Health Consequences of Thymus Removal in Adults.

BACKGROUND: The function of the thymus in human adults is unclear, and routine removal of the thymus is performed in a variety of surgical procedures. We hypothesized that the adult thymus is needed to sustain immune competence and overall health. METHODS: We evaluated the risk of death, cancer, and autoimmune disease among adult patients who had undergone thymectomy as compared with demographically matched controls who had undergone similar cardiothoracic surgery without thymectomy. T-cell production and plasma cytokine levels were also compared in a subgroup of patients. RESULTS: After exclusions, 1420 patients who had undergone thymectomy and 6021 controls were included in the study; 1146 of the patients who had undergone thymectomy had a matched control and were included in the primary cohort. At 5 years after surgery, all-cause mortality was higher in the thymectomy group than in the control group (8.1% vs. 2.8%; relative risk, 2.9; 95% confidence interval [CI], 1.7 to 4.8), as was the risk of cancer (7.4% vs. 3.7%; relative risk, 2.0; 95% CI, 1.3 to 3.2). Although the risk of autoimmune disease did not differ substantially between the groups in the overall primary cohort (relative risk, 1.1; 95% CI, 0.8 to 1.4), a difference was found when patients with preoperative infection, cancer, or autoimmune disease were excluded from the analysis (12.3% vs. 7.9%; relative risk, 1.5; 95% CI, 1.02 to 2.2). In an analysis involving all patients with more than 5 years of follow-up (with or without a matched control), all-cause mortality was higher in the thymectomy group than in the general U.S. population (9.0% vs. 5.2%), as was mortality due to cancer (2.3% vs. 1.5%). In the subgroup of patients in whom T-cell production and plasma cytokine levels were measured (22 in the thymectomy group and 19 in the control group; mean follow-up, 14.2 postoperative years), those who had undergone thymectomy had less new production of CD4+ and CD8+ lymphocytes than controls (mean CD4+ signal joint T-cell receptor excision circle [sjTREC] count, 1451 vs. 526 per microgram of DNA [P = 0.009]; mean CD8+ sjTREC count, 1466 vs. 447 per microgram of DNA [P<0.001]) and higher levels of proinflammatory cytokines in the blood. CONCLUSIONS: In this study, all-cause mortality and the risk of cancer were higher among patients who had undergone thymectomy than among controls. Thymectomy also appeared be associated with an increased risk of autoimmune disease when patients with preoperative infection, cancer, or autoimmune disease were excluded from the analysis. (Funded by the Tracey and Craig A. Huff Harvard Stem Cell Institute Research Support Fund and others.).

Piezo mechanosensory channels regulate centrosome integrity and mitotic entry.

Piezo1 and 2 are evolutionarily conserved mechanosensory cation channels known to function on the cell surface by responding to external pressure and transducing a mechanically activated Ca2+ current. Here we show that both Piezo1 and 2 also exhibit concentrated intracellular localization at centrosomes. Both Piezo1 and 2 loss-of-function and Piezo1 activation by the small molecule Yoda1 result in supernumerary centrosomes, premature centriole disengagement, multi-polar spindles, and mitotic delay. By using a GFP, Calmodulin and M13 Protein fusion (GCaMP) Ca2+-sensitive reporter, we show that perturbations in Piezo modulate Ca2+ flux at centrosomes. Moreover, the inhibition of Polo-like-kinase 1 eliminates Yoda1-induced centriole disengagement. Because previous studies have implicated force generation by microtubules as essential for maintaining centrosomal integrity, we propose that mechanotransduction by Piezo maintains pericentrosomal Ca2+ within a defined range, possibly through sensing cell intrinsic forces from microtubules.

Variants in STXBP3 are Associated with Very Early Onset Inflammatory Bowel Disease, Bilateral Sensorineural Hearing Loss and Immune Dysregulation.

BACKGROUND AND AIMS: Very early onset inflammatory bowel disease [VEOIBD] is characterized by intestinal inflammation affecting infants and children less than 6 years of age. To date, over 60 monogenic aetiologies of VEOIBD have been identified, many characterized by highly penetrant recessive or dominant variants in underlying immune and/or epithelial pathways. We sought to identify the genetic cause of VEOIBD in a subset of patients with a unique clinical presentation. METHODS: Whole exome sequencing was performed on five families with ten patients who presented with a similar constellation of symptoms including medically refractory infantile-onset IBD, bilateral sensorineural hearing loss and, in the majority, recurrent infections. Genetic aetiologies of VEOIBD were assessed and Sanger sequencing was performed to confirm novel genetic findings. Western analysis on peripheral blood mononuclear cells and functional studies with epithelial cell lines were employed. RESULTS: In each of the ten patients, we identified damaging heterozygous or biallelic variants in the Syntaxin-Binding Protein 3 gene [STXBP3], a protein known to regulate intracellular vesicular trafficking in the syntaxin-binding protein family of molecules, but not associated to date with either VEOIBD or sensorineural hearing loss. These mutations interfere with either intron splicing or protein stability and lead to reduced STXBP3 protein expression. Knock-down of STXBP3 in CaCo2 cells resulted in defects in cell polarity. CONCLUSION: Overall, we describe a novel genetic syndrome and identify a critical role for STXBP3 in VEOIBD, sensorineural hearing loss and immune dysregulation.

An integrated clinical program and crowdsourcing strategy for genomic sequencing and Mendelian disease gene discovery.

Despite major progress in defining the genetic basis of Mendelian disorders, the molecular etiology of many cases remains unknown. Patients with these undiagnosed disorders often have complex presentations and require treatment by multiple health care specialists. Here, we describe an integrated clinical diagnostic and research program using whole-exome and whole-genome sequencing (WES/WGS) for Mendelian disease gene discovery. This program employs specific case ascertainment parameters, a WES/WGS computational analysis pipeline that is optimized for Mendelian disease gene discovery with variant callers tuned to specific inheritance modes, an interdisciplinary crowdsourcing strategy for genomic sequence analysis, matchmaking for additional cases, and integration of the findings regarding gene causality with the clinical management plan. The interdisciplinary gene discovery team includes clinical, computational, and experimental biomedical specialists who interact to identify the genetic etiology of the disease, and when so warranted, to devise improved or novel treatments for affected patients. This program effectively integrates the clinical and research missions of an academic medical center and affords both diagnostic and therapeutic options for patients suffering from genetic disease. It may therefore be germane to other academic medical institutions engaged in implementing genomic medicine programs.

High-throughput mapping of regulatory DNA.

Quantifying the effects of cis-regulatory DNA on gene expression is a major challenge. Here, we present the multiplexed editing regulatory assay (MERA), a high-throughput CRISPR-Cas9-based approach that analyzes the functional impact of the regulatory genome in its native context. MERA tiles thousands of mutations across ∼40 kb of cis-regulatory genomic space and uses knock-in green fluorescent protein (GFP) reporters to read out gene activity. Using this approach, we obtain quantitative information on the contribution of cis-regulatory regions to gene expression. We identify proximal and distal regulatory elements necessary for expression of four embryonic stem cell-specific genes. We show a consistent contribution of neighboring gene promoters to gene expression and identify unmarked regulatory elements (UREs) that control gene expression but do not have typical enhancer epigenetic or chromatin features. We compare thousands of functional and nonfunctional genotypes at a genomic location and identify the base pair-resolution functional motifs of regulatory elements.