The murine gene, Traube, is essential for the growth of preimplantation embryos

Little is known about the genetic control of preimplantation development. W e have isolated, characterized, and mutated a previously undescribed mouse gene, Traube (Trb), essential for preimplantation development. Similar prot ein coding sequences are found in rats, humans, and yeast. The TRB protein contained two amino-terminal acidic domains, a leucine zipper, and three pu tative nuclear localization signals. The Trb gene was expressed at low leve ls ubiquitously early in development and became restricted to the liver and the central nervous system from E11.5 onward. Myc-tagged TRB protein was l ocalized to the nucleus, and in a large proportion of the cells to the nucl eoli. The Trb mutant embryos halted in development at the compacted morula stage at E2.5. At E3.5 they started to decompact and a day later they disin tegrated and died. The observed defect was cell autonomous, as mutant cells failed to participate in the formation of chimeric embryos. The Trb mutant embryos showed a 50% reduction of the total cell number. The mutant embryo s exhibited a paucity of ribosomes, polyribosomes, and rough endoplasmic re ticulum. This paucity of ribosomes together with the localization of TRB to the nucleoli, the site of ribosome synthesis, suggests that TRB is involve d in the synthesis of ribosomes. (C) 2000 Academic Press.