Opsin 5 is a key regulator of ultraviolet radiation-induced melanogenesis in human epidermal melanocytes

Background

Human skin, which is constantly exposed to solar ultraviolet radiation (UVR), has a unique ability to respond by increasing its pigmentation in a protective process driven by melanogenesis in human epidermal melanocytes (HEMs). However, the molecular mechanisms used by HEMs to detect and respond to UVR remain unclear.

Objectives

To investigate the function and potential mechanism of opsin 5 (OPN5), a photoreceptor responsive to UVR wavelengths, in melanogenesis in HEMs.

Methods

Melanin content in HEMs was determined using the NaOH method, and activity of tyrosinase (TYR) (a key enzyme in melanin synthesis) was determined by the l‐DOPA method. OPN5 expression in UVR‐treated vs. untreated HEMs and explant tissues was detected by reverse‐transcription quantitative polymerase chain reaction (RT‐qPCR), Western blotting and immunofluorescence. Short interfering RNA‐mediated OPN5 knockdown and a lentivirus OPN5 overexpression model were used to examine their respective effects on TYR, tyrosinase‐related protein 1 (TRP1), TRP2 and microphthalmia‐associated transcription factor (MITF) expression, under UVR. Changes in expression of TYR, TRP1 and TRP2 caused by changes in OPN5 expression level were detected by RT‐qPCR and Western blot. Furthermore, changes in signalling pathway proteins were assayed.

Results

We found that OPN5 is the key sensor in HEMs responsible for UVR‐induced melanogenesis. OPN5‐induced melanogenesis required Ca²⁺‐dependent G protein‐coupled receptor‐ and protein kinase C signal transduction, thus contributing to the UVR‐induced MITF response to mediate downstream cellular effects, and providing evidence of OPN5 function in mammalian phototransduction. Remarkably, OPN5 activation was necessary for UVR‐induced increase in cellular melanin and has an inherent function in melanocyte melanogenesis.

Conclusions

Our results provide insight into the molecular mechanisms of UVR sensing and phototransduction in melanocytes, and may reveal molecular targets for preventing pigmentation or pigment diseases.

What is already known about this topic?

Ultraviolet radiation (UVR) induces a protective response to DNA damage mediated by melanin synthesis in human epidermal melanocytes (HEMs).

Tyrosinase (TYR), with tyrosinase‐related proteins (TRP1, TRP2), are the key enzymes for melanin synthesis.

Microphthalmia‐associated transcription factor regulates key genes for melanocyte development and differentiation, and can stimulate melanogenesis by activating transcription of TYR and other pigmentation genes, including TRP1.

Opsin 5 (OPN5) is known to function as a photoreceptor responsive to wavelengths in the near UV spectrum.

What does this study add?

UVR induces melanogenesis in HEMs via OPN5.

OPN5 regulates expression of TYR, TRP1 and TRP2 through the calcium‐dependent G protein‐coupled and protein kinase C signalling pathways.

OPN5 has an inherent role in HEMs in mediating melanogenesis.

What is the translational message?

OPN5 was discovered as a key sensor for UVR‐induced melanogenesis in human skin melanocytes.

It could be a target for early treatment of pigmentation or pigment diseases, to provide a more personalized and economically feasible method.

Linked Comment: L.V.M. de Assis and A.M. de Lauro Castrucci. Br J Dermatol 2021; 185:249–250.

Plain language summary available online

Time-resolved RIXS experiment with pulse-by-pulse parallel readout data collection using X-ray free electron laser

Time-resolved resonant inelastic X-ray scattering (RIXS) is one of the developing techniques enabled by the advent of X-ray free electron laser (FEL). It is important to evaluate how the FEL jitter, which is inherent in the self-amplified spontaneous emission process, influences the RIXS measurement. Here, we use a microchannel plate (MCP) based Timepix soft X-ray detector to conduct a time-resolved RIXS measurement at the Ti L₃-edge on a charge-density-wave material TiSe₂. The fast parallel Timepix readout and single photon sensitivity enable pulse-by-pulse data acquisition and analysis. Due to the FEL jitter, low detection efficiency of spectrometer, and low quantum yield of RIXS process, we find that less than 2% of the X-ray FEL pulses produce signals, preventing acquiring sufficient data statistics while maintaining temporal and energy resolution in this measurement. These limitations can be mitigated by using future X-ray FELs with high repetition rates, approaching MHz such as the European XFEL in Germany and LCLS-II in the USA, as well as by utilizing advanced detectors, such as the prototype used in this study.

Phase stability, brittle-ductile transition, and electronic structures of the TiAl alloying with Fe, Ru, Ge, and Sn: a first-principle investigation

Phase stability, brittle-ductile transition, and electronic structures of M (M = Fe, Ru, Ge, and Sn) and content change of L10-TiAl (γ-TiAl) and B2-TiAl (β-TiAl) have been investigated using first-principle methods. It is found that M metal atoms preferentially occupy the Al (2e) sites in L10-TiAl and B2-TiAl. According to Pugh's ratio and Poisson's ratio, the brittle-ductile transition is predicted for L10-TiAl and B2-TiAl with Fe, Ru, Ge, and Sn. It is found that the brittle-ductile transition from brittle regions to ductile regions with the transition metal elements Fe and Ru in L10-TiAl and B2-TiAl at the low concentration is approximately from 0 to 6.25 at.%. However, the brittle-ductile transition of Ge and Sn at the high concentration approximates from 6.25 to 12.5 at.% in L10-TiAl, comparing with B2-TiAl which approximates from 12.5 to 18.75 at.%. Electronic structure analysis shows that the improvement of brittleness can be attributed to two factors, including different hybridizations of Al-2p (Ti-3d) orbits with Fe-3d (Ge-4p) and Ru-4d (Sn-5p) orbits and different bandwidths of pseudo-gap. Furthermore, the L10-TiAl and B2-TiAl at low concentration of Fe and Ru can increase the value of ELF, where Ge and Sn atoms become bigger at a high concentration in L10-TiAl and B2-TiAl. At last, elastic constant (C_ij), bulk modulus (B), shear modulus (G), and Young's modulus (E) of L10 and B2-TiAl with content change are systematically given.

Publisher Correction: Electronic structure of the parent compound of superconducting infinite-layer nickelates

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Heterogeneity of enhancement kinetics in dynamic contrast-enhanced MRI and implication of distant metastasis in invasive breast cancer

AIM

To investigate the heterogeneity of enhancement kinetics for breast tumour in order to demonstrate the predictive power of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) features for distant metastasis (DM) in invasive breast cancer.

MATERIALS AND METHODS

Time-signal intensity curve (TIC) patterns from 128 patients with invasive breast cancer were analysed by a pixel-based DCE-MRI analysis. This MRI technique enabled pixels with varying TIC patterns (persistent, plateau, washout and non-enhancement) to be categorised semi-automatically and the percentage of different TIC patterns in each breast tumour to be calculated. The percentage of TIC patterns was compared between the DM and non-DM groups. DM-free survival was estimated using Kaplan-Meier survival analysis.

RESULTS

This study demonstrated a larger percentage of persistent TIC and non-enhancement TIC was associated with DM in invasive breast cancer. The cut-off values of persistent TIC and non-enhancement TIC were 22.5% and 2.5%. Combining TIC patterns and traditional predictors (tumour size and axillary lymph node status) can improve the prediction efficiency. The multivariable model yielded an area under the receiver operating characteristic curve (AUC) of 0.87 with 0.70 sensitivity and 0.87 specificity in leave-one-out cross-validation (LOOCV). These predictors showed significant differences in DM-free survival by Kaplan-Meier analysis.

CONCLUSION

This study shows that breast tumours with higher heterogeneity are more likely to metastasise, and pixel-based TIC analysis has utility in predicting distant metastasis of invasive breast cancer.

Retrospective analysis of the clinical effects of endoscopic mucosal dissection on treatment of early esophagogastric precancerous lesions

INTRODUCTION

The purpose of this study was to conduct a retrospective study about the clinical effects of endoscopic mucosal dissection on the treatment of early esophagogastric precancerous lesions.

METHODS

A total of 132 patients with early esophagogastric precancerous lesions who were diagnosed and treated with concurrent surgery in our hospital from January 2018 to December 2019 were included in this retrospective study. Patients were divided into endoscopic mucosal resection (EMR) group (n = 58) and endoscopic submucosal dissection (ESD) group (n = 74) according to different surgical methods. The data in the two groups were compared and analyzed in terms of surgical indicators, treatment status and incidence of postoperative complications.

RESULTS

There were statistically significant differences between the two groups in the whole block cutting rate, fractional cutting rate and complete cutting rate (P < 0.05). The mean operation time of ESD group was significantly longer than that of EMR group (P < 0.05). There were no significant differences in the intraoperative bleeding rate, blood loss, average specimen area, length of hospital stay and treatment cost between the two groups (P > 0.05). The incidence and recurrence of postoperative complications, including bleeding, perforation and stenosis in the two groups, were observed within 1 year of postoperative follow-up. The incidence of complications in ESD group was slightly higher than that in EMR group, and the local recurrence rate in ESD group was lower than that in EMR group (P > 0.05).

CONCLUSION

ESD is an alternative surgical treatment for patients with early esophagogastric precancerous lesions.

Intercensal and Postcensal Estimation of Population Size for Small Geographic Areas in the United States

Introduction

Population estimation techniques are often used to provide updated data for a current year. However, estimates for small geographic units, such as census tracts in the United States, are typically not available. Yet there are growing demands from local policy making, program planning and evaluation practitioners for such data because small area population estimates are more useful than those for larger geographic areas.

Objectives

To estimate the population sizes at the census block level by subgroups (age, sex, and race/ethnicity) so that the population data can be aggregated up to any target small geographic areas.

Methods

We estimated the population sizes by subgroups at the census block level using an intercensal approach for years between 2000 and 2010 and a postcensal approach for the years following the 2010 decennial census (2011-2017). Then we aggregated the data to the county level (intercensal approach) and incorporated place level (postcensal approach) and compared our estimates to corresponding US Census Bureau (the Census) estimates.

Results

Overall, our intercensal estimates were close to the Census’ population estimates at the county level for the years 2000-2010; yet there were substantive errors in counties where population sizes experienced sudden changes. Our postcensal estimates were also close to the Census’ population estimates at the incorporated place level for years closer to the 2010 decennial census.

Conclusion

The approaches presented here can be used to estimate population sizes for any small geographic areas based on census blocks. The advantages and disadvantages of their application in public health practice should be considered.

Low-Voltage Domain-Wall LiNbO3 Memristors

Application of conducting ferroelectric domain walls (DWs) as functional elements may facilitate development of conceptually new resistive switching devices. In a conventional approach, several orders of magnitude change in resistance can be achieved by controlling the DW density using supercoercive voltage. However, a deleterious characteristic of this approach is high-energy cost of polarization reversal due to high leakage current. Here, we demonstrate a new approach based on tuning the conductivity of DWs themselves rather than on domain rearrangement. Using LiNbO₃ capacitors with graphene, we show that resistance of a device set to a polydomain state can be continuously tuned by application of subcoercive voltage. The tuning mechanism is based on the reversible transition between the conducting and insulating states of DWs. The developed approach allows an energy-efficient control of resistance without the need for domain structure modification. The developed memristive devices are promising for multilevel memories and neuromorphic computing applications.

Downregulated lncRNA ADAMTS9-AS2 in breast cancer enhances tamoxifen resistance by activating microRNA-130a-5p

OBJECTIVE

The aim of this study was to elucidate the regulatory effect of long non-coding RNA (lncRNA) ADAMTS9-AS2 on Tamoxifen (TAM) resistance in breast cancer (BC), and to explore its underlying mechanism.

PATIENTS AND METHODS

TAM-resistant BC cell lines were first verified. Subsequently, cell proliferation and apoptosis were detected using cell counting kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU) assay and flow cytometry, respectively. Protein levels of ABCB1, ABCC1, and ABCG2 in TAM-treated MCF-7 and MCF-7R cells were determined by Western blot. ADAMTS9-AS2 expression in BC tissues, para-cancerous tissues, as well as MCF-7 and MCF-7R cells, was accessed by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The correlation between ADAMTS9-AS2 expression with pathological grade and tumor size of BC was explored. Chromatin fractionation was conducted to elucidate the subcellular distribution of ADAMTS9-AS2. The binding condition between ADAMTS9-AS2 and microRNA-130a-5p, as well as microRNA-130a-5p and PTEN, was verified by the dual-luciferase reporter gene assay. Furthermore, regulatory effects of ADAMTS9-AS2, microRNA-130a-5p, and PTEN on the proliferation and apoptosis of MCF-7R cells were determined.

RESULTS

MCF-7R cells were identified with TAM resistance. ADAMTS9-AS2 was lowly expressed in BC tissues and MCF-7R cells. Particularly, ADAMTS9-AS2 expression in BC tissues with grade III-IV or tumor size ≥2 cm was significantly lower than that of controls. Dual-luciferase reporter gene assay confirmed the binding condition between ADAMTS9-AS2 and microRNA-130a-5p, showing a negative correlation indicated by Pearson correlation analysis. PTEN was positively correlated with ADAMTS9-AS2. Overexpression of ADAMTS9-AS2 reversed the increased viability and decreased apoptosis induced by microRNA-130a-5p mimics transfection. In addition, PTEN knockdown reversed the decreased viability and accelerated apoptosis caused by ADAMTS9-AS2 overexpression.

CONCLUSIONS

We found that ADAMTS9-AS2 is lowly expressed in BC tissues and drug-resistant BC cells. Low expression of ADAMTS9-AS2 inhibits PTEN expression and enhances tamoxifen resistance through targeting microRNA-130a-5p.

Timing of paediatric orchidopexy in universal healthcare systems: international administrative data cohort study

BACKGROUND

International guidelines in 2008 recommended orchidopexy for undescended testis at 6-12 months of age to reduce the risk of testicular cancer and infertility. Using administrative data from England, Finland, Ontario (Canada), Scotland and Sweden (with data from Victoria (Australia) and Iceland in supplementary analyses), the aim of this study was to investigate compliance with these guidelines and identify potential socioeconomic inequities in the timing of surgery before 1 and 3 years.

METHODS

All boys born in 2003-2011 with a diagnosis code of undescended testis and procedure codes indicating orchidopexy before their fifth birthday were identified from administrative health records. Trends in the proportion of orchidopexies performed before 1 and 3 years of age were investigated, as were socioeconomic inequities in adherence to the guidelines.

RESULTS

Across all jurisdictions, the proportion of orchidopexies occurring before the first birthday increased over the study period. By 2011, from 7·6 per cent (Sweden) to 27·9 per cent (Scotland) of boys had undergone orchidopexy by their first birthday and 71·5 per cent (Sweden) to 90·4 per cent (Scotland) by 3 years of age. There was limited evidence of socioeconomic inequities for orchidopexy before the introduction of guidelines (2008). Across all jurisdictions for boys born after 2008, there was consistent evidence of inequities in orchidopexy by the first birthday, favouring higher socioeconomic position. Absolute differences in these proportions between the highest and lowest socioeconomic groups ranged from 2·5 to 5·9 per cent across jurisdictions.

CONCLUSION

Consistent lack of adherence to the guidelines across jurisdictions questions whether the guidelines are appropriate.

Intraspecific Diversity and Taxonomy of Emmonsia crescens

Emmonsia crescens is known as an environmental pathogen causing adiaspiromycosis in small rodents. As the generic name Emmonsia is no longer available for this species, its taxonomic position is re-evaluated. The intraspecific variation of Emmonsia crescens was analyzed using molecular, morphological, and physiological data, and the relationship between frequency of adiaspiromycosis and body temperature of host animals was explored. A North American and a pan-global lineage could be discerned, each with subclusters at low genetic distance. European strains produced the classical type of very large adiaspores, while in the North American lineage adiaspores relatively small, resembling the broad-based budding cells of Blastomyces. Members of the closely related genus Emergomyces may exhibit large, broad-based in addition to small, narrow-based budding cells. We conclude that the morphology of the pathogenic phase in these fungi differs gradationally between species and even populations, and is therefore less suitable as a diagnostic criterion for generic delimitation. Two Emmonsia species are reclassified in Emergomyces.

[Clinical features and outcomes in relapsing and monophasic patients with anti-leucine-rich glioma-inactivated 1 encephalitis]

Objective: To analyze the differences of clinical characteristics and outcomes between relapsing and monophasic patients with anti-leucine-rich glioma-inactivated 1 (anti-LGI1) encephalitis. Methods: Medical records of confirmed anti-LGI1 encephalitic patients who underwent immunotherapy were retrospectively collected from January 2015 to January 2019 in the first affiliated hospital of Zhengzhou University. Clinical data, treatment methods, duration of treatment and outcomes were analyzed between the relapsing and monophasic groups. Results: Among the 33 anti-LGI1 encephalitic patients, there were 12 and 21 cases in the relapsing and monophasic groups, respectively. No difference was found in age, sex, precipitating factors, intensive care unit (ICU) admission, symptoms and modified Rankin Scale (mRS) score in the acute phase (P>0.05). As to the lab test and image examination, no statistic difference was found in serum and cerebral spinal fluid (CSF) positive rate, hyponatremia, abnormal rate of electrocardiogram (ECG), electroencephalogram (EEG), CSF and magnetic resonance imaging (MRI) and lesion locations (P>0.05). No difference was found in time to diagnose the disease between the 2 groups (P>0.05). The median immunotherapy period was 102.5 days in relapsing group and 194.0 days in monophasic group, with a statistic difference (P=0.001). No patients had bad outcomes in the monophasic group at the last follow-up, while 6 patients had poor outcomes in the relapsing group (4 patients died). The patients in relapsing group had a worse prognosis compared to those in the monophasic group (P=0.007). Conclusions: Relapse is common in anti-LGI1 encephalitis. Patients in the relapsing group received a shorter term of immunotherapy and had worse outcomes than those in the monophasic group.

The importance of proper and prompt treatment of ocular syphilis: a lesson from permanent vision loss in 52 eyes

BACKGROUND

Ocular involvement can occur at any stage of syphilis. Prompt diagnosis and proper treatment of ocular syphilis are vital to avoid long-term consequences.

OBJECTIVES

To describe the risk factors for ocular syphilis and clinical features of blindness caused by syphilis.

METHODS

We report risk factors for ocular syphilis amongst patients seen at the Shanghai Skin Disease Hospital between October 2009 and October 2017. We identify patients with ocular syphilis resulting in blindness and report the clinical characteristics, laboratory findings and treatment outcomes of these patients.

RESULTS

A total of 8310 new cases of syphilis were seen, of which 213 patients had ocular disease and 50 patients had blindness due to syphilis. Increasing age and higher RPR titres were associated with ocular involvement but there was no association with HIV status. Blindness in syphilis was restricted predominantly to patients with optic nerve involvement and not patients with isolated uveitis. Fifty patients (and a total of 67 eyes) met the WHO definition of blindness prior to treatment for syphilis. At the end of follow-up, vision had improved in 24 of 67 eyes (35.8%) after treatment. Successful treatment of uveitis was associated with the best improvement in visual acuity, whilst patient with underlying optic atrophy prior to treatment had the worst visual outcome.

CONCLUSIONS

Ocular involvement is an important manifestation of syphilis which may result in blindness. Our data demonstrate outcomes for ocular syphilis are poor if detected late; early recognition and diagnosis is therefore vital to avoid permanent visual loss.

SAT0182 THE ASSOCIATION BETWEEN AUTOANTIBODIES AND RITUXIMAB RESPONSE IN SYSTEMIC LUPUS ERYTHEMATOSUS

Background:

Systemic Lupus Erythematosus (SLE) is clinically and immunologically heterogeneous with a variable response to treatment. MASTERPLANS is an MRC-funded consortium that seeks to identify immunophenotypic subgroups of patients that predict response to therapy. Autoantibody profiles can differentiate subgroups of patients and have potential to predict response to treatment.

Objectives:

To determine whether known and novel autoantibodies are associated with response to rituximab (RTX), and analyse the association between these antibodies and disease involvement in various organ systems.

Methods:

Serum was obtained from 224 SLE patients in the BILAG Biologics Registry who received rituximab according to NHS England criteria (2). Patients were recruited if they were starting a first cycle of rituximab for active SLE (BILAG A or 2xBILAG B) despite previous cyclophosphamide or mycophenolate mofetil. Evidence of any single organ system involvement previous or current was taken as having a BILAG score of A-D but not E. Disease activity was measured using BILAG-2004. Clinical response was defined as improvement by >=1 grade in active BILAG-2004 systems with no worsening in other systems. Autoantibodies were measured by immunoprecipitation of proteins by sera from35S-labelled K562 cell lines, followed by SDS-PAGE separation and autoradiography. Autoantibodies not able to be detected by this technique (anti-Ro52, anti-dsDNA and aCL) were measured by ELISA. Autoantibody data was analysed in IBM SPSS and GraphPad Prism v8.2. Association between autoantibodies and RTX response was analysed using binary logistic interaction terms and Pearson’s Chi-Square test.

Results:

Of the 224 patients (201 female, 23 male, median age 40 years) the most common system involvement from the 9 BILAG domains was musculoskeletal (164 patients) and the least ophthalmic (11 patients). Patients with anti-Ro52 and anti-U1RNP/Sm had more frequent involvement of mucocutaneous (p<0.036,p<0.012) and musculoskeletal domains (p<0.015 for U1RNP) respectively.

There were 136 patients with sufficient data to define as either responders (n=67) or non-responders (n=69) to RTX at 6 months. RTX responders had a higher frequency of anti-U1RNP/Sm compared to non-responders (Figure 1). Further Pearson’s Chi-Square analysis showed a significant association between presence of anti-U1RNP/Sm and better response to RTX (p<0.018).

Conclusion:

Our findings suggest that the presence of U1RNP/Sm autoantibodies in a cohort of patients who have received treatment with RTX is associated with more frequent musculoskeletal and mucocutaneous involvement and predicts a more favourable response to treatment.

Acknowledgments :

Funded by a grant from the Medical Research Council, grant number MR/M01665X/1. BILAG BR has been funded by unrestricted educational donations from Roche, GSK and LUPUS UK. Part-funded by a grant from LUPUS UK.

Disclosure of Interests: :

Danyang Li: None declared, Hui Lu: None declared, Juliet Dunphy: None declared, Theresa Smith: None declared, Edward Vital Grant/research support from: AstraZeneca, Roche/Genentech, and Sandoz, Consultant of: AstraZeneca, GSK, Roche/Genentech, and Sandoz, Speakers bureau: Becton Dickinson and GSK, Ian N. Bruce Grant/research support from: Genzyme Sanofi, GSK, and UCB, Consultant of: Eli Lilly, AstraZeneca, UCB, Iltoo, and Merck Serono, Speakers bureau: UCB, Neil McHugh: None declared

Baseline cerebral metabolism predicts fatigue and cognition in Multiple Sclerosis patients

BACKGROUND

Cerebral metabolic rate of oxygen (CMRO₂), a measure of global oxygen metabolism, reflects resting cellular activity. The mechanisms underlying fatigue and cognitive dysfunction in multiple sclerosis (MS) remain unknown. If fatigue indeed reflects ongoing autoimmune activity and cortical reorganization, and cognitive decline is the result of gray matter atrophy and white matter degeneration, we postulate that changes in CMRO₂ should reflect disease activity and predict these symptoms.

OBJECTIVE

We sought to utilize T₂-Relaxation-Under-Spin-Tagging (TRUST) and phase-contrast (PC) MRI to measure global CMRO₂ to understand its relationships to white matter microstructure, fatigue and cognitive dysfunction.

METHODS

We measured venous oxygenation (TRUST) and cerebral blood flow (PC-MRI) in superior sagittal sinus to calculate global CMRO₂ and diffusion tensor imaging (DTI) to evaluate white matter microstructure in healthy controls (HC) and MS patients. Participants underwent neuropsychological examinations including Modified Fatigue Impact Scale (MFIS) and Symbol-Digit-Modalities Test (SDMT).

RESULTS

We observed lower CMRO₂ in MS patients compared to HC. After controlling for demographic and disease characteristics (i.e., age, education, disability, lesion volume), CMRO₂ predicted increased fatigue (MFIS) and reduced cognitive performance (SDMT) in MS patients. Finally, MS patients with higher CMRO₂ have reduced FA in normal-appearing white-matter.

CONCLUSION

Altogether, these results suggest that increased CMRO₂ reflects ongoing demyelination and autoimmune activity which plays an important role in both fatigue and cognitive dysfunction.

Precision measurement of the neutral pion lifetime

The explicit breaking of the axial symmetry by quantum fluctuations gives rise to the so-called axial anomaly. This phenomenon is solely responsible for the decay of the neutral pion π⁰ into two photons (γγ), leading to its unusually short lifetime. We precisely measured the decay width Γ of the [Formula: see text] process. The differential cross sections for π⁰ photoproduction at forward angles were measured on two targets, carbon-12 and silicon-28, yielding [Formula: see text], where stat. denotes the statistical uncertainty and syst. the systematic uncertainty. We combined the results of this and an earlier experiment to generate a weighted average of [Formula: see text] Our final result has a total uncertainty of 1.50% and confirms the prediction based on the chiral anomaly in quantum chromodynamics.