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Fig. 2. Regression of the anterior boundaries of expression of construct CHZ. (A)
By 8.5 dpc, anterior limits of expression were established at the
hindbrain/spinal cord boundary in the neural tube, and at so6/7 in the
paraxial mesoderm. The latter corresponds to the boundary of Hoxb4
expression. (B) Expression was noticeably weaker at the anterior boundaries by
8.75 dpc. (C-E) Boundaries continued to shift posteriorly until 9.5 dpc,
coming to rest alongside so6/7 in the neural tube and at so13/14 in the
paraxial mesoderm. Black arrowheads indicate the position of so7. ov, otic
vesicle; fl, forelimb bud.