A PARTIAL TRISOMY 9 CASE WITH DICENTRIC CHROMOSOME DUE TO THE ADJACENT-2 SEGREGATION OF MATERNAL RECIPROCAL TRANSLOCATION

Abstract

Duplication of the short arm (p) of chromosome (Chr.) 9 is a frequently seen abnormality while duplication of both p and long arm (q) is a rare chromosomal rearrangement derived mostly from parental translocations or inversions. The unbalanced products of the translocations are mostly derived from the 2:2 segregation of adjacent 1division while the ones due the adjacent two patterns are rare. Here, a dysmorphic infant with a pure duplication of 9pter to 9q22.31 is reported due to the product of the adjacent-2 segregation of maternal reciprocal translocation between the 9q22.31 and 22p11.1. The affected infant had two normal and one derivative/dicentric Chr.9 (carrying the centromere regions of both Chr.9 and Chr.22) with one normal Chr.22. These results were confirmed by the fluorescence in situ hybridization technique. Array-comparative genomic hybridization confirmed the breakpoints precisely and revealed a 61.75 megabases duplication of Chr.9 consisting of many genes such as BICD2, NTRK2, HNRNPK, and SMARCA2, which are mostly related to developmental delay and growth retardation. Additionally, the infant had ear abnormalities, microcephaly, and extremity abnormalities, which were the other findings of trisomy 9. In sum, the case has presented as a rare example of adjacent 2 division of 2:2 segregation and a pure partial trisomy of 9pter to 9q22.31.

Keywords

• Partial trisomy 9
• reciprocal translocation
• adjacent-2 segregation
• dicentric chromosome
• chromosomal rearrangement
• growth retardation
• fluorescence in situ hybridization
• array- comparative genomic hybridization

MATERNAL RESİPROKAL TRANSLOKASYONUN ADJACENT-2 SEGREGASYONUNA BAĞLI OLUŞAN DİSENTRİK KISMİ TRİZOMİ 9 OLGUSU

Abstract

Kromozom (Chr.) 9’un kısa koluna (p) ait duplikasyon sık görülmekle birlikte daha çok ailesel translokasyonlara ve inversiyonlara bağlı oluşan, hem kısa hem de uzun kolun (q) duplikasyonu nadir görülen bir kromozomal yeniden düzenlenmedir. Ailesel translokasyonlara bağlı oluşan dengesiz gebelik ürünleri daha çok 2:2 segregasyonun adjacent-1 aktarımı ile oluşmakta iken, adjacent 2 aktarımı nadir bir durumdur. Burada, annenin 9q22.31 ve 22p11.1 bölgeleri arasındaki resiprokal translokasyonuna bağlı 9pter ile 9q22.31 bölgeleri arasında duplikasyonu olan dismorfik bir çocuk sunulmaktadır. Etkilenmiş çocuk iki normal Chr.9, bir derivatif/disentrik Chr.9 (hem Chr.9, hem de Chr.22’nin sentromerini taşıyan), bir tane de normal Chr.22’ye sahiptir. Tüm bu sonuçları floresan insitu hibridizasyon tekniği teyit etmiştir. Kırık bölgelerini doğru olarak belirleyen array-karşılaştırmalı genomik hibridizasyon tekniği BICD2, NTRK2, HNRNPK ve SMARCA2 gibi büyüme gelişme geriliğine eşlik eden genleri de kapsayan kromozom 9’a ait 61,75 megabazlık duplikasyonu ortaya çıkarmıştır. Ek olarak mikrosefali ve ekstremite anomalileri gibi trizomi 9’a eşlik eden diğer bulgular da olguda bulunmaktadır. Özetle bu olgu, adjacent 2 tipi segregasyonun ve sadece 9pter-9q22.31 bölgelerini kapsayan kısmi trizomi 9’un nadir bir örneği olarak sunulmaktadır.

Keywords

• Kısmi trizomi 9
• resiprokal translokasyon
• büyüme geriliği
• floresan insitu hibridizasyon
• array-karşılaştırmalı genomik hibridizasyon
• adjacent-2 segregasyonu
• disentrik kromozom
• kromozomal yeniden düzenlenme

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