Summary of Transcription Activator-like Effector Nucleases (TALENs)

TALEN was originally discovered in plant pathogenic bacteria, where they bind specifically to plant DNA promoter sequences and activate host genes required for pathogen infection. The structure of TALEN is largely similar to zinc-finger nucleases (ZFNs) in that they consist of an N-terminal domain that controls translocation, a central DNA-binding repeat domain, and a C-terminal transcription activator domain. Individual repeat domains in a TALEN recognize nucleotides in a 1:1 ratio. Each repeat domain consists of 34 amino acids (aa), with aa at positions 12 and 13, the repeat variable residues (RVDs), that determine DNA-binding specificity. TALENs have impressive target versatility, limited by the fact that the base of the first repeat is thymine 5'; however, studies now show that even this limitation can be circumvented.

Fig.1 TALENs mechanism. (Steentoft, et al., 2014)

TALEN-based Glycogene Editing Technology at CD BioGlyco

CD BioGlyco offers you comprehensive in vitro and in vivo Genome Editing Services via TALENs-based editing technology. The services we provide include but are not limited to:

• Donor clone design and construction
  Aided by genome editing tools, CD BioGlyco provides customized plasmid vectors to specifically transfer your gene of interest. Moreover, our vectors combine with different selection markers and genetic elements to meet your specific needs. Our donor clones possess the highest efficiency and minimal off-target effects.
• Stable cell line engineering
  CD BioGlyco provides convenience by creating a variety of cell banks of monoclonal stable cell lines with TALEN-mediated genome modifications.
• Transgenic mice
  CD BioGlyco also offers transgenic mice with TALEN-mediated genome modifications for our clients. Our transgenic mice have been used within the scientific community around the world to study gene functions and establish numerous animal models of human disease.
• Glycogene knock-in for promoter
• Glycogene knock out genes at a chromosomal level
• Glycogene activation
• Glycogene inhibition

Fig.2 TALEN-based glycogene editing service. (CD BioGlyco)

Applications

• Model creation: We edit endogenous genes of virtually any cell line to carry disease-causing mutations that have been identified in human congenital disorders of glycosylation (CDGs).
• Screening: Investigators use targeted gene editing to probe the role of glycosylation genes with traditional cell biology methods and dissect specific structure-function relationships without necessarily performing actual analysis of carbohydrate structures.
• Drug discovery

Advantages

• Specificity: TALENs are highly specific.
• Off-target effects: It is easier to place target sites in unique sequences for TALENs compared with ZFNs because target site design and selection are less restricted for TALENs.
• Efficient delivery and expression: TALENs have high efficiencies in introducing breaks in the DNA, but efficiency varies depending on the specific target sequence and the cell type.
• Highly flexible for design and high fidelity.
• Enrichment for targeted cells: Screening for targeted cells has the advantage of enabling direct identification of multi-allelic targeted cells even in a mixed population.

CD BioGlyco has developed an advanced Glycogenomics Platform where we use site-specific nuclease technology to design and edit glycogene fragments for clients around the world. Welcome to feel free to contact us for more service information.

Reference:

1. Steentoft, C.; et al. Precision genome editing: a small revolution for glycobiology. Glycobiology. 2014, 24(8): 663-680.