Figure 6

Cells do not migrate into the malleus from the developing incudomalleal joint. Middle ear cultures labelled with DiI in the malleus (seen as orange) and DiO in the presumptive joint region (seen as blue). (A, B) Bright field. (A', A", B', B") Dark field image. (A-A") Culture 1 hour after labelling, showing distinct DiI and DiO dots. (A, A') Light and dark field images, same magnification. Arrows in (A) point to the DiI and DiO spots. (B-B") Same culture 2 days after labelling. The malleus and incus are now distinct, with the DiO label located in the joint region. No spread of the DiO labelled joint cells towards the DiI labelled malleus is observed. The DiO label has extended caudally, however, as the joint extends in this direction. (B, B') Light and dark field images, same magnification. Arrows in (B) point to the DiI and DiO spots. Malleus and incus are outlined by white dashes in (A" & B"). Scale bar in (A) = 300 μm. Scale bar in (A") = 100 μm.