The scaffold protein spectrin α2 (αII-spectrin), together with any of the five β-spectrins, has roles in various cellular processes ranging from the formation of membrane domains to providing a scaffold for signalling pathways. In Drosophila and C. elegans, deletion of αII-spectrin is embryonic lethal but, so far, little is known about its roles in vertebrate development. On page 3956, Jon Morrow and colleagues now provide insight into the functions of αII-spectrin in vertebrates by generating αII-spectrin knockout mice. Embryos with a homozygous deletion of the Spna2 gene display prominent cardiac, craniofacial and neural tube abnormalities and die between E12.5 and E16.5. On the cellular level, the loss of αII-spectrin results in a substantial reduction in βII- and βIII-spectrin and ankyrins B and G, and the redistribution of these proteins to the apical membranes of epithelial cells. Epithelial cell morphology, however, is unaffected by the loss of αII-spectrin. In vitro, Spna^−/− mouse embryonic fibroblasts (MEFs) spread and grow more slowly than wildtype MEFs, and display a spiky morphology and sparse lamellipodia. Thus, αII-spectrin is not only required for the stability and organisation of related proteins but, by being a key component of the spectrin–ankyrin scaffold, is also required for cell spreading, tissue patterning and organ development in vertebrates.

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