Prenatal and postnatal development of retinogeniculate and retinocollicular projections in the mouse

Abstract

The development of retinal projections to the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC) has been studied in fetal and neonatal mice of the pigmented C57BL/6 strain, using the anterograde transport of tritiated proline and horseradish peroxidase (HRP). Retinal efferents are present contralaterally just beyond the chiasm at E14. By E16 they have grown into both dLGN and SC. Ipsilateral fibers are limited to the proximal optic tract at E16; their growth into dLGN and SC is delayed until E18-birth. During the first 2 postnatal days, an early population of ipsilateral fibers invades the dLGN. Most of these fibers grow in or around the medio-dorsal sector of the dLGN, i.e., the future binocular segment. Fibers are also present, but at lower densities, in the ventral half of the nucleus and thereafter become dispersed or are lost, without at any stage becoming dense. Some denser labeling is also present ipsilaterally in the outer rim of dLGN, just below the optic tract, and later disappears. On the third postnatal day, the ipsilateral fibers establish a deep and denser projection along the medial and dorsal borders of dLGN; this projection overlaps part of the crossed projection, which at this age extends to the whole nucleus. The segregation of each projection starts on the fourth postnatal day, when crossed fibers begin to disappear from the small region of uncrossed projection. This process goes on for another 4 days. During this period, the ipsilateral fibers withdraw from the deepest layer of dLGN, and their terminal density increases gradually; by the eighth postnatal day, both projections are already well separated. Dense crossed projections first appear near the surface of the SC at birth. Prior to this, retinal fibers course throughout neurons of the collicular plate and underneath the pia. The uncrossed fibers invade the SC between birth and P3. They are located preferentially in the anterior and medial aspect of the SC. Subsequently, there occurs a diminution in the laminar and tangential extent of these projections, simultaneously with an intensification of the ipsilateral input to several small, longitudinally oriented clusters located deep to the crossed projections.

Contactin-1 regulates myelination and nodal/paranodal domain organization in the central nervous system

“…2B, a single oligodendrocyte outlined by NG2 expression shows overlapping staining for Contactin on the cell body and on proximal but not distal processes. At P10, Contactin was undetectable on optic axons that by this time point had innervated their targets (20,21). At P16, a dramatic change in pattern occurred, with prominent Contactin staining now delineating parallel running structures resembling myelin membranes.…”

The role of nAChR‐mediated spontaneous retinal activity in visual system development

“…In normal mice, the process of eyespecific refinement is completed between P8 and P14 (Godement et al, 1984). (Note, though the distribution of axons in mice do not form "layers" per se, we refer to the distribution as such to compare with the anatomy of other species).…”

Central visual system of the naked mole‐rat (Heterocephalus glaber)

“…For comparison to sighted species, we performed the same experiments on mice (C57 black). We chose this species because it is a rodent with a similarly sized brain and a more typical visual system that has been well characterized (for example, see Godement et al, 1984).…”