An RTEL1 Mutation Links to Infantile-Onset Ulcerative Colitis and Severe Immunodeficiency

Red flags to suspect inborn errors of immunity in patients with autoimmune diseases

Inborn errors of immunity are monogenic disorders that predispose patients to immune dysregulation, autoimmunity, and infection. Some autoimmune diseases, such as autoimmune cytopenias, systemic lupus erythematosus, and inflammatory bowel diseases, are increasingly recognized as phenotypes of inborn errors of immunity. The objective of this article was to identify red flags or clinical/laboratory markers to suspect inborn errors of immunity in patients with autoimmune cytopenias, systemic lupus erythematosus, and inflammatory bowel diseases through a systematic literature review. The study followed the systematic reviews and meta-analysis guidelines (PRISMA). After selection, we included 36 articles, and their methodological quality was verified using the Joanna Briggs Institute tools for individual risk of bias analysis. The principal red flags in autoimmune cytopenias are chronic, recurrent, and refractory cytopenias, recurrent infection, severe infectious complications associated with immunosuppressive treatment, and chronic lymphoproliferation. In systemic lupus erythematosus, red flags include age of onset before five years, severe organ involvement, chilblain lesions, and chronic lymphoproliferation. For inflammatory bowel diseases, red flags are an age of onset before two years, resistance to conventional therapies, atypical endoscopic or histologic findings, and consanguineous parents. Autoimmune diseases may be the primary manifestation of inborn errors of immunity in pediatric and adult patients. An early diagnosis of a monogenic disorder allows for the tailoring of effective treatment plans, providing prognostic information to families, and offering genetic counseling.

Inherited Telomere Biology Disorders: Pathophysiology, Clinical Presentation, Diagnostics, and Treatment

Background

Telomeres are the end-capping structures of all eukaryotic chromosomes thereby protecting the genome from damage and degradation. During the aging process, telomeres shorten continuously with each cell division until critically short telomeres prevent further proliferation whereby cells undergo terminal differentiation, senescence, or apoptosis. Premature aging due to critically short telomere length (TL) can also result from pathogenic germline variants in the telomerase complex or related genes that typically counteract replicative telomere shortening in germline and certain somatic cell populations, e.g., hematopoetic stem cells. Inherited diseases that result in altered telomere maintenance are summarized under the term telomere biology disorder (TBD).

Summary

Since TL both reflects but more importantly restricts the replicative capacity of various human tissues, a sufficient telomere reserve is particularly important in cells with high proliferative activity (e.g., hematopoiesis, immune cells, intestinal cells, liver, lung, and skin). Consequently, altered telomere maintenance as observed in TBDs typically results in premature replicative cellular exhaustion in the respective organ systems eventually leading to life-threatening complications such as bone marrow failure (BMF), pulmonary fibrosis, and liver cirrhosis.

Key Messages

The recognition of a potential congenital origin in approximately 10% of adult patients with clinical BMF is of utmost importance for the proper diagnosis, appropriate patient and family counseling, to prevent the use of inefficient treatment and to avoid therapy-related toxicities including appropriate donor selection when patients have to undergo stem cell transplantation from related donors. This review summarizes the current state of knowledge about TBDs with particular focus on the clinical manifestation patterns in children (termed early onset TBD) compared to adults (late-onset TBD) including typical treatment- and disease course-related complications as well as their prognosis and adequate therapy. Thereby, it aims to raise awareness for a disease group that is currently still highly underdiagnosed particularly when it first manifests itself in adulthood.

Exploration of the potential causative genes for inflammatory bowel disease: Transcriptome-wide association analysis, Mendelian randomization analysis and Bayesian colocalisation

Background

Inflammatory bowel disease (IBD) poses a complex challenge due to its intricate underlying mechanisms, and curative treatments remain elusive. Consequently, there is an urgent need to identify genes causally associated with IBD.

Methods

We extracted blood eQTL data from the GTExv8.ALL.Whole_Blood database, genome-wide association studies (GWAS) summary statistics of IBD from the IEU GWAS database, and performed a three-fold analysis protocol, including transcriptome-wide association analysis, Mendelian randomisation analysis, Bayesian colocalisation, and subsequent potential therapeutic agents identification.

Results

We identified four pathogenic genes, namely CARD9, RTEL1, STMN3 and ARFRP1, that promote the development of IBD, encompassing both ulcerative colitis (UC) and Crohn's disease (CD). Notably, ARFRP1 exhibited the ability to suppress IBD (encompassing UC and CD) development. Regarding drug prediction, cyclophosphamide emerged as a promising novel therapeutic option for IBD, encompassing UC and CD.

Conclusion

We identified several potential genes related to IBD (UC and CD), including CARD9, RTEL1, STMN3 and ARFRP1, warranting further investigation in functional studies to elucidate underlying disease mechanisms. Additionally, clinical studies exploring the potential of cyclophosphamide as a treatment avenue for IBD are warranted.

High-throughput omics technologies in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, relapsing intestinal disease. Elucidation of the pathogenic mechanisms of IBD requires high-throughput technologies (HTTs) to effectively obtain and analyze large amounts of data. Recently, HTTs have been widely used in IBD, including genomics, transcriptomics, proteomics, microbiomics, metabolomics and single-cell sequencing. When combined with endoscopy, the application of these technologies can provide an in-depth understanding on the alterations of intestinal microbe diversity and abundance, the abnormalities of signaling pathway-mediated immune responses and functionality, and the evaluation of therapeutic effects, improving the accuracy of early diagnosis and treatment of IBD. This review comprehensively summarizes the development and advancement of HTTs, and also highlights the challenges and future directions of these technologies in IBD research. Although HTTs have made striking breakthrough in IBD, more standardized methods and large-scale dataset processing are still needed to achieve the goal of personalized medicine.

RTEL1 is upregulated in colorectal cancer and promotes tumor progression

As one of the most common cancers worldwide, the incidence of colorectal cancer (CRC) continues to increase. Metastasis is the leading cause of death for this malignant disease. Regulator of telomere elongation helicase 1 (RTEL1) is a key factor that maintains telomere stability and contributes to DNA repair. Recent advances have suggested that RTEL1 exerts other functions through various mechanisms. However, little is known about its role in human cancers, including CRC. In this study, we revealed that the copy number of RTEL1 was significantly higher in CRC tissues, especially in metastatic CRC tissues, than in paired normal tissues, which was associated with increased expression. Increased RTEL1 expression was significantly correlated with CRC progression and poor survival. Functionally, RTEL1 knockdown suppressed the proliferation and metastasis of CRC both in vitro and in vivo. In addition, multiple signalling pathways, including the mitotic cell cycle, DNA repair, and EMT, were potentially regulated by RTEL1. Notably, GPR17 appeared to be a candidate downstream target gene that partially mediated the tumor-promoting effects of RTEL1 in CRC. Altogether, our results indicate that RTEL1 plays a crucial role in CRC progression and appears to be a promising therapeutic target and prognosis for CRC.

RTEL1 gene polymorphisms and neuroblastoma risk in Chinese children

BACKGROUND

Neuroblastoma, a neuroendocrine tumor originating from the sympathetic ganglia, is one of the most common malignancies in childhood. RTEL1 is critical in many fundamental cellular processes, such as DNA replication, DNA damage repair, genomic integrity, and telomere stability. Single nucleotide polymorphisms (SNPs) in the RTEL1 gene have been reported to confer susceptibility to multiple cancers, but their contributing roles in neuroblastoma remain unclear.

METHODS

We conducted a study on 402 neuroblastoma cases and 473 controls to assess the association between four RTEL1 SNPs (rs3761124 T>C, rs3848672 T>C, rs3208008 A>C and rs2297441 G>A) and neuroblastoma susceptibility.

RESULTS

Our results show that rs3848672 T>C is significantly associated with an increased risk of neuroblastoma [CC vs. TT/TC: adjusted odds ratio (OR)=1.39, 95% confidence interval (CI)=1.02-1.90, P=0.038]. The stratified analysis further indicated that boy carriers of the rs3848672 CC genotype had a higher risk of neuroblastoma, and all carriers had an increased risk of developing neuroblastoma of mediastinum origin. Moreover, the rs2297441 AA genotype increased neuroblastoma risk in girls and predisposed children to neuroblastoma arising from retroperitoneal.

CONCLUSION

Our study indicated that the rs3848672 CC and rs2297441 AA genotypes of the RTEL1 gene are significantly associated with an increased risk of neuroblastoma in Chinese children in a gender- and site-specific manner.

Trends in the Epidemiology of Pneumocystis Pneumonia in Immunocompromised Patients without HIV Infection

The increasing morbidity and mortality of life-threatening Pneumocystis pneumonia (PCP) in immunocompromised people poses a global concern, prompting the World Health Organization to list it as one of the 19 priority invasive fungal diseases, calling for increased research and public health action. In response to this initiative, we provide this review on the epidemiology of PCP in non-HIV patients with various immunodeficient conditions, including the use of immunosuppressive agents, cancer therapies, solid organ and stem cell transplantation, autoimmune and inflammatory diseases, inherited or primary immunodeficiencies, and COVID-19. Special attention is given to the molecular epidemiology of PCP outbreaks in solid organ transplant recipients; the risk of PCP associated with the increasing use of immunodepleting monoclonal antibodies and a wide range of genetic defects causing primary immunodeficiency; the trend of concurrent infection of PCP in COVID-19; the prevalence of colonization; and the rising evidence supporting de novo infection rather than reactivation of latent infection in the pathogenesis of PCP. Additionally, we provide a concise discussion of the varying effects of different immunodeficient conditions on distinct components of the immune system. The objective of this review is to increase awareness and knowledge of PCP in non-HIV patients, thereby improving the early identification and treatment of patients susceptible to PCP.

Genetics of human telomere biology disorders

Telomeres are specialized nucleoprotein structures at the ends of linear chromosomes that prevent the activation of DNA damage response and repair pathways. Numerous factors localize at telomeres to regulate their length, structure and function, to avert replicative senescence or genome instability and cell death. In humans, Mendelian defects in several of these factors can result in abnormally short or dysfunctional telomeres, causing a group of rare heterogeneous premature-ageing diseases, termed telomeropathies, short-telomere syndromes or telomere biology disorders (TBDs). Here, we review the TBD-causing genes identified so far and describe their main functions associated with telomere biology. We present molecular aspects of TBDs, including genetic anticipation, phenocopy, incomplete penetrance and somatic genetic rescue, which underlie the complexity of these diseases. We also discuss the implications of phenotypic and genetic features of TBDs on fundamental aspects related to human telomere biology, ageing and cancer, as well as on diagnostic, therapeutic and clinical approaches.

Regulator of telomere elongation helicase 1 gene and its association with malignancy

BACKGROUND

With the progression of next-generation sequencing technologies, researchers have identified numerous variants of the regulator of telomere elongation helicase 1 (RTEL1) gene that are associated with a broad spectrum of phenotypic manifestations, including malignancies. At the molecular level, RTEL1 is involved in the regulation of the repair, replication, and transcription of deoxyribonucleic acid (DNA) and the maintenance of telomere length. RTEL1 can act both as a promotor and inhibitor of tumorigenesis. Here, we review the potential mechanisms implicated in the malignant transformation of tissues under conditions of RTEL1 deficiency or its aberrant overexpression.

RECENT FINDINGS

A major hemostatic challenge during RTEL1 dysfunction could arise from its unbalanced activity for unwinding guanine-rich quadruplex DNA (G4-DNA) structures. In contrast, RTEL1 deficiency leads to alterations in telomeric and genome-wide DNA maintenance mechanisms, ribonucleoprotein metabolism, and the creation of an inflammatory and immune-deficient microenvironment, all promoting malignancy. Additionally, we hypothesize that functionally similar molecules could act to compensate for the deteriorated functions of RTEL1, thereby facilitating the survival of malignant cells. On the contrary, RTEL1 over-expression was directed toward G4-unwinding, by promoting replication fork progression and maintaining intact telomeres, may facilitate malignant transformation and proliferation of various pre-malignant cellular compartments.

CONCLUSIONS

Therefore, restoring the equilibrium of RTEL1 functions could serve as a therapeutic approach for preventing and treating malignancies.

Understanding inborn errors of immunity: A lens into the pathophysiology of monogenic inflammatory bowel disease

Inflammatory bowel diseases (IBD) are chronic inflammatory conditions of the gastrointestinal tract, including Crohn’s disease, ulcerative colitis and inflammatory bowel disease-undefined (IBD-U). IBD are understood to be multifactorial, involving genetic, immune, microbial and environmental factors. Advances in next generation sequencing facilitated the growing identification of over 80 monogenic causes of IBD, many of which overlap with Inborn errors of immunity (IEI); Approximately a third of currently identified IEI result in gastrointestinal manifestations, many of which are inflammatory in nature, such as IBD. Indeed, the gastrointestinal tract represents an opportune system to study IEI as it consists of the largest mass of lymphoid tissue in the body and employs a thin layer of intestinal epithelial cells as the critical barrier between the intestinal lumen and the host. In this mini-review, a selection of pertinent IEI resulting in monogenic IBD is described involving disorders in the intestinal epithelial barrier, phagocytosis, T and B cell defects, as well as those impairing central and peripheral tolerance. The contribution of disrupted gut-microbiota-host interactions in disturbing intestinal homeostasis among patients with intestinal disease is also discussed. The molecular mechanisms driving pathogenesis are reviewed along with the personalized therapeutic interventions and investigational avenues this growing knowledge has enabled.

A Case Series of Pediatric Intestinal Ganglioneuromatosis With Novel Phenotypic and Genotypic Profile

Introduction

Intestinal ganglioneuromatosis (IGN) is a rare condition with enteric involvement. Herein, we report a case series of pediatric IGN with a novel phenotypic and genotypic profile.

Methods

The clinical presentation, histopathology, immunochemistry, molecular features, treatment, and prognosis of 3 cases of IGN were assessed.

Results

The cases involved 3 boys with an age range of 1 year and 4 months to 8 years, mimicking juvenile polyps or pseudomembranous enteritis. One patient carried a novel germline mutation in RTEL1 (c.296C > T/p.Pro99Leu) along with variants in F11 (c.1489C > T/p.Arg497Xaa), NBAS (c.1514delC/p.Pro505Hisfs*15), and FECH (c.315-48T > C/splicing), who died due to intractable inflammation. The other two patients underwent recurrence without significant signs of systemic syndrome or malignant progression.

Conclusion

This case series added to the phenotypic and genotypic spectrum of pediatric IGN, which requires the accumulation of more cases and research for in-depth understanding.

Pathogenesis of Choledochal Cyst: Insights from Genomics and Transcriptomics

Choledochal cysts (CC) is characterized by extra- and/or intra-hepatic b\ile duct dilations. There are two main theories, “pancreaticobiliary maljunction” and “congenital stenosis of bile ducts” proposed for the pathogenesis of CC. Although family cases or CC associated with other anomalies have been reported, the molecular pathogenesis of CC is still poorly understood. Recent advances in transcriptomics and genomics analysis platforms have unveiled key expression signatures/genes/signaling pathways in the pathogenesis of human diseases including CC. This review summarizes insights from genomics and transcriptomics studies into the pathogenesis of CC, with the aim to improve (i) our understanding of its underlying complex pathomechanisms, and (ii) clinical management of different subtypes of CC, in particular their associated hepatic fibrotic change and their risk of malignancy transformation.