The m6A pathway facilitates sex determination in Drosophila

Abstract

The conserved modification N6-methyladenosine (m6A) modulates mRNA processing and activity. Here, we establish the Drosophila system to study the m6A pathway. We first apply miCLIP to map m6A across embryogenesis, characterize its m6A ‘writer’ complex, validate its YTH ‘readers’ CG6422 and YT521-B, and generate mutants in five m6A factors. While m6A factors with additional roles in splicing are lethal, m6A-specific mutants are viable but present certain developmental and behavioural defects. Notably, m6A facilitates the master female determinant Sxl, since multiple m6A components enhance female lethality in Sxl sensitized backgrounds. The m6A pathway regulates Sxl processing directly, since miCLIP data reveal Sxl as a major intronic m6A target, and female-specific Sxl splicing is compromised in multiple m6A pathway mutants. YT521-B is a dominant m6A effector for Sxl regulation, and YT521-B overexpression can induce female-specific Sxl splicing. Overall, our transcriptomic and genetic toolkit reveals in vivo biologic function for the Drosophila m6A pathway.

Rethinking m6A Readers, Writers, and Erasers

“…These proteins influence m 6 A levels in Drosophila S2R+ cells (Lence et al 2016), thus suggesting a conserved role in regulating methylation. In flies, Virilizer and Fl(2)d are involved in splicing of Sxl transcripts in females to control sex determination (Granadino et al 1996, Hilfiker et al 1995), and this process is dependent on m 6 A formation catalyzed by Virilizer, Fl(2)d, and IME4, the Drosophila homologs of METTL3 (Haussmann et al 2016, Kan et al 2017, Lence et al 2016). It is currently not known how KIAA1429 influences the methylation complex and why it is important for m 6 A formation.…”

RNA m6A modification and its function in diseases

“…In flies, the splicing of Sxl transcripts was critical in sex determination in females [27,28]. This process depended on m 6 A formation on Sxl transcripts formed by m 6 A methyltransferase complexes, namely, virilizer, Fl (2) d, and IME4 [65][66][67]. m 6 A also affected mRNA translation by the interaction of m 6 A readers and translation machinery proteins.…”

Mettl3-mediated m6A regulates spermatogonial differentiation and meiosis initiation

“…Recent studies have implicated an essential regulatory role of m 6 A in mRNA splicing [4,11,16,19,24,26,27,[50][51][52][53][54]. First, m 6 A alters the local structure in mRNA to facilitate the binding of some HNRNP proteins [51,53].…”