Genomic imprinting and genomic imprinting disorder

Genomic imprinting (genetic imprinting) refers to parent of origin dependent gene expression. The presence of imprinted gene can cause cells with a full parental complement of functional autosomal genes to specifically express one allele but not the other, resulting in monoallelic expression of imprinted loci. Genomic imprinting is a normal process and has been found in primary animals and plants for a long time. Imprinted genes play a critical role in fetal growth and behavioral development even though they account for less than 5% of all human genes. Abnormal imprinting effects are associated with clinical disorders of overgrowth, undergrowth, mental retardation, or behavior abnormalities. In particular, loss of imprinting (LOI) is one of the most frequent genetic alterations in cancer. This review focused on genomic imprinting and disorders of genomic imprinting.