Membrane transport proteins in melanosomes: Regulation of ions for pigmentation

Copper and Melanoma Risk: Results from NHANES 2007-2018 and Mendelian Randomization Analyses

Copper is an essential trace element obtained from food. There is a paucity of observational or prospective studies that have investigated the relationship between copper and melanoma risk. Copper serves as a cofactor for pivotal enzymes involved in mitochondrial respiration, antioxidant defense, and neurotransmitter synthesis. Undoubtedly, copper plays an indispensable role in the initiation and progression of tumors, particularly melanoma; however, further investigations are warranted to elucidate the underlying mechanisms linking copper and melanoma risk. Given the availability of dietary copper and serum copper data in the NHANES database, we conducted an investigation into the association between dietary copper intake and serum copper levels with melanoma risk. We enrolled 26,401 individuals with dietary copper data in the 2007-2018 NHANES database. To mitigate confounding variables, a propensity score matching (PSM) was performed. To assess the association between dietary copper intake and melanoma risk, we employed a multivariate logistic regression analysis before and after PSM. The restricted cubic spline analysis was utilized to determine whether there is a non-linear relationship between dietary copper intake and melanoma risk, with subgroup analysis conducted to determine beneficiaries. Then, those with blood copper data from the enrolled population with dietary copper intake were screened out, and subsequently, multivariate logistic regression models were subsequently constructed to investigate the association between serum copper levels and melanoma risk after PSM. Mendelian analysis was further utilized to validate the results of the NHANES database using serum copper as the exposure factor and melanoma as the outcome variable. The study found that melanoma risk was associated with dietary copper intake before and after PSM, demonstrated by multiple logistic regression. The relationship between dietary copper intake and melanoma risk was non-linear, with a reduced risk observed above approximately 2.5 mg/day, as shown by the RCS. The evidence suggests that an increased intake of copper is linked to a decreased risk of melanoma. To clarify the mechanism behind the increased risk of melanoma due to higher dietary copper intake, we analyzed the population data from the NHANES database on serum copper and dietary copper intake. Our results indicated that there is no causal relationship between serum copper and melanoma risk. Mendelian randomization analysis of multi-database data sources confirmed the conclusion of the NHANES database analysis. Dietary copper is a protective factor against melanoma, and serum copper or blood copper is not associated with melanoma risk. This suggests that serum or blood copper is not responsible for the protective effect of dietary copper intake on melanoma risk, and the mechanisms need to be further investigated.

Secondary growth ovarian follicles of the pigmented sterlet sturgeon Acipenser ruthenus L. 1758 (Acipenseriformes, Chondrostei, Actinopterygii, Osteichthyes) - Microscopic study of oocytes, egg envelope and diversification of follicular cells

The individual ovarian follicle of sturgeons (Acipenseriformes, Acipenseridae) contains an oocyte surrounded by follicular cells (FCs), basal lamina, and thecal cells. The late stages of the secondary growth of follicles (mid- and advanced vitellogenic) are not fully explained in Acipenseriformes. To explore and discuss the ultrastructure of oocytes, FCs, an egg envelope, and explain how micropylar cells differentiate and the canals of a multiple micropyle are formed, the samples of ovaries of the mature sterlet sturgeon Acipenser ruthenus were examined. The oocytes are polarized, the nucleus is located in the animal hemisphere, contains lampbrush chromosomes and multiple nucleoli. In the ooplasm three regions are present: a perinuclear (contains the mitochondria), an endoplasm (contains the lipid droplets and yolk platelets), and a periplasm (contains the cortical granules, melanosomes, endocytotic and exocytotic vesicles). The melanosomes in animal hemisphere form two concentric rings separated by a lighter region between them. The FCs are differentiated into bright and dark cells that are both translationally and secretory active. Diversification of FCs involves repeated and cytoskeleton-dependent change of shape. In the advanced follicles the FCs are diversified into micropylar, the animal and vegetal regions cells, and the cells that delaminated from the epithelium in the animal region. The egg envelope is present in the perioocytic space and consists of three layers: (1) an inner layer or vitelline envelope, (2) a middle layer, and (3) an outer layer. The inner layer consists of four sublayers: (a) a filamentous sublayer composed of filaments released from the oocytes, (b) a trabecular 1 sublayer and (c) a trabecular 2 sublayer named due to the sequence of the deposition, and composed of filaments, fibres and trabecules, (d) a homogeneous sublayer located between the trabecular 1 and trabecular 2 sublayers composed of filaments that adhere to each other closely. The middle layer contains two sublayers: a porous 1 and a porous 2 (composed of granular material) which are released by the oocyte and FCs. The outer layer consists of fibrillar material released by the FCs. The egg envelope is pierced by radial canals formed around the microvilli of the oocyte and the microvilli-like processes of FCs. A micropylar field in the egg envelope that covers the animal pole of the oocyte contains 1 - 4 micropylar canals. Micropylar cells are involved in their formation. The shape of these cells is icicle-like and the cytoplasm is differentiated into two regions (a basal and apical bearing a projection) equipped with different sets of organelles.

Tailoring biomaterials for skin anti-aging

Skin aging is the phenomenon of degenerative changes in the structure and function of skin tissues over time and is manifested by a gradual loss of skin elasticity and firmness, an increased number of wrinkles, and hyperpigmentation. Skin anti-aging refers to a reduction in the skin aging phenomenon through medical cosmetic technologies. In recent years, new biomaterials have been continuously developed for improving the appearance of the skin through mechanical tissue filling, regulating collagen synthesis and degradation, inhibiting pigmentation, and repairing the skin barrier. This review summarizes the mechanisms associated with skin aging, describes the biomaterials that are commonly used in medical aesthetics and their possible modes of action, and discusses the application strategies of biomaterials in this area. Moreover, the synergistic effects of such biomaterials and other active ingredients, such as stem cells, exosomes, growth factors, and antioxidants, on tissue regeneration and anti-aging are evaluated. Finally, the possible challenges and development prospects of biomaterials in the field of anti-aging are discussed, and novel ideas for future innovations in this area are summarized.

Navigating the landscape of theranostics in nuclear medicine: current practice and future prospects

Theranostics refers to the combination of diagnostic biomarkers with therapeutic agents that share a specific target expressed by diseased cells and tissues. Nuclear medicine is an exciting component explored for its applicability in theranostic concepts in clinical and research investigations. Nuclear theranostics is based on the employment of radioactive compounds delivering ionizing radiation to diagnose and manage certain diseases employing binding with specifically expressed targets. In the realm of personalized medicine, nuclear theranostics stands as a beacon of potential, potentially revolutionizing disease management. Studies exploring the theranostic profile of radioactive compounds have been presented in this review along with a detailed explanation of radioactive compounds and their theranostic applicability in several diseases. It furnishes insights into their applicability across diverse diseases, elucidating the intricate interplay between these compounds and disease pathologies. Light is shed on the important milestones of nuclear theranostics beginning with radioiodine therapy in thyroid carcinomas, MIBG labelled with iodine in neuroblastoma, and several others. Our perspectives have been put forth regarding the most important theranostic agents along with emerging trends and prospects.

Single-nucleus RNA sequencing reveals cell types, genes, and regulatory factors influencing melanogenesis in the breast muscle of Xuefeng black-bone chicken

The black-bone chicken, known for its high melanin content, holds significant economic value due to this unique trait. Particularly notable is the prominent melanin deposition observed in its breast muscle. However, the molecular mechanisms governing melanin synthesis and deposition in the breast muscle of black-bone chickens remain largely unknown. This study employed a single-nucleus transcriptome assay to identify genes associated with melanin deposition in the breast muscle of black-bone chickens, which are presumed to influence pigmentation levels. A comprehensive analysis of the nuclear transcriptome was conducted on the breast muscle of Xuefeng black-bone chickens, encompassing 18 distinct cell types, including melanocytes. Our findings revealed that STIMATE, LRRC7, ENSGALG00000049990, and GLDC play pivotal regulatory roles in melanin deposition within the breast muscle. Further exploration into the molecular mechanisms unveiled transcription factors and protein interactions suggesting that RARB, KLF15, and PRDM4 may be crucial regulators of melanin accumulation in the breast muscle. Additionally, HPGDS, GSTO1, and CYP1B1 may modulate melanin production and deposition in the breast muscle by influencing melanocyte metabolism. Our findings also suggest that melanocyte function in the breast muscle may be intertwined with intercellular signaling pathways such as PTPRK-WNT5A, NOTCH1-JAG1, IGF1R-IGF1, IDE-GCG, and ROR2-WNT5A. Leveraging advanced snRNA-seq technology, we generated a comprehensive single-cell nuclear transcriptome atlas of the breast muscle of Xuefeng black-bone chickens. This facilitated the identification of candidate genes, regulatory factors, and cellular signals potentially influencing melanin deposition and melanocyte function. Overall, our study provides crucial insights into the molecular basis of melanin deposition in chicken breast muscle, laying the groundwork for future breeding programs aimed at enhancing black-bone chicken cultivation.

Examination of wnt signaling mediated melanin transport and shell color formation in Pacific oyster (Crassostrea gigas)

Mollusca exhibit remarkable diversity in shell coloration, attributed to the presence of melanin, a widely distributed pigment with various essential roles, such as mechanical strengthening, antioxidation and thermoregulation. However, the regulatory network governing melanogenesis and melanin transport in molluscs remains poorly understood. In this study, we conducted a systematic analysis of melanin distribution and transport in the Pacific oyster, utilizing light microscopy and high-resolution transmission electron microscopy. In addition, we characterized CgWnt1 and CgWnt2b-a in Crassostrea gigas, and analyzed Wnt signaling in melanocyte formation. Expression analysis revealed that these genes were predominantly expressed in the mantle of black-shelled individuals, particularly in the outer fold of the mantle. Furthermore, we employed RNA interference and inhibitors to specifically inhibit Wnt signaling in both in vivo and in vitro. The results revealed impaired melanogenesis and diminished tyrosinase activity upon Wnt signaling inhibition. These findings suggest the crucial role of Wnt ligands and downstream factors in melanogenesis. In summary, our study provides valuable insights into the regulatory mechanism of shell pigmentation in C. gigas. By demonstrating the promotion of melanogenesis through Wnt signaling modulation, we contribute to a better understanding of the complex processes underlying molluscan melanin production and shell coloration.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-024-00221-5.

A power-based sliding window approach to evaluate the clinical impact of rare genetic variants in the nucleotide sequence or the spatial position of the folded protein

Systematic determination of novel variant pathogenicity remains a major challenge, even when there is an established association between a gene and phenotype. Here we present Power Window (PW), a sliding window technique that identifies the impactful regions of a gene using population-scale clinico-genomic datasets. By sizing analysis windows on the number of variant carriers, rather than the number of variants or nucleotides, statistical power is held constant, enabling the localization of clinical phenotypes and removal of unassociated gene regions. The windows can be built by sliding across either the nucleotide sequence of the gene (through 1D space) or the positions of the amino acids in the folded protein (through 3D space). Using a training set of 350k exomes from the UK Biobank (UKB), we developed PW models for well-established gene-disease associations and tested their accuracy in two independent cohorts (117k UKB exomes and 65k exomes sequenced at Helix in the Healthy Nevada Project, myGenetics, or In Our DNA SC studies). The significant models retained a median of 49% of the qualifying variant carriers in each gene (range 2%-98%), with quantitative traits showing a median effect size improvement of 66% compared with aggregating variants across the entire gene, and binary traits' odds ratios improving by a median of 2.2-fold. PW showcases that electronic health record-based statistical analyses can accurately distinguish between novel coding variants in established genes that will have high phenotypic penetrance and those that will not, unlocking new potential for human genomics research, drug development, variant interpretation, and precision medicine.

Proteomic Biomarkers Associated with Low Bone Mineral Density: A Systematic Review

Osteoporosis is a globally relevant public health issue. Our study aimed to summarize the knowledge on the proteomic biomarkers for low bone mineral density over the last years. We conducted a systematic review following the PRISMA guidelines; the scoured databases were PubMed, Web of Sciences, Scopus, and EBSCO, from inception to 2 June 2023. A total of 610 relevant studies were identified and 33 were assessed for eligibility. Finally, 29 studies met the criteria for this systematic review. The risk of bias was evaluated using the Joanna Briggs Institute Critical Appraisal Checklist tool. From the studies selected, 154 proteins were associated with changes of bone mineral density, from which only 10 were reported in at least two articles. The protein-protein network analysis indicated potential biomarkers involved in the skeletal system, immune system process, regulation of protein metabolic process, regulation of signaling, transport, cellular component assembly, cell differentiation, hemostasis, and extracellular matrix organization. Mass spectrometry-based proteomic profiling has allowed the discovery of new biomarkers with diagnostic potential. However, it is necessary to compare and validate the potential biomarkers in different populations to determine their association with bone metabolism and evaluate their translation to the clinical management of osteoporosis.

Malignant Melanoma: An Overview, New Perspectives, and Vitamin D Signaling

Melanoma, originating through malignant transformation of melanin-producing melanocytes, is a formidable malignancy, characterized by local invasiveness, recurrence, early metastasis, resistance to therapy, and a high mortality rate. This review discusses etiologic and risk factors for melanoma, diagnostic and prognostic tools, including recent advances in molecular biology, omics, and bioinformatics, and provides an overview of its therapy. Since the incidence of melanoma is rising and mortality remains unacceptably high, we discuss its inherent properties, including melanogenesis, that make this disease resilient to treatment and propose to use AI to solve the above complex and multidimensional problems. We provide an overview on vitamin D and its anticancerogenic properties, and report recent advances in this field that can provide solutions for the prevention and/or therapy of melanoma. Experimental papers and clinicopathological studies on the role of vitamin D status and signaling pathways initiated by its active metabolites in melanoma prognosis and therapy are reviewed. We conclude that vitamin D signaling, defined by specific nuclear receptors and selective activation by specific vitamin D hydroxyderivatives, can provide a benefit for new or existing therapeutic approaches. We propose to target vitamin D signaling with the use of computational biology and AI tools to provide a solution to the melanoma problem.

Two-pore channel 2 is required for soluble adenylyl cyclase-dependent regulation of melanosomal pH and melanin synthesis

Melanosomal pH is important for the synthesis of melanin as the rate-limiting enzyme, tyrosinase, is very pH-sensitive. The soluble adenylyl cyclase (sAC) signaling pathway was recently identified as a regulator of melanosomal pH in melanocytes; however, the melanosomal proteins critical for sAC-dependent regulation of melanosomal pH were undefined. We now systematically examine four well-characterized melanosomal membrane proteins to determine whether any of them are required for sAC-dependent regulation of melanosomal pH. We find that OA1, OCA2, and SLC45A2 are dispensable for sAC-dependent regulation of melanosomal pH. In contrast, TPC2 activity is required for sAC-dependent regulation of melanosomal pH and melanin synthesis. In addition, activation of TPC2 by NAADP-AM rescues melanosomal pH alkalinization and reduces melanin synthesis following pharmacologic or genetic inhibition of sAC signaling. These studies establish TPC2 as a critical melanosomal protein for sAC-dependent regulation of melanosomal pH and pigmentation.

Skin Hypopigmentation in Hematology Disorders

Hypopigmentation disorders pose significant diagnostic challenges in dermatology, sometimes reflecting underlying hematological conditions. This review explores the clinical presentations related to hypopigmentation in hematological disorders, focusing on vitiligo, morphea, and syndromic albinism. Vitiligo, an autoimmune disorder targeting melanocytes, involves interactions between genetic polymorphisms and immune responses, particularly regarding CD8+ T cells and IFN-γ. Drug-induced vitiligo, notably by immune checkpoint inhibitors and small-molecule targeted anticancer therapies, underscores the importance of immune dysregulation. Morphea, an inflammatory skin disorder, may signal hematological involvement, as seen in deep morphea and post-radiotherapy lesions. Syndromic albinism, linked to various genetic mutations affecting melanin production, often presents with hematologic abnormalities. Treatment approaches focus on targeting the immune pathways specific to the condition, and when that is not possible, managing symptoms. Understanding these dermatological manifestations is crucial for the timely diagnosis and management of hematological disorders.

Expression and Mutation of SLC45A2 Affects Iris Color in Quail

Iris color is a prominent phenotypic feature of quail. To understand the mechanism of melanin deposition related to quail iris color, iris tissues were selected from Beijing white and Chinese yellow quail for transcriptome analysis. Differentially expressed genes (DEGs) associated with pigmentation were identified using RNA sequencing and validated by quantitative real-time polymerase chain reaction (RT-qPCR). The identified single nucleotide polymorphisms were studied using bioinformatics and iris color correlation analyses. A total of 485 DEGs were obtained, with 223 upregulated and 262 downregulated. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed. Thirty-two genes were annotated using the GO database. Three important pigment synthesis pathways (Notch signaling, melanogenesis, and tyrosine metabolism) were identified in quail iris tissue (P < 0.05). The expression levels of solute carrier family 45 member 2 (SLC45A2), tyrosinase-related protein 1, vitamin D receptor, opsin 5, and docking protein 5 were significantly different between Beijing white and Chinese yellow quail, as verified by RT-qPCR. The c.1061C>T mutation in SLC45A2, which caused a single amino acid change at position 354 (threonine to methionine), was significantly associated with iris color in Beijing white and Chinese yellow quail, and might be the main reason for the different iris colors between these two quail species.

Inhibitory Effects of Fermented Sprouted Oat Extracts on Oxidative Stress and Melanin Overproduction

Hyperpigmentation occurs due to irregular secretion of melanin pigment in the skin. This can affect quality of life depending on its severity, so prevention and management are essential. Oats (Avena sativa L.), a grain consumed worldwide, are known to offer improved health benefits upon germination and fermentation. This study is aimed to investigate the protective effects of lactobacilli-fermented sprouted oat extracts on oxidative stress and melanin overproduction in vitro. The anti-melanogenic effect was investigated using melanin content and tyrosinase activity assays in B16F10 cells, as well as a mushroom tyrosinase-based enzyme inhibition assay. The results showed that L. casei-fermented oat extracts were the most effective for reducing melanin formation by reducing the mRNA expression of microphthalmia-associated transcription factor, tyrosinase, and tyrosinase-related protein 2. Furthermore, L. casei fermentation was effective in improving the total phenolic, flavonoid, and avenanthramide A contents of sprouted oat extracts. The results also demonstrated the antioxidant effects of L. casei-fermented sprouted oat extracts in promoting DPPH radical-scavenging activity, superoxide dismutase-like activity, and reduction in reactive oxygen species levels. Overall, the findings indicate that fermented sprouted oat extracts are promising candidates for antioxidant and anti-hyperpigmentation treatments.

<sc>A</sc> multi-hierarchical approach reveals <sc>d</sc>-serine as a hidden substrate of sodium-coupled monocarboxylate transporters

Transporter research primarily relies on the canonical substrates of well-established transporters. This approach has limitations when studying transporters for the low-abundant micromolecules, such as micronutrients, and may not reveal physiological functions of the transporters. While d-serine, a trace enantiomer of serine in the circulation, was discovered as an emerging biomarker of kidney function, its transport mechanisms in the periphery remain unknown. Here, using a multi-hierarchical approach from body fluids to molecules, combining multi-omics, cell-free synthetic biochemistry, and ex vivo transport analyses, we have identified two types of renal d-serine transport systems. We revealed that the small amino acid transporter ASCT2 serves as a d-serine transporter previously uncharacterized in the kidney and discovered d-serine as a non-canonical substrate of the sodium-coupled monocarboxylate transporters (SMCTs). These two systems are physiologically complementary, but ASCT2 dominates the role in the pathological condition. Our findings not only shed light on renal d-serine transport, but also clarify the importance of non-canonical substrate transport. This study provides a framework for investigating multiple transport systems of various trace micromolecules under physiological conditions and in multifactorial diseases.

Differential expression and alternative splicing analyses of multiple tissues reveal albinism-associated genes in the Wels catfish (Silurus glanis)

Albinism is a widespread departure from a typical body colouration due to altered melanin production. The Wels catfish (Silurus glanis) is among the largest freshwater fish species in the world, and albino individuals occur both in the wild and in aquaculture. Here, we performed transcriptome-wide analysis of albino and normally pigmented S. glanis using four tissues (skin, dorsal fin, whole eye and liver) to identify genes associated with albinism by exploring patterns of differential expression (DE) and differential alternative splicing (DAS). Multi-tissue analyses revealed a large number of genes in skin (n = 1355) and fin (n = 614) tissue associated with the albino phenotype in S. glanis, while the number of DE genes in eye and liver tissues was lower (n = 188, n = 189, respectively). Several DE genes across multiple tissues were detected as the most promising candidates (e.g., hsp4, hsp90b1, raph1, uqcrfs1, adcy-family and wnt-family) potentially causally linked to the albino phenotype in Wels catfish. Moreover, our findings supported earlier observations of physiological differences between albino and normally pigmented individuals, particularly in energy metabolism and immune response. In contrast, there were only a few pigmentation-related genes observed among DAS genes (4 in skin, 2 in fin), the overlap between DAS and DE genes was low (n = 25) and did not include known pigmentation-related genes. This suggests that DAS and DE in Wels catfish are, to a large extent, independent processes, and the observed alternative splicing cases are probably not causally linked with albinism in S. glanis. This work provides the first transcriptome-wide multi-tissue insights into the albinism of Wels catfish and serves as a valuable resource for further understanding the genetic mechanisms of pigmentation in fish.

Gene expression profiles of skin from cyclin dependent kinases 5-knockdown mice

OBJECTIVE

This study aimed to identify genes regulated by cyclin dependent kinases 5 (CDK5) that participate in hair pigmentation in mice.

METHODS

The mRNA expression profiles of skin samples from CDK5-knockdown mice were constructed using high-throughput RNA sequencing and compared with those of wild-type mice.

RESULTS

In total, 8,002 known genes were differentially expressed between CDK5-knockdown and wild-type mice. Of these, 3,658 were upregulated and 4,344 were downregulated in the skin of CDK5-knockdown mice. An additional 318 previously unknown genes were also differentially expressed, with 171 downregulated and 147 upregulated genes in the skin of CDK5-knockdown mice. Of the known genes expressed in mouse skin, 80 were associated with hair color, with 61 showing lower expression and 19 exhibiting higher expression in skin of CDK5-knockdown mice. Importantly, the expression of the tyrosinase-related protein 1 (TYRP1) and the calcium signaling pathway were also found to be regulated by CDK5, suggesting that pigmentation is regulated by CDK5 via the calcium signaling pathway and TYRP1.

CONCLUSION

The transcriptome profiles obtained from the skin of CDK5-knockdown mice compared to wild-type mice provide a valuable resource to help understand the mechanism by which CDK5 regulates melanogenesis in mice and other animals.

Identification of Candidate Genes for Red-Eyed (Albinism) Domestic Guppies Using Genomic and Transcriptomic Analyses

Guppies are small tropical fish with brightly colored bodies and variable tail shapes. There are two phenotypes of domestic guppy eye color: red and black. The wild type is black-eyed. The main object of this study was to identify candidate genes for the red-eyed phenotype in domestic guppies. We hope to provide molecular genetic information for the development of new domestic guppy strains. Additionally, the results also contribute to basic research concerning guppies. In this study, 121 domestic guppies were used for genomic analysis (GWAS), and 44 genes were identified. Furthermore, 21 domestic guppies were used for transcriptomic analysis, and 874 differentially expressed genes (DEGs) were identified, including 357 upregulated and 517 downregulated genes. Through GO and KEGG enrichment, we identified some important terms or pathways mainly related to melanin biosynthesis and ion transport. qRT-PCR was also performed to verify the differential expression levels of four important candidate genes (TYR, OCA2, SLC45A2, and SLC24A5) between red-eyed and black-eyed guppies. Based on the results of genomic and transcriptomic analyses, we propose that OCA2 is the most important candidate gene for the red-eyed phenotype in guppies.

Augmenting MEK inhibitor efficacy in BRAF wild-type melanoma: synergistic effects of disulfiram combination therapy

BACKGROUND

MEK inhibitors (MEKi) were shown to be clinically insufficiently effective in patients suffering from BRAF wild-type (BRAF WT) melanoma, even if the MAPK pathway was constitutively activated due to mutations in NRAS or NF-1. Thus, novel combinations are needed to increase the efficacy and duration of response to MEKi in BRAF WT melanoma. Disulfiram and its metabolite diethyldithiocarbamate are known to have antitumor effects related to cellular stress, and induction of endoplasmic reticulum (ER) stress was found to synergize with MEK inhibitors in NRAS-mutated melanoma cells. Therefore, we investigated the combination of both therapeutics to test their effects on BRAF-WT melanoma cells and compared them with monotherapy using the MEKi trametinib.

METHODS

The effects of combined therapy with disulfiram or its metabolite diethyldithiocarbamate and the MEKi trametinib were evaluated in a series of BRAF-WT melanoma cell lines by measuring cell viability and apoptosis induction. Cytotoxicity was additionally assessed in 3D spheroids, ex vivo melanoma slice cultures, and in vivo xenograft mouse models. The response of melanoma cells to treatment was studied at the RNA and protein levels to decipher the mode of action. Intracellular and intratumoral copper measurements were performed to investigate the role of copper ions in the antitumor cytotoxicity of disulfiram and its combination with the MEKi.

RESULTS

Diethyldithiocarbamate enhanced trametinib-induced cytotoxicity and apoptosis induction in 2D and 3D melanoma culture models. Mechanistically, copper-dependent induction of oxidative stress and ER stress led to Janus kinase (JNK)-mediated apoptosis in melanoma cells. This mechanism was also detectable in patient-derived xenograft melanoma models and resulted in a significantly improved therapeutic effect compared to monotherapy with the MEKi trametinib.

CONCLUSIONS

Disulfiram and its metabolite represent an attractive pharmaceutical approach to induce ER stress in melanoma cells that potentiates the antitumor effect of MEK inhibition and may be an interesting candidate for combination therapy of BRAF WT melanoma.

Transcriptomic Profiles of Pectoralis major Muscles Affected by Spaghetti Meat and Woody Breast in Broiler Chickens

Spaghetti meat (SM) and woody breast (WB) are breast muscle myopathies of broiler chickens, characterized by separation of myofibers and by fibrosis, respectively. This study sought to investigate the transcriptomic profiles of breast muscles affected by SM and WB. Targeted sampling was conducted on a flock to obtain 10 WB, 10 SM, and 10 Normal Pectoralis major muscle samples from 37-day-old male chickens. Total RNA was extracted, cDNA was used for pair-end sequencing, and differentially expressed genes (DEGs) were determined by a false discovery rate of <0.1 and a >1.5-fold change. Principal component and heatmap cluster analyses showed that the SM and WB samples clustered together. No DEGs were observed between SM and WB fillets, while a total of 4018 and 2323 DEGs were found when comparing SM and WB, respectively, against Normal samples. In both the SM and WB samples, Gene Ontology terms associated with extracellular environment and immune response were enriched. The KEGG analysis showed enrichment of cytokine-cytokine receptor interaction and extracellular matrix-receptor interaction pathways in both myopathies. Although SM and WB are macroscopically different, the similar transcriptomic profiles suggest that these conditions may share a common pathogenesis. This is the first study to compare the transcriptomes of SM and WB, and it showed that, while both myopathies had profiles different from the normal breast muscle, SM and WB were similar, with comparable enriched metabolic pathways and processes despite presenting markedly different macroscopic features.

Genome-wide association analysis of neck ring traits in NongHua ma male ducks

1. Male NongHua ma ducks have more colourful feathers than females, especially considering that the former have a distinctive neck ring that is different from that of females. This ring development might be influenced by sex selection, the environment, genetics and other elements.2. Genome-wide association analysis (GWAS) was used to locate candidate genes that affect the neck ring formation of male ducks to investigate the genetic basis of this phenomenon.3. In this study, the neck ring area and width of 180 male ducks were assessed at ages 80, 90, 100, 110 and 120 d. GWAS was used to identify associated genes. There were 0, 7, 14, 48 and 21 possible candidate genes annotated around the 0, 12, 25, 76 and 40 SNP loci n corresponding regions. A total of 13 candidate genes were identified around 21 SNP sites at the neck ring width of 120 d.4. These significant genes were annotated and GO and KEGG enrichment analyses were performed. All SNPs that exceeded the significance threshold were annotated and preliminarily screened as candidate genes affecting neck ring formation. From analysis of gene function and enriched KEGG pathways, genes such as THSD1, SLC6A4, DGAT2, PRKDC, B3GAT2, ROR1, GRK7, EXTL3, TXNDC12, COL4A2, PRKG1, ACTR3, were considered important candidate marker sites related to the neck ring. This provided a reference starting point for the genetic mechanism underlying duck feather colour.

SWI/SNF complexes are required for retinal pigmented epithelium differentiation and for the inhibition of cell proliferation and neural differentiation programs

During embryonic development, tissue-specific transcription factors and chromatin remodelers function together to ensure gradual, coordinated differentiation of multiple lineages. Here, we define this regulatory interplay in the developing retinal pigmented epithelium (RPE), a neuroectodermal lineage essential for the development, function and maintenance of the adjacent retina. We present a high-resolution spatial transcriptomic atlas of the developing mouse RPE and the adjacent ocular mesenchyme obtained by geographical position sequencing (Geo-seq) of a single developmental stage of the eye that encompasses young and more mature ocular progenitors. These transcriptomic data, available online, reveal the key transcription factors and their gene regulatory networks during RPE and ocular mesenchyme differentiation. Moreover, conditional inactivation followed by Geo-seq revealed that this differentiation program is dependent on the activity of SWI/SNF complexes, shown here to control the expression and activity of RPE transcription factors and, at the same time, inhibit neural progenitor and cell proliferation genes. The findings reveal the roles of the SWI/SNF complexes in controlling the intersection between RPE and neural cell fates and the coupling of cell-cycle exit and differentiation.

PKAD-2: New entries and expansion of functionalities of the database of experimentally measured pKa's of proteins

Almost all biological reactions are pH dependent and understanding the origin of pH dependence requires knowledge of the pKa's of ionizable groups. Here we report a new edition of PKAD, the PKAD-2, which is a database of experimentally measured pKa's of proteins, both wild type and mutant proteins. The new additions include 117 wild type and 54 mutant pKa values, resulting in total 1742 experimentally measured pKa's. The new edition of PKAD-2 includes 8 new wild type and 12 new mutant proteins, resulting in total of 220 proteins. This new edition incorporates a visual 3D image of the highlighted residue of interest within the corresponding protein or protein complex. Hydrogen bonds were identified, counted, and implemented as a search feature. Other new search features include the number of neighboring residues <4A from the heaviest atom of the side chain of a given amino acid. Here, we present PKAD-2 with the intention to continuously incorporate novel features and current data with the goal to be used as benchmark for computational methods.

Ethnicity is not biology: retinal pigment score to evaluate biological variability from ophthalmic imaging using machine learning

Background

Few metrics exist to describe phenotypic diversity within ophthalmic imaging datasets, with researchers often using ethnicity as an inappropriate marker for biological variability.

Methods

We derived a continuous, measured metric, the retinal pigment score (RPS), that quantifies the degree of pigmentation from a colour fundus photograph of the eye. RPS was validated using two large epidemiological studies with demographic and genetic data (UK Biobank and EPIC-Norfolk Study).

Findings

A genome-wide association study (GWAS) of RPS from UK Biobank identified 20 loci with known associations with skin, iris and hair pigmentation, of which 8 were replicated in the EPIC-Norfolk cohort. There was a strong association between RPS and ethnicity, however, there was substantial overlap between each ethnicity and the respective distributions of RPS scores.

Interpretation

RPS serves to decouple traditional demographic variables, such as ethnicity, from clinical imaging characteristics. RPS may serve as a useful metric to quantify the diversity of the training, validation, and testing datasets used in the development of AI algorithms to ensure adequate inclusion and explainability of the model performance, critical in evaluating all currently deployed AI models. The code to derive RPS is publicly available at: https://github.com/uw-biomedical-ml/retinal-pigmentation-score.

Funding

The authors did not receive support from any organisation for the submitted work.

Hybrid origin of a primate, the gray snub-nosed monkey

Hybridization is widely recognized as promoting both species and phenotypic diversity. However, its role in mammalian evolution is rarely examined. We report historical hybridization among a group of snub-nosed monkeys (Rhinopithecus) that resulted in the origin of a hybrid species. The geographically isolated gray snub-nosed monkey Rhinopithecus brelichi shows a stable mixed genomic ancestry derived from the golden snub-nosed monkey (Rhinopithecus roxellana) and the ancestor of black-white (Rhinopithecus bieti) and black snub-nosed monkeys (Rhinopithecus strykeri). We further identified key genes derived from the parental lineages, respectively, that may have contributed to the mosaic coat coloration of R. brelichi, which likely promoted premating reproductive isolation of the hybrid from parental lineages. Our study highlights the underappreciated role of hybridization in generating species and phenotypic diversity in mammals.

Generation of Albino Phenotype in Ornamental Fish by CRISPR/Cas9-Mediated Genome Editing of slc45a2 Gene

Albinism is the most common color variation described in fish and is a fascinating trait of some ornamental fish species. Albino mutants can be generated by knocking out core genes affecting melanin synthesis like slc45a2 in several fish species. However, genetic mutation remains challenging for species with unknown genome information. In this study, we generated albino mutants in two selected ornamental fish species, royal farlowella (Sturisoma panamense), and redhead cichlid (Vieja melanura). For this purpose, we carried out phylogenetic analyses of fish slc45a2 sequences and identified a highly conserved region among different fish species. A pair of degenerate primers spanning this region was designed and used to amplify a conserved slc45a2 fragment of 340 bp from the two fish species. Based on the amplified sequences, a target site in the 6^th exon was used for designing guide RNA and this targeted site was first verified by the CRISPR/Cas9 system in the zebrafish (Danio rerio) model for the effectiveness. Then, specific guide RNAs were designed for the two ornamental fish species and tested. Most of the injected larvae completely lost black pigment over the whole body and eyes. DNA sequencing confirmed a high degree of mutation at the targeted site. Overall, we described a fast and efficient method to generate albino phenotype in fish species by targeting the conserved 6^th exon of slc45a2 gene for genome editing via CRISPR/Cas9 and this approach could be a new genetic tool to generate desirable albino ornamental fish.

Post-Inflammatory Hypopigmentation: Review of the Etiology, Clinical Manifestations, and Treatment Options

Post-inflammatory hypopigmentation is a common acquired pigmentary disorder that is more prominent in skin of color, leading to great cosmetic and psychosocial implications. Often, a diagnosis with a pigmentary disorder can negatively impact an individual's health-related quality of life and may result in stigma. Although most cases of post-inflammatory hypopigmentation resolve spontaneously over time, a systematic diagnostic approach can help with identifying the underlying etiology and informing treatment strategies. It can be due to cutaneous inflammation, sequelae of inflammatory or infectious dermatoses, or dermatologic procedures. Therefore, a thorough understanding of the epidemiology, patient history, physical exam findings, and clinical features of post-inflammatory hypopigmentation phenomenon can explain the primary cause to providers and allow for patient education. It is also important to understand the various therapeutic approaches available and the efficacy of these options, which will inform providers to choose the appropriate therapy for patients. Although algorithms exist for classifying acquired disorders of hypopigmentation, there are no established algorithms for the diagnosis and treatment of post-inflammatory hypopigmentation, which warrants further exploration and discourse.

The genetic basis and potential molecular mechanism of yellow-albino northern snakehead (Channa argus)

Body colour is an important economic trait for commercial fishes. Recently, a new colour morph displaying market-favoured yellow skin (termed as yellow-mutant, YM) of northern snakehead (Channa argus) was discovered in China. We confirmed that YM snakehead is an albino with complete loss of melanin in the skin and eyes by histological and ultrastructural observations, and inherited as a recessive Mendelian trait. By applying genomic analysis approaches, in combination with gene knockdown and rescue experiments, we suggested a non-sense mutation in slc45a2 (c.383G > A) is the causation for the YM snakehead. Notably, significantly higher levels of key melanogenesis genes (tyr, tyrp1, dct and pmel) and phospho-MITF protein were detected in YM snakehead than those in wild-type individuals, and the underlying mechanism was further investigated by comparative transcriptomic analysis. Results revealed that differential expressed genes involved in pathways like MAPK, WNT and calcium signalling were significantly induced in YM snakehead, which might account for the increased amount of melanogenesis elements, and presumably be stimulated by fibroblast-derived melanogenic factors in a paracrine manner. Our study clarified the genetic basis of colour variation in C. argus and provided the preliminary clue indicating the potential involvement of fibroblasts in pigmentation in fish.

Redundancy analysis, genome-wide association studies and the pigmentation of brown trout (Salmo trutta L.)

The association of molecular variants with phenotypic variation is a main issue in biology, often tackled with genome-wide association studies (GWAS). GWAS are challenging, with increasing, but still limited, use in evolutionary biology. We used redundancy analysis (RDA) as a complimentary ordination approach to single- and multitrait GWAS to explore the molecular basis of pigmentation variation in brown trout (Salmo trutta) belonging to wild populations impacted by hatchery fish. Based on 75,684 single nucleotide polymorphic (SNP) markers, RDA, single- and multitrait GWAS allowed the extraction of 337 independent colour patterning loci (CPLs) associated with trout pigmentation traits, such as the number of red and black spots on flanks. Collectively, these CPLs (i) mapped onto 35 out of 40 brown trout linkage groups indicating a polygenic genomic architecture of pigmentation, (ii) were found to be associated with 218 candidate genes, including 197 genes formerly mentioned in the literature associated to skin pigmentation, skin patterning, differentiation or structure notably in a close relative, the rainbow trout (Onchorhynchus mykiss), and (iii) related to functions relevant to pigmentation variation (e.g., calcium- and ion-binding, cell adhesion). Annotated CPLs include genes with well-known pigmentation effects (e.g., PMEL, SLC45A2, SOX10), but also markers associated with genes formerly found expressed in rainbow or brown trout skins. RDA was also shown to be useful to investigate management issues, especially the dynamics of trout pigmentation submitted to several generations of hatchery introgression.

Increased LCN2 (lipocalin 2) in the RPE decreases autophagy and activates inflammasome-ferroptosis processes in a mouse model of dry AMD

In dry age-related macular degeneration (AMD), LCN2 (lipocalin 2) is upregulated. Whereas LCN2 has been implicated in AMD pathogenesis, the mechanism remains unknown. Here, we report that in retinal pigmented epithelial (RPE) cells, LCN2 regulates macroautophagy/autophagy, in addition to maintaining iron homeostasis. LCN2 binds to ATG4B to form an LCN2-ATG4B-LC3-II complex, thereby regulating ATG4B activity and LC3-II lipidation. Thus, increased LCN2 reduced autophagy flux. Moreover, RPE cells from cryba1 KO, as well as sting1 KO and Sting1Gt mutant mice (models with abnormal iron chelation), showed decreased autophagy flux and increased LCN2, indicative of CGAS- and STING1-mediated inflammasome activation. Live cell imaging of RPE cells with elevated LCN2 also showed a correlation between inflammasome activation and increased fluorescence intensity of the Liperfluo dye, indicative of oxidative stress-induced ferroptosis. Interestingly, both in human AMD patients and in mouse models with a dry AMD-like phenotype (cryba1 cKO and KO), the LCN2 homodimer variant is increased significantly compared to the monomer. Sub-retinal injection of the LCN2 homodimer secreted by RPE cells into NOD-SCID mice leads to retinal degeneration. In addition, we generated an LCN2 monoclonal antibody that neutralizes both the monomer and homodimer variants and rescued autophagy and ferroptosis activities in cryba1 cKO mice. Furthermore, the antibody rescued retinal function in cryba1 cKO mice as assessed by electroretinography. Here, we identify a molecular pathway whereby increased LCN2 elicits pathophysiology in the RPE, cells known to drive dry AMD pathology, thus providing a possible therapeutic strategy for a disease with no current treatment options.Abbreviations: ACTB: actin, beta; Ad-GFP: adenovirus-green fluorescent protein; Ad-LCN2: adenovirus-lipocalin 2; Ad-LCN2-GFP: adenovirus-LCN2-green fluorescent protein; LCN2AKT2: AKT serine/threonine kinase 2; AMBRA1: autophagy and beclin 1 regulator 1; AMD: age-related macular degeneration; ARPE19: adult retinal pigment epithelial cell line-19; Asp278: aspartate 278; ATG4B: autophagy related 4B cysteine peptidase; ATG4C: autophagy related 4C cysteine peptidase; ATG7: autophagy related 7; ATG9B: autophagy related 9B; BLOC-1: biogenesis of lysosomal organelles complex 1; BLOC1S1: biogenesis of lysosomal organelles complex 1 subunit 1; C57BL/6J: C57 black 6J; CGAS: cyclic GMP-AMP synthase; ChQ: chloroquine; cKO: conditional knockout; Cys74: cysteine 74; Dab2: DAB adaptor protein 2; Def: deferoxamine; DHE: dihydroethidium; DMSO: dimethyl sulfoxide; ERG: electroretinography; FAC: ferric ammonium citrate; Fe2+: ferrous; FTH1: ferritin heavy chain 1; GPX: glutathione peroxidase; GST: glutathione S-transferase; H2O2: hydrogen peroxide; His280: histidine 280; IFNL/IFNλ: interferon lambda; IL1B/IL-1β: interleukin 1 beta; IS: Inner segment; ITGB1/integrin β1: integrin subunit beta 1; KO: knockout; LC3-GST: microtubule associated protein 1 light chain 3-GST; C-terminal fusion; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; LCN2: lipocalin 2; mAb: monoclonal antibody; MDA: malondialdehyde; MMP9: matrix metallopeptidase 9; NLRP3: NLR family pyrin domain containing 3; NOD-SCID: nonobese diabetic-severe combined immunodeficiency; OS: outer segment; PBS: phosphate-buffered saline; PMEL/PMEL17: premelanosome protein; RFP: red fluorescent protein; rLCN2: recombinant LCN2; ROS: reactive oxygen species; RPE SM: retinal pigmented epithelium spent medium; RPE: retinal pigment epithelium; RSL3: RAS-selective lethal; scRNAseq: single-cell ribonucleic acid sequencing; SD-OCT: spectral domain optical coherence tomography; shRNA: small hairpin ribonucleic acid; SM: spent medium; SOD1: superoxide dismutase 1; SQSTM1/p62: sequestosome 1; STAT1: signal transducer and activator of transcription 1; STING1: stimulator of interferon response cGAMP interactor 1; TYR: tyrosinase; VCL: vinculin; WT: wild type.

The potential impact of melanosomal pH and metabolism on melanoma

Melanin is synthesized in melanocytes and is transferred into keratinocytes to block the effects of ultraviolet (UV) radiation and is important for preventing skin cancers including melanoma. However, it is known that after melanomagenesis and melanoma invasion or metastases, melanin synthesis still occurs. Since melanoma cells are no longer involved in the sun tanning process, it is unclear why melanocytes would maintain melanin synthesis after melanomagenesis has occurred. Aside from blocking UV-induced DNA mutation, melanin may provide other metabolic functions that could benefit melanoma. In addition, studies have suggested that there may be a selective advantage to melanin synthesis in melanoma; however, mechanisms regulating melanin synthesis outside the epidermis or hair follicle is unknown. We will discuss how melanosomal pH controls melanin synthesis in melanocytes and how melanosomal pH control of melanin synthesis might function in melanoma. We will also discuss potential reasons why melanin synthesis might be beneficial for melanoma cellular metabolism and provide a rationale for why melanin synthesis is not limited to benign melanocytes.

Integrated Analysis of Long Non-Coding RNA and mRNA to Reveal Putative Candidate Genes Associated with Backfat Quality in Beijing Black Pig

Pigs' backfat quality has an important impact on the quality of pork and pork products and has a strong relationship with nutrition and sensory characteristics. This study aimed to identify the related candidate genes of backfat quality and to preliminary clarify the molecular regulatory mechanism underlying pig backfat quality phenotypes. Expression assessments of long non-coding RNA (lncRNA) and mRNA profiling in backfat from high-quality (firm and white) and low-quality (soft and yellow) Beijing Black pigs were performed by RNA sequencing. Significantly different expressions were observed in 610 protein-coding genes and 290 lncRNAs between the two groups. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway annotation showed that some candidate differentially expressed genes that participate in lipid-related pathways and pigmentation terms may play a role in backfat quality in pigs. The cis-target and trans-target genes were predicted to explore the regulatory function of lncRNAs, and integrative analyses of different expression lncRNAs targets and different expression genes were performed. The results showed the regulatory networks of lncRNA-mRNA related to backfat quality, and our study obtained strong candidate genes for backfat quality: ELOVL5, SCD, DGAT2, SLC24A5, and TYRP1, which were involved in fat metabolism, adipogenesis regulation, and pigmentation. To our knowledge, this study is the first to demonstrate the molecular genetic mechanisms of backfat quality in pigs, and these findings improve the current understanding of backfat quality mechanisms and provide a foundation for further studies.

Tributyltin exposure disrupted the locomotor activity rhythms in adult zebrafish (Danio rerio) and the mechanism involved

The fish circadian rhythm system might be an emerging target of tributyltin (TBT), however, the mechanism by which TBT interferes with the circadian rhythm is poorly understood. Therefore, in the present study, zebrafish were used to assess the effects of TBT at environmental concentrations (1 and 10 ng/L) on locomotor activity rhythm. Furthermore, we focused on the visual system to explore the potential mechanism involved. After 90 d of exposure, TBT disturbed the locomotor activity rhythms in zebrafish, which manifested as: (1) low activities and lethargy during the arousing period; (2) inability to fall asleep quickly and peacefully during the period of latency to sleep; and (3) no regular "waves" of locomotor activities during the active period. After TBT exposure, the histological structure of the eyes significantly changed, the boundary between layers became blurred, and the melanin concentrations significantly decreased. Using KEGG and GSEA pathway analyses, the differentially expressed genes in the eyes screened by transcriptomics were significantly enriched in the tyrosine metabolism pathway and retinol metabolism pathway. Furthermore, a decrease in melanin and disruption of retinoic acid were found after TBT exposure, which would affect the reception of phototransduction, and then interfere with the circadian rhythm in fish. The disruption of the circadian rhythm of fish by aquatic pollutants would decrease their ecological adaptability, which should be considered in future research.

The Eyes Have It-for Idiopathic Pulmonary Fibrosis: a Preliminary Observation

Introduction

The disease origins of idiopathic pulmonary fibrosis (IPF), which occurs at higher rates in certain races/ethnicities, are not understood. The highest rates occur in white persons of European descent, particularly those with light skin, who are also susceptible to lysosomal organelle dysfunction of the skin leading to fibroproliferative disease . We had observed clinically that the vast majority of patients with IPF had light-colored eyes, suggesting a phenotypic characteristic.

Methods

We pursued this observation through a research database from the USA Veterans Administration, a population that has a high occurrence of IPF due to predominance of elderly male smokers. Using this medical records database, which included facial photos, we compared the frequency of light (blue, green, hazel) and dark (light brown, brown) eyes among white patients diagnosed with IPF compared with a control group of lung granuloma only (no other radiologic evidence of interstitial lung disease).

Results

Light eye color was significantly more prevalent in patients with IPF than in the control group with lung granuloma [114/147 (77.6%) versus 129/263 (49.0%], p < 0.001), indicating that light-colored eyes are a phenotype associated with IPF .

Conclusion

We provide evidence that light eye color is predominant among white persons with IPF.

The Dct−/− Mouse Model to Unravel Retinogenesis Misregulation in Patients with Albinism

We have recently identified DCT encoding dopachrome tautomerase (DCT) as the eighth gene for oculocutaneous albinism (OCA). Patients with loss of function of DCT suffer from eye hypopigmentation and retinal dystrophy. Here we investigate the eye phenotype in Dct^−/− mice. We show that their retinal pigmented epithelium (RPE) is severely hypopigmented from early stages, contrasting with the darker melanocytic tissues. Multimodal imaging reveals specific RPE cellular defects. Melanosomes are fewer with correct subcellular localization but disrupted melanization. RPE cell size is globally increased and heterogeneous. P-cadherin labeling of Dct^−/− newborn RPE reveals a defect in adherens junctions similar to what has been described in tyrosinase-deficient Tyr^c/c embryos. The first intermediate of melanin biosynthesis, dihydroxyphenylalanine (L-Dopa), which is thought to control retinogenesis, is detected in substantial yet significantly reduced amounts in Dct^−/− postnatal mouse eyecups. L-Dopa synthesis in the RPE alone remains to be evaluated during the critical period of retinogenesis. The Dct^−/− mouse should prove useful in understanding the molecular regulation of retinal development and aging of the hypopigmented eye. This may guide therapeutic strategies to prevent vision deficits in patients with albinism.

The Dark Side of Melanin Secretion in Cutaneous Melanoma Aggressiveness

Skin cancers are among the most common cancers worldwide and are increasingly prevalent. Cutaneous melanoma (CM) is characterized by the malignant transformation of melanocytes in the epidermis. Although CM shows lower incidence than other skin cancers, it is the most aggressive and responsible for the vast majority of skin cancer-related deaths. Indeed, 75% of patients present with invasive or metastatic tumors, even after surgical excision. In CM, the photoprotective pigment melanin, which is produced by melanocytes, plays a central role in the pathology of the disease. Melanin absorbs ultraviolet radiation and scavenges reactive oxygen/nitrogen species (ROS/RNS) resulting from the radiation exposure. However, the scavenged ROS/RNS modify melanin and lead to the induction of signature DNA damage in CM cells, namely cyclobutane pyrimidine dimers, which are known to promote CM immortalization and carcinogenesis. Despite triggering the malignant transformation of melanocytes and promoting initial tumor growth, the presence of melanin inside CM cells is described to negatively regulate their invasiveness by increasing cell stiffness and reducing elasticity. Emerging evidence also indicates that melanin secreted from CM cells is required for the immunomodulation of tumor microenvironment. Indeed, melanin transforms dermal fibroblasts in cancer-associated fibroblasts, suppresses the immune system and promotes tumor angiogenesis, thus sustaining CM progression and metastasis. Here, we review the current knowledge on the role of melanin secretion in CM aggressiveness and the molecular machinery involved, as well as the impact in tumor microenvironment and immune responses. A better understanding of this role and the molecular players involved could enable the modulation of melanin secretion to become a therapeutic strategy to impair CM invasion and metastasis and, hence, reduce the burden of CM-associated deaths.

Retrotransposon Insertion Polymorphisms (RIPs) in Pig Coat Color Candidate Genes

The diversity of livestock coat color results from human positive selection and represents an indispensable part of breed identity. As an important biodiversity resource, pigs have many special characteristics, including the most visualized feature, coat color, and excellent adaptation, and the coat color represents an important phenotypic characteristic of the pig breed. Exploring the genetic mechanisms of phenotypic characteristics and the melanocortin system is of considerable interest in domestic animals because their energy metabolism and pigmentation have been under strong selection. In this study, 20 genes related to coat color in mammals were selected, and the structural variations (SVs) in these genic regions were identified by sequence alignment across 17 assembled pig genomes, from representing different types of pigs (miniature, lean, and fat type). A total of 167 large structural variations (>50 bp) of coat-color genes, which overlap with retrotransposon insertions (>50 bp), were obtained and designated as putative RIPs. Finally, 42 RIPs were confirmed by PCR detection. Additionally, eleven RIP sites were further evaluated for their genotypic distributions by PCR in more individuals of eleven domesticated breeds representing different coat color groups. Differential distributions of these RIPs were observed across populations, and some RIPs may be associated with breed differences.

Function of the Retinal Pigment Epithelium in Patients With Neurofibromatosis Type 1

Purpose

Retinal and choroidal abnormalities in neurofibromatosis type 1 (NF1) remain poorly studied. It has been reported, however, that the function of the retinal pigment epithelium (RPE) in NF1 was abnormal, with a supra-normal Arden ratio of the electro-oculogram (EOG). This study aims to evaluate the function of the RPE, using EOG, first in patients with NF1 compared to controls and second in patients with NF1 with choroidal abnormalities compared to patients with NF1 without choroidal abnormalities.

Methods

This prospective case-control study included 20 patients with NF1 (10 patients with choroidal abnormalities and 10 patients without) and 10 healthy patients, matched for age. A complete ophthalmologic assessment with multimodal imaging, an EOG, and a full-field electroretinogram were performed for each included patient. The main outcome measured was the EOG light peak (LP)/dark trough (DT) ratio.

Results

The LP/DT ratio was 3.02 ± 0.52 in patients with NF1 and 2.63 ± 0.31 in controls (P = 0.02). DT values were significantly lower in patients with NF1 than in controls (240 vs. 325 µV, P = 0.02), while light peak values were not significantly different (P = 0.26). No difference was found for peak latencies. No significant correlation between the surface and number of choroidal abnormalities and EOG parameters was demonstrated.

Conclusions

This study confirms the dysfunction of the RPE in patients with NF1, involving a lower DT and a corresponding higher LP/DT ratio. We hypothesize that this pattern may be due to a dysregulation of the melanocytogenesis, inducing a disruption in Ca2+ ion flux and an abnormal polarization of the RPE.

Zebrafish Syndromic Albinism Models as Tools for Understanding and Treating Pigment Cell Disease in Humans

Simple Summary

Zebrafish (Danio rerio) is an emerging model for studying many diseases, including disorders originating in black pigment cells, melanocytes. In this review of the melanocyte literature, we discuss the current knowledge of melanocyte biology relevant to understanding different forms of albinism and the potential of the zebrafish model system for finding novel mechanisms and treatments.

Abstract

Melanin is the pigment that protects DNA from ultraviolet (UV) damage by absorbing excess energy. Melanin is produced in a process called melanogenesis. When melanogenesis is altered, diseases such as albinism result. Albinism can result in an increased skin cancer risk. Conversely, black pigment cell (melanocyte) development pathways can be misregulated, causing excessive melanocyte growth that leads to melanoma (cancer of melanocytes). Zebrafish is an emerging model organism used to study pigment disorders due to their high fecundity, visible melanin development in melanophores (melanocytes in mammals) from 24 h post-fertilization, and conserved melanogenesis pathways. Here, we reviewed the conserved developmental pathways in zebrafish melanophores and mammalian melanocytes. Additionally, we summarized the progress made in understanding pigment cell disease and evidence supporting the strong potential for using zebrafish to find novel treatment options for albinism.

Mahogunin Ring Finger 1 regulates pigmentation by controlling the pH of melanosomes in melanocytes and melanoma cells

Mahogunin Ring Finger 1 (MGRN1) is an E3-ubiquitin ligase absent in dark-furred mahoganoid mice. We investigated the mechanisms of hyperpigmentation in Mgrn1-null melan-md1 melanocytes, Mgrn1-KO cells obtained by CRISPR-Cas9-mediated knockdown of Mgrn1 in melan-a6 melanocytes, and melan-a6 cells depleted of MGRN1 by siRNA treatment. Mgrn1-deficient melanocytes showed higher melanin content associated with increased melanosome abundance and higher fraction of melanosomes in highly melanized maturation stages III-IV. Expression, post-translational processing and enzymatic activity of the rate-limiting melanogenic enzyme tyrosinase measured in cell-free extracts were comparable in control and MGRN1-depleted cells. However, tyrosinase activity measured in situ in live cells and expression of genes associated with regulation of pH increased upon MGRN1 repression. Using pH-sensitive fluorescent probes, we found that downregulation of MGRN1 expression in melanocytes and melanoma cells increased the pH of acidic organelles, including melanosomes, strongly suggesting a previously unknown role of MGRN1 in the regulation of melanosomal pH. Among the pH regulatory genes upregulated by Mgrn1 knockdown, we identified those encoding several subunits of the vacuolar adenosine triphosphatase V-ATPase (mostly Atp6v0d2) and a calcium channel of the transient receptor potential channel family, Mucolipin 3 (Mcoln3). Manipulation of expression of the Mcoln3 gene showed that overexpression of Mcoln3 played a significant role in neutralization of the pH of acidic organelles and activation of tyrosinase in MGRN1-depleted cells. Therefore, lack of MGRN1 led to cell-autonomous stimulation of pigment production in melanocytes mostly by increasing tyrosinase specific activity through neutralization of the melanosomal pH in a MCOLN3-dependent manner.

Skin Aging, Cellular Senescence and Natural Polyphenols

The skin, being the barrier organ of the body, is constitutively exposed to various stimuli impacting its morphology and function. Senescent cells have been found to accumulate with age and may contribute to age-related skin changes and pathologies. Natural polyphenols exert many health benefits, including ameliorative effects on skin aging. By affecting molecular pathways of senescence, polyphenols are able to prevent or delay the senescence formation and, consequently, avoid or ameliorate aging and age-associated pathologies of the skin. This review aims to provide an overview of the current state of knowledge in skin aging and cellular senescence, and to summarize the recent in vitro studies related to the anti-senescent mechanisms of natural polyphenols carried out on keratinocytes, melanocytes and fibroblasts. Aged skin in the context of the COVID-19 pandemic will be also discussed.

The Bioactivity of Thiazolidin-4-Ones: A Short Review of the Most Recent Studies

Thiazolidin-4-ones is an important heterocyclic ring system of a pharmacophore and a privileged scaffold in medicinal chemistry. This review is focused on the latest scientific reports regarding biological activities of thiazolidin-4-ones published in 2020 and 2021. The review covers recent information about antioxidant, anticancer, anti-inflammatory, analgesic, anticonvulsant, antidiabetic, antiparasitic, antimicrobial, antitubercular and antiviral properties of thiazolidin-4-ones. Additionally, the influence of different substituents in molecules on their biological activity was discussed in this paper. Thus, this study may help to optimize the structure of thiazolidin-4-one derivatives as more efficient drug agents. Presented information may be used as a practical hint for rational design of new small molecules with biological activity, especially among thiazolidin-4-ones.

Computational Investigation of the pH Dependence of Stability of Melanosome Proteins: Implication for Melanosome formation and Disease

Intravesicular pH plays a crucial role in melanosome maturation and function. Melanosomal pH changes during maturation from very acidic in the early stages to neutral in late stages. Neutral pH is critical for providing optimal conditions for the rate-limiting, pH-sensitive melanin-synthesizing enzyme tyrosinase (TYR). This dramatic change in pH is thought to result from the activity of several proteins that control melanosomal pH. Here, we computationally investigated the pH-dependent stability of several melanosomal membrane proteins and compared them to the pH dependence of the stability of TYR. We confirmed that the pH optimum of TYR is neutral, and we also found that proteins that are negative regulators of melanosomal pH are predicted to function optimally at neutral pH. In contrast, positive pH regulators were predicted to have an acidic pH optimum. We propose a competitive mechanism among positive and negative regulators that results in pH equilibrium. Our findings are consistent with previous work that demonstrated a correlation between the pH optima of stability and activity, and they are consistent with the expected activity of positive and negative regulators of melanosomal pH. Furthermore, our data suggest that disease-causing variants impact the pH dependence of melanosomal proteins; this is particularly prominent for the OCA2 protein. In conclusion, melanosomal pH appears to affect the activity of multiple melanosomal proteins.

Single organelle measurements of melanosome pH using the novel ratiometric indicator RpHiMEL

Melanocytes are specialized cells that produce melanin pigments responsible for skin, hair, and eye pigmentation. The synthesis and storage of melanin occurs in unique lysosome-related organelles called melanosomes, which regulate melanin production via complex regulatory mechanisms. Maintenance of the melanosome luminal ionic environment and pH is crucial for proper function of the main melanogenic enzymes. Defects in genes encoding pH-regulating melanosomal proteins result in oculocutaneous albinism, which is characterized by hypopigmentation, impaired vision, and increased susceptibility to skin and eye cancers. We recently uncovered several ion channels and transporters that modulate melanin synthesis by acidifying or neutralizing the luminal pH of melanosomes. However, our understanding of how melanosomes and other related organelles maintain their luminal pH is far from complete. The study of melanosome pH regulation requires robust imaging and quantification tools. Despite recent advances in the development of such methods, many limitations remain, particularly for quantitative analysis of individual organelle pH. In this chapter, we will provide an overview of the available methods used for melanosome pH determination, including their advantages, limitations, and challenges. To address the critical, unmet need for reliable melanosome pH quantification tools, we engineered a novel genetically encoded, ratiometric pH sensor for melanosomes that we named RpHiMEL. Here, we describe the design and optimization of RpHiMEL, and provide a pH quantification method for individual melanosomes in live cells. We demonstrate that RpHiMEL is a highly versatile tool with the potential to advance our understanding of pH regulation in melanosomes and related organelles.

ATP7A-Regulated Enzyme Metalation and Trafficking in the Menkes Disease Puzzle

Copper is vital for numerous cellular functions affecting all tissues and organ systems in the body. The copper pump, ATP7A is critical for whole-body, cellular, and subcellular copper homeostasis, and dysfunction due to genetic defects results in Menkes disease. ATP7A dysfunction leads to copper deficiency in nervous tissue, liver, and blood but accumulation in other tissues. Site-specific cellular deficiencies of copper lead to loss of function of copper-dependent enzymes in all tissues, and the range of Menkes disease pathologies observed can now be explained in full by lack of specific copper enzymes. New pathways involving copper activated lysosomal and steroid sulfatases link patient symptoms usually related to other inborn errors of metabolism to Menkes disease. Additionally, new roles for lysyl oxidase in activation of molecules necessary for the innate immune system, and novel adapter molecules that play roles in ERGIC trafficking of brain receptors and other proteins, are emerging. We here summarize the current knowledge of the roles of copper enzyme function in Menkes disease, with a focus on ATP7A-mediated enzyme metalation in the secretory pathway. By establishing mechanistic relationships between copper-dependent cellular processes and Menkes disease symptoms in patients will not only increase understanding of copper biology but will also allow for the identification of an expanding range of copper-dependent enzymes and pathways. This will raise awareness of rare patient symptoms, and thus aid in early diagnosis of Menkes disease patients.

Chemical and biochemical control of skin pigmentation with special emphasis on mixed melanogenesis

Melanins are widely distributed in animals and plants; in vertebrates, most melanins are present on the body surface. The diversity of pigmentation in vertebrates is mainly attributed to the quantity and ratio of eumelanin and pheomelanin synthesis. Most natural melanin pigments in animals consist of both eumelanin and pheomelanin in varying ratios, and thus, their combined synthesis is called "mixed melanogenesis." Gene expression is an established mechanism for controlling melanin synthesis; however, there are multiple factors that affect melanin synthesis besides gene expression. Due to the differential sensitivity of the eumelanin and pheomelanin synthetic pathways to pH, melanosomal pH likely plays a major role in mixed melanogenesis. Here, we focused on various factors affecting mixed melanogenesis including (1) chemical regulation of melanin synthesis, (2) melanosomal pH regulation during normal melanogenesis and effect on mixed melanogenesis, and (3) mechanisms of melanosomal pH control (proton pumps, channels, transporters, and signaling pathways).

Thioxothiazolidin derivative, 4-OST, inhibits melanogenesis by enhancing the specific recruitment of tyrosinase-containing vesicles to lysosome

Tyrosinase catalyzes the rate-limiting step in melanin synthesis. Melanin is synthesized from l-tyrosin in the melanosomes, where tyrosinase and other melanogenic factors are recruited via the vesicle transport system. Genetic and biochemical approaches have revealed a correlation between impairments in the vesicle transport system and albinism. However, the specificity of the individual transport systems for the corresponding melanogenic factors has not been well elucidated yet. Here, we report that the thioxothiazolidin derivative, 4-OST (4-[(5E)-5-[(4-fluorophenyl)methylidene]-4-oxo-2-sulfanylidene-1,3-thiazolidin-3-yl]-4-azatricyclo [5.2.1.0² ,6]dec-8-ene-3,5-dione: CAS RN. 477766-87-3) strongly inhibited melanogenesis in mouse melanoma B16F10 cells. 4-OST reduces tyrosinase protein levels without affecting its messenger RNA levels or enzymatic activity. Although a reduction in tyrosinase protein level was observed in the presence of a protein synthesis inhibitor, the reduction may be coupled with protein synthesis. Similarly, GIF-2202 (a derivative of 4-OST) lowers tyrosinase protein levels without affecting the levels of another melanogenic enzyme, tyrosinase-related protein 1 (TYRP1) level. The reduction in tyrosinase protein level is associated with an increase in the levels of the lysosomal proteinase cathepsin S. Chloroquine, a lysosome inhibitor, restored the tyrosinase protein level downregulated by GIF-2202, although no effects of other inhibitors (against proteasome, autophagy, or exocytosis) were observed. In addition, GIF-2202 segregated the immunofluorescence signals of tyrosinase from those of TYRP1. Chloroquine treatment resulted in co-localization of tyrosinase and cathepsin S signals near the perinuclear region, suggesting that 4-OST and GIF-2202 may alter the destination of the tyrosinase vesicle from the melanosome to the lysosome. 4-OST and GIF-2202 can be new tools for studying the tyrosinase-specific vesicle transport system.

Hofmeister Ions Modulate the Autocatalytic Amyloidogenesis of an Intrinsically Disordered Functional Amyloid Domain via Unusual Biphasic Kinetics

Hofmeister ions are thought to play fundamentally important roles in protein solubility, folding, stability, and function. Salt ions profoundly influence the course of protein misfolding, aggregation, and amyloid formation associated with devastating human diseases. However, the molecular origin of the salt-effect in protein aggregation remains elusive. Here, we report an unusual biphasic amyloidogenesis of a pH-responsive, intrinsically disordered, oligopeptide repeat domain of a melanosomal protein, Pmel17, that regulates the amyloid-assisted melanin synthesis in mammals via functional amyloid formation. We demonstrate that a symphony of molecular events involving charge-peptide interactions and hydration, in conjunction with secondary phenomena, critically governs the course of this biphasic amyloid assembly. We show that at mildly acidic pH, typical of melanosomes, highly amyloidogenic oligomeric units assemble into metastable, dendritic, fractal networks following the forward Hofmeister series. However, the subsequent condensation of fractal networks via conformational maturation into amyloid fibrils follows an inverse Hofmeister series due to fragmentation events coupled with secondary nucleation processes. Our results indicate that ions exert a strong influence on the aggregation kinetics as well as on the nanoscale morphology and also modulate the autocatalytic amplification processes during amyloid assembly via an intriguing dual Hofmeister effect. This unique interplay of molecular drivers will be of prime importance in delineating the aggregation pathways of a multitude of intrinsically disordered proteins involved in physiology and disease.

A new type of oculocutaneous albinism with a novel OCA2 mutation

Oculocutaneous albinism (OCA) is a group of rare genetically heterogeneous disorders, characterized by hypopigmentation of the eyes, skin, and hair, which result in ocular abnormalities and a risk of developing skin cancer. Currently, there is no ophthalmologic procedure or drug that prevents the clinical features of OCA. Here, we report a new type of OCA in two, unrelated Korean families with the same OCA2 mutation. Affected individuals in this study are different from those of previous reports in two aspects: an inheritance pattern and clinical presentation. All reported patients with OCA have shown an autosomal recessive inheritance pattern, while our patients showed an autosomal dominant inheritance pattern. Small amounts of pigment can be acquired with age in OCA, but there is no substantial variation from adolescence to adulthood in this regard. A case where the patient attained normal pigmentation levels has never been reported. However, our patients displayed completely normal pigmentation in their late twenties. Whole exome sequencing and in-silico analysis revealed a novel mutation, OCA2 c.2338G>A p.(G780S) (NM_000275) with a high likelihood of pathogenicity. Sanger sequencing of p.G780S identified the same mutation in the affected individuals, which was not found in the family members with normal phenotype. We hypothesize that OCA2 G780S not only acts as a pathogenic variant of OCA but also induces pigmentation by enhancing the melanogenesis gene expression of other modifier genes, such as SLC45A2 and TPC2. These findings may provide further understanding of melanin biosynthesis and new treatment methods for OCA.