Dnmt3a deficiency in the skin causes focal, canonical DNA hypomethylation and a cellular proliferation phenotype

The skin of the naked mole-rat and its resilience against aging and cancer

The naked mole-rat (NMR) Heterocephalus glaber (from the Greek/latin words ἕτερος, heteros = divergent, κεφαλή, kephalē = head and glabra = hairless) was first described by Rüppell (Fig. 1) and belongs to the Hystricognath (from the Greek words ὕστριξ, hystrix = porcupine and γνάθος, gnathos = jaw) as a suborder of rodents. NMR are characterized by the highest longevity among rodents and reveal a profound cancer resistance. Details of its skin-specific protective and resistance mechanisms against aging and carcinogenesis have so far not been adequately characterized. Recently, our knowledge of NMR skin biology was complemented and expanded by published data using state-of-the art histological and molecular techniques. Here we review and integrate novel published data regarding skin morphology and histology of the aging NMR and the underlying mechanisms at the cellular and molecular level. We relate this data to the longevity of the NMR and its resistance to neoplastic transformation and discuss further open questions to understand its extraordinary longevity. In addition, we will address the exposome, defined as "the total of all non-genetic, endogenous and exogenous environmental influences" on the skin, respiratory tract, stomach, and intestine. Finally, we will discuss in perspective further intriguing possibilities arising from the interaction of skin with other organs.

Research Progress of Photodynamic Therapy in Wound Healing: A Literature Review

Light is an efficient technique that has a significant influence on contemporary medicine. Photodynamic therapy (PDT), which involves the combined action of photosensitizers (PSs), oxygen, and light, has emerged as a therapeutically promising method for treating a broad variety of solid tumors and infectious diseases. Photodynamic therapy is minimally invasive, has few side effects, lightens scars, and reduces tissue loss while preserving organ structure and function. In particular, PDT has a high healing potential for wounds (PDT stimulates wound healing by enhancing re-epithelialization, promoting angiogenesis as well as modulating skin homeostasis). Wound healing involves interactions between many different processes, including coagulation, inflammation, angiogenesis, cellular migration, and proliferation. Poor wound healing with diabetes or extensive burns remains a difficult challenge. This review emphasizes PDT as a potential research field and summarizes PDT's role in wound healing, including normal wounds, chronic wounds, and aging wounds.

IRX1 is a novel gene, overexpressed in high-grade IDH-mutant astrocytomas

BACKGROUND

IDH-mutant astrocytomas include CNS WHO grade 2 (A2), grade 3 (A3) and grade 4 (A4), of which A3 and A4 are high-grade. A3 has a heterogenous clinical outcome that cannot be explained entirely by the existing molecular biomarkers. We comprehensively studied the transcriptome profile of A3 to determine clinical significance.

METHODS

TCGA mRNA-sequencing data of A3 was analyzed to derive differentially expressed genes (DEG), which were short-listed using various approaches. mRNA expression of the short-listed genes was validated using NanoString platform on a uniformly treated and molecularly characterized A3 cohort. Protein expression of one prognostically significant gene, Iroquois-class homeodomain (IRX1) was assessed by immunohistochemistry and correlated with patient survival and tumor recurrence. IRX1 expression was also studied in different grades of astrocytoma. Since DNA methyltransferase 3 alpha (DNMT3A) influences IRX1 expression, its mutations were evaluated in a subset of tumors.

RESULTS

TCGA analysis identified 96 DEG in A3 tumours. 57 genes were short-listed and finally narrowed down to 14 genes. mRNA values of 12/14 genes validated in our cohort. On multiple-variable analysis, IRX1 was the most prognostically relevant gene, with respect to progression free survival of patients. Further, IRX1 immunoexpression was significantly higher in A3 and A4 when compared to A2 and glioblastoma. Higher IRX1 immunoexpression correlated with poor prognosis in patients with A3 tumours. Also, a higher IRX1 expression was associated with DNMT3A mutation.

CONCLUSION

Our study identifies IRX1 as a novel biomarker overexpressed in high-grade IDH-mutant astrocytomas with prognostic significance in A3. DNMT3A mutation probably modulates IRX1 expression.

Melanoma in a patient with DNMT3A overgrowth syndrome

Alterations in epigenetic regulators are increasingly recognized as early events in tumorigenesis; thus, patients with acquired or inherited variants in epigenetic regulators may be at increased risk for developing multiple types of cancer. DNMT3A overgrowth syndrome (DOS), caused by germline pathogenic variants in the DNA methyltransferase gene DNMT3A, has been associated with a predisposition toward development of hematopoietic and neuronal malignancies. DNMT3A deficiency has been described to promote keratinocyte proliferation in mice. Although altered DNA methylation patterns are well-recognized in melanoma, the role of DNA methyltransferases in melanoma pathogenesis is not clear. We report the case of an adult DOS patient with a germline DNMT3A loss-of-function mutation, who developed an early-onset melanoma with regional lymph node metastatic disease. Exome sequencing of the primary tumor identified an additional acquired, missense DNMT3A mutation in the dominant tumor clone, suggesting that the loss of DNMT3A function was relevant for the development of this tumor.

A Hairy Cituation - PADIs in Regeneration and Alopecia

In this Review article, we focus on delineating the expression and function of Peptidyl Arginine Delminases (PADIs) in the hair follicle stem cell lineage and in inflammatory alopecia. We outline our current understanding of cellular processes influenced by protein citrullination, the PADI mediated posttranslational enzymatic conversion of arginine to citrulline, by exploring citrullinomes from normal and inflamed tissues. Drawing from other stem cell lineages, we detail the potential function of PADIs and specific citrullinated protein residues in hair follicle stem cell activation, lineage specification and differentiation. We highlight PADI3 as a mediator of hair shaft differentiation and display why mutations in PADI3 are linked to human alopecia. Furthermore, we propose mechanisms of PADI4 dependent fine-tuning of the hair follicle lineage progression. Finally, we discuss citrullination in the context of inflammatory alopecia. We present how infiltrating neutrophils establish a citrullination-driven self-perpetuating proinflammatory circuitry resulting in T-cell recruitment and activation contributing to hair follicle degeneration. In summary, we aim to provide a comprehensive perspective on how citrullination modulates hair follicle regeneration and contributes to inflammatory alopecia.