부산대학교 도서관

We report the identification of a new recessive prenatal lethal insertional mutation,amnionless(amn).amnmutant embryos first appear abnormal during the Early Streak stage, between E6.5 and E7.0, when they initiate mesoderm production. Subsequently, theamnmutants become developmentally arrested between the Mid and Late Streak stages of gastrulation and they die and are resorbed between E9.5 and E10.5. While extraembryonic structures, including the chorion, yolk sac blood islands, and allantois appear to develop normally, the small embryonic ectoderm remains undifferentiated and generates no amnion. In addition, the embryonic mesoderm that is produced does not become organized into node, notochord, and somites and there is no morphological evidence of neural induction. Interspecific backcross and fluorescencein situhybridization analyses map the transgene insertion, and thus theamnmutation, to the distal region of mouse chromosome 12, which has synteny with human chromosome 14q32. A gene encoding a 7.5-kb transcript has been identified at a junction between the integrated transgene and host chromosome 12 sequences that meets three criteria expected of a candidateamngene. This gene maps to the site of transgene insertion; it is transcribed during gastrulation, and its expression is disrupted inamnmutant embryos. Nucleotide sequencing studies show that the 567 amino acid protein encoded by the 7.5-kb transcript is a member of the newly defined family of putative signal transducing proteins, TRAFs, that associate with the cytoplasmic domains of members of the tumor necrosis factor (TNF) receptor superfamily. Thus, we have named the gene encoding the 7.5-kb transcriptTRAFamn.TRAFamn is identical to a recently reported protein (CD40bp, CAP-1, CRAF1, LAP1) that can bind the cytoplasmic domains of CD40 and the lymphotoxin β receptor (LTβR), both of which are known members of the TNF receptor superfamily. The implications of these findings regarding a possible role for the TNF receptor superfamily during gastrulation are discussed.