Ephrin-As and patterned retinal activity act together in the development of topographic maps in the primary visual system

J Neurosci. 2006 Dec 13;26(50):12873-84. doi: 10.1523/JNEUROSCI.3595-06.2006.

Abstract

The development of topographic maps in the primary visual system is thought to rely on a combination of EphA/ephrin-A interactions and patterned neural activity. Here, we characterize the retinogeniculate and retinocollicular maps of mice mutant for ephrins-A2, -A3, and -A5 (the three ephrin-As expressed in the mouse visual system), mice mutant for the beta2 subunit of the nicotinic acetylcholine receptor (that lack early patterned retinal activity), and mice mutant for both ephrin-As and beta2. We also provide the first comprehensive anatomical description of the topographic connections between the retina and the dorsal lateral geniculate nucleus. We find that, although ephrin-A2/A3/A5 triple knock-out mice have severe mapping defects in both projections, they do not completely lack topography. Mice lacking beta2-dependent retinal activity have nearly normal topography but fail to refine axonal arbors. Mice mutant for both ephrin-As and beta2 have synergistic mapping defects that result in a near absence of map in the retinocollicular projection; however, the retinogeniculate projection is not as severely disrupted as the retinocollicular projection is in these mutants. These results show that ephrin-As and patterned retinal activity act together to establish topographic maps, and demonstrate that midbrain and forebrain connections have a differential requirement for ephrin-As and patterned retinal activity in topographic map development.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Brain Mapping / methods*
  • Ephrin-A2 / biosynthesis
  • Ephrin-A2 / genetics
  • Ephrin-A2 / physiology
  • Ephrin-A5 / biosynthesis
  • Ephrin-A5 / genetics
  • Ephrin-A5 / physiology
  • Ephrins / biosynthesis
  • Ephrins / genetics
  • Ephrins / physiology*
  • Geniculate Bodies / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Retina / metabolism*
  • Visual Pathways / metabolism*

Substances

  • Ephrin-A2
  • Ephrin-A5
  • Ephrins