CSNB1 in Chinese families associated with novel mutations in NYX

Novel Exon 7 Deletions in TSPAN12 in a Three-Generation FEVR Family: A Case Report and Literature Review

Familial exudative vitreoretinopathy (FEVR) is a severe clinically and genetically heterogeneous disease that is characterized by vascular disorder. FEVR exhibits strikingly variable clinical phenotypes, ranging from asymptomatic to total blindness. In this case, we present a patient who was first treated as having high myopia and retinopathy but was finally diagnosed with FEVR caused by the heterozygous deletion of exon 7 in TSPAN12 with the aid of whole genome sequencing (WGS). Typical vascular changes, including vascular leakage and an avascular zone in the peripheral retina, were observed in the proband using fundus fluorescein angiography (FFA), and the macular dragging was shown to be progressing in the follow-up visit. Furthermore, the proband showed unreported TSPAN12-related phenotypes of FEVR: ERG (full-field electroretinogram) abnormalities and retinoschisis. Only mild vascular changes were exhibited in the FFA for the other three family members who carried the same deletion of exon 7 in TSPAN12. This case expands our understanding of the phenotype resulting from TSPAN12 mutations and signifies the importance of combining both clinical and molecular analysis approaches to establish a complete diagnosis.

Sequence features, structure, ligand interaction, and diseases in small leucine rich repeat proteoglycans

Small leucine rich repeat proteoglycans (SLRPs) are a group of active components of the extracellular matrix in all tissues. SLRPs bind to collagens and regulate collagen fibril growth and fibril organization. SLRPs also interact with various cytokines and extracellular compounds, which lead to various biological functions such cell adhesion and signaling, proliferation, and differentiation. Mutations in SLRP genes are associated with human diseases. Now crystal structures of five SLRPs are available. We describe some features of amino acid sequence and structures of SLRPs. We also review ligand interactions and then discuss the interaction surfaces. Furthermore, we map mutations associated with human diseases and discuss possible effects on structures by the mutations.

Leucine Rich Repeat Proteins: Sequences, Mutations, Structures and Diseases

Mutations in the genes encoding Leucine Rich Repeat (LRR) containing proteins are associated with over sixty human diseases; these include high myopia, mitochondrial encephalomyopathy, and Crohn's disease. These mutations occur frequently within the LRR domains and within the regions that shield the hydrophobic core of the LRR domain. The amino acid sequences of fifty-five LRR proteins have been published. They include Nod-Like Receptors (NLRs) such as NLRP1, NLRP3, NLRP14, and Nod-2, Small Leucine Rich Repeat Proteoglycans (SLRPs) such as keratocan, lumican, fibromodulin, PRELP, biglycan, and nyctalopin, and F-box/LRR-repeat proteins such as FBXL2, FBXL4, and FBXL12. For example, 363 missense mutations have been identified. Replacement of arginine, proline, or cysteine by another amino acid, or the reverse, is frequently observed. The diverse effects of the mutations are discussed based on the known structures of LRR proteins. These mutations influence protein folding, aggregation, oligomerization, stability, protein-ligand interactions, disulfide bond formation, and glycosylation. Most of the mutations cause loss of function and a few, gain of function.

Novel TRPM1 mutations in two Chinese families with early-onset high myopia, with or without complete congenital stationary night blindness

AIM

To investigate the relationship between high myopia [with or without complete congenital stationary night blindness (CSNB1)] and TRPM1 and NYX.

METHODS

Two unrelated families with early-onset high myopia (eoHM) and 96 normal controls were recruited. Sanger sequencing or clone sequencing were used for mutation screening. Further analyses of the available family members and the 96 normal controls were subsequently conducted to obtain additional evidence of the pathogenicity of these variants. The initial diagnosis of the probands was eoHM. We performed a further comprehensive examination of the available family members after mutations were detected in TRPM1 or NYX.

RESULTS

Two novel compound heterozygous mutations in TRPM1 were detected in the recruited families. The proband in family A with eoHM carried a c.2594C>T missense mutation in exon 19 and a c.669+3_669+6delAAGT splicing mutation, which was co-segregated with CSNB1 in this family. A patient in family B with a compound heterozygous missense mutation (c.3262G>A and c.3250T>C) was detected. No mutations were found in NYX. These two identified compound heterozygous mutations were not found in the 96 normal controls. After further examination of the family members, the patients in family A could be diagnosed as eoHM with CSNB1. However due to the limited clinic data, the patient in family B cloud not clearly diagnosed as CSNB1.

CONCLUSION

This study has expanded the mutation spectrum of TRPM1 for CSNB1 and additional studies are needed to elucidate the association between isolated high myopia and TRPM1 and NYX.

Association of ZNF644, GRM6, and CTNND2 genes with high myopia in the Han Chinese population: Jiangsu Eye Study

AimsHigh myopia is a common visual disorder in the world. The ZNF644, GRM6, and CTNND2 genes are expressed in the retina. This study aims to investigate the associations of these genes with high myopia in Han Chinese population.MethodsThe case-control association included high myopia cases (n=430) and controls (n=430) recruited from a population-based study, 'Jiangsu Eye Study'. Fourteen single-nucleotide polymorphisms (SNPs) in three genes were genotyped by the TaqMan method using the real-time PCR system.ResultsThree SNPs GRM6-rs11746675, GRM6-rs2067011, and GRM6-rs2645339 were associated with high myopia (odds ratio (OR)=0.74, P=0.003; OR=0.78, P=0.018; and OR=0.78, P=0.023; respectively). The significances of rs2067011 and rs2645339 disappeared after multiple testing corrections. Rs11746675 remained significant after correction for multiple testing. The genetic model analysis found that GRM6-rs11746675 and GRM6-rs2067011 were suggestively associated with high myopia in the recessive model (OR=0.54, P=0.004; OR=0.52, P=0.003; respectively). Haplotype GAT for GRM6 markers rs2067011-rs2645339-rs762724 showed significance (P=0.0239), but such association did not remain significant after multiple testing corrections.ConclusionsOur data suggested that genetic variants in GRM6 are associated with high myopia. The mechanism of GRM6 in the development of high myopia need to be further investigated.

Two Novel NYX Gene Mutations in the Chinese Families with X-linked Congenital Stationary Night Blindness

Mutations in NYX and CACNA1F gene are responsible for the X-linked congenital stationary night blindness (CSNB). In this study, we described the clinical characters of the two Chinese families with X-linked CSNB and detected two novel mutations of c. 371_377delGCTACCT and c.214A>C in the NYX gene by direct sequencing. These two mutations would expand the mutation spectrum of NYX. Our study would be helpful for further studying molecular pathogenesis of CSNB.

Genetics of Refraction and Myopia

Both genetic and environmental factors play roles in the development of refractive errors. Identification of genes involved in refractive errors may help in elucidating the underlying molecular mechanism related to both genetic defects and environmental pressure. Recent development of techniques for genome wide analysis provides unique opportunity in dissecting the genetic basis related to refractive errors. This chapter tries to give a brief overview on the recent progress of genetic study of refractive errors, especially myopia.

Mutation screening of TRPM1, GRM6, NYX and CACNA1F genes in patients with congenital stationary night blindness

The aim of this study was to identify mutations in the TRPM1, GRM6, NYX and CACNA1F genes in patients with congenital stationary night blindness (CSNB). Twenty-four unrelated patients with CSNB were ascertained. Sanger sequencing was used to analyze the coding exons and adjacent intronic regions of TRPM1, GRM6, NYX and CACNA1F. Six mutations were identified in six unrelated patients, including five novel and one known. Of the six, three novel hemizygous mutations, c.92G>A (p.Cys31Tyr), c.149G>C (p.Ary50Pro), and c.[272T>A;1429G>C] (p.[Leu91Gln;Gly477Arg]), were found in NYX in three patients, respectively. A novel c.[1984_1986delCTC;3001G>A] (p.[Leu662del;Gly1001Arg]) mutation was detected in CACNA1F in one patient. One novel and one known heterozygous variation, c.1267T>C (p.Cys423Arg) and c.1537G>A (p.Val513Met), were detected in GRM6 in two patients, respectively. No variations were found in TRPM1. The results expand the mutation spectrum of NYX, CACNA1F and GRM6. They also suggest that NYX mutations are a common cause of CSNB.

Differential gene expression of TRPM1, the potential cause of congenital stationary night blindness and coat spotting patterns (LP) in the Appaloosa horse (Equus caballus)

The appaloosa coat spotting pattern in horses is caused by a single incomplete dominant gene (LP). Homozygosity for LP (LP/LP) is directly associated with congenital stationary night blindness (CSNB) in Appaloosa horses. LP maps to a 6-cM region on ECA1. We investigated the relative expression of two functional candidate genes located in this LP candidate region (TRPM1 and OCA2), as well as three other linked loci (TJP1, MTMR10, and OTUD7A) by quantitative real-time RT-PCR. No large differences were found for expression levels of TJP1, MTMR10, OTUD7A, and OCA2. However, TRPM1 (Transient Receptor Potential Cation Channel, Subfamily M, Member 1) expression in the retina of homozygous appaloosa horses was 0.05% the level found in non-appaloosa horses (R = 0.0005). This constitutes a >1800-fold change (FC) decrease in TRPM1 gene expression in the retina (FC = -1870.637, P = 0.001) of CSNB-affected (LP/LP) horses. TRPM1 was also downregulated in LP/LP pigmented skin (R = 0.005, FC = -193.963, P = 0.001) and in LP/LP unpigmented skin (R = 0.003, FC = -288.686, P = 0.001) and was downregulated to a lesser extent in LP/lp unpigmented skin (R = 0.027, FC = -36.583, P = 0.001). TRP proteins are thought to have a role in controlling intracellular Ca(2+) concentration. Decreased expression of TRPM1 in the eye and the skin may alter bipolar cell signaling as well as melanocyte function, thus causing both CSNB and LP in horses.