Abstract
Purpose: :
To identify sub-populations within the migratory optic stream of neural crest cells (NCCs), corresponding to tissues of the anterior segment. We hypothesized that lens-derived factors recruit front of stream (FoS) cells to the periocular space proximal to the presumptive cornea, with back of stream (BoS) cells filling a concentric ring in the distal region.
Methods: :
Using DiI and DiO vital dyes, we labeled FoS and BoS subpopulations of NCCs in chicken embryos at HH stages 9 and 11 by microinjection of migratory cells. Embryos were re-incubated for 24 to 48 h. We also labeled different rostro-caudal positions to identify subpopulations of the optic stream arising in parallel. We observed labeled cells in the periocular region (PO) to determine the ultimate position of NCC subpopulations relative to their position of origin.
Results: :
FoS cells from the midbrain migrate to the temporal PO, while midbrain BoS cells accumulated temporally behind the FoS cells. Labeled cells remain in the same relative position and do not intermix upon reaching the PO destination. Neither subpopulation of cells originating in the midbrain region crosses into the nasal PO. When subpopulations on the rostro-caudal axis are labeled at the same lateral position and stage, the midbrain (caudal) subpopulation migrates to the temporal PO and the diencephalon (rostral) population to the nasal PO. Cells from both rostral and caudal subpopulations are evenly distributed along the dorso-ventral axis of the eye.
Conclusions: :
Neither FoS nor BoS subpopulations of the caudal optic stream move nasally beyond the temporal PO, supporting the hypothesis for lens-derived recruitment factors. This result could not account for the absence of labeled cells in the nasal PO, suggesting multiple subpopulations along the rostro-caudal axis. Nasal and temporal subpopulations of periocular cells corresponding to rostral and caudal neural tube origins, respectively, align in an evenly distributed pattern along the dorso-ventral axis of the eye, suggesting a recruitment signal emanating from the ventral midline of the developing head.
Keywords: development • anterior segment • anatomy