Sloan Roketa S, Swanson Christina I, Gavilano Lily, Smith Kristen N, Malek Pamela Y, Snow-Smith Mayronne, Duronio Robert J, Key S Catherine Silver
Department of Biology, North Carolina Central University, Durham, NC USA.
Fly (Austin). 2012 Jul-Sep;6(3):173-83. doi: 10.4161/fly.20247. Epub 2012 Jun 22.
The Drosophila lethal(2)denticleless (l(2)dtl) gene was originally reported as essential for embryogenesis and formation of the rows of tiny hairs on the larval ventral cuticle known as denticle belts. It is now well-established that l(2)dtl (also called cdt2) encodes a subunit of a Cullin 4-based E3 ubiquitin ligase complex that targets a number of key cell cycle regulatory proteins, including p21, Cdt1, E2F1 and Set8, to prevent replication defects and maintain cell cycle control. To investigate the role of l(2)dtl/cdt2 during development, we characterized existing l(2)dtl/cdt2 mutants and generated new deletion alleles, using P-element excision mutagenesis. Surprisingly, homozygous l(2)dtl/cdt2 mutant embryos developed beyond embryogenesis, had intact denticle belts, and lacked an observable embryonic replication defect. These mutants died during larval stages, affirming that loss of l(2)dtl/cdt2 function is lethal. Our data show that L(2)dtl/Cdt2 is maternally deposited, remains nuclear throughout the cell cycle, and has a previously unreported, elevated expression in the developing gonads. We also find that E2f1 regulates l(2)dtl/cdt2 expression during embryogenesis, possibly via several highly conserved putative E2f1 binding sites near the l(2)dtl/cdt2 promoter. Finally, hypomorphic allele combinations of the l(2)dtl/cdt2 gene result in a novel phenotype: viable, low-fertility males. We conclude that "denticleless" is a misnomer, but that l(2)dtl/cdt2 is an essential gene for Drosophila development.
果蝇致死（2）无齿基因（l(2)dtl）最初被报道对胚胎发育以及幼虫腹侧表皮上称为齿带的微小毛发排的形成至关重要。现在已经明确，l(2)dtl（也称为cdt2）编码一种基于Cullin 4的E3泛素连接酶复合物的亚基，该复合物靶向许多关键的细胞周期调节蛋白，包括p21、Cdt1、E2F1和Set8，以防止复制缺陷并维持细胞周期控制。为了研究l(2)dtl/cdt2在发育过程中的作用，我们利用P元素切除诱变对现有的l(2)dtl/cdt2突变体进行了表征并产生了新的缺失等位基因。令人惊讶的是，纯合的l(2)dtl/cdt2突变体胚胎在胚胎发育后仍能发育，具有完整的齿带，并且没有明显的胚胎复制缺陷。这些突变体在幼虫阶段死亡，证实了l(2)dtl/cdt2功能的丧失是致命的。我们的数据表明，L(2)dtl/Cdt2是母源沉积的，在整个细胞周期中都保持在细胞核内，并且在发育中的性腺中具有先前未报道的高表达。我们还发现，E2f1在胚胎发育过程中可能通过l(2)dtl/cdt2启动子附近的几个高度保守的假定E2f1结合位点来调节l(2)dtl/cdt2的表达。最后，l(2)dtl/cdt2基因的次等位基因组合导致了一种新的表型：存活的低育性雄性。我们得出结论，“无齿”是一个误称，但l(2)dtl/cdt2是果蝇发育所必需的基因。
