In Drosophila , the wing disc‐associated muscle precursor cells give rise to the fibrillar indirect flight muscles (IFM) and the tubular direct flight muscles (DFM). To understand early transcriptional events underlying this muscle diversification, we performed single‐cell RNA‐sequencing experiments and built a cell atlas of myoblasts associated with third instar larval wing disc. Our analysis identified distinct transcriptional signatures for IFM and DFM myoblasts that underlie the molecular basis of their divergence. The atlas further revealed various states of differentiation of myoblasts, thus illustrating previously unappreciated spatial and temporal heterogeneity among them. We identified and validated novel markers for both IFM and DFM myoblasts at various states of differentiation by immunofluorescence and genetic cell‐tracing experiments. Finally, we performed a systematic genetic screen using a panel of markers from the reference cell atlas as an entry point and found a novel gene, Amalgam which is functionally important in muscle development. Our work provides a framework for leveraging scRNA‐seq for gene discovery and details a strategy that can be applied to other scRNA‐seq datasets.

The long interspersed element-1 (LINE-1) family is the sole remaining transposable element family that is capable of autonomous retrotransposition in humans. LINE-1 expression, tightly controlled through epigenetic mechanisms, has complex effects on gene regulation. Due to their similarity to retroviruses, once activated, LINE-1s have the ability to trigger pathways involved in innate and adaptive immunity with both beneficial and detrimental effects. This review will explore the mechanisms and importance of LINE-1 epigenetic repression and the potential outcomes of LINE-1 expression, with a focus on their immunogenic roles in innate and adaptive immunity.

The Long interspersed element 1 (LINE-1) family is the sole remaining transposable element family that is capable of autonomous retrotransposition in humans. LINE-1 expression, tightly controlled through epigenetic mechanisms, has complex effects on gene regulation. Due to their viral origin, once activated, LINE-1s have the ability to trigger pathways involved in innate and adaptive immunity with both beneficial and detrimental effects. This review will explore the mechanisms and importance of LINE-1 repression and the potential outcomes of LINE-1 expression, with a focus on their immunogenic roles in innate and adaptive immunity.