ORC4 is a core subunit of the origin recognition complex (ORC), a six-protein assembly essential for initiating eukaryotic DNA replication 1. ORC4 functions as an ATP-dependent DNA-binding protein that recognizes replication origins and helps establish the pre-replication complex required for DNA synthesis initiation 2. The protein contains a conserved 19-amino acid insertion helix critical for determining ORC's selectivity for replication origins; human ORC4 lacks this motif present in yeast, resulting in chr2-landscape-dependent origin recognition rather than sequence-specific binding 3. ORC4 exhibits unexpected cellular localizations beyond chr2, including formation of a cage around chr2 destined for polar body extrusion during early mammalian development, suggesting roles in mitosis and chr2 segregation beyond canonical replication functions 1. ORC4 can stimulate formation of alternative DNA structures like T.A.T triplexes in an ATP-dependent manner, potentially facilitating origin accessibility 4. Germline mutations in ORC4 cause Meier-Gorlin syndrome (MGS), a rare autosomal recessive primordial dwarfism characterized by severe growth retardation, microtia, and patellar anomalies 2. ORC1 and ORC4 mutations produce the most severe phenotypes including microcephaly 5. ORC4 dysfunction disrupts fundamental replication mechanisms, with transcriptomic evidence showing altered ORC4 expression associates with embryonic developmental arrest and compromised competence in human preimplantation embryos 6. These findings establish ORC4 as critical for both normal organismal growth and genomic stability.