SENDROMİK VE NON-SENDROMİK KRANİYOSİNOSTOZ OLGULARINDA FGFR1-3, TWIST1, MSX2, POR, FREM1 VE RAB23 GENLERİNİN MOLEKÜLER ANALİZİ

Abstract

Amaç: Sendromik (SCS) ve non-sendromik kraniyosinostozlu (NSCS) olgularda, kraniyosinostoz tipleriyle ilişkilendirilmiş genlerde (FGFR1-3, TWIST1, MSX2, POR, FREM1 ve RAB23) mutasyonların araştırılması ve moleküler genetik tanı için akılcı bir akış şeması oluşturulması. Gereç ve Yöntem: İstanbul Üniversitesi, İstanbul Tıp Fakültesi, Tıbbi Genetik AD’da kromozom anomalisi dışlanmış, altısı prenatal ve 34’ü postnatal tanı alan, dokuzu NSCS ve 31’i SCS toplam 40 olgu ile 34 sağlıklı ebeveyn çalışmamıza dahil edildi. SCS’li olguların dokuzu Pfeiffer (PS), altısı Crouzon (CRS), beşi Apert (AS), yedisi Saethre-Chotzen (SaCS) ve dördü Muenke (MUS)/Saethre Chotzen (SaCS) idi. Kraniyosinostoz tipine göre mutasyonların en sık gözlendiği gen/ekzon bölgelerinden başlanarak, tüm gen ve ilişkili diğer genler aşamalı olarak Sanger dizileme yöntemi ile incelendi. Mutasyon saptanmayan olgularda incelenen genlerdeki büyük delesyon ve duplikasyonlar Multiplex Ligation-depended Probe Amplification (MLPA) yöntemi ile araştırıldı. Bulgular: Olgularımızın %50’sinde dizi analizi ile ve %2,5’unda MLPA yöntemi ile klinik bulguları destekleyen moleküler genetik sonuçlara ulaşıldı. Moleküler tanı oranı SCS grubunda %64,5, NSCS grubunda %11,1 oldu. Sonuç: Sendromik olgularda moleküler tanı oranı seri ortalamasının üzerinde idi. Birinci basamakta FGFR2 geni ekzon 7-8’de olası mutasyonlar dışlandıktan sonra, ikinci basamaktaki hedef ekzonlara (3, 5, 11, 14-17) ekzon 12 ve 13’ün ilavesi PS’de mutasyon saptama oranını %33 arttırdı. Çalışmamız, moleküler tanı alan ailelere özgün genetik danışma olanağı sağladı. CS olgularında izlenen akış şemasında Sanger dizileme ile 1. ve 2. basamak testlerden sonra mutasyon saptanmayan olguların yeni nesil dizileme tekniği ile klinik ekzom ve yüksek çözünürlüklü mikroarray çalışmasına alınmasının uygun olacağına karar verildi.

Keywords

• Kraniyosinostoz
• FGFR
• TWIST1

MOLECULAR ANALYSIS OF FGFR1-3, TWIST1, MSX2, POR, FREM1 AND RAB23 GENES IN SYNDROMIC AND NON-SYNDROMIC CRANIOSYNOSTOSIS CASES

Abstract

Objective: Craniosynostosis (CS) associated genes (FGFR1-3, TWIST1, MSX2, POR, FREM1 and RAB23) were investigated in order to determine the mutation rates and establish an effective flow chart for molecular genetic diagnosis for syndromic (SCS) and non-syndromic craniosynostosis (NSCS). Material and Method: A total of 40 cases, including six prenatal cases, with normal karyotypes, and 34 parents were investigated in the Medical Genetics Department of Istanbul Medical Faculty. The clinical diagnosis was NSCS in 9, Pfeiffer in 9 (PS), Crouzon in 6 (CRS), Apert in 5 (AS), Saethre-Chotzen in 7 (SaCS) and Muenke/Saethre Chotzen in 4 (MUS/SaCS) of the cases. According to the clinical diagnosis, the hot spot mutation sites of genes/exons were screened initially and the whole gene and other genes were progressively examined by Sanger sequencing. The Multiplex Ligation-Depended Probe Amplification (MLPA) technique was applied to detect deletions/duplications. Results: Molecular results were achieved in 50% of cases by sequencing and in 2.5% by MLPA. Molecular diagnosis rate was 64.5% in SCSs and 11.1% in NSCSs. Conclusion: Molecular diagnosis rate was higher in the SCS than in the NSCS group. Including exons 12 and 13 to target exons (3, 5, 11, 14-17) of FGFR2 gene increases the mutation rate by 33% in the second step of the molecular investigation in PS cases. Genetic counseling with the families following molecular diagnosis is important. Our results supported the fact that CS cases with un-identified pathogenic variants in the first and second steps of the algorithmic chart, should be followed by clinical exome and high resolution microarray techniques.

Keywords

• Craniosynostosis
• FGFR
• TWIST1

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