The expression of dynein light chain DYNLL1 (LC8-1) is persistently downregulated in glaucomatous rat retinal ganglion cells

High intraocular pressure induces glaucomatous degeneration of retinal ganglion cells (RGCs). The cellular mechanisms leading to activation of the apoptosis cascade are multidimensional and only partially understood. A small dynein subunit, the light chain DYNLL1 (synonym LC8-1, PIN) has recently been shown to be an important regulator of neuron proteins known to be involved in glaucomatous RGC death including NO synthases, the pro-apoptotic protein Bim and the dynein intermediate chain. Also, DYNLL1 is a regulator of mitochondria anchorage in axons, which is impaired in glaucoma. We investigated expression of DYNLL1 and 2 and its dynein binding partner dynein intermediate chain in a rat model of chronic glaucoma. Laser capture microdissection (LCM) allowed us to collect distinct cell layers and cell bodies from the retina to gain data highly specific for retinal ganglion cells.Glaucoma was induced in 23 rats by laser treatment to the aqueous outflow tract. RNA was extracted from LCM dissected ganglion cell layers (GCL) and 100 pooled RGCs per retina. Expression levels for 1, 2 and 4 week timepoints were analysed by quantitative PCR for DYNLL1 and 2, dynein intermediate chain and GFAP. DYNLL protein abundance in RGCs was quantified in immunostained retina sections.DYNLL gene 1 but not 2 was expressed in RGCs. In the glaucoma model DYNLL1 was strongly and persistently downregulated at all timepoints. DYNLL protein was significantly less abundant at the 4 week timepoint. In contrast, the motorprotein binding partner dynein intermediate chain 1 was more stably expressed. DYNLL2 was upregulated in glia cells at 2 weeks.Expression of DYNLL1, the only form of the dynein light chain expressed in RGCs, is downregulated persistently in glaucoma, while its binding partner dynein IC-1 is unchanged. The specific lack of DYNLL1 could have an impact on the function of their regulatory binding partners and contribute in several ways to neuron dysfunction and apoptosis.

Research highlights
► Expression of the protein regulator DYNLL was studied in glaucomatous rat retina.
► Laser capture microdissection allowed selective analysis of the ganglion cell layer.
► DYNLL1 was persistently downregulated in retinal ganglion cells.
► DYNLL2 was upregulated in retinal glia cells.
► Neurotrophic signalling related dynein intermediate chain 1B remained unchanged.