CDB15:0001588 WNT3A — FZD6

ABSTRACT: Inherited and isolated nail malformations are rare and heterogeneous conditions. We identified two consanguineous pedigrees in which some family members were affected by isolated nail dysplasia that suggested an autosomal-recessive inheritance pattern and was characterized by claw-shaped nails, onychauxis, and onycholysis. Genome-wide SNP array analysis of affected individuals from both families showed an overlapping and homozygous region of 800 kb on the long arm of chromosome 8. The candidate region spans eight genes, and DNA sequence analysis revealed homozygous nonsense and missense mutations in FZD(6), the gene encoding Frizzled 6. FZD(6) belongs to a family of highly conserved membrane-bound WNT receptors involved in developmental processes and differentiation through several signaling pathways. We expressed the FZD(6) missense mutation and observed a quantitative shift in subcellular distribution from the plasma membrane to the lysosomes, where the receptor is inaccessible for signaling and presumably degraded. Analysis of human fibroblasts homozygous for the nonsense mutation showed an aberrant response to both WNT-3A and WNT-5A stimulation; this response was consistent with an effect on both canonical and noncanonical WNT-FZD signaling. A detailed analysis of the Fzd(6)(-/-) mice, previously shown to have an altered hair pattern, showed malformed claws predominantly of the hind limbs. Furthermore, a transient Fdz6 mRNA expression was observed in the epidermis of the digital tips at embryonic day 16.5 during early claw morphogenesis. Thus, our combined results show that FZD6 mutations can result in severe defects in nail and claw formation through reduced or abolished membranous FZD(6) levels and several nonfunctional WNT-FZD pathways.

ABSTRACT: The WNT receptors of the Frizzled family comprise ten mammalian isoforms, bind WNT proteins and mediate downstream signaling to regulate stem cell fate, neuronal differentiation, cell survival and more. WNT-induced signaling pathways are either β-catenin-dependent or -independent, thereby dividing the 19 mammalian WNT proteins into two groups. So far hardly any quantitative, pharmacological information is available about WNT-FZD interaction profiles, affinities or mechanisms of signaling specification through distinct WNT/FZD pairings. This lack of knowledge originates from difficulties with WNT purification and a lack of suitable assays, such as ligand binding assays and FZD activity readouts. In order to minimize this gap, we employ fluorescence recovery after photobleaching (FRAP) to investigate WNT effects on the lateral mobility of FZD6-GFP in living cells. Pharmacological uncoupling of heterotrimeric G proteins by pertussis toxin and N-ethylmaleimide argues that changes in FZD6 mobility are related to putative precoupling of heterotrimeric Gi/o proteins to FZD6. We show that recombinant WNT-1, -2, 3A, -4, -5A, -7A, -9B and -10B affect FZD6 surface mobility and thus act on this receptor. WNT-5B and WNT-11, on the other hand, have no effect on FZD6 mobility and we conclude that they do not act through FZD6. We introduce here a novel way to assess WNT-FZD interaction by live cell imaging allowing further mapping of WNT-FZD interactions and challenging previous experimental limitations. Increased understanding of WNT-FZD selectivity provides important insight into the biological function of this crucial signaling system with importance in developmental biology, stem cell regulation oncogenesis, and human disease.

ABSTRACT: Endometrial cancer is one of the most common gynecological malignancies and has exhibited an increasing incidence rate in recent years. Cancer stem cells (CSCs), which are responsible for tumor growth and chemoresistance, have been confirmed in endometrial cancer. However, it is still challenging to identify endometrial cancer stem cells to then target for therapy.