Mck1-mediated proteolysis of CENP-A prevents mislocalization of CENP-A for chromosomal stability in Saccharomyces cerevisiae.

Centromeric localization of evolutionarily conserved CENP-A (Cse4 in Saccharomyces cerevisiae) is essential for chromosomal stability. Mislocalization of overexpressed CENP-A to non-centromeric regions contributes to chromosomal instability (CIN) in yeasts, flies, and humans. Overexpression and mislocalization of CENP-A observed in many cancers is associated with poor prognosis. Previous studies have shown that F-box proteins, Cdc4 and Met30 of the Skp, Cullin, F-box (SCF) ubiquitin ligase cooperatively regulate proteolysis of Cse4 to prevent Cse4 mislocalization and CIN under normal physiological conditions. Mck1-mediated phosphorylation of SCF-Cdc4 substrates such as Cdc6 and Rcn1 enhances the interaction of the substrates with Cdc4. Here, we report that Mck1 interacts with Cse4, and Mck1-mediated proteolysis of Cse4 prevents Cse4 mislocalization for chromosomal stability. Our results showed that mck1Δ strain overexpressing CSE4 (GAL-CSE4) exhibits lethality, defects in ubiquitin-mediated proteolysis of Cse4, mislocalization of Cse4 and reduced Cse4-Cdc4 interaction. Strain expressing GAL-cse4-3A with mutations in three potential Mck1 phosphorylation consensus site (S10, S16, and T166) also exhibits growth defects, increased stability with mislocalization of Cse4-3A, CIN, and reduced interaction with Cdc4. Constitutive expression of histone H3 (Δ16H3) suppresses the CIN phenotype of GAL-cse4-3A strain, suggesting that the CIN phenotype is linked to Cse4-3A mislocalization. We conclude that Mck1 and its three potential phosphorylation sites on Cse4 promote Cse4-Cdc4 interaction and this contributes to ubiquitin-mediated proteolysis of Cse4 preventing its mislocalization and CIN. These studies advance our understanding of pathways that regulate cellular levels of CENP-A to prevent mislocalization of CENP-A in human cancers.

DNAJC9 prevents CENP-A mislocalization and chromosomal instability by maintaining the fidelity of histone supply chains.

The centromeric histone H3 variant CENP-A is overexpressed in many cancers. The mislocalization of CENP-A to noncentromeric regions contributes to chromosomal instability (CIN), a hallmark of cancer. However, pathways that promote or prevent CENP-A mislocalization remain poorly defined. Here, we performed a genome-wide RNAi screen for regulators of CENP-A localization which identified DNAJC9, a J-domain protein implicated in histone H3-H4 protein folding, as a factor restricting CENP-A mislocalization. Cells lacking DNAJC9 exhibit mislocalization of CENP-A throughout the genome, and CIN phenotypes. Global interactome analysis showed that DNAJC9 depletion promotes the interaction of CENP-A with the DNA-replication-associated histone chaperone MCM2. CENP-A mislocalization upon DNAJC9 depletion was dependent on MCM2, defining MCM2 as a driver of CENP-A deposition at ectopic sites when H3-H4 supply chains are disrupted. Cells depleted for histone H3.3, also exhibit CENP-A mislocalization. In summary, we have defined novel factors that prevent mislocalization of CENP-A, and demonstrated that the integrity of H3-H4 supply chains regulated by histone chaperones such as DNAJC9 restrict CENP-A mislocalization and CIN.

Mad honey poisoning presenting with syncopal attack: a case report.

Mad honey contains grayanotoxin, which is commonly derived from the nectar of a few Rhododendron species. It is commonly used by natives of the Himalayas in the belief of its medicinal use. Case presentation: The authors report a case of 62 years old male with mad honey poisoning who was presented to the emergency department with loss of consciousness and had bradycardia and hypotension on arrival. The patient received intravenous fluids, atropine, and vasopressor support and was closely monitored in the coronary care unit for 48 h. Discussion: Grayanotoxin I and II are believed to be primarily responsible for mad honey intoxication and act by persistent activation of voltage-gated sodium channels. Hypotension, dizziness, nausea, vomiting, and impaired consciousness are the common presentation of mad honey intoxication. Toxic effects are usually mild and close monitoring for 24-48 h is sufficient but life-threatening complications like cardiac asystole, convulsions, and myocardial infarction have also been reported. Conclusion: Most cases of mad honey intoxication only need symptomatic treatment and close observation but the potential for deterioration and life-threatening complications must also be considered.

The histone H3/H4 chaperone CHAF1B prevents the mislocalization of CENP-A for chromosomal stability.

Restricting the localization of the evolutionarily conserved centromeric histone H3 variant CENP-A to centromeres prevents chromosomal instability (CIN). The mislocalization of CENP-A to non-centromeric regions contributes to CIN in yeasts, flies and human cells. Even though overexpression and mislocalization of CENP-A have been reported in cancers, the mechanisms responsible for its mislocalization remain poorly understood. Here, we used an imaging-based high-throughput RNAi screen to identify factors that prevent mislocalization of overexpressed YFP-tagged CENP-A (YFP-CENP-A) in HeLa cells. Among the top five candidates in the screen - the depletion of which showed increased nuclear YFP-CENP-A fluorescence - were the histone chaperones CHAF1B (or p60) and CHAF1A (or p150). Follow-up validation and characterization experiments showed that CHAF1B-depleted cells exhibited CENP-A mislocalization, CIN phenotypes and increased enrichment of CENP-A in chromatin fractions. The depletion of DAXX, a histone H3.3 chaperone, suppressed CENP-A mislocalization and CIN in CHAF1B-depleted cells. We propose that in CHAF1B-depleted cells, DAXX promotes mislocalization of the overexpressed CENP-A to non-centromeric regions, resulting in CIN. In summary, we identified regulators of CENP-A localization and defined a role for CHAF1B in preventing DAXX-dependent CENP-A mislocalization and CIN.

Matrin3 regulates mitotic spindle dynamics by controlling alternative splicing of CDC14B.

Matrin3 is an RNA-binding protein that regulates diverse RNA-related processes, including mRNA splicing. Although Matrin3 has been intensively studied in neurodegenerative diseases, its function in cancer remains unclear. Here, we report Matrin3-mediated regulation of mitotic spindle dynamics in colorectal cancer (CRC) cells. We comprehensively identified RNAs bound and regulated by Matrin3 in CRC cells and focused on CDC14B, one of the top Matrin3 targets. Matrin3 knockdown results in increased inclusion of an exon containing a premature termination codon in the CDC14B transcript and simultaneous down-regulation of the standard CDC14B transcript. Knockdown of CDC14B phenocopies the defects in mitotic spindle dynamics upon Matrin3 knockdown, and the elongated and misoriented mitotic spindle observed upon Matrin3 knockdown are rescued upon overexpression of CDC14B, suggesting that CDC14B is a key downstream effector of Matrin3. Collectively, these data reveal a role for the Matrin3/CDC14B axis in control of mitotic spindle dynamics.

Context-Dependent Function of Long Noncoding RNA PURPL in Transcriptome Regulation during p53 Activation.

PURPL is a p53-induced lncRNA that suppresses basal p53 levels. Here, we investigated PURPL upon p53 activation in liver cancer cells, where it is expressed at significantly higher levels than other cell types. Using isoform sequencing, we discovered novel PURPL transcripts that have a retained intron and/or previously unannotated exons. To determine PURPL function upon p53 activation, we performed transcriptome sequencing (RNA-Seq) after depleting PURPL using CRISPR interference (CRISPRi), followed by Nutlin treatment to induce p53. Strikingly, although loss of PURPL in untreated cells altered the expression of only 7 genes, loss of PURPL resulted in altered expression of ~800 genes upon p53 activation, revealing a context-dependent function of PURPL. Pathway analysis suggested that PURPL is important for fine-tuning the expression of specific genes required for mitosis. Consistent with these results, we observed a significant decrease in the percentage of mitotic cells upon PURPL depletion. Collectively, these data identify novel transcripts from the PURPL locus and suggest that PURPL delicately moderates the expression of mitotic genes in the context of p53 activation to control cell cycle arrest.

Pregnancy with heart disease in South Asia: A systematic review and meta-analysis of prevalence and outcome.

Background: The prevalence and paradigm of antenatal heart disease are contrasting between high-income, industrialized, and low- and middle-income countries. In this systematic review, we report the prevalence of heart disease and its spectrum in pregnant women of South Asia. Methods: We searched through different electronic databases (PubMed, Google-scholar, Embase, Cochrane Library) to locate relevant articles. Studies with sufficient data that met our inclusion criteria were included. Two reviewers independently screened the articles. Discrepancies were resolved by other reviewers. Subsequently, data extraction was done using a standardized form and quality assessment of studies using the Joanna Briggs Institute tool. Meta-analysis was done using R software. Results: After various stages of screening 25 studies were included in the final quantitative synthesis. The pooled prevalence of heart disease among pregnant women was 1.46% (95% CI 0.99-2.01). Among those with heart disease, 70.25% (95% CI 64.87-75.38) had Rheumatic heart disease and 18.10% (95% CI 14.39-22.12) had congenital heart disease. The pooled prevalence of preterm labor and delivery among pregnant women with heart disease was 17.63% (95% CI 12.18-23.80). Similarly, the pooled maternal and fetal mortality rates were 26.14 (95% CI 12.47-43.55) and 50.48 (95% CI 29.59-75.83) per 1000 pregnant women with heart disease respectively. Conclusion: As pregnancy, itself is a prolonged state of physiologic stress, heart disease further adds to the risk both for the mother and fetus. Having such a high prevalence, efforts must be made to detect and closely monitor the condition antenatally, and decisions should be made according to the clinical conditions of the patient.

Interaction of Phthalates with Lipid Bilayer Membranes.

Phthalates are esters of phthalic acid, widely used as additives in the manufacture of plastics. They are not covalently linked to polymer chains and can easily leach out, disperse in the environment, and get into contact with living organisms. Several short chain phthalates are classified as endocrine disruptors or hormonal active agents, and have also been reported to promote various kinds of cancer. However, the biological effects of longer chain analogues are less well known. Moreover, little is known on the permeation of phthalates and their metabolites through biological membranes and on their effects on the physical properties of membranes. Here we explore the interaction of a group of phthalates and their main metabolites with model biological membranes. We focus on three industrially relevant phthalates, with acyl chains of different sizes, and their monoester metabolites. We use molecular dynamics simulations to predict the distribution in model membranes, as well as permeabilities and effects on the structural, dynamic, and elastic properties of the membranes. We find that alterations of membrane properties are significant and only weakly affected by the size of acyl chains, suggesting that modifications of molecular size may not be sufficient to reduce the impact of this class of molecules on the environment and health.

Counteraction between Astrin-PP1 and Cyclin-B-CDK1 pathways protects chromosome-microtubule attachments independent of biorientation.

Defects in chromosome-microtubule attachment can cause chromosomal instability (CIN), frequently associated with infertility and aggressive cancers. Chromosome-microtubule attachment is mediated by a large macromolecular structure, the kinetochore. Sister kinetochores of each chromosome are pulled by microtubules from opposing spindle-poles, a state called biorientation which prevents chromosome missegregation. Kinetochore-microtubule attachments that lack the opposing-pull are detached by Aurora-B/Ipl1. It is unclear how mono-oriented attachments that precede biorientation are spared despite the lack of opposing-pull. Using an RNAi-screen, we uncover a unique role for the Astrin-SKAP complex in protecting mono-oriented attachments. We provide evidence of domains in the microtubule-end associated protein that sense changes specific to end-on kinetochore-microtubule attachments and assemble an outer-kinetochore crescent to stabilise attachments. We find that Astrin-PP1 and Cyclin-B-CDK1 pathways counteract each other to preserve mono-oriented attachments. Thus, CIN prevention pathways are not only surveying attachment defects but also actively recognising and stabilising mature attachments independent of biorientation.

CENP-A overexpression promotes aneuploidy with karyotypic heterogeneity.

Chromosomal instability (CIN) is a hallmark of many cancers. Restricting the localization of centromeric histone H3 variant CENP-A to centromeres prevents CIN. CENP-A overexpression (OE) and mislocalization have been observed in cancers and correlate with poor prognosis; however, the molecular consequences of CENP-A OE on CIN and aneuploidy have not been defined. Here, we show that CENP-A OE leads to its mislocalization and CIN with lagging chromosomes and micronuclei in pseudodiploid DLD1 cells and xenograft mouse model. CIN is due to reduced localization of proteins to the kinetochore, resulting in defects in kinetochore integrity and unstable kinetochore-microtubule attachments. CENP-A OE contributes to reduced expression of cell adhesion genes and higher invasion of DLD1 cells. We show that CENP-A OE contributes to aneuploidy with karyotypic heterogeneity in human cells and xenograft mouse model. In summary, our results provide a molecular link between CENP-A OE and aneuploidy, and suggest that karyotypic heterogeneity may contribute to the aggressive phenotype of CENP-A-overexpressing cancers.

Sacrococcygeal Teratoma: A Case Report.

Sacrococcygeal teratoma is rare and happens in 1:35,000 to 40,000 live births. It is more common in girls than boys with the reported ratio of 3:1 to 4:1. We herein report an unusual case of a huge sacrococcygeal teratoma, which was more than half of the size and weight of the baby which was terminated at 24 weeks of gestation.

Development of IglC and GroEL recombinant vaccines for francisellosis in Nile tilapia, Oreochromis niloticus.

Warm-water piscine francisellosis is a granulomatous bacterial disease caused by Francisella orientalis (Fo). The disease has been detected in a wide range of fish species globally, causing mortalities as high as 90% and significant economic losses. Currently there are no commercially available vaccines and few treatment options exist. In the current study, two novel recombinant vaccines were prepared using diatom-expressed IglC or bacterial-expressed GroEL proteins. The vaccine antigens were emulsified with either nanoparticles or a commercially available oil-based adjuvant. Nile tilapia, Oreochromis niloticus, fingerlings were immunized intracoelomically with the recombinant IglC or GroEL vaccines, diatoms alone or phosphate buffer saline. Approximately 840-degree days post-vaccination, fish were challenged via immersion with 106 CFU/mL of wild-type Fo. Twenty-one days post challenge (dpc), the highest relative percent survival was recorded in the IglC-Montanide group (75%), compared to 53%, 50%, 22%, 19% and 16% in the IglC-nanoparticles, GroEL-Montanide, GroEL-nanoparticles, diatoms-Montanide and diatoms-nanoparticles groups, respectively. Protection correlated with significantly higher specific antibody responses in the IglC-Montanide group. Moreover, a significantly lower bacterial load was detected in spleen samples from the IglC-Montanide survivor tilapia compared to the other experimental groups. This is the first report of recombinant vaccines against piscine francisellosis in tilapia. The Fo vaccines described in our study may facilitate development of a safe, cost-effective and highly protective vaccine against francisellosis in farmed tilapia.

End-hole Versus Microvalve Infusion Catheters in Patients Undergoing Drug-Eluting Microspheres-TACE for Solitary Hepatocellular Carcinoma Tumors: A Retrospective Analysis.

INTRODUCTION: Pre-transplant locoregional therapy for hepatocellular carcinoma (HCC) during bridge-to-transplant impacts recurrence and survival rates following liver transplantation. Optimizing the effectiveness of transarterial chemoembolization (TACE) in this population is imperative, and microvalve infusion catheters offer a means of such improvement. METHODS: All treatment-naive patients with solitary HCC tumors < 6.5 cm who underwent drug-eluting microspheres (DEM) TACE between 04/2015 and 08/2017 were retrospectively reviewed. Eighty-eight included patients underwent DEM-TACE with either standard end-hole catheters (EH) or microvalve infusion catheters (MVI). The EH (n = 70) and MVI (n = 18) cohorts had similar baseline tumor size, laboratory values, and tumor etiologies. RESULTS: Initial objective response rates were significantly higher in MVI vs. EH (100% vs. 76.5%, p = 0.019). There was no difference in adverse events between groups (p = 0.265). MVI patients exhibited lower AST (p = 0.003) and ALT (p = 0.044) at 6 months. Blinded pathological analysis of explanted livers showed greater concentrations of microspheres within the tumor relative to the surrounding tissue in MVI explants (88.7 ± 10.6%) versus the EH explants (55.3 ± 32.7%) (p = 0.002). There was significantly higher percentage tumor necrosis in the MVI group (89.0 ± 2.2%) compared with the EH group (56.1 ± 44.5%) (p = 0.006). CONCLUSION: In this retrospective study of a single-center cohort, DEM-TACE procedures with MVI were associated with improved tumor response, increased deposition of microspheres within tumor tissue, and higher percentage tumor necrosis at explant relative to those performed using EH catheters.

Spindle rotation in human cells is reliant on a MARK2-mediated equatorial spindle-centering mechanism.

The plane of cell division is defined by the final position of the mitotic spindle. The spindle is pulled and rotated to the correct position by cortical dynein. However, it is unclear how the spindle's rotational center is maintained and what the consequences of an equatorially off centered spindle are in human cells. We analyzed spindle movements in 100s of cells exposed to protein depletions or drug treatments and uncovered a novel role for MARK2 in maintaining the spindle at the cell's geometric center. Following MARK2 depletion, spindles glide along the cell cortex, leading to a failure in identifying the correct division plane. Surprisingly, spindle off centering in MARK2-depleted cells is not caused by excessive pull by dynein. We show that MARK2 modulates mitotic microtubule growth and length and that codepleting mitotic centromere-associated protein (MCAK), a microtubule destabilizer, rescues spindle off centering in MARK2-depleted cells. Thus, we provide the first insight into a spindle-centering mechanism needed for proper spindle rotation and, in turn, the correct division plane in human cells.

Mislocalization of centromeric histone H3 variant CENP-A contributes to chromosomal instability (CIN) in human cells.

Chromosomal instability (CIN) is a hallmark of many cancers and a major contributor to tumorigenesis. Centromere and kinetochore associated proteins such as the evolutionarily conserved centromeric histone H3 variant CENP-A, associate with centromeric DNA for centromere function and chromosomal stability. Stringent regulation of cellular CENP-A levels prevents its mislocalization in yeast and flies to maintain genome stability. CENP-A overexpression and mislocalization are observed in several cancers and reported to be associated with increased invasiveness and poor prognosis. We examined whether there is a direct relationship between mislocalization of overexpressed CENP-A and CIN using HeLa and chromosomally stable diploid RPE1 cell lines as model systems. Our results show that mislocalization of overexpressed CENP-A to chromosome arms leads to chromosome congression defects, lagging chromosomes, micronuclei formation and a delay in mitotic exit. CENP-A overexpressing cells showed altered localization of centromere and kinetochore associated proteins such as CENP-C, CENP-T and Nuf2 leading to weakened native kinetochores as shown by reduced interkinetochore distance and CIN. Importantly, our results show that mislocalization of CENP-A to chromosome arms is one of the major contributors for CIN as depletion of histone chaperone DAXX prevents CENP-A mislocalization and rescues the reduced interkinetochore distance and CIN phenotype in CENP-A overexpressing cells. In summary, our results establish that CENP-A overexpression and mislocalization result in a CIN phenotype in human cells. This study provides insights into how overexpression of CENP-A may contribute to CIN in cancers and underscore the importance of understanding the pathways that prevent CENP-A mislocalization for genome stability.

The use of Imatinib resistance mutation analysis to direct therapy in Philadelphia chromosome/BCR-ABL1 positive chronic myeloid leukaemia patients failing Imatinib treatment, in Patan Hospital, Nepal.

Philadelphia chromosome/BCR-ABL1 positive chronic myeloid leukaemia (CML) can be successfully treated with Glivec (Imatinib), which is available free of cost through the Glivec International Patient Assistance programme (GIPAP) to patients with proven CML without means to pay for the drug. We review the acquired mutations in the tyrosine kinase encoded by the BCR-ABL1 gene underlying Glivec failure or resistance in a cohort of 388 imatinib-treated CML patients (149 Female and 239 male) registered between February 2003 and June 2016 in Nepal. Forty-five patients (11 female 34 male) were studied; 18 different BCR-ABL1 mutations were seen in 33 patients. P-loop mutation, Kinase domain and A-loop mutations were seen in 9, 16 and 4 patients respectively. Other mutations were seen in five patients. A T315I mutation was the most common mutation, followed by F359V and M244V. Sixteen mutations showed intermediate activity to complete resistance to Glivec. Among the 45 patients evaluated for BCR-ABL1 mutations, 4 were lost to follow-up, 14 died and 27 are still alive. Among the surviving patients, 16 are receiving Nilotinib, 5 Dasatinib and 3 Ponatinib, while 3 patients were referred to India, one of who received allogenic bone marrow transplantation. Understanding the spectrum of further acquired mutations in BCR-ABL1 may help to choose more specific targeted tyrosine kinase inhibitors that can be provided by GIPAP.

Treating Philadelphia chromosome/BCR-ABL1 positive patients with Glivec (Imatinib mesylate): 10 years' experience at Patan Hospital, Nepal.

The Glivec International Patient Assistance Programme makes Glivec (Imatinib mesylate) available to Philadelphia chromosome/BCR-ABL1 positive patients with chronic myeloid leukaemia (CML) in Lower and Middle Income Countries (LMIC). We have established a large cohort of 211 CML patients who are eligible for Imatinib, in Kathmandu, Nepal. Thirty-one patients were lost to follow-up. We report on 180 CML patients with a median age of 38 years (range 9-81). Of these 180 patients, 162 underwent cytogenetic testing and 110 were investigated by reverse transcription polymerase chain reaction. One hundred and thirty-nine of the 180 patients (77·2%) had at least one optimal response. Taken together, our cohort has a 95% overall survival rate and 78% of the patients were still taking Glivec at a median time of 48·8 months (range 3-140 months). The number of patients who actually failed therapy, as defined by the LeukaemiaNet 2013 criteria, was 39 (21·7%). While our cohort has some differences with those in North America or Europe, we have shown Glivec is effective in inducing an optimal response in our patients in Nepal and that it is possible to deliver a clinical service for CML patients using tyrosine kinase inhibitors in resource-poor settings.

Donor-Derived Hepatic Neuroendocrine Tumor: Pause Before Proceeding With Liver Retransplantation.

Gastrointestinal neuroendocrine tumors (NET) are rare but the age-adjusted incidence in the United States has increased, possibly due to improved radiographic and endoscopic detection. In advanced NET, hepatic metastases are common. Orthotopic liver transplant (OLT) is currently considered an acceptable therapy for selected patients with limited hepatic disease or liver metastases where complete resection is thought to have curative intent. The development of NET of donor origin is very uncommon after organ transplant, and it is unclear if the same treatment strategies applied to hepatic NET would also be efficacious after OLT. Here, we describe a unique case of an OLT recipient with a donor-derived NET that was treated with redo OLT as the primary therapy. The donor-derived NET recurred in the recipient's second liver allograft suggesting an extrahepatic reservoir. This case describes the natural history of such a rare event. Here, we highlight the treatment options for hepatic NET and challenge the role of OLT for a donor-derived hepatic NET.

Kindlin1 regulates microtubule function to ensure normal mitosis.

Loss of Kindlin 1 (Kin1) results in the skin blistering disorder Kindler Syndrome (KS), whose symptoms also include skin atrophy and reduced keratinocyte proliferation. Kin1 binds to integrins to modulate their activation and more recently it has been shown to regulate mitotic spindles and cell survival in a Plk1-dependent manner. Here we report that short-term Kin1 deletion in mouse skin results in impaired mitosis, which is associated with reduced acetylated tubulin (ac-tub) levels and cell proliferation. In cells, impaired mitosis and reduced ac-tub levels are also accompanied by reduced microtubule stability, all of which are rescued by HDAC6 inhibition. The ability of Kin1 to regulate HDAC6-dependent cellular ac-tub levels is dependent on its phosphorylation by Plk1. Taken together, these data define a novel role for Kin1 in microtubule acetylation and stability and offer a mechanistic insight into how certain KS phenotypes, such as skin atrophy and reduced cell proliferation, arise.

Modeling of Noisy Spindle Dynamics Reveals Separable Contributions to Achieving Correct Orientation.

The mechanisms by which the mammalian mitotic spindle is guided to a predefined orientation through microtubule-cortex interactions have recently received considerable interest, but there has been no dynamic model that describes spindle movements toward the preferred axis in human cells. Here, we develop a dynamic model based on stochastic activity of cues anisotropically positioned around the cortex of the mitotic cell and we show that the mitotic spindle does not reach equilibrium before chromosome segregation. Our model successfully captures the characteristic experimental behavior of noisy spindle rotation dynamics in human epithelial cells, including a weak underlying bias in the direction of rotation, suppression of motion close to the alignment axis, and the effect of the aspect ratio of the interphase cell shape in defining the final alignment axis. We predict that the force exerted per cue has a value that minimizes the deviation of the spindle from the predefined axis. The model has allowed us to systematically explore the parameter space around experimentally relevant configurations, and predict the mechanistic function of a number of established regulators of spindle orientation, highlighting how physical modeling of a noisy system can lead to functional biological understanding. We provide key insights into measurable parameters in live cells that can help distinguish between mechanisms of microtubule and cortical-cue interactions that jointly control the final orientation of the spindle.