Human retinal ganglion cell development in early prenatal period using carbocyanine dye DiI

Early development of retinal ganglion cell morphology has been studied in human fetuses of gestational age ranging from 7-8 weeks to 19-20 weeks by retrograde labelling with a lipophilic fluorescent dye, DiI. The retinal ganglion cells with simple and relatively uniform appearance having few dendritic processes between 7 to 11 weeks of gestation show progressive growth and elaboration of dendrites at 17-18 weeks revealing some morphological variation in shapes. It is by 19-20 weeks of gestation that the three major ganglion cell types resembling the alpha, beta and gamma classes of cat ganglion cells are identifiable in the developing human retina. The dendrites of some ganglion cells exhibit varicosities, filiform processes and spines even as early as 10-11 weeks indicating a possibility of involvement in synaptic connectivity.