Novel gene variants in Polish patients with Leber congenital amaurosis (LCA)

Abstract

Background: Leber congenital amaurosis (LCA) is a rare retinal disease that is the most frequent cause of congenital blindness in children and the most severe form of inherited retinal dystrophies. To date, 25 genes have been implicated in the pathogenesis of LCA. As gene therapy is becoming available, the identification of potential treatment candidates is crucial. The aim of the study was to report the molecular basis of Leber congenital amaurosis in 22 Polish families.

Methods: Single Nucleotide Polymorphism-microarray for LCA genes or Next Generation Sequencing diagnostic panel for LCA genes (or both tests) were performed to identify potentially pathogenic variants. Bidirectional Sanger sequencing was carried out for validation and segregation analysis of the variants identified within the families.

Results: The molecular background was established in 22 families. From a total of 24 identified variants, 23 were predicted to affect protein-coding or splicing, including 10 novel variants. The variants were identified in 7 genes: CEP290, GUCY2D, RPE65, NMNAT1, CRB1, RPGRIP1, and CRX. More than one-third of the patients, with clinical LCA diagnosis confirmed by the results of molecular analysis, appeared to be affected with a severe form of the disease: LCA10 caused by the CEP290 gene variants. Intronic mutation c.2991+1655A>G in the CEP290 gene was the most frequent variant identified in the studied group.

Conclusions: This study provides the first molecular genetic characteristics of patients with Leber congenital amaurosis from the previously unexplored Polish population. Our study expands the mutational spectrum as we report 10 novel variants identified in LCA genes. The fact that the most frequent causes of the disease in the studied group of Polish patients are mutations in one out of three genes that are currently the targets for gene therapy (CEP290, GUCY2D, and RPE65) strongly emphasizes the importance of the molecular background analyses of LCA in Polish patients.

Keywords: Leber congenital amaurosis (LCA); Novel variants; SNP-microarray for LCA genes; Targeted NGS panel for LCA genes.

Fig. 1

Pedigrees of the families with novel variants in LCA genes. Filled symbols indicate individuals affected with LCA and unfilled symbols indicate unaffected individuals. A slash indicates a deceased person. Arrows indicate probands

Fig. 2

Photographs I.—Retinal features of Patient 6–18. a, b Color fundus photographs show bilateral mottled fundus appearance, foveal atrophy with focal pigmentary changes in the macula and peripheral regions (bone-spicule pigmentation), and attenuation of the vasculature and optic nerve pallor. c a 6-mm horizontal SD-OCT image of the right eye showing substantial photoreceptor loss, retinal architecture disorganization with thinning of outer layers, and enhanced choroidal signal penetration (the scan acquired above the fovea due to poor fixation). d 10 × 3.5 mm horizontal SD-OCT macular scan of the left eye demonstrating severe photoreceptor loss, focal RPE hypertrophy, and generalized retinal thinning. Photographs II.—Retinal features of Patient 13–54. a, b Color fundus images showing bilateral fine chorioretinal atrophy around the pale optic nerve with moderate vascular attenuation as well as fine peripheral pigmentary changes. c, d 10 × 3.5 mm horizontal SD-OCT scans showing intact foveal contour and symmetrical moderate thinning of outer retinal layers with enhanced choroidal signal penetration

Fig. 3

Chromatograms showing novel variants identified in LCA genes. Arrows indicate nucleotides that have been changed or the first nucleotides involved in the variation. The yellow background appears in chromatograms with frameshift variants, and it usually begins from the first nucleotide involved in the variation (excluding d, e, and j)