[Application of molecular genetics in microdeletion syndromes: report of the results of 21 FISH tests for Williams Beuren syndrome 3rd part of microdeletion project]

Twenty one FISH tests for confirmation of Williams Beuren Syndrome [19 Peripheral blood, and two amniotic cells cultures] have been performed. FISH tests in four couples with one affected child of Williams Syndrome are negative for abnormal critical segment of del [7p11-23], which indicates that the deletion in the affected children is of de novo origin. There are two negative FISH tests out of 8 candidates suspected for WS. One is positive for Prader-Willi Syndrome, the other one is negative for WS, so far. One negative FISH test out of 8 indicates the importance of FISH test in detection of microdeletion disease, especially in Williams Beuren Syndrome

[Application of molecular genetics in microdeletion diseases: report of the results 41 FISH tests for critical region segment of deletion 15q11-13 [Prader-Willi / Angelman syndrome]]

In spite of tiny deletion of chromosomal segment in microdeletion diseases the affected individual represents severe clinical manifestation. The classical cytogenetic techniques including high resolution are unable to clarify the deleted segment. It is worthy performing FISH study for clinically suspected patients. The result of 39 blood samples and two amniotic fluid samples studied by FISH of peripheral blood [1-24 years old] and two amniotic fluid including: peripheral blood samples clinically suspected for Angelman syndrome, 15 cases for Prader-Willi syndrome and five children PB and two amniotic fluid for PWS/ AS syndrome are as follows: Seven samples of Angelman syndrome, three cases of Prader-Willi syndrome, and 2 cases of other samples totally, 12 of 40 [30%] were positive for deletion of critical segment 15 [q11-q13], confirming the clinical diagnosis. One blood sample for Angelman syndrome did not growth

[ role of FISH in prenatal diagnosis of chromosomal anomalies]

FLUORESCENT in situ hybridization has multiple applications in prenatal diagnosis. It can be used for the detection of common chromosome aneuploidies of chromosomes 13,18,21, X and Y it can be used for the early detection of segmental imbalances detected in former affected offspring or resulting from balanced translocations in the carrier parents. FISH is also a useful tool for ruling in/out of mosaicism detected in routine chromosomal study as it will provide a means of screening and scoring a larger number of cells than theoretically possible with routine chromosomal study. In this report we are presenting results of prenatal diagnosis cases where we have employed FISH techniques for direct analysis or for confirmation of results otherwise obtained. In a two year period 60 FISH tests have been performed on fetal samples. Forty five cases were tested for 5 common chromosomes ten of these cases were referred for advanced maternal age, 29 for abnormal marker screening test results, and 6 for history of former offspring with chromosome aneuploidy. The remaining cases were tested for other reasons including 4 for microdeletion syndromes previously detected in other offspring, 4 for mosaicism suspected in routine chromosomal study, and 7 for possible imbalance resulting from known chromosome translocation in either parent. In all cases, the results were confirmed with another technique, most often the results of routine chromosomal study and in microdeletion cases, reanalysis on metaphases prepared from cultured cells. There was 100% correlation between the results obtained from the two techniques. Our experience shows that this technique has the advantage of a speedy result with considerable reliability for use in the detection of specific cases. We recommend the application of FISH for all high risk pregnancies

Cytogenetic analysis of 358 bone marrow samples of suspected Acute Lymphoblastic Leukemia patients

Acute Lymphoblastic leukemia [ALL] is characterized by the accumulation of malignant, immature lymphoid cells in the bone marrow and in most cases also in peripheral blood. The disease is much more common in children than in older age group, with the incidence peaking around 3-5 years of age. Initial cytogenetic studies showed chromosomal aberrations in approximately half of all patients with ALL. Later studies and the combined use of FISH and molecular techniques have shown that the rates of detected chromosomal aberrations are 70% to 80% in these patients. The rates of detection in ALL have never been reported in Iran and we are reporting our cytogenetic findings in 358 ALL cases. We evaluated the karyotypes of 358 [21%] bone marrow samples sent to our center for cytogenetic study from patients with probable clinical diagnosis of ALL. All samples were submitted to a cell count and cultures were set up accordingly using standard protocols. Chromosomal aberrations were detected in 155 [49%] out of 314 successful cultures and the remaining 159 [51%] showed normal karyotypes. Hyperdiploidy in two forms of moderate and massive was the most common chromosomal aberration, found in 63 [40%] cases, followed by 14q abnormality in 13 [8%] and deletion of long arm of chromosome 6 in 9 [6%] of the cases. The ratios of detected numerical and structural chromosomal changes are close to and comparable with various series studies based on banding cytogenetic techniques alone. We believe that the implementation of complementary FISH and molecular cytogenetic techniques, and closer communication with the referring physicians are extremely instrumental in improving the effectiveness of cytogenetics study