Cytoplasmic cilia, a specialized type of cilia in which the axoneme resides within the cytoplasm rather than within the ciliary compartment, are proposed to allow for the efficient assembly of very long cilia. Despite being found diversely in male gametes (e.g., Plasmodium falciparum microgametocytes and human and Drosophila melanogaster sperm), very little is known about cytoplasmic cilia assembly. Here, we show that a novel RNP granule containing the mRNAs for axonemal dynein motor proteins becomes highly polarized to the distal end of the cilia during cytoplasmic ciliogenesis in Drosophila sperm. This allows for the incorporation of these axonemal dyneins into the axoneme directly from the cytoplasm, possibly by localizing translation. We found that this RNP granule contains the proteins Reptin and Pontin, loss of which perturbs granule formation and prevents incorporation of the axonemal dyneins, leading to sterility. We propose that cytoplasmic cilia assembly requires the precise localization of mRNAs encoding key axonemal constituents, allowing these proteins to incorporate efficiently into the axoneme.

中文翻译：

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mRNA定位介导果蝇精子发生中细胞质纤毛的成熟

细胞质纤毛是一种特殊类型的纤毛，其中轴丝位于细胞质内而不是纤毛室内，被认为可以有效组装非常长的纤毛。尽管在雄性配子（例如，恶性疟原虫小配子细胞和人类和果蝇精子）中发现了多种细胞质纤毛组装，但人们对细胞质纤毛组装知之甚少。在这里，我们发现，在果蝇精子的细胞质纤毛发生过程中，含有轴丝动力蛋白运动蛋白 mRNA 的新型 RNP 颗粒变得高度极化至纤毛远端。这允许这些轴丝动力蛋白直接从细胞质掺入轴丝，可能是通过定位翻译。我们发现这种 RNP 颗粒含有 Reptin 和 Pontin 蛋白，它们的丢失会扰乱颗粒的形成并阻止轴丝动力蛋白的掺入，从而导致不育。我们认为细胞质纤毛组装需要编码关键轴丝成分的 mRNA 的精确定位，从而使这些蛋白质能够有效地整合到轴丝中。