Mater encodes a maternal protein in mice with a leucine-rich repeat domain homologous to porcine ribonuclease inhibitor

MATER (Maternal Antigen That Embryos Require) is an ooplasm-specific protein first identified as an antigen (OP1) associated with ovarian autoimmunity in mice. Its primary structure has been deduced from full-length cDNA that encodes a 125-kDa protein required for progression of the mouse embryo beyond two cells. Expression of the gene encoding MATER is restricted to the oocyte, which makes it one of a growing, but still limited, number of maternal-effect genes in mammals. To further investigate the function of MATER during oogenesis and early development, we have characterized the gene and resultant protein. Mater is a single-copy gene in the genome of 129/Sv mice and is located at the proximal end of Chromosome (Chr) 7. The gene, spanning approximately 32 kbp, contains 15 exons ranging in size from 48 to 1576 bp, which together encode the 1111 amino acid MATER protein. The first five exons encode 26-27 amino acid hydrophilic repeats, and exons 8-14 encode 14 leucine-rich repeats. The three-dimensional structure of the latter domain can be closely modeled on the previously determined X-ray crystallographic coordinates of porcine ribonuclease inhibitor. These characterizations of the gene and protein provide the basis for genetic investigations of MATER function in early mammalian development.