Ferda Emriye PERÇİN, Meral KARAOĞUZ YİRMİBEŞ, Kıvılcım GÜCÜYENER, Ayşegül KAYMAK ÖZTÜRK

Konvansiyonel Genetik ve Moleküler Genetik Analizler ile Genomik Damgalama Hastalıklarının Tanısı

Amaç: Prader-Willi (PWS) and Angelman sendromu (AS) entelektüel yetersizlik ile seyreden genomik damgalama hastalıklarındandır. Olguların yaklaşık %70'inde PWS'nda babadan kalıtılan, AS'nda anneden kalıtılan 15q11-q13 bölgesinde delesyon mevcuttur. PWS'nda %20-25, Angelman sendromunda ise %3-7 kromozom 15'in uniparental dizomisi (UPD) vardır. Mutasyon oranları ise AS'nda %10 iken Prader-willi sendromunda %2'dir. Yöntem: İlk aşamada tanımlama kriterlerine göre seçilmiş 11 AS, 9 PWS ön tanılı 20 olgunun yüksek rezolüsyonlu bantlama (HRB) tekniği kullanılarak sitogenetik analizleri yapılmıştır. Sonra PWS için SNRPN gen (small nuclear ribonucleoprotein polypeptide N) loküsü, AS için D15S10 loküsü Floresan in situ Hibridizasyon (FISH) tekniği ile araştırılmıştır. En son aşamada ise 15. kromozomun UPD'si ve imprinting merkezinin mutasyonları araştırılmıştır. Bulgular: FISH ile delesyonu tespit edilen bir AS hastası hariç, tüm hastaların HRB ve FISH analizlerinde herhangi bir delesyon saptanmamıştır. Tüm hastaların imprinting merkezinin mutasyon/delesyon çalışmaları da nomal bulunmuştur. Sonuç: Sonuç olarak tanımlama kriterlerine göre PWS ve AS düşünülen hastalar konvansiyonel genetik ve moleküler genetik yöntemler ile araştırılmış ve elde edilen sonuçlar ışığında genetik danışmanlık almışlardır.

Diagnosis of the Genomic Imprinting Diseases by the Usage of Conventional and Molecular Analyses

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.

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1. Clayton-Smith J, Pembrey ME. Angelman syndrome. J Med Genet 1992;29:412-5.
2. Williams CA, Beaudet AL, Clyton-Smith J, Knoll JH, Kyllerman M, Laan LA, et al. Angelman Syndrome 2005. Am J Med Genet 2006;140A:413-8
3. Williams CA, Lossie A, Driscoll D, Philips Unit RC. Angelman syndrome: mimicking conditions and phenotypes. Am J Med Genet 2001;101:59-64.
4. Angelman H, 'Puppet children': a report of three cases. Dev Med Child Neurol 1965;7:681-8.
5. Cassidy SB, Discroll DJ. Prader Willi Syndrome. Eur J Hum Genet 2009;17:3-13
6. National Center of Biotechnology Information (NCBI)- Online Mendelian Inheritance in Man (OMIM) database
7. Ensemble Database
8. Yis U, Giray O, Kurul SH, Bora E, Ulgenalp A, Erçal D, et al. Longstanding fever and Angelman syndrome:Report of two cases. Journal of Paediatrics and Child Health. 2008;44: 308-10.
9. Stevenson DA, Anaya TM, Clayton-Smith J, Hall BD, Van Allen MI, Zori RT, et al. Unexpected death and critical illness in Prader-Willi syndrome: report of ten individuals. Am J Med Genet. 2004; 124: 158-64.
10. Ramsden SC, Clayton-Smith J, Birch R, Buiting K. Practice guidelines for the molecular analysis of Prader-Willi and Angelman syndromes. BMC Medical Genetics 2010;11:70-81.