Characterizing the effect of porcupine on neural tube closure (979.3)

Abstract

Incomplete closure of the embryonic neural tube is responsible for common birth defects such as spina bifida. Wnts, a group of secreted lipid‐modified signaling proteins, are known to play a critical role in embryonic spinal cord development. Wnt proteins are palymitoylated by the enzyme Porcupine (Porcn), a transmembrane protein localized to the endoplasmic reticulum and Golgi apparatus. The proposed function of palmitoyation is to facilitate the secretion of Wnt proteins. Mutations in human Porcn can result in Focal Dermal Hypoplasia that can manifest multiple abnormalities including neural tube defects. Thus it is hypothesized that inhibition of Porcn in early stage chick embryos will cause abnormal neural tube closure. To characterize Porcn's role in neural tube closure, we developed an in vitro culture method that permitted addition of small molecule inhibitors of Porcn IWP‐1, IWP‐12 and C‐59. Surprisingly, although all of the compounds tested inhibited human Porcn, only IWP‐12 appeared to inhibit chick Porcn. Treatment with IWP‐12 revealed neural tube defects and decreased cell elongation which is consistent with a model in which IWP‐12 inhibits Wnt signaling via the planar cell polarity pathway. To test whether IWP‐1 and C‐59 are species specific inhibitors, we are currently comparing the ability of all three compounds to inhibit human and chick Porcn using an assay that measures Wnt palmitoylation.Grant Funding Source: Supported by NSF RUI MCB‐1244602, NIH‐RIMI P20MD000262, Area Grant NIH #1R15HD070206‐01A1