*Communication* **miR-7 Knockdown by Peptide Nucleic Acids in the Ascidian** *Ciona intestinalis*

**Silvia Mercurio 1, Silvia Cauteruccio 2,\*, Raoul Manenti 1, Simona Candiani 3,\*, Giorgio Scarì 4, Emanuela Licandro <sup>2</sup> and Roberta Pennati <sup>1</sup>**


Received: 18 September 2019; Accepted: 14 October 2019; Published: 16 October 2019

**Abstract:** Peptide Nucleic Acids (PNAs) are synthetic mimics of natural oligonucleotides, which bind complementary DNA/RNA strands with high sequence specificity. They display numerous advantages, but in vivo applications are still rare. One of the main drawbacks of PNAs application is the poor cellular uptake that could be overcome by using experimental models, in which microinjection techniques allow direct delivery of molecules into eggs. Thus, in this communication, we investigated PNAs efficiency in miR-7 downregulation and compared its effects with those obtained with the commercially available antisense molecule, Antagomir (Dharmacon) in the ascidian *Ciona intestinalis*. Ascidians are marine invertebrates closely related to vertebrates, in which PNA techniques have not been applied yet. Our results suggested that anti-miR-7 PNAs were able to reach their specific targets in the developing ascidian embryos with high efficiency, as the same effects were obtained with both PNA and Antagomir. To the best of our knowledge, this is the first evidence that unmodified PNAs can be applied in in vivo knockdown strategies when directly injected into eggs.

**Keywords:** microRNA; *hnRNP K*; PNA; tunicates; LNA probe
