morpholino

Morpholino is a class of synthetic antisense oligonucleotides used to modulate gene expression. Morpholino antisense oligos (MOs) are composed of morpholino rings linked by phosphorodiamidate backbones, producing a neutral, highly stable molecule that resists nucleases and reduces non-specific interactions with proteins. The morpholino ring distinguishes them chemically from DNA or RNA.

Mechanism and use: Morpholinos bind complementary RNA with high affinity, blocking access to the target sequence. Because their backbone is uncharged, they do not recruit RNase H and therefore do not degrade the target RNA. Instead, they inhibit translation initiation when targeting the ribosome binding site or start codon, or interfere with pre-mRNA splicing when directed at splice junctions. This allows researchers to decrease or alter the production of specific proteins without altering the genome.

Applications: MOs are widely used in developmental biology and genetics, particularly in zebrafish and Xenopus embryos, and also in other model systems and cell culture. They are typically delivered by microinjection or electroporation in early-stage embryos, enabling rapid, dose-dependent phenotypic analysis. To verify specificity, researchers often use multiple independent MOs, rescue experiments with exogenous mRNA, or complement with alternative approaches.

History and production: Morpholino antisense oligos were developed in the late 1990s by Summerton and Weller and have since been commercialized by specialized suppliers. They remain a common tool for transient gene knockdown, especially in embryonic studies, even as newer genome-editing methods have emerged.

Limitations: Potential off-target effects and toxicity can complicate interpretation. Delivery can be challenging in some tissues, and effects are typically transient. Proper controls and validation are essential.