22q11.2 deletion syndrome is a spectrum disorder that includes conditions formerly called DiGeorge syndrome; velocardiofacial syndrome; conotruncal anomaly face syndrome and Cayler cardiofacial syndrome. The frequency of the 22q11.2 deletion is of approximately 1:4000 livebirths. The clinical features are highly variable and include a variety of congenital anomalies, medical problems, and cognitive and neuropsychological difficulties, including facial dysmorphism, thymus absence, hypoparathyroidism, cellular immunodeficiency, cardiac abnormalities, expressive language delays, gross and fine motor difficulties and psychiatric disorders. All of which caused by recurrent copy number changes in high-homology sequences called low copy repeats (LCR). These LCRs are >96% identical, thereby making the locus vulnerable to meiotic error. Individuals present mostly the two largest repeats, LCR22A and LCR22D, that flank the typical 3-Mb (A-D) 22q11.2 region deletion, while 8-10% have a nested 1.5-Mb (A-B) deletion, and individuals with atypical deletions have also been reported. It is generally accepted that >90% of proximal deletions are de novo, whereas for an inherited deletion, the risk of transmission is 50%. Higher-order chromatin structure is an important regulator of gene expression. Structural variation, whether it is caused by copy number variants or present in a balanced form can have a profound and dramatic effect on the expression of genes. Our goal is to build a cytogenomic profile by analyzing SNPs from whole genome and evaluate gene expression in 22q11.2 deletion carriers with immunephenotypic variations and to perform a genotype-phenotype correlation for these patients.
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