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. 2014 Aug 28;10(8):e1004468. doi: 10.1371/journal.pgen.1004468

Figure 7. Molecular and morphological analysis of Sp6−/−;Sp8+/− mutant limb buds.

Figure 7

(A–C) WMISH for Fgf8 and Bmp4 showing irregular activation in the limb bud ectoderm of Sp6−/−;Sp8+/− E10 (A), E10.5 (B) and E11.5 (C) forelimb buds compared to control littermates. Note the irregular early activation and predominant posterior maintenance of Fgf8 and Bmp4 expression, except for a residual focus of anterior expression (red arrowheads). (D, D′, D″) ISH for Wnt7a and En1 to consecutive (7 microns apart) sections of control and mutant E10.5 forelimb buds (D, D′ and D″). Note the variable expansion of Wnt7a into the ventral ectoderm always associated with a corresponding proximal restriction of En1 (D′, D″) indicated by red arrowheads (D′) and red arrows (D″). (E–E′) ISH for Lmx1b and Fgf8 in consecutive sections of control and Sp6−/−;Sp8+/− E11.5 forelimb buds. The Lmx1b expression invades the ventral mesoderm distally under the broad and flat AER. (F–G) Hematoxylin-Eosin stained transverse histological sections at the autopod and zeugopod level of E15.5 control (F) and Sp6−/−;Sp8+/− (G) limbs. Some of the individual muscles and tendons are labeled. Abbreviations: EC, extensor digitorium communis; FDS, flexor digitorium sublimis; FDP, Flexor digitorium Profundus; ECR, extensor carpi radiallis; m, metacarpal; R, radius; U, ulna.