Spine control

Courtesy of Gerhard Schratt

G.M. Schratt et al., "A brain–specific microRNA regulates dendritic spine development," Nature, 439:283–8, 2006. (Cited in 98 papers)

In 2006, Michael Greenberg's group at Harvard Medical School and Austrian colleagues hypothesized that microRNAs are involved in the regulation of protein synthesis in neuronal dendrites. To test this, they overexpressed a hippocampal microRNA, miR-134, and found that it reduced the size of dendritic spines by inhibiting a protein kinase that induces spine development.

"Until that paper people thought of microRNAs as having more constitutive roles," such as permanently repressing the translation of an mRNA, says Kenneth Kosik at the University of California, Santa Barbara. Instead, this study showed for the first time that microRNAs may also play a role in synaptic plasticity and the modulation of translation.

In 2007 Kosik published evidence that nearly all microRNAs present in the neuron's cell body are also present in the dendrite ( RNA, 13:1224–34, 2007). Kosik says miR-134 was present in a concentration comparable to the other microRNAs.

First author Gerhard Schratt, now at the University of Heidelberg, is interested in how those other microRNAs might be involved in synaptic plasticity. His lab has found (but not yet published) another neuronal microRNA that works opposite to miR-134 and promotes dendritic spine development. Schratt supposes there is a network of microRNAs for fine-tuning the synapse.