MSH2-MSH3 promotes DNA end resection during homologous recombination and blocks polymerase theta-mediated end-joining through interaction with SMARCAD1 and EXO1.

DNA double-strand break (DSB) repair via homologous recombination is initiated by end resection. The extent of DNA end resection determines the choice of the DSB repair pathway. Nucleases for end resection have been extensively studied. However, it is still unclear how the potential DNA structures generated by the initial short resection by MRE11-RAD50-NBS1 are recognized and recruit proteins, such as EXO1, to DSB sites to facilitate long-range resection. We found that the MSH2-MSH3 mismatch repair complex is recruited to DSB sites through interaction with the chromatin remodeling protein SMARCAD1. MSH2-MSH3 facilitates the recruitment of EXO1 for long-range resection and enhances its enzymatic activity. MSH2-MSH3 also inhibits access of POLθ, which promotes polymerase theta-mediated end-joining (TMEJ). Collectively, we present a direct role of MSH2-MSH3 in the initial stages of DSB repair by promoting end resection and influencing the DSB repair pathway by favoring homologous recombination over TMEJ.

Precision targeting tumor cells using cancer-specific InDel mutations with CRISPR-Cas9.

An ideal cancer therapeutic strategy involves the selective killing of cancer cells without affecting the surrounding normal cells. However, researchers have failed to develop such methods for achieving selective cancer cell death because of shared features between cancerous and normal cells. In this study, we have developed a therapeutic strategy called the cancer-specific insertions-deletions (InDels) attacker (CINDELA) to selectively induce cancer cell death using the CRISPR-Cas system. CINDELA utilizes a previously unexplored idea of introducing CRISPR-mediated DNA double-strand breaks (DSBs) in a cancer-specific fashion to facilitate specific cell death. In particular, CINDELA targets multiple InDels with CRISPR-Cas9 to produce many DNA DSBs that result in cancer-specific cell death. As a proof of concept, we demonstrate here that CINDELA selectively kills human cancer cell lines, xenograft human tumors in mice, patient-derived glioblastoma, and lung patient-driven xenograft tumors without affecting healthy human cells or altering mouse growth.

HDAC6 preserves BNIP3 expression and mitochondrial integrity by deacetylating p53 at lysine 320.

HDAC6 has been reported as a deacetylase of p53 at multiple lysine residues, associated with the canonical functions of p53, such as apoptosis and tumor suppression. We have previously reported that p53 acetylation at the lysine 320 site accumulates due to the genetic ablation of HDAC6 in mice liver. However, the biological processes affected by K320 acetylation of p53 are yet to be elucidated. In this study, we demonstrate that K320 acetylation of p53 is regulated by HDAC6 deacetylase activity. HDAC6 knockout mouse brains exhibit a significant accumulation of K320 acetylated p53 compared to other tissues. The level of K320 acetylation of p53 inversely correlates with the level of BNIP3, a direct target of p53 and essential for mitophagy. Notably, overexpressing the deacetylation mimic K320R mutant p53 restored BNIP3 expression in HDAC6 knockout MEFs. Furthermore, we observed that neurons are particularly susceptible to the genetic ablation of HDAC6, impacting BNIP3 expression, which inversely correlates with the accumulation of abnormal mitochondria characterized by swollen cristae. Our findings suggest that HDAC6 plays a crucial role in maintaining BNIP3 expression by deacetylating p53 at the K320 site, which is linked to the structural integrity of mitochondria.

Two novel non-coding single nucleotide variants in the DNase1 hypersensitivity site of PRDM13 causing North Carolina macular dystrophy in Korea.

Purpose: Pathogenic variants in North Carolina macular dystrophy (NCMD) have rarely been reported in the East Asian population. Herein, we reported novel variants of NCMD in 2 Korean families. Methods: The regions associated with NCMD were analyzed with genome sequencing, and variants were filtered based on the minor allele frequency (0.5%) and heterozygosity. Non-coding variants were functionally annotated using multiple computational tools. Results: We identified two rare novel variants, chr6:g.99,598,914T>C (hg38; V17) and chr6:g.99,598,926G>A (hg38; V18) upstream of PRDM13 in families A and B, respectively. In Family 1, Grade 2 NCMD and a best-corrected visual acuity of 20/25 and 20/200 in the right and left eyes, respectively, were observed. In Family B, all affected individuals had Grade 1 NCMD with characteristic confluent drusen at the fovea and a best-corrected visual acuity of 20/20 in both eyes. These two variants are 10-22 bp downstream of the reported V10 variant within the DNase1 hypersensitivity site. This site is associated with progressive bifocal chorioretinal atrophy and congenital posterior polar chorioretinal hypertrophy and lies in the putative enhancer site of PRDM13. Conclusion: We identified two novel NCMD variants in the Korean population and further validated the regulatory role of the DNase1 hypersensitivity site upstream of PRDM13.

Expanding SPG7 dominant optic atrophy phenotype: Infantile nystagmus and optic atrophy without spastic paraplegia.

Spastic paraplegia is a neurodegenerative disorder characterized by progressive leg weakness and spasticity due to degeneration of corticospinal axons. SPG7 encodes paraplegin, and pathogenic variants in the gene cause hereditary spastic paraplegia as an autosomal recessive trait. Various ophthalmological findings including optic atrophy, ophthalmoplegia, or nystagmus have been reported in patients with spastic paraplegia type 7. We report a 15-year-old male patient with a novel heterozygous variant, c.1224T>G:p.(Asp408Glu) in SPG7 (NM_003119.3) causing early onset isolated optic atrophy and infantile nystagmus prior to the onset of neurological symptoms. Therefore, SPG7 should be considered a cause of infantile nystagmus with optic atrophy.

Retinal Proteome Analysis Reveals a Region-Specific Change in the Rabbit Myopia Model.

Uncovering region-specific changes in the myopic retina can provide clues to the pathogenesis of myopia progression. After imposing form deprivation myopia in the right eye of 6-week-old rabbits, we investigated the proteome profile of each retinal region (central, mid-periphery, and far-periphery retina), using accurate high-resolution mass spectrometry. Protein expression was analyzed using gene ontology and network analysis compared with that of the control, the left eyes. Among 2065 proteins detected from whole retinal samples, 249 differentially expressed proteins (DEPs) were identified: 164 DEPs in the far-periphery, 39 in the mid-periphery, and 83 in the central retina. In network analysis, the far-periphery retina showed the most significant connectivity between DEPs. The regulation of coagulation was the most significant biological process in upregulated DEPs in the far-periphery retina. Proteasome was the most significant Kyoto Encyclopedia of Genes and Genomes pathway in downregulated DEPs in the central retina. Antithrombin-III, fibrinogen gamma chain, and fibrinogen beta chain were identified as hub proteins for myopia progression, which were upregulated in the far-periphery retina. Proteomic analysis in this study suggested that oxidative stress can be the primary pathogenesis of myopia progression and that the far-periphery retina plays a role as the key responder.

Opposing roles of HDAC6 in liver regeneration and hepatocarcinogenesis.

Histone deacetylase 6 (HDAC6), a deacetylase of p53, has emerged as a privileged inhibitory target for cancer therapy because of its deacetylating activity for p53 at K120 and K373/382. However, intricate roles of HDAC6 in hepatocellular carcinogenesis have been suggested by recent evidence, namely that HDAC6 ablation suppresses innate immunity, which plays critical roles in tumor immunosurveillance and antitumor immune responses. Therefore, it is valuable to determine whether HDAC6 ablation inhibits hepatocellular carcinogenesis using in vivo animal models. Here, we firstly showed that HDAC6 ablation increased K320 acetylation of p53, known as pro-survival acetylation, in all tested animal models but did not always increase K120 and K373/382 acetylation of p53, known as pro-apoptotic acetylation. HDAC6 ablation induced cellular senescence in primary MEFs and inhibited cell proliferation in HepG2 cells and liver regeneration after two-thirds partial hepatectomy. However, the genetic ablation of HDAC6 did not inhibit hepatocarcinogenesis, but instead slightly enhanced it in two independent mouse models (DEN + HFD and DEN + TAA). Notably, HDAC6 ablation significantly promoted hepatocarcinogenesis in a multiple DEN treatment hepatocellular carcinoma (HCC) mouse model, mimicking chronic DNA damage in the liver, which correlated with hyperacetylation at K320 of p53 and a decrease in inflammatory cytokines and chemokines. Our data from three independent in vivo animal HCC models emphasize the importance of the complex roles of HDAC6 ablation in hepatocellular carcinogenesis, highlighting its immunosuppressive effects.

Gene expression profiles of pro-inflammatory mediators in the conjunctiva of patients with epiblepharon.

PURPOSE: To investigate the gene expression of pro-inflammatory mediators in the conjunctiva of pediatric patients with epiblepharon in a case-control study. METHODS: Twenty healthy controls and 15 pediatric patients with epiblepharon were enrolled from April 23, 2020 to June 15, 2020. Epiblepharon severity was divided into class I-III (least to moderate severity) and class IV (most severe). We obtained impression cytologic specimens from the medial palpebral conjunctiva of the participants to measure the gene expression of interleukin (IL)-1ß, IL-6, matrix metalloproteinase 9 (MMP9), and mucin 5AC (MUC5AC) using quantitative reverse transcription polymerase chain reaction. RESULTS: The mean age in the epiblepharon group was 9 years (range 7.5-11 years), and that in the healthy control group was 9.5 years (range 8-11.3 years). IL-1ß, IL-6, and MMP9 expression levels were 2.08 (p < 0.05), 2.11 (p < 0.05), and 2.48 (p < 0.05) fold higher, respectively, in the epiblepharon group than in the healthy control group. However, MUC5AC gene expression was not different between healthy subjects and patients with epiblepharon. IL-1ß, IL-6, and MMP9 expression levels in class IV patients were 1.32 (p < 0.05), 1.77 (p < 0.05), and 1.98 (p < 0.05) fold higher, respectively, than in class I-III patients. CONCLUSION: Epiblepharon may induce chronic inflammatory changes in the conjunctiva in addition to corneal epithelial damage. Therefore, early corrective surgery should be considered to prevent conjunctival inflammation.

Quantitative analysis of cell proliferation by a dye dilution assay: Application to cell lines and cocultures.

Cell proliferation represents one of the most fundamental processes in biological systems, thus the quantitative analysis of cell proliferation is important in many biological applications such as drug screening, production of biologics, and assessment of cytotoxicity. Conventional proliferation assays mainly quantify cell number based on a calibration curve of a homogeneous cell population, and therefore are not applicable for the analysis of cocultured cells. Moreover, these assays measure cell proliferation indirectly, based on cellular metabolic activity or DNA content. To overcome these shortcomings, a dye dilution assay employing fluorescent cell tracking dyes that are retained within cells was applied and was diluted proportionally by subsequent cell divisions. Here, it was demonstrated that this assay could be implemented to quantitatively analyze the cell proliferation of different types of cell lines, and to concurrently analyze the proliferation of two types of cell lines in coculture by utilizing cell tracking dyes with different spectral characteristics. The mean division time estimated by the dye dilution assay is compared with the population doubling time obtained from conventional methods and values from literature. Additionally, dye transfer between cocultured cells was investigated and it was found that it is a characteristic of the cells rather than a characteristic of the dye. It was suggested that this method can be easily combined with other flow cytometric analyses of cellular properties, providing valuable information on cell status under diverse conditions. © 2017 International Society for Advancement of Cytometry.

Sphingosine-1-phosphate is involved in inflammatory reactions in patients with Graves' orbitopathy.

OBJECTIVE: Graves' orbitopathy (GO) is initiated by excessive amount of various inflammatory mediators produced by orbital fibroblasts. This study aimed to assess the crucial role of sphingosine-1-phosphate (S1P) in the inflammatory process of GO. METHODS: Orbital adipose/connective tissue samples were obtained from 10 GO patients and 10 normal control individuals during surgery. Primary orbital fibroblast culture was done. After the expression of S1P receptors and sphingosine kinase (SphK) was assessed with the treatment of interleukin (IL)-1ß, we evaluated the expression of pro-inflammatory factors [intercellular adhesion molecule-1 (ICAM-1), cyclooxygenase-2 (COX-2) and IL-6] after treating S1P. S1P receptor antagonists and SphK 1 inhibitor were pretreated and the expression of the pro-inflammatory factors was assessed. RESULTS: IL-1ß exacerbated the inflammatory process by enhancing the expression of S1P receptors and SphK in GO orbital fibroblasts. IL-1ß also induced the expressions of ICAM-1, COX-2, and IL-6 in GO orbital fibroblasts, and these expressions were effectively inhibited by S1P receptor antagonists and SphK1 inhibitor. CONCLUSION: S1P has an important role in the pathological inflammatory process of GO, which is mediated through the SphK1-S1P- S1P receptor pathway. SphK1 inhibitors and S1P receptors or antagonists could be potential approaches for controlling the inflammatory process of GO.

Diabetic retinal pigment epitheliopathy: fundus autofluorescence and spectral-domain optical coherence tomography findings.

PURPOSE: To describe the characteristics of an unfamiliar disease entity, diabetic retinal pigment epitheliopathy (DRPE), using fundus autofluorescence (FAF) and spectral-domain optical coherence tomography (SD-OCT). METHODS: This retrospective study included 17 eyes from 10 proliferative diabetic retinopathy (PDR) patients with granular hypo-autofluorescence and/or variable hyper-autofluorescence on FAF (DRPE group) and 17 eyes from 10 age- and sex-matched PDR patients without abnormal autofluorescence (PDR group). Eyes with diabetic macular edema were excluded. Visual acuity (VA), retinal thickness (RT), and choroidal thickness (CT) were compared between the groups. RESULTS: Eyes in the DRPE group had worse logMAR VA than eyes in the PDR group (0.369 ± 0.266 vs. 0.185 ± 0.119; P = 0.026). The thickness of the retinal pigment epithelium plus the inner segment/outer segment of the photoreceptors was reduced to a greater degree in the DRPE group than the PDR group (P < 0.001). Moreover, the thickness of the outer nuclear layer plus the outer plexiform layer was thinner in the DRPE group than in the PDR (P = 0.013). However, the thickness of the inner retina showed no differences between the two groups. CT was significantly thicker in the DRPE group than in the PDR group (329.00 ± 33.76 vs. 225.62 ± 37.47 µm; P < 0.001). CONCLUSIONS: Eyes with DRPE showed reduced VA, a thinner outer retina, and thicker choroid in comparison with eyes with PDR. Alterations of autofluorescence on FAF and changes in the outer retinal thickness and CT on SD-OCT can be helpful for differentiating DRPE in patients with PDR.

Central Retinal Vein Occlusion Associated with Ulcerative Colitis.

PURPOSE: To report a case of central retinal vein occlusion without macular edema associated with ulcerative colitis and its novel treatment with intravitreal dexamethasone. CASE REPORT: A 40-year-old man with ulcerative colitis presented with sudden visual disturbances. An initial fundus examination showed subtle yellow-to-white patches within the inner retina of the right eye superotemporal to the fovea. There were intraretinal hemorrhages and cotton-wool spots within the superior vascular arcade and nasal to the optic disc. Despite initiation of systemic corticosteroids, 2 weeks later there was an increase in retinal hemorrhages, formation of cotton wool spots, and development of optic disc swelling in the right eye. The patient was eventually diagnosed with nonischemic central retinal vein occlusion associated with ulcerative colitis. He received sustained-release intravitreal dexamethasone, which led to the resolution of retinal hemorrhage, optic disc swelling, and cotton-wool spots. Three months after the injection, retinal hemorrhages were not detectable. However, ocular coherence imaging showed marked thinning of the inner retina at the locations that were previously hyper-reflective. CONCLUSIONS: Central retinal vein occlusion is an uncommon ophthalmologic manifestation associated with ulcerative colitis. Injection of intravitreal dexamethasone could be a viable treatment option in these patients even without the presence of macular edema.

Intravitreal Bevacizumab for Traumatic Choroidal Rupture.

PURPOSE: To report a case of visual loss associated with traumatic choroidal rupture after blunt ocular trauma that was successfully treated with an early intravitreal bevacizumab injection despite the absence of choroidal neovascularization (CNV). CASE REPORT: A 14-year-old boy presented with visual disturbance in his left eye after sustaining an ocular contusion 4 weeks earlier. The best-corrected visual acuity (BCVA) in the left eye was 20/50. Funduscopic examination revealed macular choroidal rupture accompanied by subretinal hemorrhage. Optical coherence tomography (OCT) showed accumulation of subretinal fluid around a disrupted retinal pigment epithelium/Bruch membrane complex extending into the juxtafoveolar area, but there was no active leakage suggestive of CNV on fluorescein angiography. Intravitreal bevacizumab (1.25 mg) injection was performed to treat persistent serous retinal detachment at macula causing visual loss. There was a reduction of subretinal fluid and concomitant improvement of BCVA to 20/30 within 1 week after intravitreal bevacizumab injection. The BCVA recovered to 20/25 in the left eye after 4 weeks, and only a minimal amount of residual fluid remained according to OCT. Complete resolution of subretinal fluid was observed by OCT at the 6-week follow-up examination, and BCVA improved to 20/20. Good visual acuity (20/20) and stable macula were maintained in the left eye at 1 year of follow-up without recurrence of subretinal fluid accumulation or hemorrhage and CNV. There were no ocular or systemic complications associated with intravitreal bevacizumab injection. CONCLUSIONS: Early intravitreal bevacizumab injection could be an effective treatment option for patients with vision loss associated with traumatic choroidal rupture and subretinal fluid within the posterior pole before development of CNV.

YAG Laser Membranotomy for Subinternal Limiting Membrane Hemorrhage.

PURPOSE: To report the use of neodymium:yttrium-aluminum-garnet (Nd:YAG) laser internal limiting membranotomy to successfully treat the first reported case of subinternal limiting membrane (sub-ILM) hemorrhage that developed after coil embolization of a cerebral aneurysm. CASE REPORT: A 59-year-old Korean woman visited our clinic complaining of central scotoma in her left eye, which developed shortly after stent-assisted coil embolization of an unruptured internal carotid artery aneurysm. Fundus examination revealed a sub-ILM hemorrhage in her left eye, and after 2 days, a Nd:YAG laser membranotomy was performed with a single 4.5-mJ burst. There was a marked reduction in the sub-ILM hemorrhage 1 day after Nd:YAG laser membranotomy, and after 1 month, her best-corrected visual acuity improved to 20/20, with complete resolution of the sub-ILM hemorrhage. CONCLUSIONS: Sub-ILM hemorrhage can develop after coil embolization of a cerebral aneurysm, and Nd:YAG laser internal limiting membranotomy can be a useful noninvasive treatment alternative to surgical intervention.

Comprehensive evaluation of ocular complications in atopic dermatitis: insights from a contemporary cohort study in Korean population.

BACKGROUND: Atopic dermatitis (AD) is a chronic inflammatory skin disorder associated with various systemic and ocular complications. This study aimed to investigate the prevalence, risk factors, and clinical characteristics of ocular complications in a cohort of Korean AD patients. METHODS: A retrospective review of medical records was conducted for AD patients who visited the dermatology and ophthalmology clinics at the same institution. Demographic data, clinical characteristics, and types of ocular complications were recorded. Logistic regression analysis was performed to identify factors associated with ocular complications. RESULTS: A total of 212 AD patients were included in the study. The intraocular complications had a prevalence of 1.9%, whereas ocular surface diseases were observed more frequently, with prevalence of 13.2%. Among the ocular complications, blepharitis was the most prevalent, followed by atopic keratoconjunctivitis. Subcapsular cataract, atrophic hole, and retinal detachment were also observed. The head and neck score in the Eczema Area and Severity Index (EASI) emerged as a significant predictor for intraocular complications, independent of age, gender, total EASI score, and family history. No significant association was found between total EASI score and ocular surface disease. CONCLUSION: This study provides insights into the prevalence and risk factors of ocular complications in Korean AD patients. The head and neck score in EASI was identified as a significant predictor for intraocular complications. These findings emphasize the importance of comprehensive evaluation and interdisciplinary care for AD patients, particularly in identifying and managing potential vision-threatening complications.

The importance of genome sequencing: unraveling SSBP1 variant missed by exome sequencing.

BACKGROUND: Single-stranded DNA-binding protein 1 (SSBP1) plays an essential role in mitochondrial DNA (mtDNA) replication and maintenance, as well as development of retina. Here, we describe the clinical findings and genetic basis of a family with two members affected with bilateral optic atrophy. MATERIALS AND METHODS: Clinical data were retrospectively collected from an electronic medical record system. Genetic results were obtained using exome sequencing (ES) and genome sequencing (GS). RESULTS: A 36-year-old man presented with low vision in both eyes since early childhood, with a best-corrected visual acuity of 20/500 in both eyes. He exhibited generalized optic atrophy and diffuse retinal nerve fiber layer thinning without retinal degeneration in both eyes. The family history was consistent with autosomal dominant traits. ES was performed; however, we did not identify any pathogenic variants in the known dominant optic atrophy genes. Subsequently, GS was performed, and it revealed a novel heterozygous c.364A>G p.(Lys122Glu) variant in SSBP1. In silico prediction supported it as deleterious, while segregation analysis detected it in his affected mother and his unaffected sister. No foveopathy or retinal degeneration was observed in the patient's family members. CONCLUSIONS: We report a novel pathogenic heterozygous SSBP1 variant in a family with autosomal dominant optic atrophy and incomplete penetrance. Furthermore, we demonstrated that GS is advantageous over ES even for the discovery of coding variants, providing uniform coverage. Therefore, GS should be emphasized to improve the molecular diagnostic rate of inherited optic neuropathy.

Factors Related to Axial Length Elongation in Myopic Children Who Received 0.05% Atropine Treatment.

Purpose: To evaluate the longitudinal changes of axial length (AL) and factors associated with AL growth in myopic children receiving 0.05% atropine. Methods: This single-center retrospective study included children aged 4-13 years with myopia of at least -0.5 diopters (D) treated with 0.05% atropine eye drops from November 2016 to May 2021. Predictive factors for AL change were evaluated using linear mixed models. Results: Among 109 patients (218 eyes), 58 (53.2%) were male and the mean age at treatment was 8.5 ± 2.0 years. At baseline measurement, the mean spherical equivalent was -4.05 ± 2.34 diopters (D), and AL was 25.00 ± 0.97 mm. The mean follow-up duration was 25.4 (12-58) months, and the mean AL elongation was 0.23 ± 0.17 mm/year during the follow-up periods. AL shortening of ≥0.05 mm at subsequent visit occurred in 18 patients (26 eyes). The mean AL change in the group without initial AL shortening was statistically larger than that in the group with initial AL shortening (0.26 ± 0.16 mm/year vs. 0.02 ± 0.17 mm/year, P < 0.001). In linear mixed model, the age at atropine treatment and initial AL shortening were significantly associated with respect to AL growth (beta coefficient: -0.032 and -0.122, respectively, P < 0.001 for both). Conclusions: Our study found that older age and initial AL shortening are predictors of favorable response after 0.05% atropine treatment. Children with AL shortening at initial subsequent visit may be associated with good long-term response, and younger children may require higher concentration of atropine for optimal response.

Genetic spectrum and characteristics of autosomal optic neuropathy in Korean: Use of next-generation sequencing in suspected hereditary optic atrophy.

Aims: To evaluate the clinical characteristics and causative genetic variants in autosomal optic atrophy diagnosed using next-generation sequencing (NGS). Methods: A cohort of 57 unrelated families affected with bilateral optic atrophy were recruited from two university-based tertiary referral hospitals from May 2016 to April 2022. Genetic variants were detected using a target enrichment panel consisting of 429 or 595 genes and known deep intronic variants associated with inherited eye diseases, exome sequencing, or genome sequencing. The results of detailed clinical examinations, disease-causing variants, and clinical diagnoses were analyzed. Results: Among the 57 probands, 33 (57.9%) were men, and the median age at genetic testing was 19.1 years (interquartile range, 7.6-42.5 years). We identified 22 likely causative variants in 18 families and corresponding diagnostic yields of 31.6% (95% confidence interval, 21.0-44.5%). The diagnostic rate of NGS was higher in patients with infantile or early childhood onset optic atrophy than in those with late-onset or unknown optic atrophy (18/39, 46.2% vs. 0/18, 0%, P < 0.001). Among the 22 variants, 15 were novel in our cohort. The OPA1 variants (n = 7) were found to be the major genetic causes, followed by the NR2F1 variant (n = 4). The causative variants in PTPN23, TMEM126A, NBAS, and WFS1 genes were identified in 4 probands with a recessive form of optic atrophy. Conclusions: Based on the results of diagnostic NGS for optic atrophy, the causative variant could be detected in 31.6% of patients. Our study also demonstrated that NGS is unlikely to help identify molecular causes in late-onset unexplained optic atrophy.