Cohesin - bridging the gap among gene transcription, genome stability, and human diseases.

The intricate landscape of cellular processes governing gene transcription, chromatin organization, and genome stability is a fascinating field of study. A key player in maintaining this delicate equilibrium is the cohesin complex, a molecular machine with multifaceted roles. This review presents an in-depth exploration of these intricate connections and their significant impact on various human diseases.

Synthetic Lethality between Cohesin and WNT Signaling Pathways in Diverse Cancer Contexts.

Cohesin is a highly conserved ring-shaped complex involved in topologically embracing chromatids, gene expression regulation, genome compartmentalization, and genome stability maintenance. Genomic analyses have detected mutations in the cohesin complex in a wide array of human tumors. These findings have led to increased interest in cohesin as a potential target in cancer therapy. Synthetic lethality has been suggested as an approach to exploit genetic differences in cancer cells to influence their selective killing. In this study, we show that mutations in ESCO1, NIPBL, PDS5B, RAD21, SMC1A, SMC3, STAG2, and WAPL genes are synthetically lethal with stimulation of WNT signaling obtained following LY2090314 treatment, a GSK3 inhibitor, in several cancer cell lines. Moreover, treatment led to the stabilization of ß-catenin and affected the expression of c-MYC, probably due to the occupancy decrease in cohesin at the c-MYC promoter. Finally, LY2090314 caused gene expression dysregulation mainly involving pathways related to transcription regulation, cell proliferation, and chromatin remodeling. For the first time, our work provides the underlying molecular basis for synthetic lethality due to cohesin mutations and suggests that targeting the WNT may be a promising therapeutic approach for tumors carrying mutated cohesin.

The synergism of SMC1A cohesin gene silencing and bevacizumab against colorectal cancer.

BACKGROUND: SMC1A is a subunit of the cohesin complex that participates in many DNA- and chromosome-related biological processes. Previous studies have established that SMC1A is involved in cancer development and in particular, is overexpressed in chromosomally unstable human colorectal cancer (CRC). This study aimed to investigate whether SMC1A could serve as a therapeutic target for CRC. METHODS: At first, we studied the effects of either SMC1A overexpression or knockdown in vitro. Next, the outcome of SMC1A knocking down (alone or in combination with bevacizumab, a monoclonal antibody against vascular endothelial growth factor) was analyzed in vivo. RESULTS: We found that SMC1A knockdown affects cell proliferation and reduces the ability to grow in anchorage-independent manner. Next, we demonstrated that the silencing of SMC1A and the combo treatment were effective in increasing overall survival in a xenograft mouse model. Functional analyses indicated that both treatments lead to atypical mitotic figures and gene expression dysregulation. Differentially expressed genes were implicated in several pathways including gene transcription regulation, cellular proliferation, and other transformation-associated processes. CONCLUSIONS: These results indicate that SMC1A silencing, in combination with bevacizumab, can represent a promising therapeutic strategy for human CRC.

Donor Cell Acute Myeloid Leukemia after Hematopoietic Stem Cell Transplantation for Chronic Granulomatous Disease: A Case Report and Literature Review.

The patient reported here underwent hematopoietic stem cell transplantation (HSCT) due to chronic granulomatous disease (CGD) caused by biallelic mutations of the NCF1 gene. Two years later, he developed AML, which was unexpected and was recognized via sex-mismatched chromosomes as deriving from the donor cells; the patient was male, and the donor was his sister. Donor cell leukemia (DCL) is very rare, and it had never been reported in patients with CGD after HSCT. In the subsequent ten years, the AML relapsed three times and the patient underwent chemotherapy and three further HSCTs; donors were the same sister from the first HSCT, an unrelated donor, and his mother. The patient died during the third relapse. The DCL was characterized since onset by an acquired translocation between chromosomes 9 and 11, with a molecular rearrangement between the MLL and MLLT3 genes-a quite frequent cause of AML. In all of the relapses, the malignant clone had XX sex chromosomes and this rearrangement, thus indicating that it was always the original clone derived from the transplanted sister's cells. It exhibited the ability to remain quiescent in the BM during repeated chemotherapy courses, remission periods and HSCT. The leukemic clone then acquired different additional anomalies during the ten years of follow-up, with cytogenetic results characterized both by anomalies frequent in AML and by different, non-recurrent changes. This type of cytogenetic course is uncommon in AML.

A novel, reusable, realistic neurosurgical training simulator for cerebrovascular bypass surgery: Iatrotek® bypass simulator validation study and literature review.

Background: Microanastomosis is a challenging technique requiring continuous training to be mastered. Several models have been proposed, but few effectively reflect a real bypass surgery; even fewer are reusable, most are not easily accessible, and the setting is often quite long. We aim to validate a simplified, ready-to-use, reusable, ergonomic bypass simulator. Methods: Twelve novice and two expert neurosurgeons completed eight End-to-End (EE), eight End-to-Side (ES), and eight Side-to-Side (SS) microanastomoses using 2-mm synthetic vessels. Data on time to perform bypass (TPB), number of sutures and time required to stop potential leaks were collected. After the last training, participants completed a Likert Like Survey for bypass simulator evaluation. Each participant was assessed using the Northwestern Objective Microanastomosis Assessment Tool (NOMAT). Results: When comparing the first and last attempts, an improvement of the mean TPB was registered in both groups for the three types of microanastomosis. The improvement was always statistically significant in the novice group, while in the expert group, it was only significant for ES bypass. The NOMAT score improved in both groups, displaying statistical significance in the novices for EE bypass. The mean number of leakages, and the relative time for their resolution, also tended to progressively reduce in both groups by increasing the attempts. The Likert score expressed by the experts was slightly higher (25 vs. 24.58 by the novices). Conclusions: Our proposed bypass training model may represent a simplified, ready-to-use, reusable, ergonomic, and efficient system to improve eye-hand coordination and dexterity in performing microanastomoses.

Transpars approach for L5-S1 foraminal and extra-foraminal lumbar disc herniations: technical note.

BACKGROUND: The short pars and the narrowed surgical corridor for far lateral L5S1 herniation make the transpars approach challenging. The aim of this study is to determine the feasibility, efficacy, and safety of the transpars microscopic approach for the treatment of L5-S1 foraminal and extraforaminal lumbar disc herniation. METHODS: From 2015 to 2019, patients with L5-S1 far lateral lumbar disc herniation were prospectively recruited. Drug intake, working days lost, NRS-leg, NRS-back, nerve-root palsy, Oswestry disability-index, Macnab criteria were recorded before surgery and at follow-up. Patients were seen at 1-6-12 months after surgery. Lumbar dynamic X-rays were performed at 6-12 months after surgery and again at 2-4 years after surgery. Key-steps of surgery are described. RESULTS: Fourteen patients were enrolled. NRS-leg and NRS-back scores significantly improved (from 7.93 to 1.43 and from 3.2 to 0.6, respectively; P<0.0001). Oswestry Score significantly decreased (from 63.14 to 19.36 at 12 months; P<0.0001). L5 Root palsy improved in all cases (from 3.72/5 to 5/5; P<0.0001). At 12-months, excellent or good outcome (Macnab criteria) was achieved in 12 (85.7%) and 2 (14.3%) patients, respectively. All patients who were not retired returned to work within 30 days after surgery. No recurrence, instability or re-operations occurred. CONCLUSIONS: The trans pars microscopic approach is feasible, safe, and effective for L5-S1 foraminal and extraforaminal disc herniation. During surgery, the key-point is the oblique working angle, directed caudally, parallel to L5 pedicle. The iliac crest does not seem to constitute an obstacle.

Case report: A novel case of parental mosaicism in SMC1A gene causes inherited Cornelia de Lange syndrome.

Ultimate advances in genetic technologies have permitted the detection of transmitted cases of congenital diseases due to parental gonadosomatic mosaicism. Regarding Cornelia de Lange syndrome (CdLS), up to date, only a few cases are known to follow this inheritance pattern. However, the high prevalence of somatic mosaicism recently reported in this syndrome (∼13%), together with the disparity observed in tissue distribution of the causal variant, suggests that its prevalence in this disorder could be underestimated. Here, we report a new case of parental gonadosomatic mosaicism in SMC1A gene that causes inherited CdLS, in which the mother of the patient carries the causative variant in very low allele frequencies in buccal swab and blood. While the affected child presents with typical CdLS phenotype, his mother does not show any clinical manifestations. As regards SMC1A, the difficulty of clinical identification of carrier females has been already recognized, as well as the gender differences observed in CdLS expressivity when the causal variant is found in this gene. Currently, the use of DNA deep-sequencing techniques is highly recommended when it comes to molecular diagnosis of patients, as well as in co-segregation studies. These enable us to uncover gonadosomatic mosaic events in asymptomatic or oligosymptomatic parents that had been overlooked so far, which might have great implications regarding genetic counseling for recurrence risk.

Calcified Epidural Hematoma after Conservative Treatment of Acute Epidural Hematoma in the Pediatric Population: A Systematic Review.

BACKGROUND: Acute traumatic epidural hematoma (EDH) is a complication in 2-3% of pediatric head injuries. Surgery is mandatory in symptomatic cases; otherwise, conservative treatment is a valid approach, especially in the pediatric population. Ossified epidural hematomas (OEHs) have been reported in the pediatric population as a rare complication of conservative EDH management, although the exact incidence remains unknown. The progressive increase in conservative management may lead to increases in the OEH incidence over the next few years. Our study aimed to systematically review OEH incidence, management strategies, characteristics (thickness, inner/outer calcifications), complication rates, time to surgery after the EDH diagnosis, and clinical outcomes. SUMMARY: A systematic review was conducted in accordance with the PRISMA guidelines. Studies reporting diagnoses and clear descriptions of OEH after EDH in pediatric patients were considered eligible. Sixteen studies, including 18 pediatric patients aged 0-18 years, were included. Head trauma was the most common cause of OEH. Seven (38.8%) OEHs were treated less than 1 month after EDH diagnosis. Surgery was performed in 17 cases (94.44%), while 1 asymptomatic case (5.56%) was managed conservatively. KEY MESSAGES: Surgery was the most commonly used treatment for OEH. Data for conservative treatment of OEH are limited. Magnetic resonance imaging or ultrasound within the first 2 months, to check for EDH resolution, may be crucial to rule out complications in pediatric patients.

The multifaceted roles of cohesin in cancer.

The cohesin complex controls faithful chromosome segregation by pairing sister chromatids after DNA replication until mitosis. In addition, it is crucial for hierarchal three-dimensional organization of the genome, transcription regulation and maintaining DNA integrity. The core complex subunits SMC1A, SMC3, STAG1/2, and RAD21 as well as its modulators, have been found to be recurrently mutated in human cancers. The mechanisms by which cohesin mutations trigger cancer development and disease progression are still poorly understood. Since cohesin is involved in a range of chromosome-related processes, the outcome of cohesin mutations in cancer is complex. Herein, we discuss recent discoveries regarding cohesin that provide new insight into its role in tumorigenesis.

Use of the SpineJack direct reduction for treating type A2, A3 and A4 fractures of the thoracolumbar spine: a retrospective case series.

BACKGROUND: Compression injuries of the thoracolumbar spine without neurological impairment are usually treated with minimally invasive procedures. Intravertebral expandable implants represent an alternative strategy in fractures with low fragments' displacement. METHODS: Patients with A2, A3 and A4 fractures of the T10-L2 spinal segment without neurological impairment, fracture gap >2 mm, vertebra plana, pedicle rupture, pedicle diameter <6 mm, spinal canal encroachment ≥50%, and vertebral body spread >30% were treated with the SpineJack device. Patients with pathological/osteoporotic fractures were excluded. Demographic and fracture-related data were assessed together with vertebral kyphosis correction, vertebral height restoration/loss of correction and final kyphosis. The modified Rankin Scale (mRS), Oswestry Disability Index (ODI), Visual Analogue Scale (VAS), Smiley-Webster Pain Scale (SWPS) and EuroQol-5D (EQ-5D) were evaluated at 1 (-post), 6 and 12 months (-fup) after surgery. Statistical analysis was performed and p values ≤0.05 were considered significant. RESULTS: Fifty-seven patients were included in the study. Patients aged >60 years reported worse kyphosis correction (<4°) with more postoperative complications, while vertebral plasticity in younger patients, fragmentation-related greater remodeling in A3/A4 fractures, and treatments within 7 days of trauma determined superior wedging corrections, with better EQ-5D-post and mRS-fup. Cement leakages did not affect functional outcome, while female gender and American Society of Anesthesiologists (ASA) score of 3-4 were associated with worse ODI-fup and VAS-fup. Although fracture characteristics and radiological outcome did not negatively influence the clinical outcome, A2 fracture was a risk factor for complications, thus indirectly compromising both the functional and radiological outcome. CONCLUSION: With spread of <30%, the SpineJack is an alternative to minimally invasive fixations for treating A3/A4 thoracolumbar fractures, being able to preserve healthy motion segments in younger patients and provide an ultra-conservative procedure for elderly and fragile patients.

Disease-associated c-MYC downregulation in human disorders of transcriptional regulation.

Cornelia de Lange syndrome (CdLS) is a rare multiorgan developmental disorder caused by pathogenic variants in cohesin genes. It is a genetically and clinically heterogeneous dominant (both autosomal and X-linked) rare disease. Increasing experimental evidence indicates that CdLS is caused by a combination of factors, such as gene expression dysregulation, accumulation of cellular damage and cellular aging, which collectively contribute to the CdLS phenotype. The CdLS phenotype overlaps with a number of related diagnoses such as KBG syndrome and Rubinstein-Taybi syndrome both caused by variants in chromatin-associated factors other than cohesin. The molecular basis underlying these overlapping phenotypes is not clearly defined. Here, we found that cells from individuals with CdLS and CdLS-related diagnoses are characterized by global transcription disturbance and share common dysregulated pathways. Intriguingly, c-MYC (subsequently referred to as MYC) is downregulated in all cell lines and represents a convergent hub lying at the center of dysregulated pathways. Subsequent treatment with estradiol restores MYC expression by modulating cohesin occupancy at its promoter region. In addition, MYC activation leads to modification in expression in hundreds of genes, which in turn reduce the oxidative stress level and genome instability. Together, these results show that MYC plays a pivotal role in the etiopathogenesis of CdLS and CdLS-related diagnoses and represents a potential therapeutic target for these conditions.

The Infratemporal Retro-Eustachian Transposition of the Temporoparietal Fascial Flap for Clival Reconstruction After Endoscopic Endonasal Approach: An Anatomic Conceptual Technique.

BACKGROUND: Reconstruction after endoscopic endonasal approaches is a key element. Lower clivus reconstruction is difficult and most of the times a pedicled flap is not available. As the complexity and the dimensions of the exposure increase, a reliable reconstruction technique becomes more and more important. OBJECTIVE: To describe the anatomic and technical nuances of the transposition of the temporoparietal fascial flap for lower clivus reconstruction. METHODS: A specific temporoparietal fascial flap (TPFF) design and tunneling technique has been studied using 4 head specimens, microscopic and endoscopic surgical techniques, and neuronavigation. RESULTS: The L-shaped flap offers several advantages. It can be tunneled directly toward the lower clivus passing through the infratemporal fossa. CONCLUSION: The infratemporal retro-eustachian transposition of an L-shaped TPFF provides a vascularized tissue virtually without dimension limits. This is the only technique that allows the flap to be tunneled directly in the lower clivus with the most vascular portion being at the bottom of the defect. Clinical validation is still required since more issues may become relevant in a real-surgery setting. Though, due to its possible complications, this methodology needs further testing and should not be attempted in less experienced hands.

Epidermoid cyst of the anterior clinoid process: report of a unique finding and literature review of the middle cranial fossa locations.

BACKGROUND: Epidermoids cysts are relatively rare, benign, congenital tumours, representing from 0.3% to 1.8% of all intracranial lesions. When extradural, they are most commonly reported in the temporal or parietal bones as intradiploic lesions; when intradural their most common location is the cerebellopontine angle and less frequently the middle cranial fossa. Herein we present a unique case of an extradural-intraosseous epidermoid cyst of the anterior clinoid process, integrating our single-case experience into a focused literature review of these lesions, when located in the middle cranial fossa. CASE DESCRIPTION: A 49 years old man came to our attention with history of head trauma. Urgent brain CT and elective brain MRI showed imaging suggestive for an anterior clinoid process epidermoid cyst. Through a pterional approach, the lesion was completely removed with microsurgical endoscope assisted technique. MRI at one year follow up showed no recurrence. METHODS: Current literature on epidermoid cysts located in middle cranial fossa was reviewed. A total of 22 papers, containing 70 epidermoid cyst were selected for the review. Symptoms at presentation; anatomic location; surgical approach; extent of resection and recurrence; outcome after surgery and at follow up were analysed for each case. CONCLUSIONS: In the 70 published cases of middle fossa epidermoid cysts, the majority presented with trigeminal neuralgia. Most of the cases were operated through a pterional approach, while recent literature showed an increasing interest in endonasal endoscopic techniques. Subtotal resection is not a straight predictive value for recurrence; post-operative neurological deficits incidence is low and generally resolve at follow-up.

Cohesin mutations are synthetic lethal with stimulation of WNT signaling.

Mutations in genes encoding subunits of the cohesin complex are common in several cancers, but may also expose druggable vulnerabilities. We generated isogenic MCF10A cell lines with deletion mutations of genes encoding cohesin subunits SMC3, RAD21, and STAG2 and screened for synthetic lethality with 3009 FDA-approved compounds. The screen identified several compounds that interfere with transcription, DNA damage repair and the cell cycle. Unexpectedly, one of the top 'hits' was a GSK3 inhibitor, an agonist of Wnt signaling. We show that sensitivity to GSK3 inhibition is likely due to stabilization of ß-catenin in cohesin-mutant cells, and that Wnt-responsive gene expression is highly sensitized in STAG2-mutant CMK leukemia cells. Moreover, Wnt activity is enhanced in zebrafish mutant for cohesin subunits stag2b and rad21. Our results suggest that cohesin mutations could progress oncogenesis by enhancing Wnt signaling, and that targeting the Wnt pathway may represent a novel therapeutic strategy for cohesin-mutant cancers.

Simplified four-step retropharyngeal approach for the upper cervical spine: technical note.

PURPOSE: In this paper, we propose a simplified four-step retropharyngeal approach, whose aim is getting straight to the upper cervical spine minimizing complications. METHODS: While the classical retropharyngeal approach includes about 11 steps, ours is a four-step approach: patient positioning, skin-platysma incision, hyoid bone superolateral dissection and retropharyngeal blunt exposure. We avoid several steps of the classical anterior retropharyngeal approach, particularly dissection of submandibular gland, facial veins, external carotid artery and thyroid artery, bellies of the digastric muscle, hypoglossal nerve, thyrohyoid membrane and the internal branch of superior laryngeal nerve. RESULTS: We have adopted this technique for five patients: two patients had a C2-C3 herniated disk with myelopathy, two patients had unstable Hangman fracture with no bone fusion after 2-month treatment with rigid collar, and one patient had a C2-C3 osteophyte with dysphagia. The intraoperative time needed for reaching the retropharyngeal space was 15 (first case), 9 (second case), 7 min (third case-illustrative case-and fourth case), 8 min (fifth case). No complications occurred. CONCLUSION: Our simplification, avoiding several steps, is simple, effective, safe, and rapid and requires a simple learning curve.

Pathogenic variants in EP300 and ANKRD11 in patients with phenotypes overlapping Cornelia de Lange syndrome.

Cornelia de Lange syndrome (CdLS), Rubinstein-Taybi syndrome (RSTS), and KBG syndrome are three distinct developmental human disorders. Variants in seven genes belonging to the cohesin pathway, NIPBL, SMC1A, SMC3, HDAC8, RAD21, ANKRD11, and BRD4, were identified in about 80% of patients with CdLS, suggesting that additional causative genes remain to be discovered. Two genes, CREBBP and EP300, have been associated with RSTS, whereas KBG results from variants in ANKRD11. By exome sequencing, a genetic cause was elucidated in two patients with clinical diagnosis of CdLS but without variants in known CdLS genes. In particular, genetic variants in EP300 and ANKRD11 were identified in the two patients with CdLS. EP300 and ANKRD11 pathogenic variants caused the reduction of the respective proteins suggesting that their low levels contribute to CdLS-like phenotype. These findings highlight the clinical overlap between CdLS, RSTS, and KBG and support the notion that these rare disorders are linked to abnormal chromatin remodeling, which in turn affects the transcriptional machinery.

The multiple facets of the SMC1A gene.

Structural Maintenance of Chromosomes (SMCs) are part of a large family of ring complexes that participates in a number of DNA transactions. Among SMCs, SMC1A gene is unique. It encodes a subunit of the cohesin-core complex that tethers sister chromatids together to ensure correct chromosome segregation in both mitosis and meiosis. As a member of the cohesin ring, SMC1A takes part in gene transcription regulation and genome organization; and it participates in the DNA Damage Repair (DDR) pathway, being phosphorylated by Ataxia Telangiectasia Mutated (ATM) and Ataxia Telangiectasia and Rad3 Related (ATR) threonine/serine kinases. It is also a component of the Recombination protein complex (RC-1) involved in DNA repair by recombination. SMC1A pathogenic variants have been described in Cornelia de Lange syndrome (CdLS), a human rare disease, and recently SMC1A variants have been associated with epilepsy or resembling Rett syndrome phenotype. Finally, SMC1A variants have been identified in several human cancers. In this review, our current knowledge of the SMC1A gene has been summarized.

Chromosome Missegregation in Single Human Oocytes Is Related to the Age and Gene Expression Profile.

The growing trend for women to postpone childbearing has resulted in a dramatic increase in the incidence of aneuploid pregnancies. Despite the importance to human reproductive health, the events precipitating female age-related meiotic errors are poorly understood. To gain new insight into the molecular basis of age-related chromosome missegregation in human oocytes, we combined the transcriptome profiles of twenty single oocytes (derived from females divided into two groups according to age <35 and ≥35 years) with their chromosome status obtained by array comparative genomic hybridization (aCGH). Furthermore, we compared the transcription profile of the single oocyte with the surrounding cumulus cells (CCs). RNA-seq data showed differences in gene expression between young and old oocytes. Dysregulated genes play a role in important biological processes such as gene transcription regulation, cytoskeleton organization, pathways related to RNA maturation and translation. The comparison of the transcription profile of the oocyte and the corresponding CCs highlighted the differential expression of genes belonging to the G protein-coupled receptor superfamily. Finally, we detected the loss of a X chromosome in two oocytes derived from women belonging to the ≥35 years age group. These aneuploidies may be caused by the detriment of REEP4, an endoplasmic reticulum protein, in women aged ≥35 years. Here we gained new insight into the complex regulatory circuit between the oocyte and the surrounding CCs and uncovered a new putative molecular basis of age-related chromosome missegregation in human oocytes.