Polyclonal origin of the Anterior Visceral Endoderm (AVE) region. (A-H) The Cer1-GFP transgenic line is used as a marker of the AVE region. Examples of two conceptuses (A-C and D-F) at E5.5 containing a red-positive clone in the VE. (A, D) Cer1-GFP pattern indicates the embryonic stage, respectively E5.5L and E5.5D. Green fluorescent projection of a confocal z series merged with a transmitted light section are shown. (B, E) VE clones labelled with a red nuclear marker. The two sides of the conceptus are shown as a red fluorescent projection of a confocal z series. Asterisks indicate autofluorescence of the parietal endoderm. (C, F) Merged confocal sections of the conceptuses, showing the colocalisation (arrowheads) of the transgenic green and clonal red markers. (G) Summary of the characteristics of conceptuses with a given Cer1-GFP pattern. Average numbers are given. D, distal ; L/D, laterodistal; L, lateral; nb, number. (H) Summary of the characteristics of red-positive clones in the transgenic line. Average numbers are given. VE, visceral endoderm. (I-J) The visceral endoderm thickening (VET) is used as a marker of the AVE region and is delineated by a white line. Examples of GFP-positive cells in wild type conceptuses, at E5.5L/D in I and E5.5D in J. Arrowheads point to the positive cells colonising the VET. I, J are green fluorescent projection of a confocal z series merged with a transmitted light section and I', J' are merged confocal sections. Scale bars 20 μm.