Assessment of Cardiac, Vascular, and Pulmonary Pathobiology In Vivo During Acute COVID‐19

Background

Acute COVID‐19–related myocardial, pulmonary, and vascular pathology and how these relate to each other remain unclear. To our knowledge, no studies have used complementary imaging techniques, including molecular imaging, to elucidate this. We used multimodality imaging and biochemical sampling in vivo to identify the pathobiology of acute COVID‐19. Specifically, we investigated the presence of myocardial inflammation and its association with coronary artery disease, systemic vasculitis, and pneumonitis.

Methods and Results

Consecutive patients presenting with acute COVID‐19 were prospectively recruited during hospital admission in this cross‐sectional study. Imaging involved computed tomography coronary angiography (identified coronary disease), cardiac 2‐deoxy‐2‐[fluorine‐18]fluoro‐D‐glucose positron emission tomography/computed tomography (identified vascular, cardiac, and pulmonary inflammatory cell infiltration), and cardiac magnetic resonance (identified myocardial disease) alongside biomarker sampling. Of 33 patients (median age 51 years, 94% men), 24 (73%) had respiratory symptoms, with the remainder having nonspecific viral symptoms. A total of 9 patients (35%, n=9/25) had cardiac magnetic resonance–defined myocarditis. Of these patients, 53% (n=5/8) had myocardial inflammatory cell infiltration. A total of 2 patients (5%) had elevated troponin levels. Cardiac troponin concentrations were not significantly higher in patients with and without myocarditis (8.4 ng/L [interquartile range, IQR: 4.0–55.3] versus 3.5 ng/L [IQR: 2.5–5.5]; P =0.07) or myocardial cell infiltration (4.4 ng/L [IQR: 3.4–8.3] versus 3.5 ng/L [IQR: 2.8–7.2]; P =0.89). No patients had obstructive coronary artery disease or vasculitis. Pulmonary inflammation and consolidation (percentage of total lung volume) was 17% (IQR: 5%–31%) and 11% (IQR: 7%–18%), respectively. Neither were associated with the presence of myocarditis.

Conclusions

Myocarditis was present in a third patients with acute COVID‐19, and the majority had inflammatory cell infiltration. Pneumonitis was ubiquitous, but this inflammation was not associated with myocarditis. The mechanism of cardiac pathology is nonischemic and not attributable to a vasculitic process.

Registration

URL: https://www.isrctn.com ; Unique identifier: ISRCTN12154994.

Reliability of Quantitative 18F-FDG PET/CT Imaging Biomarkers for Classifying Early Response to Chemoradiotherapy in Patients With Locally Advanced Non-Small Cell Lung Cancer

PURPOSE OF THE REPORT

We evaluated the reliability of 18F-FDG PET imaging biomarkers to classify early response status across observers, scanners, and reconstruction algorithms in support of biologically adaptive radiation therapy for locally advanced non-small cell lung cancer.

PATIENTS AND METHODS

Thirty-one patients with unresectable locally advanced non-small cell lung cancer were prospectively enrolled on a phase 2 trial (NCT02773238) and underwent 18F-FDG PET on GE Discovery STE (DSTE) or GE Discovery MI (DMI) PET/CT systems at baseline and during the third week external beam radiation therapy regimens. All PET scans were reconstructed using OSEM; GE-DMI scans were also reconstructed with BSREM-TOF (block sequential regularized expectation maximization reconstruction algorithm incorporating time of flight). Primary tumors were contoured by 3 observers using semiautomatic gradient-based segmentation. SUVmax, SUVmean, SUVpeak, MTV (metabolic tumor volume), and total lesion glycolysis were correlated with midtherapy multidisciplinary clinical response assessment. Dice similarity of contours and response classification areas under the curve were evaluated across observers, scanners, and reconstruction algorithms. LASSO logistic regression models were trained on DSTE PET patient data and independently tested on DMI PET patient data.

RESULTS

Interobserver variability of PET contours was low for both OSEM and BSREM-TOF reconstructions; intraobserver variability between reconstructions was slightly higher. ΔSUVpeak was the most robust response predictor across observers and image reconstructions. LASSO models consistently selected ΔSUVpeak and ΔMTV as response predictors. Response classification models achieved high cross-validated performance on the DSTE cohort and more variable testing performance on the DMI cohort.

CONCLUSIONS

The variability FDG PET lesion contours and imaging biomarkers was relatively low across observers, scanners, and reconstructions. Objective midtreatment PET response assessment may lead to improved precision of biologically adaptive radiation therapy.

Correlation between FDG-PET uptake and survival in patients with primary brain tumors

This study evaluates F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) semi-quantitative analysis as biomarker of tumor aggressiveness and predictor of survival in patients with primary brain tumors. Semi-quantitative analyses (SUVmax, SUVmean) were derived from FDG PET images in 78 patients with suspected recurrence of primary brain tumors based on MRI. SUVmax and the ratio of lesion SUVmax to the SUVmean of contralateral white matter (SUVmax/WM) were measured. A one-way Analysis of Variance (ANOVA), Kaplan-Meier analyses and the log rank test for evaluating statistical significance were utilized. There was statistical significance for time between FDG-PET and patient death. There was a significant difference with respect to FDG-PET time to death between patients with glioblastoma and patients with anaplastic oligodendroglioma, oligodendroglioma, and other histological subtypes. There is significant correlation with SUVmax/WM and patient survival following FDG-PET when a cut-point ratio of 1.90 is used. A 1.90 cut-point ratio of SUVmax/WM was associated with a difference in survival. GBM was associated with a significant difference in terms of reduced survival following FDG PET compared to most other histological sub-types. These results may inform current treatment and counseling strategies for patients with primary brain tumors.

Lipopolysaccharide endotoxemia induces amyloid-β and p-tau formation in the rat brain

Amyloid beta (Aβ) plaques are not specific to Alzheimer's disease and occur with aging and neurodegenerative disorders. Soluble brain Aβ may be neuroprotective and increases in response to neuroinflammation. Sepsis is associated with neurocognitive compromise. The objective was to determine, in a rat endotoxemia model of sepsis, whether neuroinflammation and soluble Aβ production are associated with Aβ plaque and hyperphosphorylated tau deposition in the brain. Male Sprague Dawley rats received a single intraperitoneal injection of 10 mg/kg of lipopolysaccharide endotoxin (LPS). Brain and blood levels of IL-1β, IL-6, and TNFα and cortical microglial density were measured in LPS-injected and control animals. Soluble brain Aβ and p-tau were compared and Aβ plaques were quantified and characterized. Brain uptake of [¹⁸F]flutemetamol was measured by phosphor imaging. LPS endotoxemia resulted in elevations of cytokines in blood and brain. Microglial density was increased in LPS-treated rats relative to controls. LPS resulted in increased soluble Aβ and in p-tau levels in whole brain. Progressive increases in morphologically-diffuse Aβ plaques occurred throughout the interval of observation (to 7-9 days post LPS). LPS endotoxemia resulted in increased [¹⁸F]flutemetamol in the cortex and increased cortex: white matter ratios of activity. In conclusion, LPS endotoxemia causes neuroinflammation, increased soluble Aβ and Aβ diffuse plaques in the brain. Aβ PET tracers may inform this neuropathology. Increased p-tau in the brain of LPS treated animals suggests that downstream consequences of Aβ plaque formation may occur. Further mechanistic and neurocognitive studies to understand the causes and consequences of LPS-induced neuropathology are warranted.

Correlation of Glioma Proliferation and Hypoxia by Luciferase, Magnetic Resonance, and Positron Emission Tomography Imaging

Gliomas are the most common type of primary, malignant brain tumor and significantly impact patients, who have a median survival of ~1 year depending on mutational background. Novel imaging modalities such as luciferase bioluminescence, micro-magnetic resonance imaging (micro-MRI), micro-computerized tomography (micro-CT), and micro-positron emission tomography (micro-PET) have expanded the portfolio of tools available to study this disease. Hypoxia, a key oncogenic driver of glioma and mechanism of resistance, can be studied in vivo by the concomitant use of noninvasive MRI and PET imaging. We present a protocol involving stereotactic injection of syngenic F98 luciferase-expressing glioma cells generated by our laboratory into Fischer 344 rat brains and imaging using luciferase. In addition, 18-F-fludeoxyglucose, 18F-fluoromisonidazole, and 18F-fluorothymidine PET imaging are compared with quantified luciferase flux. These tools can potentially be used for assessing tumor growth characteristics, hypoxia, mutational effects, and treatment effects.

Is Cancer Protective for Subsequent Alzheimer's Disease Risk? Evidence From the Utah Population Database

OBJECTIVE

Several studies have suggested that cancer is associated with a reduced risk of the development of Alzheimer's disease (AD). This study seeks to improve our understanding of the association between cancer and the development of AD by showing how mortality selection alters this relationship.

METHOD

A retrospective cohort study was carried out examining 92,425 individuals (47,873 women and 44,552 men) from the Utah Population Database with and without a history of any primary cancer identified by the Utah Cancer Registry. All individuals were aged 65-79 years and free of dementia in 1992 and followed for upwards of 18 years (1992-2009) for AD ascertainment, which was identified using diagnostic information from Medicare claims data.

RESULTS

We replicate previous results suggesting that cancer is associated with reduced risk of subsequent AD under specific statistical model specifications. However, these results should not be interpreted as evidence of an etiological association. We conclude that higher rates of overall mortality among individuals with cancer relative to those without cancer induce the widely reported putative protective association with cancer.

CONCLUSION

Careful consideration of model specification and the profound effects of mortality selection in the older adult population is essential when investigating the relationship between aging-related diseases such as cancer and AD. We show that cancer does not provide protection from AD as previously described in the literature. Social scientists seeking to understand social disparities in disease outcomes among older adults may therefore want to strongly consider the role of mortality selection which, if uncorrected, may generate biased associations.

Amyloid Positivity Using [18F]Flutemetamol-PET and Cognitive Deficits in Nondemented Community-Dwelling Older Adults

Little research exists examining the relationship between beta-amyloid neuritic plaque density via [18F]flutemetamol binding and cognition; consequently, the purpose of the current study was to compare cognitive performances among individuals having either increased amyloid deposition (Flute+) or minimal amyloid deposition (Flute-). Twenty-seven nondemented community-dwelling adults over the age of 65 underwent [18F]flutemetamol amyloid-positron emission tomography imaging, along with cognitive testing using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and select behavioral measures. Analysis of variance was used to identify the differences among the cognitive and behavioral measures between Flute+/Flute- groups. Flute+ participants performed significantly worse than Flute- participants on RBANS indexes of immediate memory, language, delayed memory, and total scale score, but no significant group differences in the endorsed level of depression or subjective report of cognitive difficulties were observed. Although these results are preliminary, [18F]flutemetamol accurately tracks cognition in a nondemented elderly sample, which may allow for better prediction of cognitive decline in late life.

A 2D threshold of the condylar-C1 interval to maximize identification of patients at high risk for atlantooccipital dislocation using computed tomography

OBJECTIVE Measurement of the occipital condyle-C1 interval (CCI) is important in the evaluation of atlantooccipital dislocation (AOD) in pediatric trauma patients. The authors studied a large cohort of children with and without AOD to identify a 2D measurement threshold that maximizes the diagnostic yield of the CCI on cervical spine CT scans obtained in trauma patients. METHODS This retrospective, single-center study included all children who underwent CT of the cervical spine at Primary Children's Hospital from January 1, 2011, through December 31, 2014, for trauma evaluation. Bilateral CCI measurements in the coronal (3 measurements per side) and sagittal (4 measurements per side) planes were recorded. Using an iterative method, the authors determined optimal cutoffs for the maximal CCI in each plane in relation to AOD. The primary outcome was AOD requiring occipitocervical fusion. RESULTS A total of 597 pediatric patients underwent cervical spine CT for trauma evaluation: 578 patients without AOD and 19 patients with AOD requiring occipitocervical fusion. The authors found a statistically significant correlation between CCI and age (p < 0.001), with younger patients having higher CCIs. Using a 2D threshold requiring a sagittal CCI ≥ 2.5 mm and a coronal CCI ≥ 3.5 mm predicted AOD with a sensitivity of 95%, a specificity of 73%, positive predictive value of 10.3%, and negative predictive value of 99%. The accuracy of this 2D threshold was 84%. CONCLUSIONS In the present study population, age-dependent differences in the CCI were found on CT scans of the cervical spine in a large cohort of patients with and without AOD. A 2D CCI threshold as a screening method maximizes identification of patients at high risk for AOD while minimizing unnecessary imaging studies in children being evaluated for trauma.

Relationship between 18F-Flutemetamol uptake and RBANS performance in non-demented community-dwelling older adults

OBJECTIVE

The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) has been used extensively for clinical care and in research for patients with mild cognitive impairment and Alzheimer's disease (AD); however, relatively few studies have evaluated the relationship between RBANS performance and AD imaging biomarkers. The purpose of the current study was to evaluate the association between a relatively new amyloid positron emission tomography imaging biomarker and performance on the RBANS.

METHODS

Twenty-seven nondemented community-dwelling adults over the age of 65 underwent ¹⁸F-Flutemetamol amyloid- positron emission tomography imaging, along with cognitive testing using the RBANS and select behavioral measures. Partial correlation coefficients were used to identify relationships between the imaging and behavioral markers.

RESULTS

After controlling for age and education, amyloid deposition and RBANS Indexes of Immediate Memory, Delayed Memory, and Total Scale score were significantly correlated (p's < .001, r's = -.73 to -.77, d's = 2.13-2.39), with greater amyloid burden being associated with lower RBANS scores. The Delayed Memory Index was particularly highly associated with ¹⁸F-Flutemetamol binding (r² = .59, p < .001, d = 2.39). Neither ¹⁸F-Flutemetamol binding nor RBANS performance was significantly correlated with levels of depression, subjective cognitive difficulties, or premorbid intellect.

CONCLUSIONS

Because of the limited use of amyloid imaging in clinical settings due to high cost and lack of reimbursement, these findings suggest that in particular RBANS Delayed Memory Index may be a cost-efficient tool to identify early signs of AD pathology, and its use may enlighten clinical decision-making regarding potential progression to dementia due to AD.

Short-Term Practice Effects and Brain Hypometabolism: Preliminary Data from an FDG PET Study

Practice effects are improvements in cognitive test scores due to repeated exposure to the same tests. Typically viewed as error, short-term practice effects have been shown to provide valuable clinical information about diagnosis, prognosis, and treatment outcomes in older patients with mild cognitive impairments. This study examined short-term practice effects across one week and brain hypometabolism on fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) in 25 older adults (15 intact, 10 Mild Cognitive Impairment). Averaged cerebral brain metabolism on FDG PET was correlated with multiple cognitive scores at baseline in those with Mild Cognitive Impairment, and short-term practice effects accounted for additional variance in these same subjects. The relationship between brain metabolism and cognition (either at baseline or practice effects) was minimal in the intact individuals. Although needing replication in larger samples, short-term practice effects on tests of executive functioning and memory may provide valuable information about biomarkers of Alzheimer's disease.

FDG and FLT-PET for Early measurement of response to 37.5 mg daily sunitinib therapy in metastatic renal cell carcinoma

BACKGROUND

Metastatic renal cell carcinoma has a poor prognosis and an intrinsic resistance to standard treatment. Sunitinib is an oral receptor tyrosine kinase inhibitor that has been used as a first-line targeted therapy in metastatic renal cell carcinoma. While computed tomography (CT) is currently the gold standard for response assessment in oncological trials, numerous studies have shown that positron emission tomography (PET) imaging can provide information predictive of tumor response to treatment earlier than the typical interval for standard of care follow-up CT imaging. In this exploratory study we sought to characterize early tumor response in patients with metastatic renal cell carcinoma treated with continuous daily 37.5 mg sunitinib therapy.

METHODS

Twenty patients underwent dynamic acquisition positron emission tomography (PET) imaging using (18) F-fluorodeoxyglucose (FDG) and (18) F-fluorothymidine (FLT) at baseline and early in treatment (after 1, 2, 3 or 4 weeks) with 37.5 mg continuous daily dosing of sunitinib. Semi-quantitative analyses were performed to characterize the tumor metabolic (FDG) and proliferative (FLT) responses to treatment.

RESULTS

Proliferative responses were observed in 9/19 patients and occurred in 2 patients at one week (the earliest interval evaluated) after the initiation of therapy. A metabolic response was observed in 5/19 patients, however this was not observed until after two weeks of therapy were completed. Metabolic progression was observed in 2/19 patients and proliferative progression was observed in 1/19 patients. Baseline FDG-PET tumor maximum standardized uptake values correlated inversely with overall survival (p = 0.0036). Conversely, baseline (18) F-fluorothymidine PET imaging did not have prognostic value (p = 0.56) but showed a greater early response rate at 1-2 weeks after initiating therapy.

CONCLUSIONS

While preliminary in nature, these results show an immediate and sustained proliferative response followed by a delayed metabolic response beginning after two weeks in metastatic renal cell carcinoma treated with a continuous daily dose of 37.5 mg sunitinib. The results provide evidence of tumor response to lower-dose sunitinib while also supporting the inclusion of PET imaging as a tool for early assessment in oncological clinical trials.

TRIAL REGISTRATION

ID: NCT00694096.

Functional regeneration of respiratory pathways after spinal cord injury

Spinal cord injuries (SCI) often occur at the cervical level above the phrenic motor pools, which innervate the diaphragm. Unfortunately, the untoward effects of impaired breathing are a leading cause of SCI-related death, underscoring the importance of developing strategies to restore respiratory activity. Here we show that after cervical SCI, there is upregulation of the perineuronal net (PNN) associated chondroitin sulfate proteoglycans (CSPGs) around phrenic motor neurons. Digestion of these potently inhibitory extracellular matrix molecules with Chondroitinase ABC (ChABC) can, by itself, promote plasticity of spared tracts and restore limited activity to the paralyzed diaphragm. However, when combined with application of a peripheral nerve autograft, ChABC treatment results in lengthy regeneration of serotonergic axons and other bulbospinal fibers with remarkable recovery of diaphragm function. Following recovery and initial transection of the bridge, there occurs an unusual, overall increased tonic diaphragmatic EMG activity, suggesting considerable remodeling of spinal cord circuitry after regeneration. This is followed by complete elimination of the restored activity proving that regeneration is critical for the return of function. Overall, these experiments present a way to profoundly restore function of a single muscle following debilitating CNS trauma, through both plasticity of spared tracts and regeneration of essential pathways.

Immature astrocytes promote CNS axonal regeneration when combined with chondroitinase ABC

Regeneration of injured adult CNS axons is inhibited by formation of a glial scar. Immature astrocytes are able to support robust neurite outgrowth and reduce scarring, therefore, we tested whether these cells would have this effect if transplanted into brain injuries. Utilizing an in vitro spot gradient model that recreates the strongly inhibitory proteoglycan environment of the glial scar we found that, alone, immature, but not mature, astrocytes had a limited ability to form bridges across the most inhibitory outer rim. In turn, the astrocyte bridges could promote adult sensory axon re-growth across the gradient. The use of selective enzyme inhibitors revealed that MMP-2 enables immature astrocytes to cross the proteoglycan rim. The bridge-building process and axon regeneration across the immature glial bridges were greatly enhanced by chondroitinase ABC pretreatment of the spots. We used microlesions in the cingulum of the adult rat brains to test the ability of matrix modification and immature astrocytes to form a bridge for axon regeneration in vivo. Injured axons were visualized via p75 immunolabeling and the extent to which these axons regenerated was quantified. Immature astrocytes coinjected with chondroitinase ABC-induced axonal regeneration beyond the distal edge of the lesion. However, when used alone, neither treatment was capable of promoting axonal regeneration. Our findings indicate that when faced with a minimal lesion, neurons of the basal forebrain can regenerate in the presence of a proper bridge across the lesion and when levels of chondroitin sulfate proteoglycans (CSPGs) in the glial scar are reduced.

PTPsigma is a receptor for chondroitin sulfate proteoglycan, an inhibitor of neural regeneration

Chondroitin sulfate proteoglycans (CSPGs) present a barrier to axon regeneration. However, no specific receptor for the inhibitory effect of CSPGs has been identified. We showed that a transmembrane protein tyrosine phosphatase, PTPsigma, binds with high affinity to neural CSPGs. Binding involves the chondroitin sulfate chains and a specific site on the first immunoglobulin-like domain of PTPsigma. In culture, PTPsigma(-/-) neurons show reduced inhibition by CSPG. A PTPsigma fusion protein probe can detect cognate ligands that are up-regulated specifically at neural lesion sites. After spinal cord injury, PTPsigma gene disruption enhanced the ability of axons to penetrate regions containing CSPG. These results indicate that PTPsigma can act as a receptor for CSPGs and may provide new therapeutic approaches to neural regeneration.

A point mutation in the Aspergillus nidulans sonBNup98 nuclear pore complex gene causes conditional DNA damage sensitivity

The nuclear pore complex (NPC) is embedded in the nuclear envelope where it mediates transport between the cytoplasm and nucleus and helps to organize nuclear architecture. We previously isolated sonB1, a mutation encoding a single amino acid substitution within the Aspergillus nidulans SONBnNup98 NPC protein (nucleoporin). Here we demonstrate that this mutation causes marked DNA damage sensitivity at 42 degrees . Although SONBnNup98 has roles in the G2 transition, we demonstrate that the G2 DNA damage checkpoint is functional in the sonB1 mutant at 42 degrees . The MRN complex is composed of MRE11, RAD50, and NBS1 and functions in checkpoint signaling, DNA repair, and telomere maintenance. At 42 degrees we find that the DNA damage response defect of sonB1 mutants causes synthetic lethality when combined with mutations in scaANBS1, the A. nidulans homolog of NBS1. We provide evidence that this synthetic lethality is independent of MRN cell cycle checkpoint functions or MREAMRE11-mediated DNA repair functions. We also demonstrate that the single A. nidulans histone H2A gene contains the C-terminal SQE motif of histone H2AX isoforms and that this motif is required for the DNA damage response. We propose that the sonB1 nucleoporin mutation causes a defect in a novel part of the DNA damage response.

Chronic enhancement of the intrinsic growth capacity of sensory neurons combined with the degradation of inhibitory proteoglycans allows functional regeneration of sensory axons through the dorsal root entry zone in the mammalian spinal cord

Peripherally conditioned sensory neurons have an increased capacity to regenerate their central processes. However, even conditioned axons struggle in the presence of a hostile CNS environment. We hypothesized that combining an aggressive conditioning strategy with modification of inhibitory reactive astroglial-associated extracellular matrix could enhance regeneration. We screened potential treatments using a model of the dorsal root entry zone (DREZ). In this assay, a gradient of inhibitory chondroitin sulfate proteoglycans (CSPGs) stimulates formation of dystrophic end bulbs on adult sensory axons, which mimics regeneration failure in vivo. Combining inflammation-induced preconditioning of dorsal root ganglia in vivo before harvest, with chondroitinase ABC (ChABC) digestion of proteoglycans in vitro allows for significant regeneration across a once potently inhibitory substrate. We then assessed regeneration through the DREZ after root crush in adult rats receiving the combination treatment, ChABC, or zymosan pretreatment alone or no treatment. Regeneration was never observed in untreated animals, and only minimal regeneration occurred in the ChABC- and zymosan-alone groups. However, remarkable regeneration was observed in a majority of animals that received the combination treatment. Regenerated fibers established functional synapses, as demonstrated electrophysiologically by the presence of an H-reflex. Two different postlesion treatment paradigms in which the timing of both zymosan and ChABC administration were varied after injury were ineffective in promoting regeneration. Therefore, zymosan pretreatment, but not posttreatment, of the sensory ganglia, combined with ChABC modification of CSPGs, resulted in robust and functional regeneration of sensory axons through the DREZ after root injury.

The SONBNUP98 Nucleoporin Interacts With the NIMA Kinase in Aspergillus nidulans

The Aspergillus nidulans NIMA kinase is essential for mitotic entry. At restrictive temperature, temperature-sensitive nimA alleles arrest in G2, before accumulation of NIMA in the nucleus. We performed a screen for extragenic suppressors of the nimA1 allele and isolated two cold-sensitive son (suppressor of nimA1) mutants. The sonA1 mutant encoded a nucleoporin that is a homolog of yeast Gle2/Rae1. We have now cloned SONB, a second nucleoporin genetically interacting with NIMA. sonB is essential and encodes a homolog of the human NUP98/NUP96 precursor. Similar to NUP98/NUP96, SONBNUP98/NUP96 is autoproteolytically cleaved to generate SONBNUP98 and SONBNUP96. SONBNUP98 localizes to the nuclear pore complex and contains a GLEBS domain (Gle2 binding sequence) that binds SONAGLE2. A point mutation within the GLEBS domain of SONB1NUP98 suppresses the temperature sensitivity of the nimA1 allele and compromises the physical interaction between SONAGLE2 and SONB1NUP98. The sonB1 mutation also causes sensitivity to hydroxyurea. We isolated the histone H2A-H2B gene pair as a copy-number suppressor of sonB1 cold sensitivity and hydroxyurea sensitivity. The data suggest that the nucleoporins SONAGLE2 and SONBNUP98 and the NIMA kinase interact and regulate nuclear accumulation of mitotic regulators to help promote mitosis.