Background: Silver-Russell syndrome (SRS, OMIM# 180860) features fetal and postnatal growth restriction and variable dysmorphisms. Genetic and epigenetic aberrations on chromosomes 7 and 11 are commonly found in SRS. However, a large fraction of SRS remain with unknown genetic etiology.
Methods: We studied 22 patients diagnosed with SRS (ten with H19 hypomethylation and twelve of unknown molecular etiology) and their parents with the Affymetrix 250K Sty microarray. Several analytical approaches were used to identify genomic aberrations such as copy number changes (CNCs), loss of heterozygosity (LOH), and uniparental disomy (UPD). Selected CNCs were verified with quantitative real-time PCR.
Results: The largest unambiguous CNCs were found in previously molecularly unexplained SRS patients with relatively mild phenotypes: a heterozygous deletion of chromosome 15q26.3 including the IGF1R gene (2.6 Mb), an atypical, distal 22q11.2 deletion (1.1 Mb), and a pseudoautosomal region duplication (2.7 Mb) in a male patient. We also identified LOH regions of potential relevance to the SRS phenotype. Importantly, we did not identify any duplications or UPD of chromosomes 7 or 11.
Conclusion: In summary, we found unexpected submicroscopic genomic events with pathogenic potential in three molecularly unexplained patients with mild SRS. Our findings emphasize that SRS is heterogeneous in genetic etiology beyond the major groups of H19 hypomethylation and matUPD7 and that unbiased genome-scale screens may reveal novel genotype-phenotype correlations.
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