Identifying Key Networks Linked to Light-Independent Photoreceptor Degeneration in Visual Arrestin 1 Knockout Mice.

When visual arrestin 1 (ARR1, S-antigen, 48 KDa protein) was genetically knocked out in mice (original Arr1 , designated Arr1 ), rod photoreceptors degenerated in a light-dependent manner. Subsequently, a light-independent cone dystrophy was identified with minimal rod death in ARR1 knockout mice (Arr1 Arr4 , designated Arr1 ), which were F2 littermates from breeding the original Arr1 and cone arrestin knockout 4 (Arr4 ) mice. To resolve the genetic and phenotypic differences between the two ARR1 knockouts, we performed Affymetrix™ exon array analysis to focus on the potential differential gene expression profile and to explore the molecular and cellular pathways leading to this observed susceptibility to cone dystrophy in Arr1 compared to Arr1 or control Arr1 Arr4 (wild type [WT]). Only in the Arr1 retina did we observe an up-regulation of retinal transcripts involved in the immune response, inflammatory response and JAK-STAT signaling molecules, OSMRβ and phosphorylation of STAT3. Of these responses, the complement system was significantly higher, and a variety of inflammatory responses by complement regulation and anti-inflammatory cytokine or factors were identified in Arr1 retinal transcripts. This discovery supports that Arr1 has a distinct genetic background from Arr1 that results in alterations in its retinal phenotype leading to susceptibility to cone degeneration induced by inappropriate inflammatory and immune responses.