The Sp family of transcription factors plays important functions during development and disease. An evolutionary conserved role for some Sp family members is the control of limb development. The family is characterized by the presence of three C2H2-type zinc fingers and an adjacent 10 aa region with an unknown function called the Buttonhead (BTD) box. The presence of this BTD-box in all Sp family members identified from arthropods to vertebrates, suggests that it plays an essential role during development. However, despite its conservation, the in vivo function of the BTD-box has never been studied. In this work, we have generated specific BTD-box deletion alleles for the Drosophila Sp family members Sp1 and buttonhead (btd) using gene editing tools and analyzed its role during development. Unexpectedly, btd and Sp1 mutant alleles that lack the BTD-box are viable and have almost normal appendages. However, in a sensitized background the requirement of this domain to fully regulate some of Sp1 and Btd target genes is revealed. Furthermore, we have also identified a novel Sp1 role promoting leg vs antenna identity through the repression of spineless (ss) expression in the leg, a function that also depends on the Sp1 BTD-box.

Sp家族的转录因子在发育和疾病中起着重要的作用。一些Sp家族成员的进化保守角色是对肢体发育的控制。该家族的特征是存在三个C2H2型锌指和一个功能未知的相邻10aa区域，称为纽扣盒（BTD）。从节肢动物到脊椎动物，所有Sp家族成员中都存在该BTD-box，这表明它在发育过程中起着至关重要的作用。然而，尽管保守，但尚未研究BTD-box的体内功能。在这项工作中，我们为果蝇Sp家族成员Sp1和纽扣头生成了特定的BTD-box缺失等位基因（btd）使用基因编辑工具，并分析了其在开发过程中的作用。出乎意料的是，缺少BTD-box的btd和Sp1突变等位基因是可行的，并且具有几乎正常的附件。但是，在致敏的背景下，揭示了该结构域完全调节Sp1和Btd靶基因中某些基因的要求。此外，我们还发现了一种新颖的Sp1作用，即通过抑制腿中的无脊椎（ss）表达来促进腿与天线的同一性，该功能也取决于Sp1 BTD-box。