Genetic Contribution to End-Stage Cardiomyopathy Requiring Heart Transplantation

BACKGROUND

Many cardiovascular disorders propel the development of advanced heart failure that necessitates cardiac transplantation. When treatable causes are excluded, studies to define causes are often abandoned, resulting in a diagnosis of end-stage idiopathic cardiomyopathy. We studied whether DNA sequence analyses could identify unrecognized causes of end-stage nonischemic cardiomyopathy requiring heart transplantation and whether the prevalence of genetic causes differed from ambulatory cardiomyopathy cases.

METHODS

We performed whole exome and genome sequencing of 122 explanted hearts from 101 adult and 21 pediatric patients with idiopathic cardiomyopathy from a single center. Data were analyzed for pathogenic/likely pathogenic variants in nuclear and mitochondrial genomes and assessed for nonhuman microbial sequences. The frequency of damaging genetic variants was compared among cardiomyopathy cohorts with different clinical severity.

RESULTS

Fifty-four samples (44.3%) had pathogenic/likely pathogenic cardiomyopathy gene variants. The frequency of pathogenic variants was similar in pediatric (42.9%) and adult (43.6%) samples, but the distribution of mutated genes differed (P=8.30×10-4). The prevalence of causal genetic variants was significantly higher in end-stage than in previously reported ambulatory adult dilated cardiomyopathy cases (P<0.001). Among remaining samples with unexplained causes, no damaging mitochondrial variants were identified, but 28 samples contained parvovirus genome sequences, including 2 samples with 6- to 9-fold higher levels than the overall mean levels in other samples.

CONCLUSIONS

Pathogenic variants and viral myocarditis were identified in 45.9% of patients with unexplained end-stage cardiomyopathy. Damaging gene variants are significantly more frequent among transplant compared with patients with ambulatory cardiomyopathy. Genetic analyses can help define cause of end-stage cardiomyopathy to guide management and risk stratification of patients and family members.

Efficient in vivo genome editing prevents hypertrophic cardiomyopathy in mice

Dominant missense pathogenic variants in cardiac myosin heavy chain cause hypertrophic cardiomyopathy (HCM), a currently incurable disorder that increases risk for stroke, heart failure and sudden cardiac death. In this study, we assessed two different genetic therapies-an adenine base editor (ABE8e) and a potent Cas9 nuclease delivered by AAV9-to prevent disease in mice carrying the heterozygous HCM pathogenic variant myosin R403Q. One dose of dual-AAV9 vectors, each carrying one half of RNA-guided ABE8e, corrected the pathogenic variant in ≥70% of ventricular cardiomyocytes and maintained durable, normal cardiac structure and function. An additional dose provided more editing in the atria but also increased bystander editing. AAV9 delivery of RNA-guided Cas9 nuclease effectively inactivated the pathogenic allele, albeit with dose-dependent toxicities, necessitating a narrow therapeutic window to maintain health. These preclinical studies demonstrate considerable potential for single-dose genetic therapies to correct or silence pathogenic variants and prevent the development of HCM.

Damaging variants in FOXI3 cause microtia and craniofacial microsomia

PURPOSE

Craniofacial microsomia (CFM) represents a spectrum of craniofacial malformations, ranging from isolated microtia with or without aural atresia to underdevelopment of the mandible, maxilla, orbit, facial soft tissue, and/or facial nerve. The genetic causes of CFM remain largely unknown.

METHODS

We performed genome sequencing and linkage analysis in patients and families with microtia and CFM of unknown genetic etiology. The functional consequences of damaging missense variants were evaluated through expression of wild-type and mutant proteins in vitro.

RESULTS

We studied a 5-generation kindred with microtia, identifying a missense variant in FOXI3 (p.Arg236Trp) as the cause of disease (logarithm of the odds = 3.33). We subsequently identified 6 individuals from 3 additional kindreds with microtia-CFM spectrum phenotypes harboring damaging variants in FOXI3, a regulator of ectodermal and neural crest development. Missense variants in the nuclear localization sequence were identified in cases with isolated microtia with aural atresia and found to affect subcellular localization of FOXI3. Loss of function variants were found in patients with microtia and mandibular hypoplasia (CFM), suggesting dosage sensitivity of FOXI3.

CONCLUSION

Damaging variants in FOXI3 are the second most frequent genetic cause of CFM, causing 1% of all cases, including 13% of familial cases in our cohort.

An ancient founder mutation located between ROBO1 and ROBO2 is responsible for increased microtia risk in Amerindigenous populations

Microtia is a congenital malformation that encompasses mild hypoplasia to complete loss of the external ear, or pinna. Although the contribution of genetic variation and environmental factors to microtia remains elusive, Amerindigenous populations have the highest reported incidence. Here, using both transmission disequilibrium tests and association studies in microtia trios (parents and affected child) and microtia cohorts enrolled in Latin America, we map an ∼10-kb microtia locus (odds ratio = 4.7; P = 6.78e-18) to the intergenic region between Roundabout 1 (ROBO1) and Roundabout 2 (ROBO2) (chr3: 78546526 to 78555137). While alleles at the microtia locus significantly increase the risk of microtia, their penetrance is low (<1%). We demonstrate that the microtia locus contains a polymorphic complex repeat element that is expanded in affected individuals. The locus is located near a chromatin loop region that regulates ROBO1 and ROBO2 expression in induced pluripotent stem cell–derived neural crest cells. Furthermore, we use single nuclear RNA sequencing to demonstrate ROBO1 and ROBO2 expression in both fibroblasts and chondrocytes of the mature human pinna. Because the microtia allele is enriched in Amerindigenous populations and is shared by some East Asian subjects with craniofacial malformations, we propose that both populations share a mutation that arose in a common ancestor prior to the ancient migration of Eurasian populations into the Americas and that the high incidence of microtia among Amerindigenous populations reflects the population bottleneck that occurred during the migration out of Eurasia.

Isolation of Nuclei from Mammalian Cells and Tissues for Single-Nucleus Molecular Profiling

Both single-cell RNA sequencing (scRNAseq) and single-nucleus RNA sequencing (snRNAseq) can be used to characterize the transcriptional profile of individual cells, and based on these transcriptional profiles, help define cell type distribution in mixed cell populations. However, scRNAseq analyses are confounded if some of the cells are large (>50 µm) or if some of cells adhere more tightly to some adjacent cells than to others. Further, single cell isolation for scRNAseq requires fresh tissue, which may not be available for human or animal model tissues. Additionally, the current enzymatic and mechanical methods for single-cell dissociation can lead to stress-induced transcriptional artifacts. Nuclei for snRNAseq, on the other hand, can be isolated from any cell, regardless of size, and from either fresh or frozen tissues, and compared to whole cells, they are more resistant to mechanical pressures and appear not to exhibit as many cell isolation-based transcriptional artifacts. Here, we describe a time- and cost-effective procedure to isolate nuclei from mammalian cells and tissues. The protocol incorporates steps to mechanically disrupt samples to release nuclei. Compared to conventional nuclei isolation protocols, the approach described here increases overall efficiency, eliminates risk of contaminant exposure, and reduces volumes of expensive reagents. A series of RNA quality control checks are also incorporated to ensure success and reduce costs of subsequent snRNAseq experiments. Nuclei isolated by this procedure can be separated on the 10× Genomics Chromium system for either snRNAseq and/or Single-Nucleus ATAC-Seq (snATAC-Seq), and is also compatible with other single cell platforms. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Sample preparation and quality control check via RNA Isolation and Analysis Basic Protocol 2: Nuclei Isolation.

Chlamydial infection preceding the development of rheumatoid arthritis: a brief report

Chlamydia trachomatis-triggered reactive arthritis is a well-documented entity that has been extensively described. We do not have a clear understanding about the inflammatory oligoarthritis associated with the presence of this organism. It is rarely cultured from the synovial fluid, but is usually detectable by molecular biological techniques. Typically, Chlamydia trachomatis causes a sterile but inflammatory oligoarthritis. We report an unusual case of inflammatory monoarthritis in a young woman in whom Chlamydia was isolated from the synovial fluid. This is the first case of documented isolation of Chlamydia from synovial fluid, which subsequently was diagnosed as rheumatoid arthritis.

Wegener's granulomatosis in pregnancy

This report describes a case of severe limited Wegener's granulomatosis (WG) presenting in the third trimester of pregnancy with pansinusitis and necrotizing pneumonitis. The patient was treated successfully with a combination of corticosteroids and cyclophosphamide (CYC). The outcomes in the mother and the newborn were excellent. In a review of the English-language literature, we found 10 similar cases of WG with 13 pregnancies. WG occurring during pregnancy may have a more aggressive course and may require more aggressive treatment compared with WG occurring at other times. The treatment options for WG in pregnancy are discussed.

Knee laxity in symptomatic osteoarthritis

Twenty-two patients with primary osteoarthritis (OA) of the knee were studied to determine the effects of OA on laxity of the knee joint. Laxity was measured with a Genucom Knee Analysis System. Ten knees had mild OA (> 50% preservation of joint space). Fifteen knees had moderate OA (some preservation of joint space, but < 50%). Eighteen knees had severe OA (no joint space). A group of 18 knees from 9 healthy (asymptomatic) subjects of ages similar to those of the OA patients were used as controls. Compared to control knees, severe OA knees had less total anteroposterior (AP) translation (12.2 versus 6.6 mm, p < 0.025) and less total tibial rotation (79 versus 59 degrees, p < 0.01). Compared to early OA knees, knees with severe OA had 57% less average total AP translation (15.2 versus 6.6 mm, p < 0.01), 31% less total varus/valgus rotation (15 degrees versus 10.4 degrees, p < 0.016), and 26% less total internal/external tibial rotation (80.1 degrees versus 59 degrees, p < 0.007). These data indicate that osteoarthritic knees tend to have less laxity than normal knees, probably because of a combination of contracture of the ligaments and pressure of osteophytes against ligaments and other capsular structures.

Late-onset, seropositive, erosive rheumatoid arthritis

This report describes the natural history, clinical features, and therapeutic requirements of late-onset seropositive and/or erosive rheumatoid arthritis (LORA). One hundred twenty-nine patients with mean disease duration of 6 years and mean age of disease onset of 66 years were studied. All patients met American Rheumatism Association criteria for rheumatoid arthritis (RA). Ninety-one percent were seropositive for rheumatoid factor, 83% had erosive disease, and 58% had significant medical problems. Therapeutically, most patients required sequential use of multiple second-line agents. Functional classification did not change significantly despite treatment, and complete remissions were unusual even with remittive therapy. It is concluded that a subset of LORA patients have seropositive aggressive, destructive disease.

Amyloidosis in a case of ankylosing spondylitis with a review of the literature

A 53-year-old man with a 20-year history of ankylosing spondylitis presented with proteinuria and acute renal insufficiency. Amyloidosis was diagnosed on renal biopsy. The association of secondary amyloidosis has been described with collagen vascular diseases, however, a review of the literature reveals few cases associated with the spondyloarthropathies. We were able to find only 2 cases in the American literature. Thus, although a rare complication, amyloidosis should be considered in the differential diagnosis of proteinuria and renal insufficiency in spondyloarthropathy.

Bilateral pigmented villonodular synovitis of the wrists

The wrist is an unusual anatomic location for pigmented villonodular synovitis (PVNS). PVNS is generally a benign or minimally destructive process, but in our patient it resulted in progressive erosive changes in a bilateral wrist distribution. This is the first histologically documented case of bilateral PVNS in this anatomic distribution, to our knowledge. Although uncommon, PVNS should be considered a possible cause of unexplained upper extremity inflammatory arthritis.

Causes and management of shoulder arthritis

We recommend that physicians distinguish shoulder arthritis from periarticular disorders. A specific diagnosis should be made in the former, if possible. A number of arthritides have frequent shoulder involvement, and they should be kept in mind. Septic arthritis should always be suspected when there is acute pain and swelling. Joint fluid aspiration should almost always be performed when fluid is present. The diagnosis of gout or CPPD deposition disease usually requires crystal identification from joint fluid for diagnosis. Treatment of shoulder arthritis with oral anti-inflammatory medication is usually indicated; appropriate treatment of the underlying disorder, e.g., rheumatoid arthritis, is necessary. Physical therapy started early, often combined with IA corticosteroids, helps to maintain or improve shoulder motion.

Scintigraphic detection of metoclopramide esophageal stimulation in progressive systemic sclerosis

Supine radionuclide esophageal scintigraphy (RES) and manometry were used to prospectively evaluate metoclopramide effect on esophageal function and pressure amplitudes in 14 patients (12 females and two males; median time since diagnosis: 2 yr) with progressive systemic sclerosis (PSS). Quantitation of RES included calculation of percent emptying at 30 sec, and standard manometric measurements were obtained. RES and manometry were performed before and 10 min following the i.v. administration of metoclopramide. RES showed a significant increase in mean percent emptying from 36% to 46% after drug administration (p less than 0.01), while mean lower esophageal pressure (end-expiratory) increased from 2 to 11 mm of Hg (p less than 0.001). Manometry failed to reveal a significant increase in either distal or proximal mean esophageal contractile amplitude, and no correlation was found between the increase in percent emptying at RES and the change in lower esophageal pressure in the individual patient. RES is the only quantitative method presently available to evaluate bolus propagation in the esophagus, and it documented improved esophageal function after metoclopramide administration in a PSS population. When drug therapy is directed at augmentation of esophageal emptying, RES is an ideal method to evaluate drug response.

Progressive systemic sclerosis: radionuclide esophageal scintigraphy and manometry

Radionuclide esophageal scintigraphy (RES) and manometry were used for prospective evaluation of esophageal involvement and disease severity in 11 patients (nine women and two men; median time since diagnosis, 1 year) with progressive systemic sclerosis (PSS). Quantitation of RES included calculation of the percentage of emptying at 30 seconds, while manometry provided measurements of proximal, distal, and lower esophageal sphincter (LES) pressures. The findings of both RES and manometry were abnormal in all 11 patients. There was a high correlation between the percentage of emptying and either distal esophageal pressure (r = .86, P less than .01) or LES pressure (r = .79, P less than .01). No significant correlation was found between the percentage of emptying and proximal esophageal pressure (r = .28, P = .39). RES is a safe, simple procedure that is readily accepted by patients and can be used in place of manometry for the detection and staging of esophageal involvement in PSS.

Cells that mediate NK like cytotoxicity are present in the human delayed type hypersensitivity response

By inducing delayed type hypersensitivity (DTH) responses under previously formed skin blisters we determined that cells which mediate natural killer (NK) like cytotoxicity are present in the DTH response in man. Similar levels of killing were not present in cells obtained from skin blisters not associated with positive DTH responses. The DTH response associated killer cell was found to be a mononuclear cell that had presumably undergone stimulation since it not only killed NK sensitive K-562 cells, but also NK resistant Daudi target cells.

NK cell activity and skin test antigen stimulation of NK like CMC in vitro are decreased to different degrees in pregnancy and sarcoidosis

Peripheral blood mononuclear cells (PBMNC) isolated from normal subjects, pregnant women and patients with sarcoidosis were assayed for natural killer (NK) cell activity on day 0 and for NK like cell-mediated cytolysis (CMC) after 5 days of exposure, in vitro to Candida antigen, purified protein derivative (PPD), and human leucocyte interferon (IFN). Pregnant women and women with sarcoidosis had significantly decreased levels of NK cell activity compared to normal women. Pregnant women had the lowest mean NK cell activity. Cells from women with sarcoidosis and from pregnant women also had lower levels of killing than those from the normal women after in vitro stimulation of NK like CMC with Candida antigen, PPD and IFN. The lowest stimulations of NK like killing occurred in the cells from women with sarcoidosis. Skin test antigen stimulation of NK like CMC in vitro and the DTH response in vivo were strongly correlated for both Candida antigen and PPD in the sarcoidosis patients. There was no correlation between the level of NK cell activity in the PBMNC of sarcoid patients on day 0 and the amount of NK like CMC that was present in cells from those patients after 5 days of culture with Candida antigen, PPD or IFN. A significant correlation was found, however, between Candida antigen stimulation of NK like CMC and IFN stimulation of NK like CMC in both pregnant and sarcoid groups. Reduced NK cell activity on day 0 in a given patient thus did not necessarily indicate that skin test antigen or IFN stimulation of NK like CMC on day 5 would also be depressed. In addition, NK cell activity was often noted to be normal in patients with depressed in vitro stimulation of NK like CMC.

The skin test antigen stimulated killer (STAK) cell mediating NK like CMC is OKM1 positive and OKT3 negative

Recently we demonstrated that candida antigen stimulated natural killer cell like cell-mediated cytolysis (NK like CMC) in peripheral blood mononuclear cells (PBMNC) isolated from normal individuals (Tartof et al., 1980). Utilizing monoclonal antibodies directed against human mononuclear cell subpopulations in conjunction with a fluorescence activated cell sorter (FACS) we determined that, similar to the previously described NK cell, the skin test antigen stimulated killer (STAK) cell is a larger OKM1 positive, OKT3 negative cell. We obtained similar results using two different skin test antigens. Thus, stimulation of NK like CMC in PBMNC by skin test antigens probably represents activation of NK or NK like cells.

Shoulder arthritis. Distinguishing among the many causes of inflammation

Shoulder inflammation occurs in many rheumatic diseases. It is present in about half of the patients with rheumatoid arthritis but in a higher percentage of patients with less common diseases (eg, amyloid arthropathy, polymyalgia rheumatica). Shoulder arthritis, probably more than arthritis involving any other joint, requires prompt diagnosis and treatment to prevent loss of motion and function. For most patients, antiinflammatory medications, range of motion exercises, and instruction in joint protection constitute adequate treatment. A baseline shoulder roentgenogram is usually recommended. Intraarticular corticosteroid therapy may be a helpful adjunct, provided infection has been excluded.