers of FA mutation also exhibited hallmarks of an in vivo prooxidant state behaving in a similar manner as FA patients. On the other hand, the oxidant state of cells in FA male carriers and idBMF families failed to show any significant difference vs. controls. We demonstrate that the altered oxidant state influences susceptibility of cells to apoptosis in both FA patients and female carriers. The results highlight the need for further research of the possible role of mitochondrial inheritance in the pathogenesis of FA.

Fanconi anemia is characterized by delayed repair kinetics of DNA double-strand breaks.

Among patients with bone marrow failure (BMF) syndrome, some are happened to have underlying Fanconi anemia (FA), a genetically heterogeneous disease, which is characterized by progressive pancytopenia and cancer susceptibility. Due to heterogeneous nature of the disease, a single genetic test, as in vitro response to DNA cross-linking agents, usually is not enough to make correct diagnosis. The aim of this study was to evaluate whether measuring repair kinetics of radiation-induced DNA double-strand breaks (DSBs) can distinguish Fanconi anemia from other BMF patients. An early step in repair of DSBs is phosphorylation of the histone H2AX, generating gamma-H2AX histone, which extends over mega base-pair regions of DNA from the break site and is visualised as foci (gamma-H2AX foci) with specific antibodies. The primary fibroblasts, established from FA patients, were exposed to gamma-rays, a dose of 2 Gy ((60)Co), incubated for up to 24 hours under repair-permissive conditions, and assayed for the level of gamma-H2AX foci and apoptosis at different recovery times after the treatment. Cell lines originating from FA patients displayed a significant delay in the repair of radiation-induced DNA DSBs relative to non-FA bone marrow failure (non-FA BMF) and control cell lines. The delay is especially evident at recovery time of 24 hours, and is seen as about 8-fold increase of residual gamma-H2AX foci compared to self-state before irradiation. The delay in repair kinetics of FA cells represents the unique feature of FA cellular phenotype, which should be exploited to distinguish FA cellular phenotype.

A complex rearrangement involving cryptic deletion of ETV6 and CDKN1B genes in a case of childhood acute lymphoblastic leukemia.

We report on a case of childhood B-cell lineage acute lymphoblastic leukemia (ALL). Conventional cytogenetic analysis at diagnosis showed the karyotype: 47,XY,add(3)(q?),-12,+2mar[4]/46,XY[18]. Fluorescence in situ hybridization (FISH) revealed a complex rearrangement: 47,XY,der(3)(3pter->3q29::12q13->12q24.33::12p13.31->12p13.2::12q24.33->12qter),der(12)(12pter->12p13.31::12p12.3->12q12::3q29->3qter),+del(21)(q?). The derivative chromosome 3 arose likely from multiple events due to clonal evolution. After insertion of the segment of the short arm of the chromosome 12 to the distal part of the long arm of chromosome 12 [ins(12)(q24.33p13.31p13.2)], a translocation occurred between chromosome 3 and derivative chromosome 12. Additional FISH results disclosed two heterozygous deletions flanking the translocated region on both 12p13.2 approximately p12.3 and 12q12 approximately q13.13. The deleted segment on 12p contains several genes, among the tumor suppressor genes ETV6 and CDKN1B, which are frequently involved in 12p abnormalities in childhood ALL. Thus, the present study documents the loss of both ETV6 and CDKN1B genes accompanying the occurrence of a complex rearrangement involving chromosomes 3 and 12 in a case of childhood ALL.

Deletion and duplication screening in the DMD gene using MLPA.

We have designed a multiplex ligation-dependent probe amplification (MLPA) assay to simultaneously screen all 79 DMD gene exons for deletions and duplications in Duchenne and Becker muscular dystrophy (DMD/BMD) patients. We validated the assay by screening 123 unrelated patients from Serbia and Montenegro already screened using multiplex PCR. MLPA screening confirmed the presence of all previously detected deletions. In addition, we detected seven new deletions, nine duplications, one point mutation, and we were able to precisely determine the extent of all rearrangements. To facilitate MLPA-based screening in laboratories lacking specific equipment, we designed the assay such that it can also be performed using agarose gel analysis and ethidium bromide staining. The MLPA assay as described provides a simple and cheap method for deletion and duplication screening in DMD/BMD patients. The assay outperforms the Beggs and Chamberlain multiplex-PCR test, and should be considered as the method of choice for an initial DNA analysis of DMD/BMD patients.

Spectrum of cystic fibrosis mutations in Serbia and Montenegro and strategy for prenatal diagnosis.

We have screened 175 patients for molecular defects in the cystic fibrosis transmembrane conductance regulator (CFTR) gene using nondenaturing polyacrylamide gel electrophoresis (PAGE), denaturing gradient gel electrophoresis (DGGE), and sequencing. Six different mutations (F508del, G542X, 621+1G --> T, 2789+5G --> A, R1070Q, and S466X) accounted for 79.71% of CF alleles, with the F508del mutation showing a frequency of 72.28%. Another 12 mutations (R334W, 2184insA, I507del, 1525-1G --> A, E585X, R75X, M1I, 457TAT --> G, 574delA, 2723delTT, A120T, and 2907delTT) covered an additional 3.36%. A novel mutation (2723delTT) was found in one CF patient (F508del/2723delTT). Thus, a total of 18 mutations cover 82.57% of CF alleles. During our study, 72% of families at risk for having a CF child were found to be fully informative for prenatal diagnosis. Prenatal diagnosis was performed on 56 families; 76 analyses resulting in 16 affected, 38 carriers, and 22 healthy fetuses. These results imply that the molecular basis of CF in Serbia and Montenegro is highly heterogeneous, as is observed in other eastern and southern European populations. Because we detected more then 80% of CFTR alleles, results could be used for planning future screening and appropriate genetic counseling programs in our country.