Factor Analysis of Patients Who Find Tablets or Capsules Difficult to Swallow Due to Their Large Size: Using the Personal Health Record Infrastructure of Electronic Medication Notebooks.

BACKGROUND: Understanding patient preference regarding taking tablet or capsule formulations plays a pivotal role in treatment efficacy and adherence. Therefore, these preferences should be taken into account when designing formulations and prescriptions. OBJECTIVE: This study investigates the factors affecting patient preference in patients who have difficulties swallowing large tablets or capsules and aims to identify appropriate sizes for tablets and capsules. METHODS: A robust data set was developed based on a questionnaire survey conducted from December 1, 2022, to December 7, 2022, using the harmo smartphone app operated by harmo Co, Ltd. The data set included patient input regarding their tablet and capsule preferences, personal health records (including dispensing history), and drug formulation information (available from package inserts). Based on the medication formulation information, 6 indices were set for each of the tablets or capsules that were considered difficult to swallow owing to their large size and concomitant tablets or capsules (used as controls). Receiver operating characteristic (ROC) analysis was used to evaluate the performance of each index. The index demonstrating the highest area under the curve of the ROC was selected as the best index to determine the tablet or capsule size that leads to swallowing difficulties. From the generated ROCs, the point with the highest discriminative performance that maximized the Youden index was identified, and the optimal threshold for each index was calculated. Multivariate logistic regression analysis was performed to identify the risk factors contributing to difficulty in swallowing oversized tablets or capsules. Additionally, decision tree analysis was performed to estimate the combined risk from several factors, using risk factors that were significant in the multivariate logistic regression analysis. RESULTS: This study analyzed 147 large tablets or capsules and 624 control tablets or capsules. The "long diameter + short diameter + thickness" index (with a 21.5 mm threshold) was identified as the best indicator for causing swallowing difficulties in patients. The multivariate logistic regression analysis (including 132 patients with swallowing difficulties and 1283 patients without) results identified the following contributory risk factors: aged <50 years (odds ratio [OR] 1.59, 95% CI 1.03-2.44), female (OR 2.54, 95% CI 1.70-3.78), dysphagia (OR 3.54, 95% CI 2.22-5.65), and taking large tablets or capsules (OR 9.74, 95% CI 5.19-18.29). The decision tree analysis results suggested an elevated risk of swallowing difficulties for patients with taking large tablets or capsules. CONCLUSIONS: This study identified the most appropriate index and threshold for indicating that a given tablet or capsule size will cause swallowing difficulties, as well as the contributory risk factors. Although some sampling biases (eg, only including smartphone users) may exist, our results can guide the design of patient-friendly formulations and prescriptions, promoting better medication adherence.

A novel mitosis-specific Cep215 domain interacts with Cep192 and phosphorylated Aurora A for organization of spindle poles.

The centrosome, which consists of centrioles and pericentriolar material (PCM), becomes mature and assembles mitotic spindles by increasing the number of microtubules (MTs) emanating from the PCM. Among the molecules involved in centrosome maturation, Cep192 and Aurora A (AurA, also known as AURKA) are primarily responsible for recruitment of γ-tubulin and MT nucleators, whereas pericentrin (PCNT) is required for PCM organization. However, the role of Cep215 (also known as CDK5RAP2) in centrosome maturation remains elusive. Cep215 possesses binding domains for γ-tubulin, PCNT and MT motors that transport acentrosomal MTs towards the centrosome. We identify a mitosis-specific centrosome-targeting domain of Cep215 (215N) that interacts with Cep192 and phosphorylated AurA (pAurA). Cep192 is essential for targeting 215N to centrosomes, and centrosomal localization of 215N and pAurA is mutually dependent. Cep215 has a relatively minor role in γ-tubulin recruitment to the mitotic centrosome. However, it has been shown previously that this protein is important for connecting mitotic centrosomes to spindle poles. Based on the results of rescue experiments using versions of Cep215 with different domain deletions, we conclude that Cep215 plays a role in maintaining the structural integrity of the spindle pole by providing a platform for the molecules involved in centrosome maturation.

MCPH1 is essential for cellular adaptation to the G2-phase decatenation checkpoint.

Cellular checkpoints controlling entry into mitosis monitor the integrity of the DNA and delay mitosis onset until the alteration is fully repaired. However, this canonical response can weaken, leading to a spontaneous bypass of the checkpoint, a process referred to as checkpoint adaptation. Here, we have investigated the contribution of microcephalin 1 (MCPH1), mutated in primary microcephaly, to the decatenation checkpoint, a less-understood G2 pathway that delays entry into mitosis until chromosomes are properly disentangled. Our results demonstrate that, although MCPH1 function is dispensable for activation and maintenance of the decatenation checkpoint, it is required for the adaptive response that bypasses the topoisomerase II inhibition----mediated G2 arrest. MCPH1, however, does not confer adaptation to the G2 arrest triggered by the ataxia telangiectasia mutated- and ataxia telangiectasia and rad3 related-based DNA damage checkpoint. In addition to revealing a new role for MCPH1 in cell cycle control, our study provides new insights into the genetic requirements that allow cellular adaptation to G2 checkpoints, a process that remains poorly understood.-Arroyo, M., Kuriyama, R., Guerrero, I., Keifenheim, D., Cañuelo, A., Calahorra, J., Sánchez, A., Clarke, D. J., Marchal, J. A. MCPH1 is essential for cellular adaptation to the G2-phase decatenation checkpoint.

Differential control of Eg5-dependent centrosome separation by Plk1 and Cdk1.

Cyclin-dependent kinase 1 (Cdk1) is thought to trigger centrosome separation in late G2 phase by phosphorylating the motor protein Eg5 at Thr927. However, the precise control mechanism of centrosome separation remains to be understood. Here, we report that in G2 phase polo-like kinase 1 (Plk1) can trigger centrosome separation independently of Cdk1. We find that Plk1 is required for both C-Nap1 displacement and for Eg5 localization on the centrosome. Moreover, Cdk2 compensates for Cdk1, and phosphorylates Eg5 at Thr927. Nevertheless, Plk1-driven centrosome separation is slow and staggering, while Cdk1 triggers fast movement of the centrosomes. We find that actin-dependent Eg5-opposing forces slow down separation in G2 phase. Strikingly, actin depolymerization, as well as destabilization of interphase microtubules (MTs), is sufficient to remove this obstruction and to speed up Plk1-dependent separation. Conversely, MT stabilization in mitosis slows down Cdk1-dependent centrosome movement. Our findings implicate the modulation of MT stability in G2 and M phase as a regulatory element in the control of centrosome separation.

Myosin phosphatase targeting subunit1 controls localization and motility of Rab7-containing vesicles: Is myosin phosphatase a cytoplasmic dynein regulator?

Myosin phosphatase targeting subunit1 (MYPT1) is a critical subunit of myosin phosphatase (MP), which brings PP1Cδ phosphatase and its substrate together. We previously showed that MYPT1 depletion resulted in oblique chromatid segregation. Therefore, we hypothesized that MYPT1 may control microtubule-dependent motor activity. Dynein, a minus-end microtubule motor, is known to be involved in mitotic spindle assembly. We thus examined whether MYPT1 and dynein may interact. Proximity ligation assay and co-immunoprecipitation revealed that MYPT1 and dynein intermediate chain (DIC) were associated. We found that DIC phosphorylation is increased in MYPT1-depleted cells in vivo, and that MP was able to dephosphorylate DIC in vitro. MYPT1 depletion also altered the localization and motility of Rab7-containing vesicles. MYPT1-depletion dispersed the perinuclear Rab7 localization to the peripheral in interphase cells. The dispersed Rab7 localization was rescued by microinjection of a constitutively active, truncated MYPT1 mutant, supporting that MP is responsible for the altered Rab7 localization. Analyses of Rab7 vesicle trafficking also revealed that minus-end transport was reduced in MYPT1-depleted cells. These results suggest an unexpected role of MP: MP controls dynein activity in both mitotic and interphase cells, possibly by dephosphorylating dynein subunits including DIC.

Centriole assembly in CHO cells expressing Plk4/SAS6/SAS4 is similar to centriogenesis in ciliated epithelial cells.

Centriole assembly is initiated by Plk4, a Polo-like kinase 4, which causes the recruitment of downstream regulators, such as SAS6 and SAS4, to a nascent centriole. Simultaneous expression of Plk4, SAS6 and SAS4 in CHO cells resulted in the formation of massive fibrogranular aggregates of various sizes and shapes. These aggregates were surrounded by dense particles of about 70 nm in diameter, similar to the centriolar satellite that has been observed around the centrosome in normal cycling cells. Within the fibrillar material, ring-like structures appeared and eventually differentiated into centrioles by association with short microtubule bundles. Centrioles were also assembled around a parent centriole in a cluster, a configuration that has been described as a "flower structure" formation [Kleylein-Sohn et al.,2007]. This pattern of centriole duplication is reminiscent of the arrangement of new centrioles induced in normal ciliated trachea/oviduct cells by the centriole-dependent pathway, which was reported several decades ago [Sorokin,1968; Anderson and Brenner,1971; Dirksen,1971]. Prior to the production of hundreds of centrioles, these differentiating epithelial cells were also shown to induce a dense filamentous material similar to that detected in transfected CHO cells. These results suggest a common mechanism of centriole assembly regulated by Plk4 in both transfected cycling cells and normal ciliated epithelial cells undergoing differentiation. Cell Motil. Cytoskeleton 2009. (c) 2009 Wiley-Liss, Inc.

Interaction of Aurora-A and centrosomin at the microtubule-nucleating site in Drosophila and mammalian cells.

A mitosis-specific Aurora-A kinase has been implicated in microtubule organization and spindle assembly in diverse organisms. However, exactly how Aurora-A controls the microtubule nucleation onto centrosomes is unknown. Here, we show that Aurora-A specifically binds to the COOH-terminal domain of a Drosophila centrosomal protein, centrosomin (CNN), which has been shown to be important for assembly of mitotic spindles and spindle poles. Aurora-A and CNN are mutually dependent for localization at spindle poles, which is required for proper targeting of gamma-tubulin and other centrosomal components to the centrosome. The NH2-terminal half of CNN interacts with gamma-tubulin, and induces cytoplasmic foci that can initiate microtubule nucleation in vivo and in vitro in both Drosophila and mammalian cells. These results suggest that Aurora-A regulates centrosome assembly by controlling the CNN's ability to targeting and/or anchoring gamma-tubulin to the centrosome and organizing microtubule-nucleating sites via its interaction with the COOH-terminal sequence of CNN.

CHO1, a mammalian kinesin-like protein, interacts with F-actin and is involved in the terminal phase of cytokinesis.

CHO1 is a kinesin-like protein of the mitotic kinesin-like protein (MKLP)1 subfamily present in central spindles and midbodies in mammalian cells. It is different from other subfamily members in that it contains an extra approximately 300 bp in the COOH-terminal tail. Analysis of the chicken genomic sequence showed that heterogeneity is derived from alternative splicing, and exon 18 is expressed in only the CHO1 isoform. CHO1 and its truncated isoform MKLP1 are coexpressed in a single cell. Surprisingly, the sequence encoded by exon 18 possesses a capability to interact with F-actin, suggesting that CHO1 can associate with both microtubule and actin cytoskeletons. Microinjection of exon 18-specific antibodies did not result in any inhibitory effects on karyokinesis and early stages of cytokinesis. However, almost completely separated daughter cells became reunited to form a binulceate cell, suggesting that the exon 18 protein may not have a role in the formation and ingression of the contractile ring in the cortex. Rather, it might be involved directly or indirectly in the membrane events necessary for completion of the terminal phase of cytokinesis.

Characterization of Cep135, a novel coiled-coil centrosomal protein involved in microtubule organization in mammalian cells.

By using monoclonal antibodies raised against isolated clam centrosomes, we have identified a novel 135-kD centrosomal protein (Cep135), present in a wide range of organisms. Cep135 is located at the centrosome throughout the cell cycle, and localization is independent of the microtubule network. It distributes throughout the centrosomal area in association with the electron-dense material surrounding centrioles. Sequence analysis of cDNA isolated from CHO cells predicted a protein of 1,145-amino acid residues with extensive alpha-helical domains. Expression of a series of deletion constructs revealed the presence of three independent centrosome-targeting domains. Overexpression of Cep135 resulted in the accumulation of unique whorl-like particles in both the centrosome and the cytoplasm. Although their size, shape, and number varied according to the level of protein expression, these whorls were composed of parallel dense lines arranged in a 6-nm space. Altered levels of Cep135 by protein overexpression and/or suppression of endogenous Cep135 by RNA interference caused disorganization of interphase and mitotic spindle microtubules. Thus, Cep135 may play an important role in the centrosomal function of organizing microtubules in mammalian cells.

Requirement of hCenexin for proper mitotic functions of polo-like kinase 1 at the centrosomes.

Outer dense fiber 2 (Odf2) was initially identified as a major component of sperm tail cytoskeleton and later was suggested to be a widespread component of centrosomal scaffold that preferentially associates with the appendages of the mother centrioles in somatic cells. Here we report the identification of two Odf2-related centrosomal components, hCenexin1 and hCenexin1 variant 1, that possess a unique C-terminal extension. Our results showed that hCenexin1 is the major isoform expressed in HeLa cells, whereas hOdf2 is not detectably expressed. Mammalian polo-like kinase 1 (Plk1) is critical for proper mitotic progression, and its association with the centrosome is important for microtubule nucleation and function. Interestingly, depletion of hCenexin1 by RNA interference (RNAi) delocalized Plk1 from the centrosomes and the C-terminal extension of hCenexin1 was crucial to recruit Plk1 to the centrosomes through a direct interaction with the polo-box domain of Plk1. Consistent with these findings, the hCenexin1 RNAi cells exhibited weakened gamma-tubulin localization and chromosome segregation defects. We propose that hCenexin1 is a critical centrosomal component whose C-terminal extension is required for proper recruitment of Plk1 and other components crucial for normal mitosis. Our results further suggest that the anti-Odf2 immunoreactive centrosomal antigen previously detected in non-germ line cells is likely hCenexin1.

Role of the midbody matrix in cytokinesis: RNAi and genetic rescue analysis of the mammalian motor protein CHO1.

CHO1 is a kinesin-like motor protein essential for cytokinesis in mammalian cells. To analyze how CHO1 functions, we established RNAi and genetic rescue assays. CHO1-depleted cells reached a late stage of cytokinesis but fused back to form binucleate cells because of the absence of the midbody matrix in the middle of the intercellular bridge. Expression of exogenous CHO1 restored the formation of the midbody matrix and rescued cytokinesis in siRNA-treated cells. By analyzing phenotypes rescued with different constructs, it was shown that both motor and stalk domains function in midbody formation, whereas the tail is essential for completion of cytokinesis after the midbody matrix has formed. During the terminal stage of cytokinesis, different subregions of the tail play distinctive roles in stabilizing the midbody matrix and maintaining an association between the midbody and cell cortex. These results demonstrate that CHO1 consists of functionally differentiated subregions that act in concert to ensure complete cell separation.

Kinesin-like protein CHO1 is required for the formation of midbody matrix and the completion of cytokinesis in mammalian cells.

CHO1 is a mammalian kinesin-like motor protein of the MKLP1 subfamily. It associates with the spindle midzone during anaphase and concentrates to a midbody matrix during cytokinesis. CHO1 was originally implicated in karyokinesis, but the invertebrate homologues of CHO1 were shown to function in the midzone formation and cytokinesis. To analyze the role of the protein in mammalian cells, we mutated the ATP-binding site of CHO1 and expressed it in CHO cells. Mutant protein (CHO1F') was able to interact with microtubules via ATP-independent microtubule-binding site(s) but failed to accumulate at the midline of the central spindle and affected the localization of endogenous CHO1. Although the segregation of chromosomes, the bundling of midzone microtubules, and the initiation of cytokinesis proceeded normally in CHO1F'-expressing cells, the completion of cytokinesis was inhibited. Daughter cells were frequently entering interphase while connected by a microtubule-containing cytoplasmic bridge from which the dense midbody matrix was missing. Depletion of endogenous CHO1 via RNA-mediated interference also affected the formation of midbody matrix in dividing cells, caused the disorganization of midzone microtubules, and resulted in abortive cytokinesis. Thus, CHO1 may not be required for karyokinesis, but it is essential for the proper midzone/midbody formation and cytokinesis in mammalian cells.

The G-protein regulatory (GPR) motif-containing Leu-Gly-Asn-enriched protein (LGN) and Gialpha3 influence cortical positioning of the mitotic spindle poles at metaphase in symmetrically dividing mammalian cells.

We addressed the role of the G-protein regulatory (GPR) motif-containing Leu-Gly-Asn-enriched protein (LGN) and G-proteins (Gialpha3) in the positioning of the spindle pole during mammalian cell division. Immunocytochemistry indicated that both LGN and Gialpha3 co-localized at the spindle pole and at the midbody and the cell cortex during the different phases of mitosis. In marked contrast to the positioning of the spindle pole at metaphase midway between the cell cortex and the metaphase plate, the spindle pole was juxtaposed with the cell cortex at metaphase following increased expression of Gialpha3 and LGN. This repositioning of the spindle pole required the interaction of LGN with Gialpha. The influence of LGN and Gialpha3 on the cortical positioning of the spindle pole likely reflects either stronger pulling forces on the spindle pole exerted from the cell cortex or increased pushing forces exerted on the spindle pole from the mitotic spindle indicating that these events are regulated by GPR motif-containing proteins and G-proteins independent of asymmetry.

BAR Domain-Containing FAM92 Proteins Interact with Chibby1 To Facilitate Ciliogenesis.

Chibby1 (Cby1) is a small, conserved coiled-coil protein that localizes to centrioles/basal bodies and plays a crucial role in the formation and function of cilia. During early stages of ciliogenesis, Cby1 is required for the efficient recruitment of small vesicles at the distal end of centrioles to facilitate basal body docking to the plasma membrane. Here, we identified family with sequence similarity 92, member A (FAM92A) and FAM92B, which harbor predicted lipid-binding BAR domains, as novel Cby1-interacting partners using tandem affinity purification and mass spectrometry. We found that in cultured cell lines, FAM92A colocalizes with Cby1 at the centrioles/basal bodies of primary cilia, while FAM92B is undetectable. In airway multiciliated cells, both FAM92A and -92B colocalize with Cby1 at the base of cilia. Notably, the centriolar localization of FAM92A and -92B depends largely on Cby1. Knockdown of FAM92A in RPE1 cells impairs ciliogenesis. Consistent with the membrane-remodeling properties of BAR domains, FAM92A and -92B in cooperation with Cby1 induce deformed membrane-like structures containing the small GTPase Rab8 in cultured cells. Our results therefore suggest that FAM92 proteins interact with Cby1 to promote ciliogenesis via regulation of membrane-remodeling processes.

Differential Response to High Glucose in Skin Fibroblasts of Monozygotic Twins Discordant for Type 1 Diabetes.

CONTEXT: Most epigenetic studies in diabetes compare normal cells in "high glucose" (HG) to cells in "normal glucose" (NG) and cells returned from HG to NG. Here we challenge this approach. OBJECTIVE: The objective was to determine whether there were differences in gene expression in skin fibroblasts of monozygotic twins (MZT) discordant for type 1 diabetes (T1D). DESIGN: Skin fibroblasts were grown in NG (5.5 mmol/L) and HG (25 mmol/L) for multiple passages. SETTING: This study was conducted at the University of Minnesota. PATIENTS: Patients were nine MZT pairs discordant for T1D. MAIN OUTCOME MEASURE(S): Gene expression was assessed by mRNA-Seq, using the Illumina HiSeq 2000 instrument. Pathway analysis tested directionally consistent group differences within the Kyoto Encyclopedia of Genes and Genomes pathways. RESULTS: A total of 3308 genes were differentially expressed between NG and HG in T1D MZT vs 889 in non-T1D twins. DNA replication, proteasome, cell cycle, base excision repair, homologous recombination, pyrimidine metabolism, and spliceosome pathways had overrepresented genes with increased expression in T1D twins with P values ranging from 7.21 × 10(-10) to 1.39 × 10(-4). In a companion article, we demonstrate that these pathway changes are related to diabetic nephropathy risk. There were no pathways statistically significant differently expressed in nondiabetic twins in HG vs NG. CONCLUSIONS: In vivo exposure to diabetes alters cells in a manner that markedly changes their in vitro responses to HG. These results highlight the importance of using cells directly derived from diabetic patients for studies examining the effects of HG in diabetes.

THE MITOTIC APPARATUS ISOLATED IN GLYCEROL-CONTAINING MEDIUM.

The mitotic apparatus of the sea urchin egg was isolated at 30°C in an isolation medium containing glycerol which is known to stabilize microtubules. After isolation in the 1 m glycerol-isolation medium, the mitotic apparatus was stabilized on addition of glycerol to a final concentration of 3 to 4 m. Without the addition, the chromosomes were disjoined from the spindle and the interzonal region between separating chromosomes was fragile resulting in separation of half spindles. Lowering the temperature of the isolation medium to 20°C or below, the isolation procedure allowed to isolate spindles. The isolated spindle behaved in a manner similar to the mitotic apparatus on the effect of glycerol concentration. The glycerol-mitotic apparatus contained tubulin which was extractable with the isolation medium containing Ca ions or an organic mercurial. Tubulin was also extracted upon lowering the temperature to 0°C in the presence of GTP. Addition of KCl to a final concentration of 0.6 m immediately dispersed the mitotic apparatus. The extract revealed a colchicine binding of 0.001 mole per 105,000 ×g of protein. The colchicine binding complex was found to have a molecular weight of 105,000. The DEAE Sephadex column chromatography of the KCl extract allowed to elute tubulin fraction which bound 0.1 mole colchicine per 105,000 ×g of protein. The mitotic apparatus tubulin was shown to contain α and ß subunits with mobilities quite identical with those of brain tubulin subunits. The molecular weights of the α and ß subunits were 55,000 ± 1,000 and 51,000 ± 1,000, respectively.

THE GLYCEROL-ISOLATED MITOTIC APPARATUS: A RESPONSE TO PORCINE BRAIN TUBULIN AND INDUCTION OF CHROMOSOME MOTION.

The birefringence of the MAs or spindles isolated from sea urchin eggs with the 1 M glycerol-isolation medium was stabilized when more than 0.5 mg/ml tubulin was contained in the medium. The addition of glycerol up to a final concentration of of 4 M strongly stabilized the MAs even in the absence of GTP and tubulin. The birefringence of the spindle and asters was not reduced even for the periods of several hours. The incorporation of heterogeneous tubulin into the isolated anaphase MAs was demonstrated by augmentation of the birefringence at the interzonal region as well as half spindles accompanied by enlargement of spindle and asters. In the anaphase MAs isolated in the absence of brain tubulin, chromosomes moved a short distance toward the poles upon addition of ATP, Mg2+ and 0.5 mg/ml tubulin. When the MAs were isolated in the presence of 0.5 mg/ml tubulin, the chromosomes moved in a more regular fashion to half the way to the poles accompanied by an increase in spindle length by 10 to 15%. GTP could not be substituted for ATP for inducing the motion. The chromosome motion of the isolated anaphase spindle was less significant than that of the isolated MA. Increasing tubulin concentration to 3 mg/ml, the chromosomes in the isolated MA separated at random by an unusual growth of the spindle. The stretch of the interzonal region by incorporating heterogeneous tubulin seemed to push the chromosomes apart abnormally. It was suggested that brain tubulin in a range of 0.5 mg/ml supports a tubulin-MA microtubule equilibrium favoring more regular motion of chromosomes in vitro.

INDUCTION OF CHROMOSOME MOTION IN THE GLYCEROL-ISOLATED MITOTIC APPARATUS: NUCLEOTIDE SPECIFICITY AND EFFECTS OF ANTIDYNEIN AND MYOSIN SERA ON THE MOTION.

Chromosome motion in glycerol-isolated mitotic apparatus (MA) of sea urchin and starfish eggs was investigated with respect to nucleotide specificity and the effects of antisera against tryptic fragment (Fragment A) of flagellar dynein and starfish egg myosin. The motion was highly specific for ATP. GTP, ITP, CTP, UTP, and ADP caused no displacement of the chromosomes towards the poles. The anti-Fragment A serum completely inhibited chromosome motion in the MA of the sea urchin egg, while antiserum against starfish egg myosin as well as its γ-globulin fraction did not inhibit the motion in the isolated MA of the starfish egg, suggesting that chromosome motion depends upon dynein-microtubule but not upon myosin-actin interaction. In addition, colchicine completely suppressed the chromosome motion in vitro.

Chibby promotes ciliary vesicle formation and basal body docking during airway cell differentiation.

Airway multiciliated epithelial cells play crucial roles in the mucosal defense system, but their differentiation process remains poorly understood. Mice lacking the basal body component Chibby (Cby) exhibit impaired mucociliary transport caused by defective ciliogenesis, resulting in chronic airway infection. In this paper, using primary cultures of mouse tracheal epithelial cells, we show that Cby facilitates basal body docking to the apical cell membrane through proper formation of ciliary vesicles at the distal appendage during the early stages of ciliogenesis. Cby is recruited to the distal appendages of centrioles via physical interaction with the distal appendage protein CEP164. Cby then associates with the membrane trafficking machinery component Rabin8, a guanine nucleotide exchange factor for the small guanosine triphosphatase Rab8, to promote recruitment of Rab8 and efficient assembly of ciliary vesicles. Thus, our study identifies Cby as a key regulator of ciliary vesicle formation and basal body docking during the differentiation of airway ciliated cells.

Abnormal centrosomal structure and duplication in Cep135-deficient vertebrate cells.

Centrosomes are key microtubule-organizing centers that contain a pair of centrioles, conserved cylindrical, microtubule-based structures. Centrosome duplication occurs once per cell cycle and relies on templated centriole assembly. In many animal cells this process starts with the formation of a radially symmetrical cartwheel structure. The centrosomal protein Cep135 localizes to this cartwheel, but its role in vertebrates is not well understood. Here we examine the involvement of Cep135 in centriole function by disrupting the Cep135 gene in the DT40 chicken B-cell line. DT40 cells that lack Cep135 are viable and show no major defects in centrosome composition or function, although we note a small decrease in centriole numbers and a concomitant increase in the frequency of monopolar spindles. Furthermore, electron microscopy reveals an atypical structure in the lumen of Cep135-deficient centrioles. Centrosome amplification after hydroxyurea treatment increases significantly in Cep135-deficient cells, suggesting an inhibitory role for the protein in centrosome reduplication during S-phase delay. We propose that Cep135 is required for the structural integrity of centrioles in proliferating vertebrate cells, a role that also limits centrosome amplification in S-phase-arrested cells.