Gastroenterology Practice Patterns Contribute to Missed Diagnoses of Eosinophilic Gastritis and Duodenitis.

Background and Aims: Eosinophilic gastritis and eosinophilic duodenitis (EoG/EoD) are often misdiagnosed as functional gastrointestinal (GI) disorders. Consequently, patients with GI symptoms of EoG/EoD may not undergo the necessary steps for diagnosis. We studied gastroenterologists' evaluations of patients with chronic, unexplained, moderate-to-severe GI symptoms that were unresponsive to over-the-counter medications. Methods: We performed a cross-sectional online survey of 202 board-certified gastroenterologists at office-based practices, community hospitals, or academic institutions. Respondents had been in active clinical practice for 3-35 years post-residency training, spent most of their time on direct patient care, managed ≥1 patient with irritable bowel syndrome and/or functional dyspepsia, and performed ≥1 endoscopy per month. Responses were analyzed to identify barriers to EoG/EoD diagnosis and management. Results: Respondents managed a mean of 1880 patients per year; the most common diagnoses were functional dyspepsia (36%) and gastroesophageal reflux disease (19%). Mean proportions of patients who underwent upper endoscopy ranged from 42% to 84%. Biopsies were collected from >90% of patients with visible endoscopic mucosal abnormalities vs 42%-72% of patients with normal-appearing mucosae. Approximately 20% of respondents collected only 1-2 biopsies from each site of the GI tract. Only 30% routinely requested pathologists to count eosinophils, and nearly 40% had no histologic threshold for EoG/EoD diagnosis. Conclusion: Gastroenterologists vary in their evaluation of patients with chronic, unexplained moderate-to-severe GI symptoms. Limited gastric and duodenal biopsy collection, particularly from normal-appearing mucosae, and failure to request tissue eosinophil counts might contribute to underdiagnosis of EoG/EoD. Availability and awareness of EoG/EoD diagnostic guidelines should improve detection in clinical practice.

Determination of Biopsy Yield That Optimally Detects Eosinophilic Gastritis and/or Duodenitis in a Randomized Trial of Lirentelimab.

BACKGROUND & AIMS: Eosinophilic gastritis (EG) and eosinophilic duodenitis (EoD), characterized by chronic gastrointestinal (GI) symptoms and increased numbers or activation of eosinophils and mast cells in the GI tract, are likely underdiagnosed. We aimed to determine rates of EG and EoD and number of biopsies required to optimize detection using screening data from a randomized trial of lirentelimab (AK002), an antibody against siglec-8 that depletes eosinophils and inhibits mast cells. We also characterized endoscopic features and symptoms of EG and EoD. METHODS: Subjects with moderate-to-severe GI symptoms, assessed daily through a validated patient-reported outcome questionnaire, underwent endoscopy with a systematic gastric and duodenal biopsy protocol and histopathologic evaluation. EG diagnosis required presence of ≥30 eosinophils/high-power field (eos/hpf) in ≥5 hpfs and EoD required ≥30 eos/hpf in ≥3 hpfs. We analyzed diagnostic yields for EG and EoD and histologic, endoscopic, and clinical findings. RESULTS: Of 88 subjects meeting symptom criteria, 72 were found to have EG and/or EoD (EG/EoD), including patients with no prior diagnosis of EG/EoD. We found that GI eosinophilia was patchy and that examination of multiple biopsies was required for diagnosis-an average of only 2.6 per 8 gastric biopsies and 2.2 per 4 duodenal biopsies per subject met thresholds for EG/EoD. Evaluation of multiple nonoverlapping hpfs in each of 8 gastric and 4 duodenal biopsies was required to capture 100% of EG/EoD cases. Neither endoscopic findings nor symptom severity correlated with eosinophil counts. CONCLUSIONS: In an analysis of patients with moderate-to-severe GI symptoms participating in a clinical trial of lirentelimab for EG/EoD, we found eosinophilia to be patchy in gastric and duodenal biopsies. Counting eosinophils in at least 8 gastric and 4 duodenal biopsies is required to identify patients with EG/EoD, so they can receive appropriate treatment. (ClinicalTrials.gov, Number: NCT03496571).

Diagnostic Delay in Patients with Eosinophilic Gastritis and/or Duodenitis: A Population-Based Study.

BACKGROUND: Eosinophilic gastritis and/or eosinophilic duodenitis (EG/EoD) is characterized by persistent symptoms and elevated eosinophils in the gastrointestinal tract. Limited disease awareness and lack of diagnostic guidelines suggest that patients may remain undiagnosed or endure diagnostic delay. OBJECTIVE: To characterize the path to diagnosis for patients with EG/EoD in a representative population. METHODS: In this observational cohort study, 4108 eligible patients diagnosed with EG/EoD between 2008 and 2018 were identified in an administrative claims database in the United States. Patient medical claim history was analyzed to describe events related to diagnosis. RESULTS: Mean year from symptom presentation to diagnosis of EG/EoD was 3.6; factors contributing to diagnostic delay included delayed gastroenterologist referral, delayed esophagogastroduodenoscopy (EGD), and lack of biopsy collection and/or histopathologic evaluation. Missed diagnosis on index EGD occurred in 38.2% of patients, resulting in a mean increase of 1.6 years in time to diagnosis versus patients diagnosed on index EGD. Patients presented with nonspecific symptoms and 44.3% were diagnosed with another gastrointestinal condition before EG/EoD diagnosis. Independent predictors of >2-year diagnostic delay included adult age; prior diagnosis of irritable bowel syndrome, functional dyspepsia, or gastric/peptic ulcer; use of other procedures such as colonoscopy; presence of edema; and history of certain allergic diseases. CONCLUSIONS: This study found that patients with EG/EoD experienced an average of 3.6 years between initial symptom presentation and diagnosis and revealed several factors contributing to diagnostic delay. We hope that these findings, together with heightened awareness and standardization of diagnostic guidelines, will improve the diagnostic journey of patients with EG/EoD.

Rbfox proteins regulate alternative mRNA splicing through evolutionarily conserved RNA bridges.

Alternative splicing (AS) enables programmed diversity of gene expression across tissues and development. We show here that binding in distal intronic regions (>500 nucleotides (nt) from any exon) by Rbfox splicing factors important in development is extensive and is an active mode of splicing regulation. Similarly to exon-proximal sites, distal sites contain evolutionarily conserved GCATG sequences and are associated with AS activation and repression upon modulation of Rbfox abundance in human and mouse experimental systems. As a proof of principle, we validated the activity of two specific Rbfox enhancers in KIF21A and ENAH distal introns and showed that a conserved long-range RNA-RNA base-pairing interaction (an RNA bridge) is necessary for Rbfox-mediated exon inclusion in the ENAH gene. Thus we demonstrate a previously unknown RNA-mediated mechanism for AS control by distally bound RNA-binding proteins.

The splicing regulator Rbfox2 is required for both cerebellar development and mature motor function.

The Rbfox proteins (Rbfox1, Rbfox2, and Rbfox3) regulate the alternative splicing of many important neuronal transcripts and have been implicated in a variety of neurological disorders. However, their roles in brain development and function are not well understood, in part due to redundancy in their activities. Here we show that, unlike Rbfox1 deletion, the CNS-specific deletion of Rbfox2 disrupts cerebellar development. Genome-wide analysis of Rbfox2(-/-) brain RNA identifies numerous splicing changes altering proteins important both for brain development and mature neuronal function. To separate developmental defects from alterations in the physiology of mature cells, Rbfox1 and Rbfox2 were deleted from mature Purkinje cells, resulting in highly irregular firing. Notably, the Scn8a mRNA encoding the Na(v)1.6 sodium channel, a key mediator of Purkinje cell pacemaking, is improperly spliced in RbFox2 and Rbfox1 mutant brains, leading to highly reduced protein expression. Thus, Rbfox2 protein controls a post-transcriptional program required for proper brain development. Rbfox2 is subsequently required with Rbfox1 to maintain mature neuronal physiology, specifically Purkinje cell pacemaking, through their shared control of sodium channel transcript splicing.

A systems level, functional genomics analysis of chronic epilepsy.

Neither the molecular basis of the pathologic tendency of neuronal circuits to generate spontaneous seizures (epileptogenicity) nor anti-epileptogenic mechanisms that maintain a seizure-free state are well understood. Here, we performed transcriptomic analysis in the intrahippocampal kainate model of temporal lobe epilepsy in rats using both Agilent and Codelink microarray platforms to characterize the epileptic processes. The experimental design allowed subtraction of the confounding effects of the lesion, identification of expression changes associated with epileptogenicity, and genes upregulated by seizures with potential homeostatic anti-epileptogenic effects. Using differential expression analysis, we identified several hundred expression changes in chronic epilepsy, including candidate genes associated with epileptogenicity such as Bdnf and Kcnj13. To analyze these data from a systems perspective, we applied weighted gene co-expression network analysis (WGCNA) to identify groups of co-expressed genes (modules) and their central (hub) genes. One such module contained genes upregulated in the epileptogenic region, including multiple epileptogenicity candidate genes, and was found to be involved the protection of glial cells against oxidative stress, implicating glial oxidative stress in epileptogenicity. Another distinct module corresponded to the effects of chronic seizures and represented changes in neuronal synaptic vesicle trafficking. We found that the network structure and connectivity of one hub gene, Sv2a, showed significant changes between normal and epileptogenic tissue, becoming more highly connected in epileptic brain. Since Sv2a is a target of the antiepileptic levetiracetam, this module may be important in controlling seizure activity. Bioinformatic analysis of this module also revealed a potential mechanism for the observed transcriptional changes via generation of longer alternatively polyadenlyated transcripts through the upregulation of the RNA binding protein HuD. In summary, combining conventional statistical methods and network analysis allowed us to interpret the differentially regulated genes from a systems perspective, yielding new insight into several biological pathways underlying homeostatic anti-epileptogenic effects and epileptogenicity.

The splicing regulator Rbfox1 (A2BP1) controls neuronal excitation in the mammalian brain.

The Rbfox family of RNA binding proteins regulates alternative splicing of many important neuronal transcripts, but its role in neuronal physiology is not clear. We show here that central nervous system-specific deletion of the gene encoding Rbfox1 results in heightened susceptibility to spontaneous and kainic acid-induced seizures. Electrophysiological recording revealed a corresponding increase in neuronal excitability in the dentate gyrus of the knockout mice. Whole-transcriptome analyses identified multiple splicing changes in the Rbfox1(-/-) brain with few changes in overall transcript abundance. These splicing changes alter proteins that mediate synaptic transmission and membrane excitation. Thus, Rbfox1 directs a genetic program required in the prevention of neuronal hyperexcitation and seizures. The Rbfox1 knockout mice provide a new model to study the post-transcriptional regulation of synaptic function.

A genomic screen for modifiers of tauopathy identifies puromycin-sensitive aminopeptidase as an inhibitor of tau-induced neurodegeneration.

Neurofibrillary tangles (NFT) containing tau are a hallmark of neurodegenerative diseases, including Alzheimer's disease (AD). NFT burden correlates with cognitive decline and neurodegeneration in AD. However, little is known about mechanisms that protect against tau-induced neurodegeneration. We used a cross species functional genomic approach to analyze gene expression in multiple brain regions in mouse, in parallel with validation in Drosophila, to identify tau modifiers, including the highly conserved protein puromycin-sensitive aminopeptidase (PSA/Npepps). PSA protected against tau-induced neurodegeneration in vivo, whereas PSA loss of function exacerbated neurodegeneration. We further show that human PSA directly proteolyzes tau in vitro. These data highlight the utility of using both evolutionarily distant species for genetic screening and functional assessment to identify modifiers of neurodegeneration. Further investigation is warranted in defining the role of PSA and other genes identified here as potential therapeutic targets in tauopathy.