Extensive incorporation, polarisation and improved maturation of transplanted human cones in a murine cone degeneration model

Once human photoreceptors die, they do not regenerate, thus photoreceptor transplantation has emerged as a potential treatment approach for blinding diseases. Improvements in transplant organization, donor cell maturation and synaptic connectivity to the host will be critical in advancing this technology to clinical practice. Unlike the unstructured grafts of prior cell suspension transplantations into end-stage degeneration models, we describe extensive incorporation of iPSC retinal organoid-derived human photoreceptors into mice with cone dysfunction. This incorporative phenotype was validated in both cone-only as well as pan-photoreceptor transplantations. Rather than forming a glial barrier, Müller cells extend throughout the graft, even forming a common outer limiting membrane. Donor-host interaction appears to promote polarisation as well as development of morphological features critical for light detection, namely formation of inner and well stacked outer segments oriented towards the RPE. Putative synapse formation and graft function is evident both at a structural and electrophysiological level. Overall, these results show that human photoreceptors interact readily with a partially degenerated retina. Moreover, incorporation into the host retina appears to be beneficial to graft maturation, polarisation and function.

Blue Cone Monochromatism with Foveal Hypoplasia Caused by the Concomitant Effect of Variants in OPN1LW/OPN1MW and GPR143 Genes

Blue cone monochromatism (BCM) is an X-linked recessive cone dysfunction disorder caused by mutations in the OPN1LW/OPN1MW gene cluster, encoding long (L)- and middle (M)-wavelength-sensitive cone opsins. Here, we report on the unusual clinical presentation of BCM caused by a novel mutation in the OPN1LW gene in a young man. We describe in detail the phenotype of the proband, and the subclinical morpho-functional anomalies shown by his carrier mother. At a clinical level, the extensive functional evaluation demonstrated in the proband the M/L cone affection and the sparing of S-cone function, distinctive findings of BCM. Interestingly, spectral-domain optical coherence tomography showed the presence of foveal hypoplasia with focal irregularities of the ellipsoid layer in the foveal area, reported to be associated with some cases of cone-rod dystrophy and achromatopsia. At a molecular level, we identified the novel mutation c.427T > C p.(Ser143Pro) in the OPN1LW gene and the common missense mutation c.607T > C (p.Cys203Arg) in the OPN1MW gene. In addition, we discovered the c.768-2_769delAGTT splicing variant in the GPR143 gene. To our knowledge, this is the first case of foveal hypoplasia in a BCM patient and of mild clinical affection in a female carrier caused by the concomitant effect of variants in OPN1LW/OPN1MW and GPR143 genes, thus as the result of the simultaneous action of two independent genetic defects.

Retinitis Pigmentosa; Epidemiology, Pathophysiology, and Classification

Retinitis pigmentosa (RP) is the most common hereditary retinal degeneration. It primarily affects rods and then cone photoreceptors. RP manifests with night blindness and concentric visual field loss, reflecting the dysfunction of rod photoreceptors. Central visual acuity loss occurs last period of disease due to cone dysfunction; otherwise, macula involvements like cystoid macular edema. Classically described fundus appearance of RP includes mottling and granularity of the retina pigment epithelium, bone spicule intraretinal pigmentation, attenuated retinal vessels, and optic disc head pallor. RP can be transmitted as Mendelian’s an autosomal dominant, autosomal recessive, or X-linked trait. Mitochondrial or digenic forms also rarely have been described. However, the sporadic or simplex form is the most commonly seen in the clinic. Recently great progress has been made in the identification of the causative genes. This review presents a comprehensive overview of the clinical, genetic, and fundus photography, optical coherence tomography, fundus autofluorescence, microperimetry dark adaptometer, and ocular electrophysiology characteristics of RP.

Blue Cone Monochromatism: A Case Report with Opsoclonus and Light Exposure

Blue cone monochromatism (BCM) is a rare X-linked congenital vision disorder that is characterized by a cone dysfunction. We present a case of a 3-year-old boy referred to our department with abnormal eye movements since birth, impaired vision, and difficulties in distinguishing colors. A tendency to stare at the sun was noted. Examination revealed severe loss of visual acuity, high myopia, and opsoclonus. A mutation screening of OPN1LW/OPN1MW gene cluster was performed showing a nucleotide substitution encoding a Cys203Arg (C203R) missense mutation. The diagnosis of BCM in this case was clear and the patient harbored the most frequent genetic alteration. Opsoclonus and continued voluntary light exposure are novel features that have not been previously reported in BCM.