Table 1.
The LaacZ library: frequency of embryos with N events of recombination.
Table 2.
The LaacZ library: size composition of the clones.
Table 3.
The lox-LacZ library of clones induced at E6.5 and observed at E14.5.
Figure 1.
SE labelling induced from E6.5 to E13.5 reveals a single clonal strategy for all regions of the embryo.
(A–C) [ROSAcre-ERT×R26R] and (D–F) [CT2×R26R] embryos. Pregnant mice injected with 4-OHT at E13.5 (A), E12.5 (B), E9.5 (C), E8.5 (D), E7.5 (E), E6.5 (F). Observation of E14.5 embryos. Growth is isotropic (A); dorso-ventrally oriented and coherent in (B) to (D). In (E) and (F), growth is dispersive and results in longitudinally dorso-ventrally oriented stripes. (G), (I), (K–Q) Examples of clones observed in LaacZ embryos; (H), (J) Examples of clones observed in lox-LacZ embryos induced at E6.5. (G)–(J) in head regions, (K) to (P) in the trunk and (Q) in the tail. Arrowheads indicate the most dorsal position to which the clones contribute.
Figure 2.
Ancestral and founder cells of the surface ectoderm.
Examples of clones dispersed along the entire SE observed in E14.5 LaacZ embryos. (A)–(J′) non-SE-restricted clones classified from biggest to smallest. (K–K′) the biggest SE-restricted clone. (L–L′) the biggest non SE-restricted clone. (M–M′′′) Superimposition of (B–B′′′), (D–D′′′), (F–F′′′), (H–H′′′), and (J–J′′′); note the lack of labelling in the most dorsal region of SE delimited by the lines. (A), (C), (E), (G), (I) in toto X-gal staining. (B), (D), (F), (H), (J) drawings of their SE contribution.
Figure 3.
Three pools of SE-forming cells at E6-5-E7.5, following distinct modes of growth in the head and the trunk.
(A) Schematic representation of the pattern of the 64 clones in E14.5 lox-LacZ embryos induced at E6.5–E7.5. Horizontal lines represent the boundaries between the regions of the body in A. Each vertical orange line corresponds to a single clone; no contribution to the levels where the line is interrupted. Dark red lines represent the contribution of the clone to the contralateral side. Clones were first classified according to size (long on left and short on right) and then according to the most anterior region to which they contribute. (B) Schematic representation of an E14.5 embryo showing the regions used in A. (C)–(M) Examples of E14.5 lox-LacZ embryos. (C)–(G) and (M) long clones; (H) and (I) posterior short clones; (J)–(L) anterior short clones. (N) is a spontaneous clone (in a CT2 embryo) labelled only in the head and the tail. (O) Schematic representation, as in fig. 4, of the pattern of the clones in E14.5 LaacZembryos. All clones were classified according to size (long on left and short on right) and then according to the most anterior region to which they contribute. (P), (P′) Pattern of clones expected from the labelling of cells in the pool of precursors classified according to the most posterior region to which they contribute for two representative models for their production: self-renewing pool of cells (P); and from the regional mode (P′). Each column (of different colour) represents a clone. (Q)–(R) Schematic representation, of the LaacZ clones that contribute (Q) to regions 6 to 9 (see B); (R) to regions 1 to 5 (see B). Clones were classified according to size (long on left and short on right) and the most posterior region to which they contribute. Note that clones from ancestral cells of the SE (shown in O) have been removed. (Q) Long clones that contribute to all regions are present on the left. (R) Clones from ancestral cells of head SE are shown on the left. Note the absence of clones that contribute to all five sub-regions.
Figure 4.
Cell arrangement of the clonally related P-DVCUs in the trunk.
(A)–(G): Examples of clonal organisation in the trunk. The most dorsal positions of the DV-oriented stripes have been connected by one (A)–(D), two (E) or several (F), (G) lines, defining five discrete DV positions: dorsal (D), dorso-lateral (A), latero-medial (A, magenta line), mid-ventral (B), and ventral (C), schematically represented by yellow lines in (H and H′). A–A′, B and E–E′, from the LaacZ library; C, D, from the E6.5 lox- LacZ library; F, G: spontaneous labelling. A–A′ and E–E′ are two different views of the same embryo. d: dorsal, dl: dorsal-lateral, lm: lateral-medial, mv: mid-ventral, v: ventral.
Figure 5.
Cell arrangement of the clonally related P-DVCUs in the head.
(A)–(G): Examples of clonal organisation in the head. The most dorsal positions of the DV-oriented stripes have been connected by one (A)–(C), two (D), (E) or three (F)–(G′′) lines, defining four discrete DV positions: dorsal (A), dorso-lateral (B),(E), latero-medial (C) and mid-ventral (D), (F), (G). Points indicate the most dorsal position of the DVCU. The red lines connect DVCUS in the head, the magenta lines connect DVCUS in the trunk. (H), (I): Ventral labelling in the head. These labellings are connected with more dorsal head regions (arrowheads) but not with the ventral trunk region. (A), (F), (G) from the E6.5 lox-LacZ library; (B)–(E), (H)–(I): from the LaacZ library (F, F′, F′′; G, G′, G′′ and E, E′, E′′ different views of the same embryo).
Figure 6.
Spacing of the clonally related P-DVCUs.
(A)–(D): Examples of spacing in the head for the four DV positions: (A), dorsal, (B), dorso-lateral; (C), latero-medial and (D) medial. In D the magenta point indicates a second dorsal line of dispersion. (E)–(I): Examples of spacing in the trunk for the five DV positions dorsal (E), dorso-lateral (F); latero-medial (G, red points); medial (G, magenta points and H); and ventral (I). Note that the spacing is greater dorsally than ventrally. (A), (E), (G), (I) from the E6.5 lox-LacZ library; (B)–(D), (F): from the LaacZ library; B and F are two views of the same embryo; (H): spontaneous labelling. The points represent the most dorsal position of the DVCUs.
Figure 7.
Relationship between the pools of founder cells.
(A)–(C′): examples of clones whose contribution is restricted to the head and the tail. (D)–(E′): examples of clones that contribute to both the trunk and posterior regions. (F): an example of a clone that stops at the level of the hindlimb. (A–A′, D, E–E′, F) from the E6.5 lox-LacZ library; (B–B′): spontaneous labelling; (C–C′) from the LaacZ library.