G-quadruplex folding in Xist RNA antagonizes PRC2 activity for stepwise regulation of X chromosome inactivation.

How Polycomb repressive complex 2 (PRC2) is regulated by RNA remains an unsolved problem. Although PRC2 binds G-tracts with the potential to form RNA G-quadruplexes (rG4s), whether rG4s fold extensively in vivo and whether PRC2 binds folded or unfolded rG4 are unknown. Using the X-inactivation model in mouse embryonic stem cells, here we identify multiple folded rG4s in Xist RNA and demonstrate that PRC2 preferentially binds folded rG4s. High-affinity rG4 binding inhibits PRC2's histone methyltransferase activity, and stabilizing rG4 in vivo antagonizes H3 at lysine 27 (H3K27me3) enrichment on the inactive X chromosome. Surprisingly, mutagenizing the rG4 does not affect PRC2 recruitment but promotes its release and catalytic activation on chromatin. H3K27me3 marks are misplaced, however, and gene silencing is compromised. Xist-PRC2 complexes become entrapped in the S1 chromosome compartment, precluding the required translocation into the S2 compartment. Thus, Xist rG4 folding controls PRC2 activity, H3K27me3 enrichment, and the stepwise regulation of chromosome-wide gene silencing.

Effect of Corneal and Lens Eccentricity Difference on Rigid Corneal Lens Treatment in Patients With Keratoconus.

OBJECTIVE: To evaluate the effects of rigid corneal lenses (RCL) in patients with keratoconus, based on eccentricity. METHODS: Eighty-four eyes from 84 patients were included in this retrospective comparative study. Based on the median value of eccentricity difference between the cornea and back surface of the RCL, the patients were divided into groups 1 (<0.08) and 2 (≥0.08). Visual acuity, refractive index, and corneal topography indices were compared before and three months after lens use. RESULTS: Visual acuity, astigmatism, refractive error, corneal curvature, and corneal thickness improved significantly in both groups. Apical power and anterior elevation improved significantly in group 1, with small differences in eccentricity, but not in group 2. Changes in apical power before and after lens use were significantly different between the two groups. CONCLUSION: The RCL was effective for the cornea of keratoconus, especially when the prescription was made with a small difference in eccentricity.

Electroretinography in congenital nystagmus patients with a normal fundus examination.

PURPOSE: To identify the ophthalmic causes of congenital nystagmus with normal eye examination by electroretinography (ERG). STUDY DESIGN: Retrospective observational study. METHODS: We reviewed the medical records of patients younger than 6 months of age who presented between June 2008 and November 2011 with nystagmus and no other neurological signs following an otherwise normal eye examination. A complete ophthalmic examination and ERG (Nicolet Bravo system; Nicolet Biomedial & RETIscan; Roland Instruments), fundus photography, and Ishihara color test were performed to identify any ophthalmic causes of congenital nystagmus. RESULTS: Thirty-three patients met the criteria. Rod dysfunction was diagnosed in 4 patients (12.1%), cone dysfunction in 2 patients (6.1%), and cone-rod dysfunction in 1 patient (3.0%). The results of ERG were negative in 2 patients (6.1%). Idiopathic infantile nystagmus was diagnosed in the remaining 24 patients (72.7%) based on their normal ERG examination. CONCLUSIONS: In Korean congenital nystagmus patients with a normal fundus examination, achromatopsia and Leber's congenital amaurosis are uncommon causes. ERG is needed to make a definite diagnosis and provide prognostic information in congenital idiopathic nystagmus patients with a normal fundus examination.

Expression of microRNAs related to apoptosis in the aqueous humor and lens capsule of patients with glaucoma.

Background: The aim of this study is to investigate the expression profiles of microRNAs (miRNAs) related to apoptosis in the aqueous humor (AH) and lens capsule (LC) of patients with glaucoma. Methods: AH and LC samples were collected from patients with open-angle glaucoma and control participants who were scheduled for cataract surgery. A miRNA PCR array comprising 84 miRNAs was used to analyze the AH (glaucoma, n = 3; control, n = 3) and LC samples (glaucoma, n = 3; control, n = 4). Additionally, the AH and LC samples (glaucoma, n = 3; control, n = 4) were subjected to quantitative real-time PCR to validate the differentially expressed miRNAs determined using the PCR array. Bioinformatics analysis was performed to identify the interactions between miRNAs and diseases. Additionally, the differential expression of these miRNAs and the target gene was validated through in vitro experiments using a retinal ganglion cell (RGC) model. Results: Expression levels of 19 and 3 miRNAs were significantly upregulated in the AH and LC samples of the glaucoma group, respectively (p < 0.05). Of these, the expression levels of hsa-miR-193a-5p and hsa-miR-222-3p showed significant differences in both AH and LC samples. Bioinformatics analysis showed experimentally validated 8 miRNA:gene pairs. Among them, PTEN was selected to analyze the expression level in AH and LC from separate cohort (glaucoma, n = 5; control, n = 4). The result showed downregulation of PTEN concurrent with upregulation of the two miRNAs in LC samples of glaucoma group. In vitro experiments validated that the expression levels of hsa-miR-193a-5p and hsa-miR-222-3p were significantly upregulated, and that of PTEN was significantly downregulated in the H2O2-treated RGC, while the level of PTEN was recovered through co-treatment with miR-193a inhibitor or miR-222 inhibitor. Conclusion: This is the first study to investigate the differential expression of apoptosis-related miRNAs in the AH and LC of patients with glaucoma. Hsa-miR-193a-5p and hsa-miR-222-3p, which were upregulated in both AH and LC, may be considered potential biomarkers for glaucoma.

Clinical Outcomes and Indications of In-Office Sutureless Dried Gamma Ray-Sterilized Human Amniotic Membrane Transplantation With Bandage Contact Lenses in Various Ocular Surface Disorders.

PURPOSE: The purpose of this study was to investigate the efficacy and indications of using dried gamma ray-sterilized amniotic membrane (AM) transplantation with bandage contact lenses for the in-office sutureless treatment of various ocular surface diseases. METHODS: This study retrospectively included 56 eyes of 52 patients with various ocular surface diseases treated with sutureless dehydrated AM-assisted therapeutic contact lenses. The patients were followed up and assessed 1, 2, and 4 weeks after the treatment, and the therapeutic contact lenses were removed after 1 or 2 weeks. The size of the corneal lesion and the degree of pain experienced by each patient before and after the procedure were measured. Corneal re-epithelization rate and clinical aspects related to re-epithelialization were evaluated. RESULTS: Complete corneal re-epithelialization of the epithelial defect was observed in 40 eyes. The complete re-epithelialization rates of persistent epithelial defect caused by infectious ulcers, neurotrophic ulcers, ulcers due to burn, toxic keratopathy, previous penetrating keratoplasty or other corneal surgeries, and severe dry eye disease were 69.2%, 80.0%, 77.8%, 100%, 75.0%, and 100%, respectively. Five patients with uncontrolled infectious ulcers, neurotrophic ulcer, bullous keratopathy, and ulcers associated with rheumatic disease did not show significant improvement. Patient pain scores significantly decreased after the procedure. CONCLUSIONS: Dehydrated AM transplantation with a bandage contact lens is minimally invasive and easily applicable through in-office procedures. This approach is expected to be more actively applied in various ocular surface disorders, not only in severe corneal diseases but also in relatively mild corneal surface diseases.

Compressive optic neuropathy due to posterior ethmoid mucocele.

Mucoceles are cystic formations characterized by the presence of mucus-secreting epithelial cells, which enlarge when the excretory duct becomes obstructed. Posterior ethmoidal mucoceles are rare conditions that can lead to severe ocular complications requiring immediate intervention. The close anatomical proximity of posterior ethmoidal mucoceles to the optic nerve underscores their significance. In this case report, we present a case of rapidly progressing compressive optic neuropathy secondary to a posterior ethmoidal mucocele. A previously healthy forty-six-year-old woman presented with sudden visual loss in her left eye, preceded by left-sided headache and periorbital pain. Clinical examination and imaging studies revealed an oval-shaped mass within the posterior ethmoid cell compressing the left optic nerve. Emergency surgery was performed to alleviate optic nerve compression, which successfully relieved periocular pain. However, the patient's visual acuity and visual field defect remained unchanged postoperatively. Thinning of the ganglion cell layer in the macula region was observed during follow-up examinations. The role of corticosteroids and antibiotics in visual rehabilitation and the impact of delayed surgical decompression on visual outcome remain subjects of debate. Additional cases of mucocele-associated optic neuropathy should be published and analyzed to establish optimal treatment approaches.

Application of Femtosecond Laser in Challenging Cataract Cases.

Femtosecond laser can provide precise and customized incision of ocular tissue with excellent accuracy and predictability. Thus, femtosecond laser-assisted cataract surgery (FLACS) can theoretically enhance the safety and efficacy of cataract surgery by providing reproducible and reliable clear corneal incision, limbal relaxing incision, anterior capsulotomy, and lens fragmentation. However, thus far, the superiority of the anatomical and visual outcomes of FLACS over those of conventional cataract surgery have been unclear. Nevertheless, studies have indicated that FLACS can potentially be helpful in improving the safety of cataract surgery in challenging situations, such as zonular weakness, preexisting capsular tear, white cataract, shallow anterior chamber, and pediatric cataracts, which may contribute to enhanced visual and anatomical outcomes. In this review, we provide a summary of the application of femtosecond laser in general cataract cases. In addition, we introduce the application of FLACS in the abovementioned challenging situations and discuss the results of studies regarding the safety and outcome of FLACS in these challenging cases.

Central retina thickness measured with spectral-domain optical coherence tomography in Parkinson disease: A meta-analysis.

BACKGROUND: Optical coherence tomography (OCT) can detect visual alterations associated with Parkinson disease, such as damage to the retinal nerve fiber layer or changes in retinal vasculature. Macula thinning in association with Parkinson disease (PD) remains controversial. Therefore, we conducted a meta-analysis to investigate the central retina thickness in PD measured using spectral-domain OCT (SD-OCT). METHODS: We searched PubMed and the Excerpta Medica database to identify studies that compared macular thickness between patients with PD and healthy controls published before July 31, 2021. A random-effects model was used to examine PD-associated changes in macular thickness. Meta-regression analysis was performed by assessing heterogeneity, publication bias, and study quality. RESULTS: Thirty-two studies with a cross-sectional design were selected, including 2118 patients with PD and 2338 controls. We identified significant differences in the thickness of the ganglion cell-inner plexiform layer (standardized mean difference [SMD], -0.41; 95% confidence interval [CI], -0.66 to -0.16; I2 = 80%), ganglion cell complex (SMD, -0.33; 95% CI, -0.50 to -0.17; I2 = 0%), and of all inner and outer sectors of the macula (SMD range, -0.21 to -0.56; all P < .05) between patients with PD and controls. DISCUSSION: These results corroborate the increased prevalence of changes in OCT measures in individuals with PD, highlighting the efficacy of SD-OCT-determined macular thickness as a biomarker for PD. Our findings may provide helpful guidelines for clinicians in rapidly evolving areas of PD diagnosis.

Site-specific R-loops induce CGG repeat contraction and fragile X gene reactivation.

Here, we describe an approach to correct the genetic defect in fragile X syndrome (FXS) via recruitment of endogenous repair mechanisms. A leading cause of autism spectrum disorders, FXS results from epigenetic silencing of FMR1 due to a congenital trinucleotide (CGG) repeat expansion. By investigating conditions favorable to FMR1 reactivation, we find MEK and BRAF inhibitors that induce a strong repeat contraction and full FMR1 reactivation in cellular models. We trace the mechanism to DNA demethylation and site-specific R-loops, which are necessary and sufficient for repeat contraction. A positive feedback cycle comprising demethylation, de novo FMR1 transcription, and R-loop formation results in the recruitment of endogenous DNA repair mechanisms that then drive excision of the long CGG repeat. Repeat contraction is specific to FMR1 and restores the production of FMRP protein. Our study therefore identifies a potential method of treating FXS in the future.

SELENBP1 overexpression in the prefrontal cortex underlies negative symptoms of schizophrenia.

The selenium-binding protein 1 (SELENBP1) has been reported to be up-regulated in the prefrontal cortex (PFC) of schizophrenia patients in postmortem reports. However, no causative link between SELENBP1 and schizophrenia has yet been established. Here, we provide evidence linking the upregulation of SELENBP1 in the PFC of mice with the negative symptoms of schizophrenia. We verified the levels of SELENBP1 transcripts in postmortem PFC brain tissues from patients with schizophrenia and matched healthy controls. We also generated transgenic mice expressing human SELENBP1 (hSELENBP1 Tg) and examined their neuropathological features, intrinsic firing properties of PFC 2/3-layer pyramidal neurons, and frontal cortex (FC) electroencephalographic (EEG) responses to auditory stimuli. Schizophrenia-like behaviors in hSELENBP1 Tg mice and mice expressing Selenbp1 in the FC were assessed. SELENBP1 transcript levels were higher in the brains of patients with schizophrenia than in those of matched healthy controls. The hSELENBP1 Tg mice displayed negative endophenotype behaviors, including heterotopias- and ectopias-like anatomical deformities in upper-layer cortical neurons and social withdrawal, deficits in nesting, and anhedonia-like behavior. Additionally, hSELENBP1 Tg mice exhibited reduced excitabilities of PFC 2/3-layer pyramidal neurons and abnormalities in EEG biomarkers observed in schizophrenia. Furthermore, mice overexpressing Selenbp1 in FC showed deficits in sociability. These results suggest that upregulation of SELENBP1 in the PFC causes asociality, a negative symptom of schizophrenia.

Clinical outcomes of new multifocal intraocular lenses with hydroxyethyl methacrylate and comparative results of contrast sensitivity, objective scatter, and subjective photic phenomena.

BACKGROUND: We investigate the performance of new hydrophobic diffractive multifocal intraocular lenses (IOL) with hydroxyethyl methacrylate (HEMA) and compare their optical quality, contrast sensitivity, and subjective photic phenomena. METHODS: Medical records of patients who underwent routine simple cataract surgery and insertion of an existing multifocal IOL (TFNT, TF group) or a new multifocal IOL (CNWT, CN group) were retrospectively reviewed. Clinical data was collected 2 months postoperatively and included optical quality analysis system (OQAS) indices, contrast sensitivity, and subjective degrees of photic phenomena. RESULTS: One hundred thirty-five eyes of 135 patients were included (CN group, 71; TF group, 64). There was no significant difference between the two groups in the visual acuity and defocus curve. The indices of OQAS did not show a significant difference between groups. Contrast sensitivity was significantly better in the CN group at all degrees, including the area under the log contrast sensitivity function (p = 0.01). The subjective photic phenomena survey showed better results for the CN group, with the proportion of patients reporting no photic phenomena as 9.9% and 3.1% in the CN and TF groups, respectively. The proportion of patients who reported severe photic phenomena was 11.3% in the CN group and 25.0% in the TF group. Although the follow-up period was only 2 months, glistening, surface scattering, and posterior capsule opacity were not observed in any patient. CONCLUSIONS: The new multifocal IOL with HEMA is safe, and provides stable visual acuity as well as superior contrast sensitivity and lower subjective photic phenomena, over the prior IOL.

In Vitro Characterization of the Physical Interactions between the Long Noncoding RNA TERRA and the Telomeric Proteins TRF1 and TRF2.

RNA-protein interactions drive key cellular pathways such as protein translation, nuclear organization and genome stability maintenance. The human telomeric protein TRF2 binds to the long noncoding RNA TERRA through independent domains, including its N-terminal B domain. We previously demonstrated that TRF2 B domain binding to TERRA supports invasion of TERRA into telomeric double stranded DNA, leading to the formation of telomeric RNA:DNA hybrids. The other telomeric protein TRF1, which also binds to TERRA, suppresses this TRF2-associated activity by preventing TERRA-B domain interactions. Herein, we show that the binding of both TRF1 and TRF2 to TERRA depends on the ability of the latter to form G-quadruplex structures. Moreover, a cluster of arginines within the B domain is largely responsible for its binding to TERRA. On the other side, a patch of glutamates within the N-terminal A domain of TRF1 mainly accounts for the inhibition of TERRA-B domain complex formation. Finally, mouse TRF2 B domain binds to TERRA, similarly to its human counterpart, while mouse TRF1 A domain lacks the inhibitory activity. Our data shed further light on the complex crosstalk between telomeric proteins and RNAs and suggest a lack of functional conservation in mouse.

Optical regulation of endogenous RhoA reveals selection of cellular responses by signal amplitude.

How protein signaling networks respond to different input strengths is an important but poorly understood problem in cell biology. For example, RhoA can promote focal adhesion (FA) growth or disassembly, but how RhoA activity mediates these opposite outcomes is not clear. Here, we develop a photoswitchable RhoA guanine nucleotide exchange factor (GEF), psRhoGEF, to precisely control endogenous RhoA activity. Using this optical tool, we discover that peak FA disassembly selectively occurs upon activation of RhoA to submaximal levels. We also find that Src activation at FAs selectively occurs upon submaximal RhoA activation, identifying Src as an amplitude-dependent RhoA effector. Finally, a pharmacological Src inhibitor reverses the direction of the FA response to RhoA activation from disassembly to growth, demonstrating that Src functions to suppress FA growth upon RhoA activation. Thus, rheostatic control of RhoA activation by psRhoGEF reveals that cells can use signal amplitude to produce multiple responses to a single biochemical signal.

Dispersion Stability of 14 Manufactured Nanomaterials for Ecotoxicity Tests Using Raphidocelis subcapitata.

The development of nanotechnology has increased concerns about the exposure of ecosystems to manufactured nanomaterials, the toxicities of which are now being researched. However, when manufactured nanomaterials are mixed with algae in a culture medium for ecotoxicity tests, the results are vulnerable to distortion by an agglomeration phenomenon. Here, we describe a dispersion method commonly applicable to ecotoxicity tests for the 14 types of manufactured nanomaterials specified by the Organisation of Economic Co-operation and Development's Sponsorship Programme, namely aluminum oxide (Al2O3), carbon black, single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), cerium oxide (CeO2), dendrimers, fullerene, gold (Au), iron (Fe), nanoclays, silver (Ag), silicon dioxide (SiO2), titanium dioxide (TiO2), and zinc oxide (ZnO). The type of dispersant, sonication time, and stirring speed were carefully considered. Consequently, 1500 mg/L of gum arabic was selected as a dispersant; for sonication time, 1 h was selected for dendrimers, 2 h for SiO2, 24 h for SWCNTs and Au, and 4 h for the other nanomaterials. Dispersion stability was achieved for all materials at a stirring speed of 200 rpm. To verify the effect of this dispersion method on ecotoxicity tests, toxicity was measured through cell counts for SWCNTs and TiO2 using Raphidocelis subcapitata. The half-maximal effective concentrations (EC50) were 18.0 ± 4.6 mg/L for SWCNTs and 316.6 ± 64.7 mg/L for TiO2.

Comparative Study of Algae-Based Measurements of the Toxicity of 14 Manufactured Nanomaterials.

With the increasing use of nanomaterials in recent years, determining their comparative toxicities has become a subject of intense research interest. However, the variety of test methods available for each material makes it difficult to compare toxicities. Here, an accurate and reliable method is developed to evaluate the toxicity of manufactured nanomaterials, such as Al2O3, carbon black, single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), CeO2, dendrimers, fullerene, gold, iron, nanoclays, silver, SiO2, TiO2, and ZnO. A series of 72 h chronic and 8 h acute toxicity tests was performed using cell counting, chlorophyll, and delayed fluorescence methods. Comparable toxicities using the chlorophyll and delayed fluorescence methods were impossible to determine because the EC50 of some of the nanomaterials could not be measured. All three test methods were successfully applied to the chronic toxicity tests of manufactured nanomaterials, and cell counting was the only method applicable to acute toxicity tests. The toxicity data and the proposal of measurement method for manufactured nanomaterials obtained in this study can be helpful for preparing exposure standards and investigating the toxicities of other nanomaterials in the future.

Association of High-Sensitivity C-Reactive Protein and Alcohol Consumption on Metabolic Syndrome in Korean Men.

Background: This study aimed to examine the effect of both alcohol consumption and high-sensitivity C-reactive protein (hsCRP) on metabolic syndrome (MetS) in Korean men. Methods: A cohort of 364 men included in this study was divided into four groups according to the amount of alcohol they consumed: the nondrinkers (ND), low moderate drinkers (LM, ≤7 standard drinks per week), high moderate drinkers (HM, 7 to 14 drinks per week), and heavy drinkers (HD, >14 drinks per week). Logistic regression analyses were performed after adjusting for age, exercise, and smoking. Results: The risk of MetS in the LM group with a high hsCRP level (1.0 or more mg/dL) was not significant. However, the risks of MetS were significantly higher in the HM and HD groups with high hsCRP levels than that in the ND group. The odds ratios of MetS in the HM and HD groups with high hsCRP levels were 3.44 (95% confidence interval (CI), 1.25−9.52) and 3.14 (95% CI, 1.07−9.23), respectively. Conclusion: This study suggests that the risk of MetS is higher in men who consume more than seven drinks a week with high hsCRP levels than that in nondrinkers.

Multiple births and low birth weight: Evidence from South Korea.

OBJECTIVE: The proportion of multiple births has risen rapidly worldwide. Multiple births are likely to affect birth weight, which results in low birth weight (LBW) of less than 2500 g, possibly, because multiples are more likely to be born prematurely or less than 37 weeks into pregnancy. Using data from South Korea, this study aims to estimate the contribution of the rise in multiples to the rise in LBW incidence. METHODS: Based on data from 2000 to 2017, we estimated the effect of multiples on LBW rates using linear regression analysis. Based on the regression analysis and the change in the proportion of multiples during this period, we calculated the contribution of the rise in multiples to the rise in LBW incidence using the total differential. In other words, we divided the change in LBW during the period due to the change in multiples by the total change during the period. The data are from the birth registry of the National Statistical Office, which contains information on the 8.4 million live births during the period 2000-2017. RESULTS: We found that a 1 percentage point increase in multiples increases the proportion of LBWs by 0.495 percentage points. In addition, because the changes in the proportion of multiples and LBWs from 2000 to 2017 are 2.2 and 2.4 percentage points, respectively, 1.1 percentage points or 45.8% of the increase in LBWs over the period is due to the increase in multiples. CONCLUSION: Since the Korean government introduced a measure to reduce the number of transferred embryos recently, one may expect that multiples in Korea would reduce in the near future, as it did in other countries. Subsequently, the incidence of LBW children is also likely to reduce, which is desirable in terms of the children's health outcomes.

Validation of the Simplified Palliative Prognostic Index to Predict Survival for Advanced Cancer Patients in Home Hospice Setting.

BACKGROUND: The simplified Palliative Prognostic Index (sPPI) substitutes a single item from the Communication Capacity Scale (CCS) for the delirium item of the original PPI. This study aimed to examine the validity of the sPPI for patients with advanced cancer in a home-based hospice care setting. METHODS: This study included 75 patients with advanced cancer who received home-based hospice care. We used medical records maintained by professional hospice nurses who had visited the patients in their homes. Based on their sPPI score, patients were divided into three groups-A (<4), B (≥4 and <6), and C (≥6)-to compare survival. Further, we investigated the sPPI's accuracy using the area under the receiver operating characteristic curve (AUC) and sensitivity and specificity for 3- and 6-week survival. We used three sPPIs including different substitutions for the delirium item (two methods using the CCS and one using the Korean Nursing Delirium Screening Scale). RESULTS: The median survival was 60-61 days for group A, 27-30 days for group B, and 12-16 days for group C. The difference in survival was significant (P<0.05). The AUC was 0.814-0.867 for 3-week survival and 0.736-0.779 for 6-week survival. For 3- and 6-week survival, prognostic prediction showed sensitivities of 76.2%-90.9% and 76.3%-86.8%, and specificities of 64.2%-88.7% and 51.4%-70.3%, respectively. CONCLUSION: The sPPI, which is measured by professional hospice nurses, has acceptable validity to predict survival for patients with advanced cancer in a home hospice setting in South Korea.

Correlation analysis between lower limb muscle architectures and cycling power via ultrasonography.

The primary purpose was to examine the relationship between the muscle architectural characteristics of short and long-distance cyclist-including muscle thickness, fascicle angle, and fascicle length-of the anterior thigh and posterior leg and its impact in 20-s cycling power. The secondary purpose was to clarify the muscle variables that predict the cycling power by using ultrasonography to measure the muscle architectural characteristics. Twenty-four varsity cyclists participated in this study, of whom 12 were short-distance cyclists and 12 were long-distance cyclists. B-mode ultrasonography was used to measure muscle architecture parameters. A cycle ergometer was used to measure the cycling power. The rectus femoris, vastus medialis, and medial head of gastrocnemius were significantly thicker in short-distance cyclists than in long-distance cyclists at every site (p < 0.05). Our analysis revealed that the rectus femoris fascicle length at the 30% level of the thigh was a significant independent predictor of the 20-s cycling power in short-distance cyclists, while the rectus femoris fascicle angle at the 50% level was that of the 20-s cycling power in long-distance cyclists. These findings highlight the significance of rectus femoris muscle architecture to cycling power.