Abstract
Purpose: :
Linkers of the Nucleoskeleton to the Cytoskeleton (LINC complexes) designate evolutionary-conserved macromolecular complexes that span the nuclear envelope and physically connect the nuclear interior to cytoskeletal networks and molecular motors. They form through direct interactions between inner nuclear membrane Sun proteins (Sun1 and Sun2) and outer nuclear membrane Nesprins (Nesprin 1, 2, 3 and 4) within the perinuclear space. In C.elegans and D. melanogaster, mutation of Sun and Nesprin orthologs prevent nuclear anchorage and/or migration within cells or syncitia. Mouse models deficient for both Sun1 and Sun2 expression display abnormal migration of cortical neurons. Our goal is to identify the role of LINC complexes during mammalian CNS tissue development and homeostasis. To this end, the mouse retina offers several advantages because 1) different types of nucleokinetic events such as interkinetic nuclear migration and postmitotic neuronal migration can be targeted in vivo without affecting other CNS tissues, 2) the retina consists of a laminated tissue where nuclei of various cell types are anchored at specific spatial positions and 3) retinal neurons are amenable to functional testing thereby allowing for functional analyses in vivo.
Methods: :
Using immunofluorescence microscopy, we characterized the expression of LINC complex components during mouse retinal development. We further developed a new versatile transgenic mouse model allowing for the conditional disruption of LINC complexes in retinal neurons.
Results: :
We report the ectopic positioning of cone photoreceptor nuclei upon LINC complex disruption. These results demonstrate the possibility to target the disruption of LINC complexes in vivo in a cell type-specific manner and further emphasize the relevance of Sun proteins and Nesprins in the positioning of cone photoreceptor nuclei.
Conclusions: :
Our mouse model will allow the analysis of the contribution of LINC complexes to nuclear positioning within additional retinal neurons and as well as in the molecular mechanisms that govern the development of the laminar organization of the mammalian retina.
Keywords: retinal development • transgenics/knock-outs • photoreceptors