Lorna E. Young PhD

Lorna E. Young of the Department of Biochemistry, Geisel School of Medicine at Dartmouth, was named by the Molecular Biology of the Cell (MBoC) Editorial Board as the recipient of the 25th annual MBoC Paper of the Year Award. As a postdoc in

Henry Higgs’ lab, Young was the first author of the article “Cell type-dependent mechanisms for formin-mediated assembly of filopodia” (Mol. Biol. Cell 25, 4646-4659).

In their paper, Young and her colleagues addressed the question of how filopodia form. This has been the subject of some debate, with two predominant models: convergent elongation and tip nucleation. In convergent elongation, a dendritic network of actin filaments nucleated by the Arp2/3 complex is proposed to give rise to filopodia via reorganization and extension of the network by formins, by ENA/VASP, or by some combination of the two. In tip nucleation, the formins are proposed to be responsible for both the initial nucleation and the subsequent extension of the filaments that form the core of the filopodium.

Young et al. approached this problem by use of a model system in which transfection of a number of cell types, both suspended and adherent, with fluorescently tagged formin, elicits filopodium formation and discovered that filopodium assembly is highly context-dependent. Specifically, in cells grown in suspension, formin-dependent filopodium formation is absolutely dependent on the Arp2/3 complex. In contrast, when made adherent by culture on a substrate, formin-dependent filopodium formation can occur without the help of Arp2/3. Moreover, one particular formin (mDia1) and VASP contribute to filopodium formation only in adherent cells. In addition to demonstrating a surprising degree of context-dependent variation in filopodium formation, the authors propose a general model of filopodium assembly.

Young will present her research at a Minisymposium at the ASCB Annual Meeting in San Francisco this December.