To identify potential cellular pathways involved in the cone dystrophy in the
Nrl −/− Grk1 −/− mouse, we performed microarray analysis in triplicate and analyzed our results using statistical analysis software (Genomic Suite; Partek) and IPA. The data reveal statistically significant differences (
P ≤ 0.005) and average fold changes (AFCs) ≥1.2 of 422 mapped genes using two-way ANOVA (Supplementary Table S1). The genes with statistically significant upregulation and an AFC <2.5 are listed in
Table 1, the statistically significantly downregulated genes with an AFC less than −3.0 are listed in
Table 2. Expression of 10 known genes (pituitary tumor transforming gene 1,
Pttg1; tetratricopeptide repeat domain,
28Ttc28; solute carrier family 6 [proline IMINO transporter], member 20,
Slc6a20; Ubxn4 UBX domain protein 4,
Ubxn4; Fanconi anemia, complementation group C,
Fancc; adenylate cyclase-associated protein 1,
Cap1; kallikrein 2,
Klk2; sorbin and SH3 domain containing 1,
Sorbs; coiled-coil domain containing 21,
Ccdc21; transmembrane protein 30A,
Tmem30A) was significantly increased in the
Nrl −/− Grk1 −/− compared with the
Nrl −/− group. On examination of the transcripts with the highest fold increases,
Pttg1 appears twice with a 130.7- and 70.0-fold increase (
Table 1). The
Pttg1 gene encodes for a transcription regulatory protein that can shuttle between the cytoplasm and nucleus with alternative roles in sister chromatid segregation.
23 Interestingly, Crumbs homolog 1 (
Crb1) transcript levels were decreased in
Nrl −/− Grk1 −/− mice approximately −6.3-fold compared with
Nrl −/− mice. This deregulation of
Crb1 and
Pttg1 has been observed in two separate photoreceptor dystrophy models, the Crb1- and Ras protein-specific guanine nucleotide releasing factor 1 (RasGRF1) null mutant mice, both of which demonstrate dystrophic retinas and are proposed models for retinal disease studies.
23,24 Klk2, with a fold increase of 29.7, was also examined because of its serine protease and autoantigenic functions and was recently identified as a major contributor in an experimental model for autoimmune keratoconjunctivitis sicca in Lewis rats.
25