What is the difference between CRISPR (clustered regularly interspaced short palindromic repeats) and TALENs (transcription-activator-like effector nucleases)?

Like zinc finger nucleases (ZFNs), TALENs (transcription-activator-like effector nucleases) developed as a result of the fusion of transcription activator-like (TAL) proteins and a nuclease (FokI). TAL proteins contain amino acid repeating motifs with variable positions which can recognize specific nucleotides. When fused to nucleases, DNA binding domains (DBDs) can be used to induce double strand breaks (DSBs), with the resulting frame-shift mutations into subsequent genes potentially resulting in their knockout.

Unlike CRISPR, which can introduce multiple gene mutations concurrently with a single injection, TALENs are limited to simple mutations.1 CRISPR transfections also have a higher efficiency, whereas TALEN editing often results in mosaicism, where a mutant allele is present only in some of their cells transfected.

1. H. Wang, et al., "One-Step Generation of Mice Carrying Mutations in Multiple Genes by CRISPR/Cas-Mediated Genome Engineering," Cell 153(4):910-918, 2013.