John R. Heckenlively

Autoimmune retinopathy (AIR) was often mistaken for retinitis pigmentosa (RP), due to an overlap of clinical findings, but increasingly has been recognized as a unique entity in the last decade. AIR has distinctive features: sudden onset of photopsias and scotomata in patients with no family history of RP, followed by visual field and central vision loss. Initially, retina exams are normal with no sign of pigment deposits or retinal degeneration. A family history of autoimmune diseases (all types) occurs in 60% of patients. One hallmark of AIR has been the presence of anti-retinal autoimmune antibodies (ARAs) in patients’ sera, but patients can continue to have ARAs even when the disease has been quiescent for years. The accumulation of ARAs represents a breakdown of retinal immune tolerance with many different immunoreactive bands found at different reference weights in AIR patients. We began investigating cellular immunity using flow cytometry and found abnormal distributions (>2 StDev) of increased memory lymphocytes and NK cells and decreased regulatory B cell subsets in many AIR patients compared to normal controls. Culture of patient lymphocytes with small amounts (25 μg) of recoverin protein for 6 days led to significant elevations of interferon gamma (IFNγ) and in some cases tumor necrosis factor alpha (TNFα) production. We found the IFNγ/IL-10 ratio in response to recoverin was elevated in patients with more active disease (defined by visual field contraction between visits), but in some patients, there also appeared to be independent factors influencing severity, suggesting other autoimmune mechanisms were at play. These cellular immune parameters may provide improved markers for active AIR.

To develop a reliable and efficient digital method to quantify planimetric Goldmann visual field (GVF) data to monitor disease course and treatment responses in retinal degenerative diseases.

Purpose.: To determine the proportion of male patients presenting simplex retinal degenerative disease (RD: retinitis pigmentosa [RP] or cone/cone-rod dystrophy [COD/CORD]) with mutations in the X-linked retinal degeneration genes RPGR and RP2. Methods.: Simplex males were defined as patients with no known affected family members. Patients were excluded if they had a family history of parental consanguinity. Blood samples from a total of 214 simplex males with a diagnosis of retinal degeneration were collected for genetic analysis. The patients were screened for mutations in RPGR and RP2 by direct sequencing of PCR-amplified genomic DNA. Results.: We identified pathogenic mutations in 32 of the 214 patients screened (15%). Of the 29 patients with a diagnosis of COD/CORD, four mutations were identified in the ORF15 mutational hotspot of the RPGR gene. Of the 185 RP patients, three patients had mutations in RP2 and 25 had RPGR mutations (including 12 in the ORF15 region). Conclusions.: This study represents mutation screening of RPGR and RP2 in the largest cohort, to date, of simplex males affected with RP or COD/CORD. Our results demonstrate a substantial contribution of RPGR mutations to retinal degenerations, and in particular, to simplex RP. Based on our findings, we suggest that RPGR should be considered as a first tier gene for screening isolated males with retinal degeneration.

To establish the normal range of values for rod-isolated b-wave amplitudes in achromatopsia and cone dystrophies.

Animal models of human disease are an invaluable component of studies aimed at understanding disease pathogenesis and therapeutic possibilities. Mutations in the gene encoding retinitis pigmentosa GTPase regulator (RPGR) are the most common cause of X-linked retinitis pigmentosa (XLRP) and are estimated to cause 20% of all retinal dystrophy cases. A majority of RPGR mutations are present in ORF15, the purine-rich terminal exon of the predominant splice-variant expressed in retina. Here we describe the genetic and phenotypic characterization of the retinal degeneration 9 (Rd9) strain of mice, a naturally occurring animal model of XLRP. Rd9 mice were found to carry a 32-base-pair duplication within ORF15 that causes a shift in the reading frame that introduces a premature-stop codon. Rpgr ORF15 transcripts, but not protein, were detected in retinas from Rd9/Y male mice that exhibited retinal pathology, including pigment loss and slowly progressing decrease in outer nuclear layer thickness. The levels of rhodopsin and transducin in rod outer segments were also decreased, and M-cone opsin appeared mislocalized within cone photoreceptors. In addition, electroretinogram (ERG) a- and b-wave amplitudes of both Rd9/Y male and Rd9/Rd9 female mice showed moderate gradual reduction that continued to 24 months of age. The presence of multiple retinal features that correlate with findings in individuals with XLRP identifies Rd9 as a valuable model for use in gaining insight into ORF15-associated disease progression and pathogenesis, as well as accelerating the development and testing of therapeutic strategies for this common form of retinal dystrophy.

Retinitis pigmentosa (RP) is a clinically and genetically heterogeneous group of retinal disorders that causes progressive loss of visual function due to rod and cone photoreceptor degeneration. The X-linked forms of RP (XLRP) account for 10% to 20% of all RP cases.^1-3 Two genes have been cloned for XLRP: retinitis pigmentosa GTPase regulator, RPGR (OMIM 312610),⁴ and RP2 (OMIM 312600),^5,6 which together account for more than 80% of XLRP.^7-10