Lrwd1, also known as ORCA, is a nuclear protein involved in multiple biological processes. It functions in maintaining the silencing of heterochromatin regions through its interaction with repressive histone marks using the WD40 domain, and is associated with the origin recognition complex (ORC) to facilitate prereplication complex formation at late-replicating origins [1].

Gene-trap generated Lrwd1 knockout mice showed that Lrwd1 is ubiquitously expressed in the developing mouse embryo. Depletion of LRWD1 did not affect embryonic development, but the postnatal growth of homozygous mutants was retarded. In vitro, mouse embryonic fibroblasts (MEFs) depleted of LRWD1 had reduced proliferation. Also, the knockout of Lrwd1 in MEFs increased the expression of epigenetically silenced repetitive elements with minimal effect on protein-coding gene expression, suggesting its role in postnatal development by regulating cell proliferation likely via modulating DNA replication [1].

In conclusion, Lrwd1 plays an important but non-essential role in postnatal development by regulating cell proliferation. The use of Lrwd1 knockout mouse models has revealed its function in modulating DNA replication and maintaining the silencing of repetitive DNA elements, which may have implications for understanding postnatal growth-related processes.