Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, USA.
Dev Dyn. 2022 Feb;251(2):377-389. doi: 10.1002/dvdy.403. Epub 2021 Jul 29.
EIF2A is an unconventional translation factor required for initiation of protein synthesis from non-AUG codons from a variety of transcripts, including oncogenes and stress related transcripts in mammalian cells. Its function in multicellular organisms has not been reported.
Here, we identify and characterize mutant alleles of the CG7414 gene, which encodes the Drosophila EIF2A ortholog. We identified that CG7414 undergoes sex-specific splicing that regulates its male-specific expression. We characterized a Mi{Mic} transposon insertion that disrupts the coding regions of all predicted isoforms and is a likely null allele, and a PBac transposon insertion into an intron, which is a hypomorph. The Mi{Mic} allele is homozygous lethal, while the viable progeny from the hypomorphic PiggyBac allele are male sterile and female fertile. In dEIF2A mutant flies, sperm failed to individualize due to defects in F-actin cones and failure to form and maintain cystic bulges, ultimately leading to sterility.
These results demonstrate that EIF2A is essential in a multicellular organism, both for normal development and spermatogenesis, and provide an entrée into the elucidation of the role of EIF2A and unconventional translation in vivo.
EIF2A 是一种非常规的翻译因子，对于从哺乳动物细胞中的各种转录本（包括癌基因和应激相关转录本）中的非 AUG 密码子起始蛋白质合成是必需的。其在多细胞生物中的功能尚未被报道。
在这里，我们鉴定并表征了编码果蝇 EIF2A 同源物的 CG7414 基因的突变等位基因。我们发现 CG7414 经历性别特异性剪接，从而调节其雄性特异性表达。我们对一个破坏所有预测同工型编码区的 Mi{Mic}转座子插入进行了特征分析，这可能是一个无效等位基因，以及一个 PBac 转座子插入到内含子中，这是一个次等位基因。Mi{Mic}等位基因纯合致死，而来自次等位基因 PiggyBac 的可存活后代是雄性不育和雌性可育。在 dEIF2A 突变果蝇中，由于 F-肌动蛋白锥体的缺陷以及无法形成和维持囊状膨出，精子无法个体化，最终导致不育。
这些结果表明，EIF2A 对于多细胞生物的正常发育和精子发生都是必不可少的，并为阐明 EIF2A 和非传统翻译在体内的作用提供了一个切入点。
