HOLOPROSENCEPHALY: CHROMOSOMAL ABNORMALITIES IN THE ETIOPATHOGENESIS OF 127 ANTENATAL CASES

Abstract

Objective: Holoprosencephaly (HPE, #MIM 236100) is the most common developmental defect of midline cleavage in the human forebrain. Environmental, genetic, and multifactorial causes are involved in its etiology. About half of the cases have chromosome aberrations such as trisomies 13 and 18, triploidy and structural imbalances. Single gene mutations have been shown in ~25% of cases. In this retrospective study, we aimed to determine the etiological factors related to HPE in 127 fetuses. Material and Method: This study comprises 127 prenatally diagnosed fetal HPE samples from a period of 25 years, which were evaluated by karyotyping, fluorescence in situ hybridization (FISH) and aCGH investigation. Results: A total of 64 (50.39%) chromosome aberrations were identified in this cohort. The predominant chromosomal abnormality was trisomy 13 (n=38), which was followed by trisomy 18 (n=8) and triploidy (n=5). Terminal 7q deletion was the most frequent structural anomaly (n=10, of which 5 were de novo deletion, 4 were an unbalanced product of maternal translocations and one unknown in origin) and the deletion of 18p was detected in one case. In the remaining two cases, we detected trisomy 20 and pericentric inversion 11 coincidentally. Conclusion: This study, indicates that in the presence of clinical findings suggesting HPE, cytogenetic and molecular cytogenetic studies should be performed. An aCGH study must also be done for submicroscopic chromosomal anomalies, to determine their sizes, real breakpoints and identify possible novel genes that might play a role in HPE etiology.

Keywords

• Holoprosencephaly
• HPE
• #MIM 236100
• nervous system malformations
• prenatal diagnosis

HOLOPROZENSEFALİ: 127 ANTENATAL OLGUNUN ETYOPATOGENEZİNDE KROMOZOM ANOMALİLERİ

Abstract

Amaç: Holoprosensefali (HPE, #MIM 236100), ön beyin orta hat bölünmesinde en sık görülen gelişimsel bozukluktur. Etiyolojisinde, çevresel, genetik ve multifaktöriyel hastalıklar rol oynamaktadır. Vakaların yaklaşık yarısında, trizomi 13 başta olmak üzere, trizomi 18 ve triploidi gibi sayısal anomaliler ve yapısal kromozom anomalileri bulunmaktadır. Olguların ~%25'inde tek gen mutasyonları gösterilmiştir. Bu retrospektif çalışmada fetal dönemde saptanan 127 fetüste HPE etiyolojisinde rol oynayan faktörlerin araştırılması planlandı. Gereç ve Yöntem: Bu çalışma, 25 yıllık bir periyotta fetal ultrasonografide HPE tanısı konmuş 127 fetusta yapılan klasik karyotipleme, floresan in situ hibridizasyon (FISH) ve aCGH incelemelerinin sonuçlarını içermektedir. Bulgular: Bu kohortta olguların 64 (%50,39)’ünde bir kromozom anomalisi tespit edildi. En sık görülen sayısal kromozomal anomali beklendiği gibi trizomi 13 (n=38) idi , bunu sırasıyla trizomi 18 (n=8) ve triploidi (n=5) izlemiştir. Yapısal kromozom anomalilerinden terminal 7q delesyonu en sık görülen anomaliydi (n=10, 5’i de novo, 4’ü maternal translokasyonun dengesiz ürünü, 1 olgunun kökeni ise bilinmiyordu). Bir olguda 18. kromozomun p kolunda bir delesyon saptandı. Kalan 2 olguda tesadüfi olarak trizomi 20 ve 11. kromozomda perisenttrik bir inversiyon saptandı. Sonuç: Bu çalışma, HPE klinik bulguların varlığında sitogenetik ve moleküler sitogenetik çalışmaların birlikte veya tamamlayıcı olarak yapılması gerektiğini göstermektedir. Özellikle aCGH çalışması submikroskopik yapısal kromozomal anomalilerin boyutlarını ve kırık noktalarını, bölgede yer alan genleri belirlemekte olduğu kadar HPE etiyolojisinde rol oynayabilecek olası yeni genleri tanımlamak için de yapılmalıdır.

Keywords

• Holoprosensefali
• HPE
• #MIM 236100
• merkezi sinir sistemi
• prenatal tanı

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