Abstract
Objective: Prader-Willi (PWS) and Angelman syndromes (AS) are genomic imprinting diseases with intellectual disability. In approximately 70 % of the cases, there is a cytogenetic deletion involving the chromosome 15q11-q13 inherited from patient’s father (in PWS) and from patient’s mother (in AS). In approximately 20-25% and 3-7% of the cases, there is an uniparental disomy (UPD) of chromosome 15 in PWS and AS patients, respectively. The mutation ratio in AS patients is approximately 10 %, while the ratio is two percent in PWS patients. Methods: In the first step cytogenetic analyses were performed by using high resolution banding (HRB) for 20 patients who were selected by diagnostic criteria (11 pre-diagnosed with AS and 9 pre-diagnosed with PWS). Then, via Fluorescent in situ Hybridization (FISH) technique, SNRPN gene (small nuclear ribonucleoprotein polypeptide N gene) locus for PWS, D15S10 locus for AS were searched. Finally the uniparental disomy of chromosome 15 along with the mutation/deletion of imprinting center were examined. Results: HRB and FISH analyses revealed no deletion except in one AS patient whose D15S10 region was found deleted via FISH technique. Mutation/deletion of imprinting center analyses in all of them were evaluated as normal. Conclusion: As a result, by this project patients with PWS and AS, who were selected by the diagnostic criteria for each syndrome, were evaluated via conventional genetic and molecular genetics methods and they were offered with the efficient genetic counseling.
Highlights
Examination of two different probes which are specific to 15q11.2 locus, D15S10 probe for Angelman syndromes (AS) and small nuclear ribonucleoprotein polypeptide N (SNRPN gene probe) probe for Prader-Willi Syndrome (PWS), via Fluorescent in situ Hybridization (FISH) technique revealed only one deletion in a patient who is the fifteen-month pre-diagnosed with AS having significant developmental retardation, microcephalia, behavioral problems and especially lighter hair color according to other family members (Table 2, Figure 1)
As a result before being oriented to the other diseases whose clinical findings are concordant with AS and PWS, these well-known two microdeletion syndromes should be studied via with efficient, reliable, lowcost techniques
If in the result of tests that are performed; genetic modification that is concordant with AS and PWS is identified, genetic counseling in an appropriate way for each patient should be offered
Summary
The study was approved by Ethical Committee of Gazi University at 19th January 2009 (issue number 33). Diagnostic criteria for PWS and AS was used from National Center of Biotechnology Information (NCBI)- Online Mendelian Inheritance in Man (OMIM) database (6). From each patient (11 pre-diagnosed with AS and 9 pre-diagnosed with PWS) who carry defined diagnostic criteria, 10 ml blood sample was taken: 5ml for DNA isolation (in tubes with EDTA) and 5ml for acquiring chromosomes (in tubes with heparin). High Resolution Banding tissue culture has been preferred for conventional chromosome analysis because of targeted high resolution banding pattern (550 bands or more). High-quality 20 metaphase plaques from each patient were analyzed. The slides which were used in FISH technique had been obtained via tissue culture method. Interphase and metaphase plaques, whose details were explained below, were analyzed under microscope with fluorescence attachment
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