Abstract
Uniparental disomy (UPD), the inheritance of both homologues of a chromosome from only one parent, has been reported for nearly all human chromosomes. Depending on its mode of formation and time of occurrence, UPD can be present in all cells of an organism, or restricted to some cell lines as a mosaic UPD. Though its general frequency is unknown, it becomes clinically relevant when it produces homozygosity for recessive pathogenic variations, or is associated with chromosomal imbalances; but its most prominent feature is the association of specific UPDs with imprinting disorders. Beyond its clinical and diagnostic significance, detection of UPD has value for research in the identification of putative disease mechanisms and genomic regions of interest. Furthermore, detection of UPD in a cluster of similar clinical cases can lead to definition of new genetic syndromes and imprinted loci, thereby elucidating imprinting regulation and epigenetic mechanisms in general. In this review, we will focus on constitutional UPDs originating from meiotic and early postzygotic nondisjunction events and their relevance for imprinting disorders.
Highlights
Uniparental disomy (UPD), the inheritance of both homologues of a chromosome from only one parent, was first proposed by Eric Engel in 1980 [1], another eight years passed before the first case of UPD was reported [2]
UPD can be associated with chromosomal disturbances, UPD can be associated with chromosomal disturbances, but they are most well-known for their association with imprinting disorders
The term “genome-wide UPD” is commonly used in literature, but we suggest using the term “uniparental diploidy” instead
Summary
Uniparental disomy (UPD), the inheritance of both homologues of a chromosome from only one parent, was first proposed by Eric Engel in 1980 [1], another eight years passed before the first case of UPD was reported [2]. In a variety of human cancers, acquired UPD is a common molecular event leading to homozygosity for tumor suppressor genes as well as oncogenes [3]. UPD has pathological significance as it can result in homozygosity for pathogenic gene variations. The term “isozygosity” is used to describe homozygosity of a recessive variant when inherited from the same parent and will be used throughout this review. UPD can be associated with chromosomal disturbances, UPD can be associated with chromosomal disturbances, but they are most well-known for their association with imprinting disorders. We will focus on UPDs originating from meiotic and early postzygotic nondisjunction events and their relevance for imprinting disorders and their elucidation
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