Interaction between fidgetin and protein kinase A-anchoring protein AKAP95 is critical for palatogenesis in the mouse

Exploring AKAPs in visual signaling

The complex nature of the retina demands well-organized signaling to uphold signal accuracy and avoid interference, a critical aspect in handling a variety of visual stimuli. A-kinase anchoring proteins (AKAPs), known for binding protein kinase A (PKA), contribute to the specificity and efficiency of retinal signaling. They play multifaceted roles in various retinal cell types, influencing photoreceptor sensitivity, neurotransmitter release in bipolar cells, and the integration of visual information in ganglion cells. AKAPs like AKAP79/150 and AKAP95 exhibit distinct subcellular localizations, impacting synaptic transmission and receptor sensitivity in photoreceptors and bipolar cells. Furthermore, AKAPs are involved in neuroprotective mechanisms and axonal degeneration, particularly in retinal ganglion cells. In particular, AKAP6 coordinates stress-specific signaling and promotes neuroprotection following optic nerve injury. As our review underscores the therapeutic potential of targeting AKAP signaling complexes for retinal neuroprotection and enhancement, it acknowledges challenges in developing selective drugs that target complex protein-protein interactions. Overall, this exploration of AKAPs provides valuable insights into the intricacies of retinal signaling, offering a foundation for understanding and potentially addressing retinal disorders.

Comprehensive characterization of Fidgetin on tumor immune microenvironment evaluation and immunotherapy in human hepatocellular carcinoma

Most cancers have a downregulation of Fidgetin (FIGN), which has been linked to tumor growth. However, there aren't many papers that mention FIGN's connection to hepatocellular carcinoma (HCC). Here, FIGN expression in HCC tissues was markedly reduced as compared to nearby normal liver tissues. According to univariate and multivariate Cox regression, it served as an independent predictor of survival outcomes. Patients with high levels of FIGN expression had a worse outcome. FIGN was shown to be engaged in immune-related pathways and to have a positive correlation with immunological score and immune cells according to KEGG pathway analysis. In HCC patients, FIGN was substantially linked with immunological checkpoints and the hot tumor state. Additionally, immunotherapy and chemotherapy showed a significant therapeutic response in HCC patients with low FIGN expression. This research revealed that FIGN expression was tightly related to hepatoma immunity and might be employed as a biomarker to predict patient prognosis and guide medication.

The fidgetin family: Shaking things up among the microtubule-severing enzymes

The microtubule cytoskeleton is required for several crucial cellular processes, including chromosome segregation, cell polarity and orientation, and intracellular transport. These functions rely on microtubule stability and dynamics, which are regulated by microtubule-binding proteins (MTBPs). One such type of regulator is the microtubule-severing enzymes (MSEs), which are ATPases Associated with Diverse Cellular Activities (AAA+ ATPases). The most recently identified family are the fidgetins, which contain three members: fidgetin, fidgetin-like 1 (FL1), and fidgetin-like 2 (FL2). Of the three known MSE families, the fidgetins have the most diverse range of functions in the cell, spanning mitosis/meiosis, development, cell migration, DNA repair, and neuronal function. Furthermore, they offer intriguing novel therapeutic targets for cancer, cardiovascular disease, and wound healing. In the two decades since their first report, there has been great progress in our understanding of the fidgetins; however, there is still much left unknown about this unusual family. This review aims to consolidate the present body of knowledge of the fidgetin family of MSEs and to inspire deeper exploration into the fidgetins and the MSEs as a whole.

Suppression of microRNA 124-3p and microRNA 340-5p ameliorates retinoic acid-induced cleft palate in mice

The etiology of cleft lip with or without cleft palate (CL/P), a common congenital birth defect, is complex, with genetic and epigenetic, as well as environmental, contributing factors. Recent studies suggest that fetal development is affected by maternal conditions through microRNAs (miRNAs), a group of short noncoding RNAs. Here, we show that miR-129-5p and miR-340-5p suppress cell proliferation in both primary mouse embryonic palatal mesenchymal cells and O9-1 cells, a neural crest cell line, through the regulation of Sox5 and Trp53 by miR-129-5p, and the regulation of Chd7, Fign and Tgfbr1 by miR-340-5p. Notably, miR-340-5p, but not miR-129-5p, was upregulated following all-trans retinoic acid (atRA; tretinoin) administration, and a miR-340-5p inhibitor rescued the cleft palate (CP) phenotype in 47% of atRA-induced CP mice. We have previously reported that a miR-124-3p inhibitor can also partially rescue the CP phenotype in atRA-induced CP mouse model. In this study, we found that a cocktail of miR-124-3p and miR-340-5p inhibitors rescued atRA-induced CP with almost complete penetrance. Taken together, our results suggest that normalization of pathological miRNA expression can be a preventive intervention for CP.

A nuclear localization signal is required for the nuclear translocation of Fign and its microtubule‑severing function

It is commonly known that the specific function of a given ATPase associated with diverse cellular activities protein (i.e., a member of the AAA superfamily of proteins) depends primarily on its subcellular location. The microtubule-severing protein fidgetin (Fign) possesses a nuclear localization signal (NLS) that facilitates its translocation to the nucleus, where its assembly is finalized; here, Fign contributes to the regulation of microtubule configuration by cutting and trimming microtubule polymers. In the present study, Fign was found to be a nuclear protein, whose N-terminal sequence (SSLKRKAFYM; residues 314–323) acts as an NLS. Following substitution (KR to NN; 317–318) or deletion (NT; 314–323) mutations within the NLS, Fign, which is predominantly expressed in the nucleus, was found to reside in the cytoplasm of transfected cells. Furthermore, Fign was found to have an essential role in microtubule severing by preferentially targeting highly-tyrosinated microtubules (tyr-MTs). Mutation of the Fign NLS did not affect its microtubule-severing function or the cleavage of tyr-MTs, but did affect the cellular distribution of the Fign protein itself. Taken altogether, an NLS for Fign was identified, and it was demonstrated that the basic amino acids K317 and R318 are necessary for regulating its entry into the nucleus, whereas an increase in Fign in the cytosol due to mutations of the NLS did not affect its cleavage function.

Fidgetin as a potential prognostic biomarker for hepatocellular carcinoma

Background: Fidgetin (FIGN), a conserved ATP-dependent enzyme, is regarded as a hepatocellular carcinoma (HCC) risk gene, but the prognostic implication of FIGN in HCC remains obscure. In this study, we investigate the expression of FIGN in HCC and to evaluate its prognostic value. Methods: A total of 216 patients with HCC who experienced hepatectomy were recruited in this study. The expression of FIGN in HCC samples was evaluated by quantitative real-time PCR, immunohistochemistry and immunoblotting analysis. And Cox regression model was used to evaluate the prognostic value of all covariates. Results: Of the 216 HCC patients, 67 (31.0%) had tumors with high FIGN expression and 149 (69.0%) had tumors with low FIGN expression. FIGN expression was positively correlated with TNM stage (P = 0.039), tumor with incomplete capsule (P = 0.036), microvascular invasion (P = 0.023), and portal vein tumor thrombus (P = 0.003). High expression of FIGN indicated shorter overall survival (OS) (hazard ratio: 4.569, P = 0.036) and disease-free survival (DFS) (hazard ratio: 6.487, P = 0.001). Conclusion: Our results indicate that high Fidgetin expression is associated with tumor progression and suggest a worse prognosis in HCC. Fidgetin might serve as a potential target for therapy.

Confirmation of BRD4 haploinsufficiency role in Cornelia de Lange-like phenotype and delineation of a 19p13.12p13.11 gene contiguous syndrome

Cornelia de Lange syndrome (CdLS) is a genetically and clinical heterogeneous condition characterized by congenital malformation, intellectual disability, and peculiar dysmorphic features. Recently, BRD4 (19p13.12) was proposed as a new critical gene associated with a mild CdLS because of a similar presentation of the patients carrying point mutations and of its involvement in the NIPBL pathway. Patients harboring a 19p interstitial deletion shared some physical features with BRD4 mutation carriers, which results in a more complex phenotype because of the involvement of several neighboring genes. We report a new 19p deletion in a patient clinically diagnosed as CdLS, partially overlapping with previously published cases with the aim to support the role of BRD4 haploinsufficiency in a CdL-like phenotype and to improve the delineation of 19p13.12p13.11 deletion as a new nonrecurrent gene contiguous syndrome, spanning GIPC1, NOTCH3, BRD4, AKAP8, AKAP8L, CASP14, and EPS15L1 genes. Previously described cases are reviewed, attempting to delineate a genotype-phenotype correlation.

Gene datasets associated with mouse cleft palate

This article presents data on genes associated with cleft palate (CP), retrieved through both a full-text systematic review and a mouse genome informatics (MGI) database search. In order to group CP-associated genes according to function, pathway, biological process, and cellular component, the genes were analyzed using category enrichment bioinformatics tools, the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO). This approach provides invaluable opportunities for the identification of candidate pathways and genes in CP research.

Generation of a biotinylatable Sox2 mouse model to identify Sox2 complexes in vivo

Sox2 is a Sry-box containing family member of related transcription factors sharing homology in their DNA binding domain. Sox2 is important during different stages of development, and previously we showed that Sox2 plays an important role in branching morphogenesis and epithelial cell differentiation in lung development. The transcriptional activity of Sox2 depends on its interaction with other proteins, leading to ‘complex-specific’ DNA binding and transcriptional regulation. In this study, we generated a mouse model containing a biotinylatable-tag targeted at the translational start site of the endogenous Sox2 gene (bioSox2). This tag was biotinylated by the bacterial birA protein and the resulting bioSox2 protein was used to identify associating partners of Sox2 at different phases of lung development in vivo (the Sox2 interactome). Homozygous bioSox2 mice are viable and fertile irrespective of the biotinylation of the bio tag, indicating that the bioSox2 gene is normally expressed and the protein is functional in all tissues. This suggests that partners of Sox2 are most likely able to associate with the bioSox2 protein. BioSox2 complexes were isolated with high affinity using streptavidin beads and analysed by MALDI-ToF mass spectrometry analysis. Several of the identified binding partners are already shown to have a respiratory phenotype. Two of these partners, Wdr5 and Tcf3, were validated to confirm their association in Sox2 complexes. This bioSox2 mouse model will be a valuable tool for isolating in vivo Sox2 complexes from different tissues.

A Genetic Variant in FIGN Gene Reduces the Risk of Congenital Heart Disease in Han Chinese Populations

Congenital heart disease (CHD) is one of the most common birth anomalies worldwide. Folate deficiency is an independent risk factor for CHD. Genome-wide association studies (GWAS) revealed that human folate level could be significantly influenced by fidgetin (FIGN), methylenetetrahydrofolate reductase (MTHFR), prickle homolog 2 (PRICKLE2), synaptotagmin 9 (SYT9), gamma-aminobutyric acid B receptor 2 (GABBR2), and alkaline phosphatase (ALPL) genes. The association between the above-mentioned six variants and CHD was examined in the two independent case-control studies in a total of 868 CHD patients and 931 healthy controls. Our results showed that the G > C (rs2119289) variant in intron 4 of FIGN led to a significant reduction of CHD susceptibility in both the separate and combined case-control studies (allele distribution P < 0.001, genotype distribution P < 0.001). Specifically, by analyzing the combined samples, we observed that the risks of CHD in individuals carrying the heterozygous G/C and homozygous C/C genotypes were reduced by 45% (adjusted OR 0.55, 95% CI 0.47-0.67) and 66% (adjusted OR 0.34, 95% CI 0.23-0.50), respectively, in comparison with individuals carrying the wild-type G/G genotype. Our findings have demonstrated that the C allele of variant rs2119289 of FIGN gene is an important genetic marker for decreased CHD risk. Considering that the rs2119289 of FIGN gene is related to the appropriate folate level, FIGN might play an important role in CHD by upregulating plasma folate concentration during embryo heart development. This work provides a new insight for risk assessment of CHD.

The A-kinase Anchoring Protein GSKIP Regulates GSK3β Activity and Controls Palatal Shelf Fusion in Mice

A-kinase anchoring proteins (AKAPs) represent a family of structurally diverse proteins, all of which bind PKA. A member of this family is glycogen synthase kinase 3β (GSK3β) interaction protein (GSKIP). GSKIP interacts with PKA and also directly interacts with GSK3β. The physiological function of the GSKIP protein in vivo is unknown. We developed and characterized a conditional knock-out mouse model and found that GSKIP deficiency caused lethality at birth. Embryos obtained through Caesarean section at embryonic day 18.5 were cyanotic, suffered from respiratory distress, and failed to initiate breathing properly. Additionally, all GSKIP-deficient embryos showed an incomplete closure of the palatal shelves accompanied by a delay in ossification along the fusion area of secondary palatal bones. On the molecular level, GSKIP deficiency resulted in decreased phosphorylation of GSK3β at Ser-9 starting early in development (embryonic day 10.5), leading to enhanced GSK3β activity. At embryonic day 18.5, GSK3β activity decreased to levels close to that of wild type. Our findings reveal a novel, crucial role for GSKIP in the coordination of GSK3β signaling in palatal shelf fusion.

Vertebrate Fidgetin Restrains Axonal Growth by Severing Labile Domains of Microtubules

Individual microtubules (MTs) in the axon consist of a stable domain that is highly acetylated and a labile domain that is not. Traditional MT-severing proteins preferentially cut the MT in the stable domain. In Drosophila, fidgetin behaves in this fashion, with targeted knockdown resulting in neurons with a higher fraction of acetylated (stable) MT mass in their axons. Conversely, in a fidgetin knockout mouse, the fraction of MT mass that is acetylated is lower than in the control animal. When fidgetin is depleted from cultured rodent neurons, there is a 62% increase in axonal MT mass, all of which is labile. Concomitantly, there are more minor processes and a longer axon. Together with experimental data showing that vertebrate fidgetin targets unacetylated tubulin, these results indicate that vertebrate fidgetin (unlike its fly ortholog) regulates neuronal development by tamping back the expansion of the labile domains of MTs.

Human Fidgetin is a microtubule severing the enzyme and minus-end depolymerase that regulates mitosis

Fidgetin is a member of the AAA protein superfamily with important roles in mammalian development. Here we show that human Fidgetin is a potent microtubule severing and depolymerizing the enzyme used to regulate mitotic spindle architecture, dynamics and anaphase A. In vitro, recombinant human Fidgetin severs taxol-stabilized microtubules along their length and promotes depolymerization, primarily from their minus-ends. In cells, human Fidgetin targets to centrosomes, and its depletion with siRNA significantly reduces the velocity of poleward tubulin flux and anaphase A chromatid-to-pole motion. In addition, the loss of Fidgetin induces a microtubule-dependent enlargement of mitotic centrosomes and an increase in the number and length of astral microtubules. Based on these data, we propose that human Fidgetin actively suppresses microtubule growth from and attachment to centrosomes.

Microtubule-severing enzymes at the cutting edge

ATP-dependent severing of microtubules was first reported in Xenopus laevis egg extracts in 1991. Two years later this observation led to the purification of the first known microtubule-severing enzyme, katanin. Katanin homologs have now been identified throughout the animal kingdom and in plants. Moreover, members of two closely related enzyme subfamilies, spastin and fidgetin, have been found to sever microtubules and might act alongside katanins in some contexts (Roll-Mecak and McNally, 2010; Yu et al., 2008; Zhang et al., 2007). Over the past few years, it has become clear that microtubule-severing enzymes contribute to a wide range of cellular activities including mitosis and meiosis, morphogenesis, cilia biogenesis and disassembly, and migration. Thus, this group of enzymes is revealing itself to be among the most important of the microtubule regulators. This Commentary focuses on our growing understanding of how microtubule-severing enzymes contribute to the organization and dynamics of diverse microtubule arrays, as well as the structural and biophysical characteristics that afford them the unique capacity to catalyze the removal of tubulin from the interior microtubule lattice. Our goal is to provide a broader perspective, focusing on a limited number of particularly informative, representative and/or timely findings.

Caenorhabditis elegans fidgetin homolog FIGL-1, a nuclear-localized AAA ATPase, binds to SUMO

Fidgetin is a member of the AAA (ATPases associated with diverse cellular activities) chaperones. It is well-known that the specific function of a given AAA protein primarily depends upon its subcellular localization and interacting partners. FIGL-1, a Caenorhabditis elegans homolog of mammalian fidgetin, is localized in the nucleus. Here, we identified that the N-terminal PKRVK sequence of FIGL-1 functions as a monopartite nuclear localization signal. Nuclear localization of FIGL-1 is required for its function. We also found that FIGL-1 specifically interacted with SMO-1, a C. elegans homolog of small ubiquitin-like modifier (SUMO), using a yeast two-hybrid assay. Furthermore, the direct physical interaction between FIGL-1 and SMO-1 was demonstrated by pull-down assay using purified proteins as well as immunoprecipitation assay using lysates from epitope-tagged SMO-1-expressing worms. Binding of FIGL-1 to SMO-1 is required for its function. The depletion of FIGL-1 and SMO-1 resulted in developmental defects in C. elegans. Taken altogether, our results indicate that FIGL-1 is a nuclear protein and that in concert with SMO-1, FIGL-1 plays an important role in the regulation of C. elegans development.

Cyclic AMP-mediated immune regulation--overview of mechanisms of action in T cells

The canonical second messenger cAMP is well established as a potent negative regulator of T cell immune function. Through protein kinase A (PKA) it regulates T cell function at the level of transcription factors, members of the mitogen-activated protein kinase pathway, phospholipases (PLs), Ras homolog (Rho)A and proteins involved in the control of cell cycle progression. Type I PKA is the predominant PKA isoform in T cells. Furthermore, whereas type II PKA is located at the centrosome, type I PKA is anchored close to the T cell receptor (TCR) in lipid rafts by the Ezrin-ERM-binding phosphoprotein of 50 kDa (EBP50)-phosphoprotein associated with glycosphingolipid-enriched microdomains (PAG) scaffold complex. The most TCR-proximal target for type I PKA is C-terminal Src kinase (Csk), which upon activation by raft recruitment and phosphorylation inhibits the Src family tyrosine kinases Lck and Fyn and thus functions to maintain T cell homeostasis. Recently, induction of cAMP levels in responder T cells has emerged as one of the mechanisms by which regulatory T (T(R)) cells execute their suppressive action. Thus, the cAMP-type I PKA-Csk pathway emerges as a putative target for therapeutic intervention in autoimmune disorders as well as in cancer, where T(R) cell-mediated suppression contributes to suboptimal local immune responses.

Mechanisms of protein kinase A anchoring

The second messenger cyclic adenosine monophosphate (cAMP), which is produced by adenylyl cyclases following stimulation of G-protein-coupled receptors, exerts its effect mainly through the cAMP-dependent serine/threonine protein kinase A (PKA). Due to the ubiquitous nature of the cAMP/PKA system, PKA signaling pathways underlie strict spatial and temporal control to achieve specificity. A-kinase anchoring proteins (AKAPs) bind to the regulatory subunit dimer of the tetrameric PKA holoenzyme and thereby target PKA to defined cellular compartments in the vicinity of its substrates. AKAPs promote the termination of cAMP signals by recruiting phosphodiesterases and protein phosphatases, and the integration of signaling pathways by binding additional signaling proteins. AKAPs are a heterogeneous family of proteins that only display similarity within their PKA-binding domains, amphipathic helixes docking into a hydrophobic groove formed by the PKA regulatory subunit dimer. This review summarizes the current state of information on compartmentalized cAMP/PKA signaling with a major focus on structural aspects, evolution, diversity, and (patho)physiological functions of AKAPs and intends to outline newly emerging directions of the field, such as the elucidation of AKAP mutations and alterations of AKAP expression in human diseases, and the validation of AKAP-dependent protein-protein interactions as new drug targets. In addition, alternative PKA anchoring mechanisms employed by noncanonical AKAPs and PKA catalytic subunit-interacting proteins are illustrated.

Microtubule-severing enzymes

In 1993, an enzyme with an ATP-dependent microtubule-severing activity was purified from sea urchin eggs and named katanin, after the Japanese word for sword. Now we know that katanin, spastin, and fidgetin form a family of closely related microtubule-severing enzymes that is widely distributed in eukaryotes ranging from Tetrahymena and Chlamydomonas to humans. Here we review the diverse in vivo functions of these proteins and the recent significant advances in deciphering the biophysical mechanism of microtubule severing.

Genome-wide association study of antipsychotic-induced parkinsonism severity among schizophrenia patients

RATIONALE

Antipsychotic-induced parkinsonism (AIP) is a severe adverse affect of neuroleptic treatment. Interindividual heterogeneity in AIP development and severity is associated with risk factors such as antipsychotic drug type, old age, and female gender. There is evidence for genetic predisposition to develop AIP but the variants that confer susceptibility or protection are mostly unknown.

OBJECTIVE

To identify genes related to AIP susceptibility, we performed a pharmacogenomic genome-wide association study (GWAS) for AIP severity.

METHODS

Three hundred ninety-seven American schizophrenia patients who participated in the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE)-GWAS project were included in our analysis. Patients had been randomized to treatment with antipsychotic monotherapy for periods ranging from 2 weeks to 18 months during phase 1 of the CATIE trial. They were regularly assessed for AIP severity using the modified Simpson-Angus Scale (SAS). For statistical analysis, patients were dichotomized as cases (average SAS mean global score > 0.3 during CATIE phase 1, N = 199) or controls (average SAS mean global score 0, N = 198).

RESULTS

Using logistic regression and controlling for population stratification, age, gender, SAS score at baseline, and concomitant use of anticholinergic drugs, we identified several single-nucleotide polymorphisms associated with AIP severity. Although none reached the GWAS significance level of P < 4.2 x 10(-7), some promising candidate genes for further research on genetic predisposition to AIP were identified including EPF1, NOVA1, and FIGN.

CONCLUSIONS

Our finding may contribute to understanding of the pathophysiology of AIP as well as to a priori identification of patients vulnerable for development of AIP.

Suppression of LPS-induced TNF-alpha production in macrophages by cAMP is mediated by PKA-AKAP95-p105

The activation of macrophages through Toll-like receptor (TLR) pathways leads to the production of a broad array of cytokines and mediators that coordinate the immune response. The inflammatory potential of this response can be reduced by compounds, such as prostaglandin E(2), that induce the production of cyclic adenosine monophosphate (cAMP). Through experiments with cAMP analogs and multigene RNA interference (RNAi), we showed that key anti-inflammatory effects of cAMP were mediated specifically by cAMP-dependent protein kinase (PKA). Selective inhibitors of PKA anchoring, time-lapse microscopy, and RNAi screening suggested that differential mechanisms of PKA action existed. We showed a specific role for A kinase-anchoring protein 95 in suppressing the expression of the gene encoding tumor necrosis factor-alpha, which involved phosphorylation of p105 (also known as Nfkb1) by PKA at a site adjacent to the region targeted by inhibitor of nuclear factor kappaB kinases. These data suggest that crosstalk between the TLR4 and cAMP pathways in macrophages can be coordinated through PKA-dependent scaffolds that localize specific pools of the kinase to distinct substrates.

AKAP-scaffolding proteins and regulation of cardiac physiology

A kinase anchoring proteins (AKAPs) compose a growing list of diverse but functionally related proteins defined by their ability to bind to the regulatory subunit of protein kinase A. AKAPs perform an integral role in the spatiotemporal modulation of a multitude of cellular signaling pathways. This review highlights the extensive role of AKAPs in cardiac excitation/contraction coupling and cardiac physiology. The literature shows that particular AKAPs are involved in cardiac Ca(2+) influx, release, reuptake, and myocyte repolarization. Studies have also suggested roles for AKAPs in cardiac remodeling. Transgenic studies show functional effects of AKAPs, not only in the cardiovascular system but in other organ systems as well.

A multi-angular mass spectrometric view at cyclic nucleotide dependent protein kinases: in vivo characterization and structure/function relationships

Mass spectrometry has evolved in recent years to a well-accepted and increasingly important complementary technique in molecular and structural biology. Here we review the many contributions mass spectrometry based studies have made in recent years in our understanding of the important cyclic nucleotide activated protein kinase A (PKA) and protein kinase G (PKG). We both describe the characterization of kinase isozymes, substrate phosphorylation, binding partners and post-translational modifications by proteomics based methodologies as well as their structural and functional properties as revealed by native mass spectrometry, H/D exchange MS and ion mobility. Combining all these mass spectrometry based data with other biophysical and biochemical data has been of great help to unravel the intricate regulation of kinase function in the cell in all its magnificent complexity.

The etiopathogenesis of cleft lip and cleft palate: usefulness and caveats of mouse models

Cleft lip and cleft palate are frequent human congenital malformations with a complex multifactorial etiology. These orofacial clefts can occur as part of a syndrome involving multiple organs or as isolated clefts without other detectable defects. Both forms of clefting constitute a heavy burden to the affected individuals and their next of kin. Human and mouse facial traits are utterly dissimilar. However, embryonic development of the lip and palate are strikingly similar in both species, making the mouse a model of choice to study their normal and abnormal development. Human epidemiological and genetic studies are clearly important for understanding the etiology of lip and palate clefting. However, our current knowledge about the etiopathogenesis of these malformations has mainly been gathered throughout the years from mouse models, including those with mutagen-, teratogen- and targeted mutation-induced clefts as well as from mice with spontaneous clefts. This review provides a comprehensive description of the numerous mouse models for cleft lip and/or cleft palate. Despite a few weak points, these models have revealed a high order of molecular complexity as well as the stringent spatiotemporal regulations and interactions between key factors which govern the development of these orofacial structures.

Coordinated expression of cytoskeleton regulating genes in the accelerated neurite outgrowth of P19 embryonic carcinoma cells

The embryonal carcinoma P19 cells provide a model to study neuronal differentiation. Cells that are exposed to retinoic acid become mature neurons within a few days with a pronounced axonal and dendritic polarity. Notably, an accelerated rate of neurite extension characterizes densely but not sparsely plated cells. DNA microarray experiments show maximal differences in gene expression of the dense compared to sparse plated cultures at 18 h after plating. The differentially expressed genes are enriched by functions of cell adhesion and cytoskeletal regulation. Doublecortin, Lis1, Reelin, Map2 and dozens of proteins that regulate cytoskeleton dynamics increase in concordance with a rapid neurite extension. A brief elevation in intracellular cAMP via PKA is sufficient to instigate the phenotype of accelerated neurite extension with no effect on P19 cell fate. Furthermore, we show that the cAMP dependent changes in the expression of cytoskeleton regulators such as doublecortin are restricted to a short time window prior to the establishment of functional neurons. We propose that the wave of gene expression of cytoskeletal regulators that is accompanied by accelerated neurite extension acts in remodeling young developing neurons in the CNS.

Three microtubule severing enzymes contribute to the "Pacman-flux" machinery that moves chromosomes

Chromosomes move toward mitotic spindle poles by a Pacman-flux mechanism linked to microtubule depolymerization: chromosomes actively depolymerize attached microtubule plus ends (Pacman) while being reeled in to spindle poles by the continual poleward flow of tubulin subunits driven by minus-end depolymerization (flux). We report that Pacman-flux in Drosophila melanogaster incorporates the activities of three different microtubule severing enzymes, Spastin, Fidgetin, and Katanin. Spastin and Fidgetin are utilized to stimulate microtubule minus-end depolymerization and flux. Both proteins concentrate at centrosomes, where they catalyze the turnover of γ-tubulin, consistent with the hypothesis that they exert their influence by releasing stabilizing γ-tubulin ring complexes from minus ends. In contrast, Katanin appears to function primarily on anaphase chromosomes, where it stimulates microtubule plus-end depolymerization and Pacman-based chromatid motility. Collectively, these findings reveal novel and significant roles for microtubule severing within the spindle and broaden our understanding of the molecular machinery used to move chromosomes.