K. Burnat

Age-dependent alterations in CRMP2 and CRMP4 protein expression profiles in cat visual cortex.

We monitored the protein expression profiles of collapsin response mediator protein 2 and 4 (CRMP2 and CRMP4) throughout cat primary visual area 17 at different postnatal ages. Single immunocytochemical stainings revealed a clear effect of cortical maturation on the spatial and laminar distribution profile of CRMP2 and CRMP4. In kittens of postnatal day 10 (P10) and 30 (P30), CRMP2 and CRMP4 immunoreactivity was exclusively present in fibers running perpendicular to the cortical surface and crossing all cortical layers, but was never found in neuronal cell bodies. The immunoreactive fibers were embedded in an intensely and homogeneously stained neuropil. In contrast, mature visual cortex immunocytochemistry located CRMP2 and CRMP4 in the somatodendritic compartment of neurons with a clear CRMP-specific lamination pattern. Similar to kitten, neuropil staining was clearly observed but showed a decreasing gradient from layer I to VI in adult area 17. Detailed analysis of cellular morphology and size classified the CRMP2- and CRMP4-immunopositive cells in distinct neuronal populations. Double labeling of CRMP2 or CRMP4 with the typical interneuron marker parvalbumin (PV) showed many double-labeled cells immunoreactive for CRMP4 and PV, but not for CRMP2 and PV, corroborating the cell type-specific character of each CRMP. Our present results clearly illustrate that CRMP2 and CRMP4 may play an important role in visual cortex, possibly providing different classes of neurons with the potential to form a functionally meaningful network, not only during development, but also in adulthood, coincident with the belief that CRMPs are involved in neurite growth and guidance.

Age- and experience-dependent expression of Dynamin I and Synaptotagmin I in cat visual system

Dynamin I (Dyn I) and Synaptotagmin I (Syt I) are essential for endocytosis‐exocytosis processes, thus for neurotransmission. Despite their related function at presynaptic terminals, Dyn I and Syt I displayed opposite expression patterns during visual cortex maturation in the cat. Dyn I was more abundantly expressed in adults, while Syt I exhibited higher levels in kittens of postnatal day 30 (P30). In area 17 this developmental difference was most obvious in layers II/III. Layer VI displayed a strong hybridization signal for both molecules, independent of age. In addition, Syt I levels were higher in posterior compared to anterior area 17 in adult subjects. Moreover, in higher‐order visual areas Syt I was unevenly distributed over the cortical layers, thereby setting clear areal boundaries in mature cortex. In contrast, Dyn I was rather homogeneously distributed over extrastriate areas at both ages. Both molecules thus demonstrated a widespread but different distribution and an opposite temporal expression pattern during visual system development. Notably, monocular deprivation during the critical period of ocular dominance plasticity significantly decreased Syt I expression levels in area 17 ipsilateral to the deprived eye, while no effect was observed on Dyn I expression. We therefore conclude that visual experience induces changes in Syt I expression that may reflect changes in constitutive exocytosis involved in postnatal structural refinements of the visual cortex. On the other hand, the spatial and temporal expression patterns of Dyn I correlate with the establishment and maintenance of the mature neuronal structure rather than neurite remodeling. J. Comp. Neurol. 504:254–264, 2007.

Lack of early pattern stimulation prevents normal development of the alpha (Y) retinal ganglion cell population in the cat

Binocular deprivation of pattern vision (BD) early in life permanently impairs global motion perception. With the SMI‐32 antibody against neurofilament protein (NFP) as a marker of the motion‐sensitive Y‐cell pathway (Van der Gucht et al. [2001] Cereb. Cortex 17:2805–2819), we analyzed the impact of early BD on the retinal circuitry in adult, perceptually characterized cats (Burnat et al. [2005] Neuroreport 16:751–754). In controls, large retinal ganglion cells exhibited a strong NFP signal in the soma and in the proximal parts of the dendritic arbors. The NFP‐immunoreactive dendrites typically branched into sublamina a of the inner plexiform layer (IPL), i.e., the OFF inner plexiform sublamina. In the retina of adult BD cats, however, most of the NFP‐immunoreactive ganglion cell dendrites branched throughout the entire IPL. The NFP‐immunoreactive cell bodies were less regularly distributed, often appeared in pairs, and had a significantly larger diameter compared with NFP‐expressing cells in control retinas. These remarkable differences in the immunoreactivity pattern were typically observed in temporal retina. In conclusion, we show that the anatomical organization typical of premature Y‐type retinal ganglion cells persists into adulthood even if normal visual experience follows for years upon an initial 6‐month period of BD. Binocular pattern deprivation possibly induces a lifelong OFF functional domination, normally apparent only during development, putting early high‐quality vision forward as a premise for proper ON–OFF pathway segregation. These new observations for pattern‐deprived animals provide an anatomical basis for the well‐described motion perception deficits in congenital cataract patients. J. Comp. Neurol. 520:2414–2429, 2012.