Copy Number Variants in the 11p15.5 Associated Imprinting Disorders: An Attempt to Establish a Genotype-Phenotype Correlation.

Copy number variations (CNVs) affecting the imprinted regions in 11p15.5 (imprinting centre 1 and 2/IC1, IC2) account for more than 2% of the molecular disturbances in Beckwith-Wiedemann and Silver-Russell syndrome (BWS, SRS) and are associated with a recurrence probability of up to 50%. However, their clinical impact can be challenging to estimate, as it depends on the type of imbalance, the parental origin of the affected allele, its size and genomic content. As a result, a genotype-phenotype correlation of 11p15.5 alterations is still missing, at least for CNVs affecting only parts of the IC1 or IC2. By comprehensively summarising all published CNVs within 11p15.5 and the available clinical data of their carriers, we aim to further delineate a correlation of these disturbances with BWS and SRS features. In fact, consistent correlations could be delineated only for duplications including either both the telomeric and centromeric regions or complete gains of one of them. In contrast, CNVs encompassing only parts of these regions lead to heterogeneous phenotypes. In summary, our literature review provides support for pathogenicity assessment of CNVs in 11p15.5 as basis for genetic counselling. However, this dataset underlines the need for further research to enlighten the molecular complexity of this region and to better understand the regulation of genomic imprinting mechanisms in 11p15.5.