Biomedical subjects

Jeffrey R Miller

Publications and source records attributed to Jeffrey R Miller.

9 recordsLinked to original sources

PubMed2006

Regulation of somitogenesis by Ena/VASP proteins and FAK during Xenopus development.

The metameric organization of the vertebrate body plan is established during somitogenesis as somite pairs sequentially form along the anteroposterior axis. Coordinated regulation of cell shape, motility and adhesion are crucial for directing the morphological segmentation of somites. We show that members of the Ena/VASP family of actin regulatory proteins are required for somitogenesis in Xenopus. Xenopus Ena (Xena) localizes to the cell periphery in the presomitic mesoderm (PSM), and is enriched at intersomitic junctions and at myotendinous junctions in somites and the myotome, where it co-localizes with beta1-integrin, vinculin and FAK. Inhibition of Ena/VASP function with dominant-negative mutants results in abnormal somite formation that correlates with later defects in intermyotomal junctions. Neutralization of Ena/VASP activity disrupts cell rearrangements during somite rotation and leads to defects in the fibronectin (FN) matrix surrounding somites. Furthermore, inhibition of Ena/VASP function impairs FN matrix assembly, spreading of somitic cells on FN and autophosphorylation of FAK, suggesting a role for Ena/VASP proteins in the modulation of integrin-mediated processes. We also show that inhibition of FAK results in defects in somite formation, blocks FN matrix deposition and alters Xena localization. Together, these results provide evidence that Ena/VASP proteins and FAK are required for somite formation in Xenopus and support the idea that Ena/VASP and FAK function in a common pathway to regulate integrin-dependent migration and adhesion during somitogenesis.

Animals↗

PubMed2005

Regulation of actin cytoskeleton architecture by Eps8 and Abi1.

BACKGROUND: The actin cytoskeleton participates in many fundamental processes including the regulation of cell shape, motility, and adhesion. The remodeling of the actin cytoskeleton is dependent on actin binding proteins, which organize actin filaments into specific structures that allow them to perform various specialized functions. The Eps8 family of proteins is implicated in the regulation of actin cytoskeleton remodeling during cell migration, yet the precise mechanism by which Eps8 regulates actin organization and remodeling remains elusive. RESULTS: Here, we show that Eps8 promotes the assembly of actin rich filopodia-like structures and actin cables in cultured mammalian cells and Xenopus embryos, respectively. The morphology of actin structures induced by Eps8 was modulated by interactions with Abi1, which stimulated formation of actin cables in cultured cells and star-like structures in Xenopus. The actin stars observed in Xenopus animal cap cells assembled at the apical surface of epithelial cells in a Rac-independent manner and their formation was accompanied by recruitment of N-WASP, suggesting that the Eps8/Abi1 complex is capable of regulating the localization and/or activity of actin nucleators. We also found that Eps8 recruits Dishevelled to the plasma membrane and actin filaments suggesting that Eps8 might participate in non-canonical Wnt/Polarity signaling. Consistent with this idea, mis-expression of Eps8 in dorsal regions of Xenopus embryos resulted in gastrulation defects. CONCLUSION: Together, these results suggest that Eps8 plays multiple roles in modulating actin filament organization, possibly through its interaction with distinct sets of actin regulatory complexes. Furthermore, the finding that Eps8 interacts with Dsh and induced gastrulation defects provides evidence that Eps8 might participate in non-canonical Wnt signaling to control cell movements during vertebrate development.

Actin Cytoskeleton↗

PubMed2005

Non-traditional roles for the Adenomatous Polyposis Coli (APC) tumor suppressor protein.

The Adenomatous Polyposis Coli (APC) tumor suppressor is a multifunctional protein that is mutated in a majority of colon cancers. The role of APC as an antagonist of the Wnt signaling pathway is well known and it is widely accepted that inappropriate activation of this pathway through loss of APC function contributes to the progression of colon cancers. However, a body of evidence is growing to support the idea that APC plays non-traditional functions outside of the Wnt pathway with roles in cell migration, adhesion, chromosome segregation, spindle assembly, apoptosis, and neuronal differentiation. This review highlights the research into alternate functions for APC beyond its role in Wnt signaling and discusses the possible contributions for these non-traditional functions of APC in tumor formation.

Adenomatous Polyposis Coli Protein↗

PubMed2005

Cloning and developmental expression of Xenopus Enabled (Xena).

Regulation of actin dynamics, organization, and interaction with cell surface adhesion proteins is critical for tissue morphogenesis during development. The Ena/VASP family of actin-binding proteins function in several cellular processes that involve dynamic regulation of the actin cytoskeleton, including axon guidance, platelet aggregation, cell migration, and cell adhesion. The vertebrate Ena/VASP family is composed of three genes: Ena (Enabled), VASP (Vasodilator Stimulated Phosphoprotein), and Evl (Ena/VASP-Like). To better understand the role of Ena/VASP proteins during vertebrate development, we have cloned and characterized the developmental expression of Ena in Xenopus laevis. Analysis of the temporal expression of Xenopus Ena (Xena) demonstrates that multiple isoforms of Xena are detected throughout embryogenesis and that the presence of different isoforms is developmentally regulated. In situ hybridization analyses reveal that Xena is broadly expressed throughout development. During gastrulation and neurulation, Xena is detected in the neuroepithelium, notochord, and somites. In tadpoles, Xena expression is restricted to dorsal regions of the brain, whereas it is expressed at lower levels throughout the spinal cord. Xena expression is also detected in the notochord, myotome, heart, pronephros, and cranial placodes, including the olfactory and otic placodes. Analysis of the subcellular localization of Xena using a GFP fusion protein revealed that Xena localizes to adherens junctions and focal adhesions in Xenopus animal caps and NIH3T3 fibroblasts, respectively. These results define spatiotemporal windows in which Xena may function during early Xenopus development to modulate actin-dependent processes such as cell adhesion and migration.

Amino Acid Sequence↗

PubMed2005

Molecular cloning and expression of Ena/Vasp-like (Evl) during Xenopus development.

Ena/VASP proteins are actin-binding proteins implicated in the regulation of axon guidance, platelet aggregation, cell motility, and cell adhesion. The vertebrate Ena/VASP family is comprised of three genes: Ena (Enabled), VASP (Vasodilator Stimulated Phosphoprotein), and Evl (Ena/VASP-Like). We have cloned and characterized cDNAs encoding three alternatively spliced isoforms of Xenopus laevis Evl, designated Xevl, Xevl-I and Xevl-H. Analysis of the temporal expression of Xevl, Xevl-I and Xevl-H demonstrates that transcripts for each isoform are first detectable at low levels at stage 18, show increased abundance by stage 23, and persist throughout the remainder of embryogenesis. In situ hybridization analyses using a probe that detects all three Xevl isoforms or a probe that specifically detects the Xevl-H isoform revealed expression in the cement gland, brain, neural tube, myotome, and neural placodes, including the otic, lateral line, and olfactory placodes. These results suggest roles for Xevl in regulating actin dynamics and cell adhesion in neural and mesodermal tissues during later stages of Xenopus development.

Alternative Splicing↗

PubMed2005

Income inequality and risk of suicide in New York City neighborhoods: a multilevel case-control study.

Evidence on the relationship between income inequality and suicide is inconsistent. Data from the New York City Office of the Chief Medical Examiner for all fatal injuries was collected to conduct a multilevel case-control study. In multilevel models, suicide decedents (n=374) were more likely than accident controls (n=453) to reside in neighborhoods with greater income inequality even after controlling for individual characteristics; this relation was modified by age with an effect overall and among decedents aged 15-34 but not among decedents 35-64. These data suggest that income inequality may contribute to the risk of suicide in younger adults.

Adolescent↗

PubMed2003

Dishevelled activates Ca2+ flux, PKC, and CamKII in vertebrate embryos.

Wnt ligands and Frizzled (Fz) receptors have been shown to activate multiple intracellular signaling pathways. Activation of the Wnt-beta-catenin pathway has been described in greatest detail, but it has been reported that Wnts and Fzs also activate vertebrate planar cell polarity (PCP) and Wnt-Ca2+ pathways. Although the intracellular protein Dishevelled (Dsh) plays a dual role in both the Wnt-beta-catenin and the PCP pathways, its potential involvement in the Wnt-Ca2+ pathway has not been investigated. Here we show that a Dsh deletion construct, XDshDeltaDIX, which is sufficient for activation of the PCP pathway, is also sufficient for activation of three effectors of the Wnt-Ca2+ pathway: Ca2+ flux, PKC, and calcium/calmodulin-dependent protein kinase II (CamKII). Furthermore, we find that interfering with endogenous Dsh function reduces the activation of PKC by Xfz7 and interferes with normal heart development. These data suggest that the Wnt-Ca2+ pathway utilizes Dsh, thereby implicating Dsh as a component of all reported Fz signaling pathways.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Dapper, a Dishevelled-associated antagonist of beta-catenin and JNK signaling, is required for notochord formation.

Dapper was isolated in a screen for proteins interacting with Dishevelled, a key factor in Wnt signaling. Dapper and Dishevelled colocalize intracellularly and form a complex with Axin, GSK-3, CKI, and beta-catenin. Overexpression of Dapper increases Axin and GSK-3 in this complex, resulting in decreased soluble beta-catenin and decreased activation of beta-catenin-responsive genes. Dapper also inhibits activation by Dishevelled of c-Jun N-terminal kinase (JNK), a component of beta-catenin-independent Frizzled signaling. Inhibition of Dapper activates both beta-catenin-responsive genes and an AP1-responsive promoter, demonstrating that Dapper is a general Dishevelled antagonist. Depletion of maternal Dapper RNA from Xenopus embryos results in loss of notochord and head structures, demonstrating that Dapper is required for normal vertebrate development.

Adaptor Proteins, Signal Transducing↗

PubMed2001

The Wnts.

SUMMARY: The Wnt genes encode a large family of secreted protein growth factors that have been identified in animals from hydra to humans. In humans, 19 WNT proteins have been identified that share 27% to 83% amino-acid sequence identity and a conserved pattern of 23 or 24 cysteine residues. Wnt genes are highly conserved between vertebrate species sharing overall sequence identity and gene structure, and are slightly less conserved between vertebrates and invertebrates. During development, Wnts have diverse roles in governing cell fate, proliferation, migration, polarity, and death. In adults, Wnts function in homeostasis, and inappropriate activation of the Wnt pathway is implicated in a variety of cancers.

Animals↗