Investigation of Genetic Causes in Oculoauriculovertebral Spectrum Etiology

Oculo-Auriculo-Vertebral Spectrum (OAVS) is a genetically and phenotypically heterogeneous disorder which occurs due to a developmental defect in the first and second pharyngeal arches. In this study, 23 OAVS patients with diverse clinical findings were studied to identify the genetic etiology of this disorder. Patients were screened for copy number variations using the Affymetrix CytoScan Optima array Kit and also screened for MYT1 mutations using BigDye terminator on an ABI Prism 3500 genetic analyzer. Furthermore, two patients underwent WES analysis. Using these approaches, three CNVs (one deletion, two duplications) were found in chromosomes 8, 15, 16. The clinical relevance of the copy number variations is discussed within the framework of incomplete penetrance and monoallelic expression. In addition, the deletion on the 8th chromosome was thought to be associated with clinical findings by altering the genome architecture. In addition, a de novo unbalanced translocation; between X and 4th chromosomes was found in one of the patients and was considered pathogenic. No causative mutation was found in MYT1 gene. WES analysis revealed a novel heterozygous nonsense mutation in EFTUD2; responsible for Mandibulofacial Dysostosis with Microcephaly that has common clinical findings with OAVS. In the other patient who underwent WES analysis a novel heterozygous missense mutation was identified in RNF213, which was previously suspected as a candidate gene for OAVS. Duplication of 16p13.11 region, aneuploidies of X chromosome and EFTUD2 mutations were previously implicated in OAVS molecular etiology. This study provides further genetic heterogeneity to this disorder, confirming the importance of microarray-based studies and whole exome sequencing analysis in patients with a complex phenotypic disorder such as OAVS.Bu çalışma HÜTF Bilimsel Araştırma Projeleri Koordinasyon Birimi tarafından desteklenmiştir (TTU-2018-16935).Okulo-aurikulo-vertebral spektrum (OAVS) birinci ve ikinci farengeal arkların gelişimsel defektleri sonucunda oluşan genetik ve fenotipik heterojenite gösteren nadir bir hastalıktır. Bu çalışmada çeşitli klinik bulgulara sahip 23 OAVS hastasında genetik etyoloji araştırılmıştır. İlk basamakta kopya sayısı değişikliklerini saptamaya yönelik Affymetrix CytoScan Optima platformunda mikrodizin analizleri yapılmıştır. Sonra ABI Prism 3500 cihazında Sanger dizileme yöntemi ile MYT1 geni dizi analizleri tamamlanmıştır. Ek olarak; iki hastada tüm ekzom dizileme gerçekleştirilmiştir. Bu yaklaşımlar sonucunda; üç hastada 8., 15., ve 16. kromozomlarda kopya sayısı değişiklikleri gösterilmiştir. İlgili değişikliklerin klinik ilişkisi inkomplet penetrans ve monoalelik ekspresyon çerçevesinde tartışılmıştır. Ayrıca 8. kromozomdaki delesyonun genom mimarisini değiştirerek klinik ile ilişkili olacağı düşünülmüştür. Ek olarak; hastaların bir tanesinde periferik kandan yapılan kromozom analizi sonucunda X ve 4. kromozomlar arasında de novo dengesiz translokasyon gösterilmiş ve patojenik olarak değerlendirilmiştir. MYT1 geni dizi analizi sonucunda klinik anlamlı bir değişiklik bulunmamıştır. Tüm ekzom dizileme analizi sonucunda ise; hastaların birinde OAVS ile örtüşen klinik bulgular görülen Mandibulofasiyal Dizostozis ve Mikrosefali birlikteliğinden sorumlu EFTUD2 geninde novel heterozigot mutasyon saptanmıştır. Tüm ekzom dizileme yapılan diğer hastada; OAVS aday geni olarak nitelendirilen RNF213 geninde novel missense bir mutasyon gözlenmiştir. 16p13.11 bölgesi duplikasyonu, X kromozomu anöploidileri ve EFTUD2 genindeki değişiklikler önceki çalışmalarda da OAVS moleküler etyolojisinde tanımlanmış durumdadır. Hastalarda farklı kromozomlarda kopya sayısı değişikliklerinin yanı sıra tek gen değişikliklerinin gösterilmesi spektrumdaki geniş genetik heterojeniteyi desteklemektedir. Bu çalışma; OAVS benzeri kompleks fenotipik bulgulara sahip hastalıklarda genetik etyolojinin tanımlanmasında mikrodizin analizi ve tüm ekzom dizileme gibi genom boyu ölçeğinde gerçekleştirilen yöntemlerin önemini ortaya koymaktadır

A Monogenic Disease with a Variety of Phenotypes: Deficiency of Adenosine Deaminase 2

Objective: Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive autoinflammatory disorder associated with ADA2 mutations. We aimed to investigate the characteristics and ADA2 enzyme activities of patients with DADA2 compared to non-DADA2 patients. Methods: This is a descriptive study of 24 patients with DADA2 who were admitted to the Adult and Pediatric Rheumatology, Pediatric Haematology, and Pediatric Immunology Departments of Hacettepe University. All ADA2 exons were screened by Sanger sequencing. Serum ADA2 enzyme activity was measured by modified spectrophotometric method. Results: Twenty-four patients with DADA2 were included: 14 with polyarteritis nodosa (PAN)-like phenotype (Group 1); 9 with Diamond-Blackfan anemia (DBA)-like features, and 1 with immunodeficiency (Group 2). Fourteen PAN-like DADA2 patients did not have the typical thrombocytosis seen in classic PAN. Inflammatory attacks were evident only in Group 1 patients. Serum ADA2 activity was low in all patients with DADA2 except one, who was tested after hematopoietic stem cell transplantation. There was no significant difference in ADA2 activities between PAN-like and DBA-like patients. In DADA2 patients with one ADA2 mutation, serum ADA2 activities were as low as those of patients with homozygote DADA2. ADA2 activities were normal in non-DADA2 patients. ADA2 mutations were affecting the dimerization domain in Group 1 patients and the catalytic domain in Group 2 patients. Conclusion: We suggest assessing ADA2 activity along with genetic analysis because there are patients with one ADA2 mutation and absent enzyme activity. Our data suggest a possible genotype-phenotype correlation in which dimerization domain mutations are associated with PAN-like phenotype, and catalytic domain mutations are associated with hematological manifestations.PubMe