Fig. 2. Molecular identification of lulu and expression of Lulu protein. (A) Domain structure of Epb4.1l5, showing the lulu mutation site and the gene trap insertions. The FERM domain consists of amino acids (aa) 43 to 350. The cladogram shows FERM-domain relatedness among Lulu homologs and related mouse ERM proteins. (B) E8.5 lulu/Epb4.1l5^GT1 transheterozygous mutant embryo (right; abnormal allantois, bracket), with its wild-type sibling (left). (C) lulu/Epb4.1l5^GT2 transheterozygote (right) and wild-type sibling (left) at E9.5. (D-F) Anti-Lulu immunofluorescence on transverse sections of wild-type (D,E) and Epb4.1l5^GT1 homozygous (F) embryos. Lulu is apically enriched in the E7.5 epiblast (D, arrowheads in inset) and E8.5 neural tube (E). Lulu is found at the periphery of cells ingressing in the primitive streak (D, bracket; inset is 2x magnification of the streak). (F) E8.5 neural plate from an Epb4.1l5^GT1 homozygous embryo lacks detectable Lulu. (G) E7.5 transverse section of an Epb4.1l5^GT2/+ embryo, showing apical GT2-ß-galactosidase activity. Anterior is up in B and left in C,D; dorsal is up in E,F. Scale bars: 150 µm in B,C; 50 µm in D,F,G; 20 µm in E.