The environmentally ubiquitous fungus Mucor circinelloides is a primary cause of the emerging disease mucormycosis. Mucor infection is notable for causing high morbidity and mortality, especially in immunosuppressed patients, while being inherently resistant to the majority of clinically available antifungal drugs. A new, RNA interference (RNAi)-dependent, and reversible epigenetic mechanism of antifungal resistance-epimutation-was recently discovered in M. circinelloides However, the effects of epimutation in a host-pathogen setting were unknown. We employed a systemic, intravenous murine model of Mucor infection to elucidate the potential impact of epimutation in vivo Infection with an epimutant strain resistant to the antifungal agents FK506 and rapamycin revealed that the epimutant-induced drug resistance was stable in vivo in a variety of different organs and tissues. Reversion of the epimutant-induced drug resistance was observed to be more rapid in isolates from the brain than in isolates recovered from the liver, spleen, kidney, or lungs. Importantly, infection with a wild-type strain of Mucor led to increased rates of epimutation after strains were recovered from organs and exposed to FK506 stress in vitro. Once again, this effect was more pronounced in strains recovered from the brain than from other organs. In summary, we report the rapid induction and reversion of RNAi-dependent drug resistance after in vivo passage through a murine model, with pronounced impact in strains recovered from brain. Defining the role played by epimutation in drug resistance and infection advances our understanding of Mucor and other fungal pathogens and may have implications for antifungal therapy.IMPORTANCE The emerging fungal pathogen Mucor circinelloides causes a severe infection, mucormycosis, which leads to considerable morbidity and mortality. Treatment of Mucor infection is challenging because Mucor is inherently resistant to nearly all clinical antifungal agents. An RNAi-dependent and reversible mechanism of antifungal resistance, epimutation, was recently reported for Mucor Epimutation has not been studied in vivo, and it was unclear whether it would contribute to antifungal resistance observed clinically. We demonstrate that epimutation can both be induced and reverted after in vivo passage through a mouse; rates of both induction and reversion are higher after brain infection than after infection of other organs (liver, spleen, kidneys, or lungs). Elucidating the roles played by epimutation in drug resistance and infection will improve our understanding of Mucor and other fungal pathogens and may have implications for antifungal treatment.

中文翻译：

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在人类真菌病原体毛霉引起的小鼠感染期间，耐药表观突变体表现出器官特异性稳定性和诱导作用。

环境中无处不在的真菌 Mucor circinelloides 是新发疾病毛霉菌病的主要原因。毛霉菌感染以导致高发病率和死亡率而著称，尤其是在免疫抑制患者中，同时对大多数临床可用的抗真菌药物具有固有耐药性。最近在 M. circinelloides 中发现了一种新的、依赖于 RNA 干扰 (RNAi) 且可逆的抗真菌抗性表观遗传机制 - 表观突变。然而，表观突变在宿主-病原体环境中的影响尚不清楚。我们采用了系统的，毛霉菌感染的静脉内小鼠模型，以阐明表突变在体内的潜在影响 用抗真菌剂 FK506 和雷帕霉素的表突变菌株感染表明，表突变诱导的耐药性在体内各种不同的器官和组织中是稳定的。与从肝脏、脾脏、肾脏或肺中回收的分离株相比，观察到表突变体诱导的耐药性逆转在来自大脑的分离株中更快。重要的是，在从器官中回收菌株并在体外暴露于 FK506 应激后，感染野生型 Mucor 菌株会导致外突变率增加。再一次，这种效应在从大脑中回收的菌株中比从其他器官中回收的菌株更为明显。总之，我们报告了体内通过小鼠模型后 RNAi 依赖性耐药性的快速诱导和逆转，对从大脑中恢复的菌株有显着影响。确定表观突变在耐药性和感染中所起的作用，加深了我们对毛霉和其他真菌病原体的理解，并可能对抗真菌治疗产生影响。重要性新出现的真菌病原体毛霉引起严重感染，毛霉菌病，导致相当大的发病率和死亡率。毛霉菌感染的治疗具有挑战性，因为毛霉菌对几乎所有临床抗真菌剂具有固有耐药性。最近报道了一种抗真菌耐药性的 RNAi 依赖性和可逆机制，表观突变，最近报道了毛霉的表观突变尚未在体内研究，尚不清楚它是否会导致临床观察到的抗真菌耐药性。我们证明表观突变可以在体内通过小鼠后被诱导和恢复；脑部感染后的诱导率和逆转率均高于其他器官（肝、脾、肾或肺）感染后。阐明表观突变在耐药性和感染中所起的作用将提高我们对毛霉和其他真菌病原体的理解，并可能对抗真菌治疗产生影响。