Ablation of H+/glucose Exporter SLC45A2 Enhances Melanosomal Glycolysis to Inhibit Melanin Biosynthesis and Promote Melanoma Metastasis

The metabolism of melanin synthesis-From melanocytes to melanoma

Melanin synthesis involves the successful coordination of metabolic pathways across multiple intracellular compartments including the melanosome, mitochondria, ER/Golgi, and cytoplasm. While pigment production offers a communal protection from UV damage, the process also requires anabolic and redox demands that must be carefully managed by melanocytes. In this report we provide an updated review on melanin metabolism, including recent data leveraging new techniques, and technologies in the field of metabolism. We also discuss the many aspects of melanin synthesis that intersect with metabolic pathways known to impact melanoma phenotypes and behavior. By reviewing the metabolism of melanin synthesis, we hope to highlight outstanding questions and opportunities for future research that could improve patient outcomes in pigmentary and oncologic disease settings.

In silico analysis of the solute carrier (SLC) family in cancer indicates a link among DNA methylation, metabolic adaptation, drug response, and immune reactivity

Introduction: The oncogenic transformation is driven by genetic and epigenetic alterations influencing cancer cell fate. These alterations also result in metabolic reprogramming by modulating the expression of membrane Solute Carrier (SLC) transporters involved in biomolecules trafficking. SLCs act as tumor suppressors or promoters influencing cancer methylome, tumor growth, immune-escape, and chemoresistance. Methods: This in silico study aimed to identify the deregulated SLCs in various tumor types compared to normal tissues by analyzing the TCGA Target GTEx dataset. Furthermore, the relationship between SLCs expression and the most relevant tumor features was tackled along with their genetic regulation mediated by DNA methylation. Results: We identified 62 differentially expressed SLCs, including the downregulated SLC25A27 and SLC17A7, as well as the upregulated SLC27A2 and SLC12A8. Notably, SLC4A4 and SLC7A11 expression was associated with favorable and unfavorable outcome, respectively. Moreover, SLC6A14, SLC34A2, and SLC1A2 were linked to tumor immune responsiveness. Interestingly, SLC24A5 and SLC45A2 positively correlated with anti-MEK and anti-RAF sensitivity. The expression of relevant SLCs was correlated with hypo- and hyper-methylation of promoter and body region, showing an established DNA methylation pattern. Noteworthy, the positive association of cg06690548 (SLC7A11) methylation with cancer outcome suggests the independent predictive role of DNA methylation at a single nucleotide resolution. Discussion: Although our in silico overview revealed a wide heterogeneity depending on different SLCs functions and tumor types, we identified key SLCs and pointed out the role of DNA methylation as regulatory mechanism of their expression. Overall, these findings deserve further studies to identify novel cancer biomarkers and promising therapeutic targets.

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.

Oculo-Cutaneous Albinism Type 4 (OCA4): Phenotype-Genotype Correlation

Albinism is a genetic disorder, present worldwide, caused by mutations in genes affecting melanin production or transport in the skin, hair and eyes. To date, mutations in at least 20 different genes have been identified. Oculo-cutaneous Albinism type IV (OCA4) is the most frequent form in Asia but has been reported in all populations, including Europeans. Little is known about the genotype-phenotype correlation. We identified two main phenotypes via the analysis of 30 OCA4 patients with a molecularly proven diagnosis. The first, found in 20 patients, is clinically indistinguishable from the classical OCA1 phenotype. The genotype-to-phenotype correlation suggests that this phenotype is associated with homozygous or compound heterozygous nonsense or deletion variants with frameshift leading to translation interruption in the SLC45A2 gene. The second phenotype, found in 10 patients, is characterized by very mild hypopigmentation of the hair (light brown or even dark hair) and skin that is similar to the general population. In this group, visual acuity is variable, but it can be subnormal, foveal hypoplasia can be low grade or even normal, and nystagmus may be lacking. These mild to moderate phenotypes are associated with at least one missense mutation in SLC45A2.