SCAPER-Related Autosomal Recessive Retinitis Pigmentosa with Intellectual Disability: Confirming and Extending the Phenotypic Spectrum and Bioinformatics Analyses.

Mutations in the gene SCAPER (S phase Cyclin A-Associated Protein residing in the Endoplasmic Reticulum) have recently been associated with retinitis pigmentosa (RP) and intellectual disability (ID). In 2011, a possible involvement of SCAPER in human diseases was discovered for the first time due to the identification of a homozygous mutation causing ID in an Iranian family. Later, five studies were published in 2019 that described patients with autosomal recessive syndromic retinitis pigmentosa (arRP) accompanied by ID and attention-deficit/hyperactivity disorder (ADHD). This present study describes three patients from an Arab consanguineous family in Israel with similar clinical features of the SCAPER syndrome. In addition, new manifestations of ocular symptoms, nystagmus, glaucoma, and elevator palsy, were observed. Genetic testing of the patients and both parents via whole-exome sequencing revealed the homozygous mutation c.2023-2A>G in SCAPER. Phenotypic and genotypic descriptions for all available cases described in the literature including our current three cases (37 cases) were carried out, in addition to a bioinformatics analysis for all the genetic variants that was undertaken. Our study confirms and extends the clinical manifestations of SCAPER-related disorders.

Syndromic retinitis pigmentosa caused by biallelic SCAPER frameshift variant.

PURPOSE: Mutations in the SCAPER gene have previously been reported to be a rare cause of syndromic and non-syndromic autosomal recessive retinitis pigmentosa (RP). We report a case of syndromic RP caused by a frameshift heterozygous mutation in SCAPER. Our case has a relatively mild ocular phenotype with the presence of cone involvement noted on full field electroretinogram (ffERG) without impacting central or color vision. MATERIALS AND METHODS: A 17-year-old male presented with progressive nyctalopia in both eyes. He underwent ophthalmic examination and multimodal imaging. A complete retinal degeneration panel consisting of 322 genes was used to screen for molecular causes of retinal dystrophy in this patient along with family segregation analysis. RESULTS: Fundus examination of the proband revealed mild RP phenotype with waxy pallor of optic discs, attenuated retinal arterioles, and single bone spicule like pigmentary change in the mid-periphery bilaterally. Multimodal imaging and ffERG demonstrated a picture of RP with cone dysfunction without impacting central or color vision bilaterally. Examined family members were found to be normal. The proband was found to be heterozygous for two novel frameshift pathogenic variants in SCAPER c.3781del, p. (Val1261Serfs*26), c.868_869del, p. (Glu290Serfs*7) both leading to predicted premature termination. The family members tested were found to be heterozygous for SCAPER c.868_869del, p. (Glu290Serfs*7) pathogenic variant confirming their carrier status. CONCLUSION: We report a case of a syndromic RP of previously unreported ocular phenotype associated with SCAPER pathogenic variant, which will add to the phenotypic spectrum of retinopathy and systemic features associated with pathogenic variants in SCAPER.

Homozygous variants in the gene SCAPER cause syndromic intellectual disability.

The S-Phase Cyclin A Associated Protein In The ER (SCAPER) gene is a ubiquitously expressed gene with unknown function in the brain. Recently, biallelic SCAPER variants were described in four patients from three families with retinitis pigmentosa (RP) and intellectual disability (ID). Here, we expand the spectrum of pathogenic variants in SCAPER and report on 10 further patients from four families with ID, RP, and additional dysmorphic features carrying homozygous variants in SCAPER. The variants found comprise frameshift, nonsense, and missense variants as well as an intragenic homozygous deletion, which spans SCAPER exons 15 and 16 and introduces a frameshift and a premature stop codon. Analyses of SCAPER expression in human and mouse brain revealed an upregulation of SCAPER expression during cortical development and a higher expression of SCAPER in neurons compared to neural progenitors. In the adult brain SCAPER is expressed in several regions including the cerebral cortex where it shows a layer-specific expression with an expression peak in lower layer glutamatergic neurons. Our study supports the role of SCAPER variants in the pathogenesis of ID and RP, expands the variant spectrum and highlights the need for functional studies concerning the role of SCAPER during brain development and function.

SCAPER-associated nonsyndromic autosomal recessive retinitis pigmentosa.

Mutations in the gene SCAPER (S-phase CyclinA Associated Protein residing in the Endoplasmic Reticulum) have recently been identified as causing syndromic autosomal recessive retinitis pigmentosa with the extraocular manifestations of intellectual disability and attention-deficit/hyperactivity disorder. We present the case of an 11-year-old boy that presented to our clinic with the complaint of decreased night vision. Clinical presentation, family history, and diagnostic imaging were congruent with the diagnosis of autosomal recessive retinitis pigmentosa. Genetic testing of the patient and both parents via whole-exome sequencing revealed the homozygous mutation c.2023-2A>G in SCAPER. Unique to our patient's presentation is the absence of intellectual disability and attention-deficit/hyperactivity disorder, suggesting that SCAPER-associated retinitis pigmentosa can also present without systemic manifestations.

Mutations in SCAPER cause autosomal recessive retinitis pigmentosa with intellectual disability.

BACKGROUND: Retinitis pigmentosa (RP) is the most common form of inherited retinal dystrophy, with a worldwide prevalence of 1 in 4000 persons. While in most cases of RP, the disease is limited to the eye (non-syndromic), over 40 forms of syndromic RP have been described. OBJECTIVES: To identify the genetic basis for syndromic RP in three unrelated families from Israel and Spain. METHODS: Whole exome sequencing was conducted in one Israeli and two Spanish families segregating autosomal recessive RP with intellectual disability. Complete ophthalmic examination included best-corrected visual acuity, funduscopy, optical coherence tomography, fluorescein angiography, flash visual evoked potentials, and electroretinography. Reverse transcription (RT)-PCR and immunostaining were used to examine the spatial and temporal expression pattern of SCAPER. RESULTS: In all patients, biallelic SCAPER mutations were observed. Clinically, patients with SCAPER mutations show signs of typical RP. In addition, they have mild to moderate intellectual disability and attention-deficit/hyperactivity disorder. SCAPER was found to be ubiquitously expressed in a wide range of human tissues, including retina and brain. Furthermore, RT-PCR analysis revealed that in both mouse eye and brain, Scaper is expressed as early as embryonic day 14. In the mouse retina, SCAPER is located in multiple layers, including the retinal pigment epithelium, photoreceptor outer and inner segments, the inner plexiform layer and the ganglion cell layer. CONCLUSIONS: Deleterious SCAPER mutations were identified in four patients from three unrelated families of different ethnic backgrounds, thereby confirming the involvement of this gene in the aetiology of autosomal recessive syndromic RP.