Abstract
Malassezia is the dominant fungus in the human skin mycobiome and is associated with common skin disorders including atopic eczema (AE)/dermatitis. Recently, it was found that Malassezia sympodialis secretes nanosized exosome-like vesicles, designated MalaEx, that carry allergens and can induce inflammatory cytokine responses. Extracellular vesicles from different cell-types including fungi have been found to deliver functional RNAs to recipient cells. In this study we assessed the presence of small RNAs in MalaEx and addressed if the levels of these RNAs differ when M. sympodialis is cultured at normal human skin pH versus the elevated pH present on the skin of patients with AE. The total number and the protein concentration of the released MalaEx harvested after 48 h culture did not differ significantly between the two pH conditions nor did the size of the vesicles. From small RNA sequence data, we identified a set of reads with well-defined start and stop positions, in a length range of 16 to 22 nucleotides consistently present in the MalaEx. The levels of small RNAs were not significantly differentially expressed between the two different pH conditions indicating that they are not influenced by the elevated pH level observed on the AE skin.
Highlights
To inhibition and degradation of the mRNA and producing post-transcriptional modification of gene expression levels12. miRNAs have been identified in humans[13], plants[14] and viruses[15] and small RNAs with miRNA-like properties have been detected in the plant pathogens Magnaporthe oryzae[16], Sclerotinia sclerotiorum[17], Botrytis cinerea[18] and Phytophthora sojae[19], and in the filamentous fungi Neurospora crassa[20]
To elucidate M. sympodialis host-microbe interactions we here aimed to assess whether small RNAs are present in MalaEx and, if so, address whether the levels of these RNAs differ in MalaEx isolated from M. sympodialis cultured at normal skin pH compared to the higher pH on the skin of atopic eczema (AE) patients
Transmission electron microscopy (TEM) analysis of sucrose gradient fractions revealed no significant morphological differences between MalaEx derived from cultures at pH 5.5 (Fig. 1A) compared with pH 6.1 (Fig. 1B)
Summary
To inhibition and degradation of the mRNA and producing post-transcriptional modification of gene expression levels12. miRNAs have been identified in humans[13], plants[14] and viruses[15] and small RNAs with miRNA-like properties (milRNAs) have been detected in the plant pathogens Magnaporthe oryzae[16], Sclerotinia sclerotiorum[17], Botrytis cinerea[18] and Phytophthora sojae[19], and in the filamentous fungi Neurospora crassa[20]. MiRNAs have been identified in humans[13], plants[14] and viruses[15] and small RNAs with miRNA-like properties (milRNAs) have been detected in the plant pathogens Magnaporthe oryzae[16], Sclerotinia sclerotiorum[17], Botrytis cinerea[18] and Phytophthora sojae[19], and in the filamentous fungi Neurospora crassa[20] These milRNAs can play internal roles or, alternatively, impact host machinery. We reported that M. sympodialis secretes nanosized exosome-like vesicles[29] These vesicles, designated MalaEx, carry allergens and can induce inflammatory cytokine responses with a significantly higher IL-4 production in peripheral blood mononuclear cells (PBMC) from patients with AE compared to healthy controls[29].
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