TERT and TERC mutations detected in cryptic dyskeratosis congenita suppress telomerase activity

Telomere length and telomerase reverse transcriptase gene polymorphism as potential markers of complete chimerism and GvHD development after allogeneic haematopoietic stem cell transplantation

INTRODUCTION

Telomerase reverse transcriptase (TERT) is a catalytic subunit of telomerase that maintains genome stability by maintaining telomere length (TL). The massive proliferation of donor cells in the recipient's body for engraftment results in accelerated telomere shortening. Genetic variability within the TERT gene affects telomerase activity, and was shown to influence of haematopoietic stem cell transplantation (HSCT) outcome. In the present study, we aimed to analyse the effect of recipient and donor TL and TERT single nucleotide polymorphism (SNP) on the occurrence of post-HSCT complications.

METHODS

Our study included 120 recipient-donor pairs. TERT promoter (TERTp) SNP (rs2853669) SNP variant was detected with the use of the LightSNiP typing assay employing real-time polymerase chain reaction (PCR) amplifications. Telomere length measurements were performed using qPCR test kits (ScienCell's Absolute Human Telomere Length Quantification qPCR Assay Kit [AHTLQ], Carlsbad, CA, USA).

RESULTS

The presence of TERTp rs2853669 T allele in the recipient was associated with a higher risk for acute graft-versus-host-disease (aGvHD) manifestation (p = 0.046) and a significantly shorter aGvHD-free survival (p = 0.041). The latter association was further confirmed in a Cox proportional hazards model (p = 0.043). However, no statistically significant association between telomere length and post-transplant complications was observed. Furthermore, we found that shorter TL characterized donors of patients with late complete chimerism at 180 day after HSCT (p = 0.011).

CONCLUSION

Our results suggest that recipient allele TERTp rs2853669 T is a marker of unfavourable outcome in the context of aGvHD. Shorter TL in donors could be associated with later achievement of complete chimerism.

TERT de novo mutation-associated dyskeratosis congenita and porto-sinusoidal vascular disease: a case report

BACKGROUND

Dyskeratosis congenita is a rare genetic disease due to telomere biology disorder and characterized by heterogeneous clinical manifestations and severe complications. "Porto-sinusoidal vascular disease" has been recently proposed, according to new diagnostic criteria, to replace the term "idiopathic non-cirrhotic portal hypertension." TERT plays an important role in telomeric DNA repair and replication. A TERT c.2286 + 1G/A mutation in a splicing consensus site was identified in a patient with pulmonary fibrosis. Recently, a pathogenic de novo TERT c.280A > T variant was associated with diffuse lung disease in an infant.

CASE PRESENTATION

A 16-year-old Han male patient experienced unexplained black stool for 7 days, accompanied by dizziness and fatigue. On examination, there were mesh pigmentations on the exposed areas of the skin on both hands and feet. Laboratory testing revealed moderate hemorrhagic anemia and mild elevation of alanine aminotransferase. A computed tomography scan showed portal hypertension, esophageal and gastric varices, and splenomegaly. The liver stiffness measurement by FibroScan was 6.0 kPa. Liver biopsy revealed typical features of porto-sinusoidal vascular disease. Whole exome sequencing identified a heterozygous TERT c.2286 + 1G > A de novo mutation and quantitative polymerase chain reaction revealed very short telomeres (less than the first percentile for his age). The patient was diagnosed as TERT de novo mutation-related dyskeratosis congenita and porto-sinusoidal vascular disease. He underwent esophageal and gastric variceal ligation treatment and received a carvedilol tablet (12.5 mg) every morning. After 6 months, he has moderate iron deficiency anemia and has started receiving polysaccharide iron complex therapy.

CONCLUSION

When discovering reticular rash and unknown portal hypertension, it is necessary to perform whole exome sequencing and chromosome length testing to clarify the possibility of dyskeratosis congenita/telomere biology disorder with porto-sinusoidal vascular disease.

Functional genomics for curation of variants in telomere biology disorder associated genes: A systematic review

PURPOSE

Patients with an underlying telomere biology disorder (TBD) have variable clinical presentations, and they can be challenging to diagnose clinically. A genomic diagnosis for patients presenting with TBD is vital for optimal treatment. Unfortunately, many variants identified during diagnostic testing are variants of uncertain significance. This complicates management decisions, delays treatment, and risks nonuptake of potentially curative therapies. Improved application of functional genomic evidence may reduce variants of uncertain significance classifications.

METHODS

We systematically searched the literature for published functional assays interrogating TBD gene variants. When possible, established likely benign/benign and likely pathogenic/pathogenic variants were used to estimate the assay sensitivity, specificity, positive predictive value, negative predictive value, and odds of pathogenicity.

RESULTS

In total, 3131 articles were screened and 151 met inclusion criteria. Sufficient data to enable a PS3/BS3 recommendation were available for TERT variants only. We recommend that PS3 and BS3 can be applied at a moderate and supportive level, respectively. PS3/BS3 application was limited by a lack of assay standardization and limited inclusion of benign variants.

CONCLUSION

Further assay standardization and assessment of benign variants are required for optimal use of the PS3/BS3 criterion for TBD gene variant classification.

Challenges in the interpretation of a germline TERT variant in a patient with juvenile myelomonocytic leukemia

Dyskeratosis congenita (DC) is a bone marrow failure syndrome with extrahematopoietic abnormalities. DC is a paradigmatic telomere biology disorder (TBD) caused by germline mutations in genes responsible for telomere maintenance including TERT. Cryptic TBD is a bone marrow failure syndrome due to premature telomere shortening but without additional symptoms, frequently clinically indistinguishable from severe aplastic anemia (SAA) or hypoplastic myelodysplastic syndrome. We present the complex diagnostic pathway in a boy with a rare germline p.Thr726Met TERT variant with previous reports of SAA association and compromised enzymatic function who presented with juvenile myelomonocytic leukemia, which is a rare myelodysplastic/myeloproliferative neoplasm of childhood.

Relative Leukocyte Telomere Length and Telomerase Complex Regulatory Markers Association with Leber's Hereditary Optic Neuropathy

Background and Objectives: To evaluate the association of relative leukocyte telomere length (RLTL) and telomerase complex regulatory markers with Leber’s hereditary optic neuropathy (LHON). Material and Methods: A case-control study was performed in patients with LHON (≥18 years) and healthy subjects. The diagnosis of LHON was based on a genetic blood test (next-generation sequencing with Illumina MiSeq, computer analysis: BWA2.1 Illumina BaseSpace, Alamut, and mtDNA Variant analyzer 1000 were performed) and diagnostic criteria approved by the LHON disease protocol. Statistical analysis was performed using the standard statistical software package, IBM SPSS Statistics 27. Statistically significant results were considered when p < 0.05. Results: Significantly longer RLTL was observed in LHON patients than in healthy controls (p < 0.001). RLTL was significantly longer in women and men with LOHN than in healthy women and men in the control group (p < 0.001 and p = 0.003, respectively). In the elderly group (>32 years), RLTL was statistically significantly longer in LHON patients compared with healthy subjects (p < 0.001). The GG genotype of the TERC rs12696304 polymorphism was found to be statistically significantly higher in the LHON group (p = 0.041), and the C allele in the TERC rs12696304 polymorphism was found to be statistically significantly less common in the LHON group (p < 0.001). The RLTL of LHON patients was found to be statistically significantly longer in the TERC rs12696304 polymorphism in all tested genotypes (CC, p = 0.005; CG, p = 0.008; GG, p = 0.025), TEP1 rs1760904 polymorphism in the GA genotype (p < 0.001), and TEP1 gene rs1713418 in the AA and AG genotypes (p = 0.011 and p < 0.001, respectively). Conclusions: The RLTL in LHON patients was found to be longer than in healthy subjects regardless of treatment with idebenone. The TERC rs12696304 polymorphism, of all studied polymorphisms, was the most significantly associated with changes in LHON and telomere length.