Journal of Neuroscience, Vol 1, 1193-1204, Copyright © 1981 by Society for Neuroscience
The distribution of melanin in the developing optic cup and stalk and its relation to cellular degeneration
AC Strongin and RW Guillery
The early distribution of melanin in the developing optic cup and stalk and
its relationship to cellular degeneration have been studied during
intrauterine development in hamsters, mice, ferrets, and humans. The
extensive degenerative changes that occur in the region of the optic
fissure do not involve any pigment-bearing cells. Melanin is not formed at
the site of the fissure until after the processes of fusion and the
associated degenerative changes are complete. In contrast to this, there is
a small region near the junction of the cup and stalk where melanin is
particularly related to degenerative changes. Melanosomes form dense clumps
associated with basophilic, apparently degenerate areas of cytoplasm, and
these melanosome complexes themselves undergo further degenerative changes.
The two types of degenerative changes, pigmented and unpigmented, are
limited to the same two regions of the developing eye in all four species.
However, the pigment degeneration is more extensive in ferrets and humans
than in mice and hamsters. These observations raise the possibility that
the lysis of melanosomes plays a significant but undefined local role in
ocular development.