Mouse mutants for the nicotinic acetylcholine receptor ß2 subunit display changes in cell adhesion and neurodegeneration response genes.

Mice lacking expression of the ß2 subunit of the neuronal nicotinic acetylcholine receptor (CHRNB2) display abnormal retinal waves and a dispersed projection of retinal ganglion cell (RGC) axons to their dorsal lateral geniculate nuclei (dLGNs). Transcriptomes of LGN tissue from two independently generated Chrnb2-/- mutants and from wildtype mice were obtained at postnatal day 4 (P4), during the normal period of segregation of eye-specific afferents to the LGN. Microarray analysis reveals reduced expression of genes located on the cell membrane or in extracellular space, and of genes active in cell adhesion and calcium signaling.

Dendrites of rod bipolar cells sprout in normal aging retina.

The aging nervous system is known to manifest a variety of degenerative and regressive events. Here we report the unexpected growth of dendrites in the retinas of normal old mice. The dendrites of many rod bipolar cells in aging mice were observed to extend well beyond their normal strata within the outer plexiform layer to innervate the outer nuclear layer where they appeared to form contacts with the spherules of rod photoreceptors.

Formation of eye-specific retinogeniculate projections occurs prior to the innervation of the dorsal lateral geniculate nucleus by cholinergic fibers.

We compared the developmental periods in the mouse when projections from the two eyes become segregated in the dorsal lateral geniculate nucleus with the time when this nucleus becomes innervated by cholinergic fibers from the brainstem. Changes in labeling patterns of different tracers injected into each eye revealed that segregation of retinogeniculate inputs commences at postnatal day five (P5) and is largely complete by P8. Immunocytochemical staining showed that cholinergic neurons are present in the parabrachial region of the brain stem on the day of birth.