Association of Somatic TET2 Mutations With Giant Cell Arteritis

OBJECTIVE

Giant cell arteritis (GCA) is an age-related vasculitis. Prior studies have identified an association between GCA and hematologic malignancies (HMs). How the presence of somatic mutations that drive the development of HMs, or clonal hematopoiesis (CH), may influence clinical outcomes in GCA is not well understood.

METHODS

To examine an association between CH and GCA, we analyzed sequenced exomes of 470,960 UK Biobank (UKB) participants for the presence of CH and used multivariable Cox regression. To examine the clinical phenotype of GCA in patients with and without somatic mutations across the spectrum of CH to HM, we performed targeted sequencing of blood samples and electronic health record review on 114 patients with GCA seen at our institution. We then examined associations between specific clonal mutations and GCA disease manifestations.

RESULTS

UKB participants with CH had a 1.48-fold increased risk of incident GCA compared to UKB participants without CH. GCA risk was highest among individuals with cytopenia (hazard ratio [HR] 2.98, P = 0.00178) and with TET2 mutation (HR 2.02, P = 0.00116). Mutations were detected in 27.2% of our institutional GCA cohort, three of whom had HM at GCA diagnosis. TET2 mutations were associated with vision loss in patients with GCA (odds ratio 4.33, P = 0.047).

CONCLUSIONS

CH increases risk for development of GCA in a genotype-specific manner, with the greatest risk being conferred by the presence of mutations in TET2. Somatic TET2 mutations likewise increase the risk of GCA-associated vision loss. Integration of somatic genetic testing in GCA diagnostics may be warranted in the future.

Nonsense Variant PRDM16-Q187X Causes Impaired Myocardial Development and TGF-β Signaling Resulting in Noncompaction Cardiomyopathy in Humans and Mice

BACKGROUND

PRDM16 plays a role in myocardial development through TGF-β (transforming growth factor-beta) signaling. Recent evidence suggests that loss of PRDM16 expression is associated with cardiomyopathy development in mice, although its role in human cardiomyopathy development is unclear. This study aims to determine the impact of PRDM16 loss-of-function variants on cardiomyopathy in humans.

METHODS

Individuals with PRDM16 variants were identified and consented. Induced pluripotent stem cell-derived cardiomyocytes were generated from a proband hosting a Q187X nonsense variant as an in vitro model and underwent proliferative and transcriptional analyses. CRISPR (clustered regularly interspaced short palindromic repeats)-mediated knock-in mouse model hosting the Prdm16Q187X allele was generated and subjected to ECG, histological, and transcriptional analysis.

RESULTS

We report 2 probands with loss-of-function PRDM16 variants and pediatric left ventricular noncompaction cardiomyopathy. One proband hosts a PRDM16-Q187X variant with left ventricular noncompaction cardiomyopathy and demonstrated infant-onset heart failure, which was selected for further study. Induced pluripotent stem cell-derived cardiomyocytes prepared from the PRDM16-Q187X proband demonstrated a statistically significant impairment in myocyte proliferation and increased apoptosis associated with transcriptional dysregulation of genes implicated in cardiac maturation, including TGF-β-associated transcripts. Homozygous Prdm16Q187X/Q187X mice demonstrated an underdeveloped compact myocardium and were embryonically lethal. Heterozygous Prdm16Q187X/WT mice demonstrated significantly smaller ventricular dimensions, heightened fibrosis, and age-dependent loss of TGF-β expression. Mechanistic studies were undertaken in H9c2 cardiomyoblasts to show that PRDM16 binds TGFB3 promoter and represses its transcription.

CONCLUSIONS

Novel loss-of-function PRDM16 variant impairs myocardial development resulting in noncompaction cardiomyopathy in humans and mice associated with altered TGF-β signaling.

State dependence of CO2 forcing and its implications for climate sensitivity

When evaluating the effect of carbon dioxide (CO2) changes on Earth's climate, it is widely assumed that instantaneous radiative forcing from a doubling of a given CO2 concentration (IRF2×CO2) is constant and that variances in climate sensitivity arise from differences in radiative feedbacks or dependence of these feedbacks on the climatological base state. Here, we show that the IRF2×CO2 is not constant, but rather depends on the climatological base state, increasing by about 25% for every doubling of CO2, and has increased by about 10% since the preindustrial era primarily due to the cooling within the upper stratosphere, implying a proportionate increase in climate sensitivity. This base-state dependence also explains about half of the intermodel spread in IRF2×CO2, a problem that has persisted among climate models for nearly three decades.

PRDM16 Deletion Is Associated With Sex-dependent Cardiomyopathy and Cardiac Mortality: A Translational, Multi-Institutional Cohort Study

BACKGROUND

1p36 deletion syndrome can predispose to pediatric-onset cardiomyopathy. Deletion breakpoints are variable and may delete the transcription factor PRDM16. Early studies suggest that deletion of PRDM16 may underlie cardiomyopathy in patients with 1p36 deletion; however, the prognostic impact of PRDM16 loss is unknown.

METHODS

This retrospective cohort included subjects with 1p36 deletion syndrome from 4 hospitals. Prevalence of cardiomyopathy and freedom from death, cardiac transplantation, or ventricular assist device were analyzed. A systematic review cohort was derived for further analysis. A cardiac-specific Prdm16 knockout mouse (Prdm16 conditional knockout) was generated. Echocardiography was performed at 4 and 6 to 7 months. Histology staining and qPCR were performed at 7 months to assess fibrosis.

RESULTS

The retrospective cohort included 71 patients. Among individuals with PRDM16 deleted, 34.5% developed cardiomyopathy versus 7.7% of individuals with PRDM16 not deleted (P=0.1). In the combined retrospective and systematic review cohort (n=134), PRDM16 deletion-associated cardiomyopathy risk was recapitulated and significant (29.1% versus 10.8%, P=0.03). PRDM16 deletion was associated with increased risk of death, cardiac transplant, or ventricular assist device (P=0.04). Among those PRDM16 deleted, 34.5% of females developed cardiomyopathy versus 16.7% of their male counterparts (P=0.2). We find sex-specific differences in the incidence and the severity of contractile dysfunction and fibrosis in female Prdm16 conditional knockout mice. Further, female Prdm16 conditional knockout mice demonstrate significantly elevated risk of mortality (P=0.0003).

CONCLUSIONS

PRDM16 deletion is associated with a significantly increased risk of cardiomyopathy and cardiac mortality. Prdm16 conditional knockout mice develop cardiomyopathy in a sex-biased way. Patients with PRDM16 deletion should be assessed for cardiac disease.

One gene, two modes of inheritance, four diseases: A systematic review of the cardiac manifestation of pathogenic variants in JPH2-encoded junctophilin-2

Rare variants in JPH2 have been associated with a range of cardiac disease, including hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), arrhythmias, and sudden cardiac death (SCD); however, our understanding of how variants in JPH2 correspond to specific modes of inheritance and correlate clinical phenotypes has not been comprehensively explored. In this systematic review, we assess current case reports and series that describe patients with JPH2 variants and cardiac disease. We identified a total of 61 variant-positive individuals, approximately 80% of whom had some form of cardiac disease, including 47% HCM, 18% DCM, and 14% arrhythmia/SCD. In analyzing the 24 probands described in the studies, we found that autosomal recessive, loss-of-function variants are associated with severe, early onset DCM, while autosomal dominant missense variants are associated with a wider range of cardiac disease, including HCM, arrhythmia, SCD, and cardiac conduction disease.

Partnerships for the future. A new vision for the Catholic healthcare ministry

Collaboration among healthcare providers will help them more effectively meet the needs of their communities in the 1990s. San Francisco-based Catholic Healthcare West (CHW), formed in 1986, strives to provide high-quality healthcare by collaborating with Catholic and non-Catholic providers. CHW leaders believe that Catholic providers make ideal partners; however, they have found that Catholic healthcare providers often must look outside the Catholic healthcare ministry to find these partnership opportunities in order to remain viable and effectively carry out their mission. Besides system-to-system or hospital-to-hospital linkages, collaboration is also achievable with other types of healthcare providers, such as physicians. In collaborations between Catholic and non-Catholic healthcare providers, Catholic providers must strive to maintain their Catholic identity. When evaluating potential partners, they must consider issues such as corporate culture, organizational compatibility, and sponsor influence. CHW leaders believe that for any merger or affiliation to be successful, it must clearly produce market and financial advantages for the new partnership and offer the community a significant improvement in quality of care and services.

Dissecting thoracic aortic aneurysm in a 16-year-old

A 16-year-old boy presented with a one-hour history of left lower extremity pain and weakness, and was found to have a dissecting aortic aneurysm. The patient underwent emergency aortic angiography and immediate reparative aortic aneurysm surgery. He died on the fifth postoperative day. Because the majority of cases occur in the fifth to sixth decade of life, dissecting aortic aneurysm is a rare and usually fatal condition in adolescents. Potentially favorable outcome in this age group depends on prompt diagnosis and immediate medical and surgical intervention.

Atrial fibrillation--a marker for abnormal left ventricular function in coronary heart disease

Retrospective study of 1176 patients with known coronary heart disease by cardiac catheterisation disclosed 10 patients (0.8%) with atrial fibrillation. Comparison with 25 randomly selected patients with coronary heart disease with sinus rhythm showed that atrial fibrillation correlated significantly with impaired haemodynamic function, mitral regurgitation, and abnormalities of left ventricular contraction. Atrial fibrillation is, therefore, a useful marker of extensive myocardial dysfunction.

Electron microscopic and peroxidase cytochemical analysis of pink pseudo-Chediak-Higashi granules in acute myelogenous leukemia

Giant round pink inclusions (congruent to 2 micrometers) were seen in neutrophilic myeloblasts, promyelocytes, and myelocytes from three patients with acute myelogenous leukemia. On preliminary examination of the bone marrow smears, these inclusions looked like ingested red blood cells in that they were pink and not azurophilic. The bone marrow specimens were processed for the electron microscopic demonstration of peroxidase with 3,3'-diaminobenzidine and H2O2 at pH 7.6. In all three cases, the inclusions were determined to be large peroxidase-positive granules since they were limited by a single unit membrane and, unlike endocytized red blood cells, were not contained within phagocytic vasuoles. The granules were homogeneously dense for peroxidase and showed no obvious crystalline structure when examined stained or unstained on grid. We believe that they correspond to the giant pink round granules Van Slyck and Rebuck observed in immature leukemic granulocytes in 1974 and termed the pseudo-Chediak-Higashi anomaly. Like the giant purple granules seen in leukemia with this anomaly, these granules also appear to be an abnormal variant of peroxidase-positive azurophil (primary) granules. Their lack of azurophilia is due to the absence of sulfated glycoaminoglycans.

Renal arteriovenous fistula masquerading as severe valvar heart disease

Two patients with renal arteriovenous fistulae are described, who presented in high output failure. Murmurs were detected in these patients on routine physical examination years before, and when cardiac failure ensued they were assumed to have decompensated valvar heart disease. Full investigation revealed the arteriovenous fistulae and both patients made a good recovery after surgical ligation.

Unusual complications of coronary bypass surgery

Five patients after coronary bypass surgery developed unusual complications. Three developed new apical thrombi which are thought to be due to the trauma of the left ventricular vent or deterioration of the left ventricular contraction. Significant new mitral regurgitation in one patient probably is secondary to papillary muscle dysfunction as the result of stenosis distal to anastomoses. The leakage of angoigraphic material around distal anastomatic site is due to technical error. Although these unusual complications are very rare, however, they should be considered as potential source of morbidity in asymptomatic patients who leave the hospital after bypass surgery.