Stickler syndrome associated with epilepsy: report of three cases

Genetic Characteristics and Phenotype of Korean Patients with Stickler Syndrome: A Korean Multicenter Analysis Report No. 1

Stickler syndrome is an inherited connective tissue disorder of collagen. There are relatively few reports of East Asian patients, and no large-scale studies have been conducted in Korean patients yet. In this study, we retrospectively analyzed the genetic characteristics and clinical features of Korean Stickler syndrome patients. Among 37 genetically confirmed Stickler syndrome patients, 21 types of gene variants were identified, of which 12 were novel variants. A total of 30 people had variants in the COL2A1 gene and 7 had variants in the COL11A1 gene. Among the types of pathogenic variants, missense variants were found in 11, nonsense variants in 8, and splice site variants in 7. Splicing variants were frequently associated with retinal detachment (71%) followed by missense variants. This is the first large-scale study of Koreans with Stickler syndrome, which will expand the spectrum of genetic variations of Stickler syndrome.

Mutation Spectrum and De Novo Mutation Analysis in Stickler Syndrome Patients with High Myopia or Retinal Detachment

Stickler syndrome is a connective tissue disorder that affects multiple systems, including the visual system. Seven genes were reported to cause Stickler syndrome in patients with different phenotypes. In this study, we aimed to evaluate the mutation features of the phenotypes of high myopia and retinal detachment. Forty-two probands diagnosed with Stickler syndrome were included. Comprehensive ocular examinations were performed. A targeted gene panel test or whole exome sequencing was used to detect the mutations, and Sanger sequencing was conducted for verification and segregation analysis. Among the 42 probands, 32 (76%) presented with high myopia and 29 (69%), with retinal detachment. Pathogenic mutations were detected in 35 (83%) probands: 27 (64%) probands had COL2A1 mutations, and eight (19%) probands had COL11A1 mutations. Truncational mutations in COL2A1 were present in 21 (78%) probands. Missense mutations in COL2A1 were present in six probands, five of which presented with retinal detachment. De novo COL2A1 mutations were detected in 10 (37%) probands, with a mean paternal childbearing age of 29.64 ± 4.97 years old. The mutation features of probands with high myopia or retinal detachment showed that the probands had a high prevalence of COL2A1 mutations, truncational mutations, and de novo mutations.

Integrated analysis of COL2A1 variant data and classification of type II collagenopathies

The COL2A1 gene encodes the alpha-1 chain of type II procollagen. Type II collagen, comprised of three identical alpha-1 chains, is the major component of cartilage. COL2A1 gene variants are the etiologies of genetic diseases, termed type II collagenopathies, with a wide spectrum of clinical presentations. To date, at least 460 distinct COL2A1 mutations, identified in 663 independent probands, and 21 definite disorders have been reported. Nevertheless, a well-defined genotype-phenotype correlation has not been established, and few hot spots of mutation have been reported. In this study, we analyzed data of COL2A1 variants and clinical information of patients obtained from the Leiden Open Variation Database 3.0, as well as the currently available relevant literature. We determined the characteristics of the COL2A1 variants and distributions of the clinical manifestations in patients, and identified four likely genotype-phenotype correlations. Moreover, we classified 21 COL2A1-related disorders into five categories, which may assist clinicians in understanding the essence of these complex phenotypes and prompt genetic screening in clinical practice.

Targeted next‑generation sequencing identifies two novel COL2A1 gene mutations in Stickler syndrome with bilateral retinal detachment

Stickler syndrome is a group of inherited connective tissue disorders characterized by distinctive facial and ocular abnormalities, hearing loss and early‑onset arthritis. The aim of the present study was to investigate the genetic changes in two Chinese patients with Stickler syndrome, manifested as bilateral retinal detachment and peripheral retinal degeneration. Complete ophthalmic examinations, including best‑corrected visual acuity, slit‑lamp examination and fundus examination, were performed. Genomic DNA was extracted from leukocytes of the peripheral blood collected from the patients, their unaffected family members and 200 unrelated control subjects from the same population. Next‑generation sequencing of established genes associated with ocular disease was performed. A heterozygous collagen type II α1 chain (COL2A1) mutation c.1310G>C (p.R437P) in exon 21 was identified in Family 1 and a heterozygous COL2A1 mutation c.2302‑1G>A in intron 34 was identified in Family 2. The functional effects of the mutations were assessed by polymorphism phenotyping (PolyPhen) and sorting intolerant from tolerant (SIFT) analysis. The c.1310G>C mutation was predicted to damage protein structure and function, and the c.2302‑1G>A mutation was predicted to result in a splicing defect. The findings of the current study expand the established mutation spectrum of COL2A1, and may facilitate genetic counseling and development of therapeutic strategies for patients with Stickler syndrome.

Frequent mutations of RetNet genes in eoHM: Further confirmation in 325 probands and comparison with late-onset high myopia based on exome sequencing

In our previous study, potential pathological mutations of RetNet genes were detected in 23.8% (71/298) of probands with early-onset high myopia (eoHM), based on whole exome sequencing (WES). The current study aimed to confirm this finding in an additional 325 probands with eoHM and to clarify its specificity by comparison of 195 probands with late-onset high myopia (loHM). Variants in the 234 RetNet genes were selected from whole-exome sequencing data and were filtered using multistep bioinformatics analyses. Potential pathological variants in 33 genes were detected in 76 of 325 (23.4%) probands with eoHM and 14 of 195 (7.2%) probands with loHM. Thirty-five of the 76 (46.1%) probands with eoHM had mutations in COL2A1, COL11A1, RPGR, and CACNAIF, while only 2/14 (14.3%) probands with eoHM were detected. The mutation frequency and spectrum of RetNet genes in the 325 probands with eoHM were similar to our previous study but were significantly different in 195 probands with loHM (P = 2 × 10^-6 and 0.04). Data from eoHM and loHM strongly suggest that a significant proportion of eoHM is caused by mutations in RetNet genes. These results also provide initial genetic evidence that eoHM is different from loHM. The presence of mutations in 7.2% probands with loHM raises questions about pathogenicity and the variable manifestation of some mutations. The functional studies of the mutations in question and more extensive investigations of related phenotypes in the mutation carriers and their family members may provide valuable information to address these questions.