Eukaryotic translation initiation factor eIF4E-5 is required for spermiogenesis inDrosophila melanogaster

Abstract

Drosophila sperm development is characterized by extensive post-transcriptional regulation whereby thousands of transcripts are preserved for translation during later stages. A key step in translation initiation is the binding of eukaryotic initiation factor 4E (eIF4E) to the 5’ mRNA cap. In addition to canonical eIF4E-1, Drosophila has multiple eIF4E paralogs, including four (eIF4E-3, -4, -5, and -7) that are highly expressed in the testis. Among these, only eIF4E-3 has been characterized genetically. Here, using CRISPR/Cas9 mutagenesis, we determined that eIF4E-5 is essential for male fertility. eIF4E-5 protein localizes to the distal ends of elongated spermatid cysts, and eIF4E-5 mutants exhibit defects during post-meiotic stages, including a mild defect in spermatid cyst polarization. eIF4E-5 mutants also have a fully penetrant defect in individualization, resulting in failure to produce mature sperm. Indeed, our data indicate that eIF4E-5 regulates non-apoptotic caspase activity during individualization by promoting local accumulation of the E3 ubiquitin ligase inhibitor Soti. Our results further extend the diversity of non-canonical eIF4Es that carry out distinct spatiotemporal roles during spermatogenesis.

Spatially revealed roles for lncRNAs in Drosophila spermatogenesis, Y chromosome function and evolution

“…The hybridization chain reaction (HCR) FISH protocol used 56 was optimized for use with Drosophila testes with the following modifications. In most cases, testes were cut in half while in PBS, then fixed on polylysine-coated slides as previously described 57 . When not used immediately, sample-containing slides were stored at 4 °C in 95% ethanol and, prior to use, rinsed 3× for 5 min in PBS.…”

eIF4E as a molecular wildcard in metazoans RNA metabolism

“…eIF4E-3 and eIF4E-5 proteins are specifically expressed in the testis and, together with eIF4E-1, play crucial roles in different processes to produce mature sperm. Indeed, eIF4E-1, eIF4E-3, and eIF4E-5 proteins are essential for spermatogenesis, and loss-of-function or mutation analyses showed that males lacking eIF4E-1, eIF4E-3, or eIF4E-5 are sterile (Ghosh & Lasko, 2015;Hern andez et al, 2012;Shao et al, 2023) (Fig. 6C).…”

“…eIF4E‐3 is expressed in germline cells from the primary spermatocyte stage to the early differentiating spermatids immediately before the onset of spermiogenesis, and is required for cytokinesis and meiotic chromosome segregation and sperm individualization (Hernández et al ., 2012). eIF4E‐5 localises to the distal ends of elongated spermatid cysts and is required for post‐meiotic stages, including spermatid cyst polarisation and sperm individualization (Shao et al ., 2023).…”

“…Yeast two‐hybrid assay (Hernández et al ., 2005; Shao et al ., 2023) and fluorescent binding assays with a short eIF4G peptide containing the eIF4E‐binding motif (Zuberek et al ., 2016) reported positive interactions between eIF4E‐5 and 4E‐BP, eIF4G, eIF4G‐2, 4E‐T, and Cup. Thus, eIF4E‐1, eIF4E‐3, and eIF4E‐5 may form various complexes to regulate translation initiation during sperm development.…”

Loss-of-function in testis-specific serine/threonine protein kinase (TSSKs) triggers male infertility in an invasive moth

“…Consequently, post-transcriptional regulation plays a pivotal role in the overall coordination of gene expression 31 . It is important to highlight that the maturation of insect sperm involves extensive posttranscriptional regulation, whereby a signi cant number of transcripts are preserved for translation at a later stage 32 . In recent years, long non-coding RNAs (lncRNAs) have emerged as crucial factors in posttranscriptional regulatio 33,34 .…”