Mutations in WNT1 Cause Different Forms of Bone Fragility
AMERICAN JOURNAL OF HUMAN GENETICS
2013; 92 (4): 565-574
We report that hypofunctional alleles of WNT1 cause autosomal-recessive osteogenesis imperfecta, a congenital disorder characterized by reduced bone mass and recurrent fractures. In consanguineous families, we identified five homozygous mutations in WNT1: one frameshift mutation, two missense mutations, one splice-site mutation, and one nonsense mutation. In addition, in a family affected by dominantly inherited early-onset osteoporosis, a heterozygous WNT1 missense mutation was identified in affected individuals. Initial functional analysis revealed that altered WNT1 proteins fail to activate canonical LRP5-mediated WNT-regulated ?-catenin signaling. Furthermore, osteoblasts cultured in vitro showed enhanced Wnt1 expression with advancing differentiation, indicating a role of WNT1 in osteoblast function and bone development. Our finding that homozygous and heterozygous variants in WNT1 predispose to low-bone-mass phenotypes might advance the development of more effective therapeutic strategies for congenital forms of bone fragility, as well as for common forms of age-related osteoporosis.
View details for DOI 10.1016/j.ajhg.2013.02.010
View details for Web of Science ID 000317449700008
View details for PubMedID 23499309
Structural Architecture and Functional Evolution of Wnts
2012; 23 (2): 227-232
The crystal structure of a Wnt morphogen bound to its Frizzled receptor ectodomain provides insights into the evolutionary provenance of this complex fold and offers an explanation for why Wnts utilize both lipid- and protein-mediated contacts to engage Frizzleds.
View details for DOI 10.1016/j.devcel.2012.07.011
View details for Web of Science ID 000307695500001
View details for PubMedID 22898770
Structural Basis of Wnt Recognition by Frizzled
2012; 337 (6090): 59-64
Wnts are lipid-modified morphogens that play critical roles in development principally through engagement of Frizzled receptors. The 3.25 angstrom structure of Xenopus Wnt8 (XWnt8) in complex with mouse Frizzled-8 (Fz8) cysteine-rich domain (CRD) reveals an unusual two-domain Wnt structure, not obviously related to known protein folds, resembling a "hand" with "thumb" and "index" fingers extended to grasp the Fz8-CRD at two distinct binding sites. One site is dominated by a palmitoleic acid lipid group projecting from serine 187 at the tip of Wnt's thumb into a deep groove in the Fz8-CRD. In the second binding site, the conserved tip of Wnt's "index finger" forms hydrophobic amino acid contacts with a depression on the opposite side of the Fz8-CRD. The conservation of amino acids in both interfaces appears to facilitate ligand-receptor cross-reactivity, which has important implications for understanding Wnt's functional pleiotropy and for developing Wnt-based drugs for cancer and regenerative medicine.
View details for DOI 10.1126/science.1222879
View details for Web of Science ID 000306053100042
View details for PubMedID 22653731
Recognition of a signal peptide by the signal recognition particle
2010; 465 (7297): 507-U139
Targeting of proteins to appropriate subcellular compartments is a crucial process in all living cells. Secretory and membrane proteins usually contain an amino-terminal signal peptide, which is recognized by the signal recognition particle (SRP) when nascent polypeptide chains emerge from the ribosome. The SRP-ribosome nascent chain complex is then targeted through its GTP-dependent interaction with SRP receptor to the protein-conducting channel on endoplasmic reticulum membrane in eukaryotes or plasma membrane in bacteria. A universally conserved component of SRP (refs 1, 2), SRP54 or its bacterial homologue, fifty-four homologue (Ffh), binds the signal peptides, which have a highly divergent sequence divisible into a positively charged n-region, an h-region commonly containing 8-20 hydrophobic residues and a polar c-region. No structure has been reported that exemplifies SRP54 binding of any signal sequence. Here we have produced a fusion protein between Sulfolobus solfataricus SRP54 (Ffh) and a signal peptide connected via a flexible linker. This fusion protein oligomerizes in solution through interaction between the SRP54 and signal peptide moieties belonging to different chains, and it is functional, as demonstrated by its ability to bind SRP RNA and SRP receptor FtsY. We present the crystal structure at 3.5 A resolution of an SRP54-signal peptide complex in the dimer, which reveals how a signal sequence is recognized by SRP54.
View details for DOI 10.1038/nature08870
View details for Web of Science ID 000278043700041
View details for PubMedID 20364120