The low excretor phenotype of glutaric acidemia type I is a source of false negative newborn screening results and challenging diagnoses.

BACKGROUND: Glutaric acidemia type I (GA1) is an organic acidemia that is often unrecognized in the newborn period until patients suffer an acute encephalopathic crisis, which can be mistaken for nonaccidental trauma. Presymptomatic identification of GA1 patients is possible by newborn screening (NBS). However, the biochemical "low-excretor" (LE) phenotype with nearly normal levels of disease metabolites can be overlooked, which may result in untreated disease and irreversible neurological sequelae. The LE phenotype is also a potential source of false negative (FN) NBS results that merits further investigation. METHODS: Samples from six LE GA1 patients were analyzed by biochemical and molecular methods and newborn screen outcomes were retrospectively investigated. RESULTS: Five LE GA1 patients were identified that had normal NBS results and three of these presented clinically with GA1 symptoms. One additional symptomatic patient was identified who did not undergo screening. Semiquantitative urine organic acid analysis was consistent with a GA1 diagnosis in two (33%) of the six patients, while plasma glutarylcarnitine was elevated in four (67%) of the six and urine glutarylcarnitine was elevated in four (80%) of five patients. Five GCDH variants were identified in these patients; three of which have not been previously linked to the biochemical LE phenotype. CONCLUSIONS: The data presented here raise awareness of potential FN NBS results for LE GA1 patients. The LE phenotype is not protective against adverse clinical outcomes, and the possibility of FN NBS results calls for high vigilance amongst clinicians, even in the setting of a normal NBS result.

Familial variability of cerebrotendinous xanthomatosis lacking typical biochemical findings.

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive disorder of bile acid synthesis caused by pathogenic variants in the CYP27A1 gene encoding the mitochondrial enzyme sterol 27-hydroxylase. Patients with CTX can present with a wide range of symptoms, but most often have evidence of tendon xanthomas along with possible cataracts, atherosclerosis, or neurological dysfunction. Regardless of clinical phenotype, CTX patients typically exhibit levels of cholestanol and bile acid precursors in the circulation that are many fold increased over normal control concentrations. Here we report two siblings, one with the rare spinal xanthomatosis phenotype and the other with a very mild form of CTX manifesting as minor tendon xanthomatosis and gastrointestinal complaints who both carry compound heterozygous variants in CYP27A1: NM_000784.3: c.410G > A (p.Arg137Gln) and c.1183C > T (p.Arg395Cys). However, biochemical analysis of these patients revealed normal levels of serum cholestanol and relatively mild elevations of the bile acid precursors 7α-hydroxy-4-cholesten-3-one and 7α,12α-dihydroxy-4-cholesten-3-one. The atypical biochemical presentation of these cases represents a diagnostic challenge for a disorder once thought to have a sensitive biomarker in cholestanol and highlight the need for thorough investigation of patients with symptomatology consistent with CTX that includes bile acid precursor biochemical testing and molecular analysis.

Clinical utility of next generation sequencing to detect IGH/IL3 rearrangements [t(5;14)(q31.1;q32.1)] in B-lymphoblastic leukemia/lymphoma.

The t(5;14)(q31.1;q32.1) associated with B-lymphoblastic leukemia/lymphoma (B-ALL/LBL) is a rare, recurrent genetic abnormality recognized as a distinct entity by the 2017 World Health Organization (WHO) classification. In these cases, the IGH enhancer region (14q32.1) is juxtaposed to the vicinity of the IL3 gene (5q31.1), resulting in increased production of interleukin-3 (IL3) and subsequently a characteristic reactive eosinophilia. B-ALL with t(5;14)(q31.1;q32.1) may have a low lymphoblast count that can complicate detection of t(5;14)(q31.1;q32.1) by conventional chromosome studies. We have identified four patients with IGH/IL3 rearrangements despite normal conventional chromosome studies in each case [one patient had a non-clonal t(5;14)(q31;q32) finding]. Fluorescence in situ hybridization utilizing a laboratory-developed IGH break-apart probe set identified IGH rearrangements in three of four cases, and a next generation sequencing (NGS) based assay, mate-pair sequencing (MPseq), was required to characterize the IGH/IL3 rearrangements in each case. Three patients demonstrated a balanced t(5;14)(q31.1;q32.1) while one patient had a cryptic insertion of the IL3 gene into the IGH region. These results demonstrate that NGS-based assays, such as MPseq, confer an advantage in the detection of IGH/IL3 rearrangements that are otherwise challenging to characterize by traditional cytogenetic methodologies.

The critical role of psychosine in screening, diagnosis, and monitoring of Krabbe disease.

PURPOSE: Newborn screening (NBS) for Krabbe disease (KD) is performed by measurement of galactocerebrosidase (GALC) activity as the primary test. This revealed that GALC activity has poor specificity for KD. Psychosine (PSY) was proposed as a disease marker useful to reduce the false positive rate for NBS and for disease monitoring. We report a highly sensitive PSY assay that allows identification of KD patients with minimal PSY elevations. METHODS: PSY was extracted from dried blood spots or erythrocytes with methanol containing d5-PSY as internal standard, and measured by liquid chromatography-tandem mass spectrometry. RESULTS: Analysis of PSY in samples from controls (N = 209), GALC pseudodeficiency carriers (N = 55), GALC pathogenic variant carriers (N = 27), patients with infantile KD (N = 26), and patients with late-onset KD (N = 11) allowed for the development of an effective laboratory screening and diagnostic algorithm. Additional longitudinal measurements were used to track therapeutic efficacy of hematopoietic stem cell transplantion (HSCT). CONCLUSION: This study supports PSY quantitation as a critical component of NBS for KD. It helps to differentiate infantile from later onset KD variants, as well as from GALC variant and pseudodeficiency carriers. Additionally, this study provides further data that PSY measurement can be useful to monitor KD progression before and after treatment.

Pathogenic implications of dysregulated miRNAs in propionic acidemia related cardiomyopathy.

Cardiac alterations (hypertrophic/dilated cardiomyopathy, and rhythm alterations) are one of the major causes of mortality and morbidity in propionic acidemia (PA), caused by the deficiency of the mitochondrial enzyme propionyl-CoA carboxylase (PCC), involved in the catabolism of branched-chain amino acids, cholesterol, and odd-chain fatty acids. Impaired mitochondrial oxidative phosphorylation has been documented in heart biopsies of PA patients, as well as in the hypomorphic Pcca-/-(A138T) mouse model, in the latter correlating with increased oxidative damage and elevated expression of cardiac dysfunction biomarkers atrial and brain natriuretic peptides (ANP and BNP) and beta-myosin heavy chain (ß-MHC). Here we characterize the cardiac phenotype in the PA mouse model by histological and echocardiography studies and identify a series of upregulated cardiac-enriched microRNAs (miRNAs) in the PA mouse heart, some of them also altered as circulating miRNAs in PA patients' plasma samples. In PA mice hearts, we show alterations in signaling pathways regulated by the identified miRNAs, which could be contributing to cardiac remodeling and dysfunction; notably, an activation of the mammalian target of rapamycin (mTOR) pathway and a decrease in autophagy, which are reverted by rapamycin treatment. In vitro studies in HL-1 cardiomyocytes indicate that propionate, the major toxic metabolite accumulating in the disease, triggers the increase in expression levels of miRNAs, BNP, and ß-MHC, concomitant with an increase in reactive oxygen species. Our results highlight miRNAs and signaling alterations in the PCC-deficient heart which may contribute to the development of PA-associated cardiomyopathy and provide a basis to identify new targets for therapeutic intervention.

Mitochondrial Integrity and Function in the Progression of Early Pressure Overload-Induced Left Ventricular Remodeling.

BACKGROUND: Following pressure overload, compensatory concentric left ventricular remodeling (CR) variably transitions to eccentric remodeling (ER) and systolic dysfunction. Mechanisms responsible for this transition are incompletely understood. Here we leverage phenotypic variability in pressure overload-induced cardiac remodeling to test the hypothesis that altered mitochondrial homeostasis and calcium handling occur early in the transition from CR to ER, before overt systolic dysfunction. METHODS AND RESULTS: Sprague Dawley rats were subjected to ascending aortic banding, (n=68) or sham procedure (n=5). At 3 weeks post-ascending aortic banding, all rats showed CR (left ventricular volumes < sham). At 8 weeks post-ascending aortic banding, ejection fraction was increased or preserved but 3 geometric phenotypes were evident despite similar pressure overload severity: persistent CR, mild ER, and moderate ER with left ventricular volumes lower than, similar to, and higher than sham, respectively. Relative to sham, CR and mild ER phenotypes displayed increased phospholamban, S16 phosphorylation, reduced sodium-calcium exchanger expression, and increased mitochondrial biogenesis/content and normal oxidative capacity, whereas moderate ER phenotype displayed decreased p-phospholamban, S16, increased sodium-calcium exchanger expression, similar degree of mitochondrial biogenesis/content, and impaired oxidative capacity with unique activation of mitochondrial autophagy and apoptosis markers (BNIP3 and Bax/Bcl-2). CONCLUSIONS: After pressure overload, mitochondrial biogenesis and function and calcium handling are enhanced in compensatory CR. The transition to mild ER is associated with decrease in mitochondrial biogenesis and content; however, the progression to moderate ER is associated with enhanced mitochondrial autophagy/apoptosis and impaired mitochondrial function and calcium handling, which precede the onset of overt systolic dysfunction.

Experimental cardiac radiation exposure induces ventricular diastolic dysfunction with preserved ejection fraction.

Breast cancer radiotherapy increases the risk of heart failure with preserved ejection fraction (HFpEF). Cardiomyocytes are highly radioresistant, but radiation specifically affects coronary microvascular endothelial cells, with subsequent microvascular inflammation and rarefaction. The effects of radiation on left ventricular (LV) diastolic function are poorly characterized. We hypothesized that cardiac radiation exposure may result in diastolic dysfunction without reduced EF. Global cardiac expression of the sodium-iodide symporter (NIS) was induced by cardiotropic gene (adeno-associated virus serotype 9) delivery to 5-wk-old rats. SPECT/CT (125I) measurement of cardiac iodine uptake allowed calculation of the 131I doses needed to deliver 10- or 20-Gy cardiac radiation at 10 wk of age. Radiated (Rad; 10 or 20 Gy) and control rats were studied at 30 wk of age. Body weight, blood pressure, and heart rate were similar in control and Rad rats. Compared with control rats, Rad rats had impaired exercise capacity, increased LV diastolic stiffness, impaired LV relaxation, and elevated filling pressures but similar LV volume, EF, end-systolic elastance, preload recruitable stroke work, and peak +dP/dt Pathology revealed reduced microvascular density, mild concentric cardiomyocyte hypertrophy, and increased LV fibrosis in Rad rats compared with control rats. In the Rad myocardium, oxidative stress was increased and in vivo PKG activity was decreased. Experimental cardiac radiation exposure resulted in diastolic dysfunction without reduced EF. These data provide insight into the association between cardiac radiation exposure and HFpEF risk and lend further support for the importance of inflammation-related coronary microvascular compromise in HFpEF.NEW & NOTEWORTHY Cardiac radiation exposure during radiotherapy increases the risk of heart failure with preserved ejection fraction. In a novel rodent model, cardiac radiation exposure resulted in coronary microvascular rarefaction, oxidative stress, impaired PKG signaling, myocardial fibrosis, mild cardiomyocyte hypertrophy, left ventricular diastolic dysfunction, and elevated left ventricular filling pressures despite preserved ejection fraction.

FOXO3a regulates BNIP3 and modulates mitochondrial calcium, dynamics, and function in cardiac stress.

The forkhead box O3a (FOXO3a) transcription factor has been shown to regulate glucose metabolism, muscle atrophy, and cell death in postmitotic cells. Its role in regulation of mitochondrial and myocardial function is not well studied. Based on previous work, we hypothesized that FOXO3a, through BCL2/adenovirus E1B 19-kDa protein-interacting protein 3 (BNIP3), modulates mitochondrial morphology and function in heart failure (HF). We modulated the FOXO3a-BNIP3 pathway in normal and phenylephrine (PE)-stressed adult cardiomyocytes (ACM) in vitro and developed a cardiotropic adeno-associated virus serotype 9 encoding dominant-negative FOXO3a (AAV9.dn-FX3a) for gene delivery in a rat model of HF with preserved ejection fraction (HFpEF). We found that FOXO3a upregulates BNIP3 expression in normal and PE-stressed ACM, with subsequent increases in mitochondrial Ca2+, leading to decreased mitochondrial membrane potential, mitochondrial fragmentation, and apoptosis. Whereas dn-FX3a attenuated the increase in BNIP3 expression and its consequences in PE-stressed ACM, AAV9.dn-FX3a delivery in an experimental model of HFpEF decreased BNIP3 expression, reversed adverse left ventricular remodeling, and improved left ventricular systolic and, particularly, diastolic function, with improvements in mitochondrial structure and function. Moreover, AAV9.dn-FX3a restored phospholamban phosphorylation at S16 and enhanced dynamin-related protein 1 phosphorylation at S637. Furthermore, FOXO3a upregulates maladaptive genes involved in mitochondrial apoptosis, autophagy, and cardiac atrophy. We conclude that FOXO3a activation in cardiac stress is maladaptive, in that it modulates Ca2+ cycling, Ca2+ homeostasis, and mitochondrial dynamics and function. Our results suggest an important role of FOXO3a in HF, making it an attractive potential therapeutic target.

Mucosal vaccination by adenoviruses displaying reovirus sigma 1.

We developed adenovirus serotype 5 (Ad5) vectors displaying the sigma 1 protein from reovirus as mucosal vaccines. Ad5-sigma retargets to JAM-1 and sialic acid, but has 40-fold reduced gene delivery when compared to Ad5. While weaker at transduction, Ad5-sigma generates stronger T cell responses than Ad5 when used for mucosal immunization. In this work, new Ad5-fiber-sigma vectors were generated by varying the number of fiber ß-spiral shaft repeats (R) between the fiber tail and sigma. Increasing chimera length led to decreasing insertion of these proteinsAd5 virions. Ad-R3 and R14 vectors effectively targeted JAM-1 in vitro while R20 did not. When wereused to immunize mice by the intranasal route, Ad5-R3-sigma produced higher serum and vaginal antibody responses than Ad5. These data suggest optimized Ad-sigma vectors may be useful vectors for mucosal vaccination.

Long-term sex-biased correction of circulating propionic acidemia disease markers by adeno-associated virus vectors.

Propionic academia (PA) occurs because of mutations in the PCCA or PCCB genes encoding the two subunits of propionyl-CoA carboxylase, a pivotal enzyme in the breakdown of certain amino acids and odd-chain fatty acids. There is no cure for PA, but dietary protein restriction and liver transplantation can attenuate its symptoms. We show here that a single intravenous injection of adeno-associated virus 2/8 (AAV8) or AAVrh10 expressing PCCA into PA hypomorphic mice decreased systemic propionylcarnitine and methyl citrate for up to 1.5 years. However, long-term phenotypic correction was always better in male mice. AAV-mediated PCCA expression was similar in most tissues in males and females at early time points and differed only in the liver. Over 1.5 years, luciferase and PCCA expression remained elevated in cardiac tissue for both sexes. In contrast, transgene expression in the liver and skeletal muscles of female, but not male, mice waned­suggesting that these tissues were major sinks for systemic phenotypic correction. These data indicate that single systemic intravenous therapy by AAV vectors can mediate long-term phenotype correction for PA. However, tissue-specific loss of expression in females reduces efficacy when compared with males. Whether similar sex-biased AAV effects occur in human gene therapy remains to be determined.

Effects of adeno-associated virus serotype and tissue-specific expression on circulating biomarkers of propionic acidemia.

Propionic acidemia (PA) is an autosomal recessive inborn error of metabolism caused by deficiency of propionyl-CoA carboxylase (PCC). This enzyme is composed of six PCCA and six PCCB subunits and mediates a critical step in catabolism of odd chain fatty acids and certain amino acids. Current treatment options for PA are limited to stringent dietary restriction of protein consumption and some patients undergo elective liver transplantation. We previously generated a hypomorphic model of PA, designated Pcca(-/-)(A138T), with 2% of wild-type enzyme activity that mimics many aspects of the human disease. In this study, we used the differing tissue tropisms of adeno-associated virus (AAV) to probe the ability of liver or muscle-directed gene therapy to treat systemic aspects of this disease that affects many cell types. Systemic therapy with muscle-biased AAV1, liver-biased AAV8, and broadly tropic AAVrh10 mediated significant biochemical corrections in circulating propionylcarnitine (C3) and methyl citrate by all vectors. The innate tissue bias of AAV1 and AAV8 gene expression was made more specific by the use of muscle-specific muscle creatine kinase (specifically MCK6) and hepatocyte-specific transthyretin (TTR) promoters, respectively. Under these targeted conditions, both vectors mediated significant long-term correction of circulating metabolites, demonstrating that correction of muscle and likely other tissue types in addition to liver is necessary to fully correct pathology caused by PA. Liver-specific AAV8-TTR-PCCA mediated better correction than AAV1-MCK-PCCA. These data suggest that targeted gene therapy may be a viable alternative to liver transplantation for PA. They also demonstrate the effects of tissue-specific and broad gene therapy on a cell autonomous systemic genetic disease.

Generation of a hypomorphic model of propionic acidemia amenable to gene therapy testing.

Propionic acidemia (PA) is a recessive genetic disease that results in an inability to metabolize certain amino acids and odd-chain fatty acids. Current treatment involves restricting consumption of these substrates or liver transplantation. Deletion of the Pcca gene in mice mimics the most severe forms of the human disease. Pcca(-) mice die within 36 hours of birth, making it difficult to test intravenous systemic therapies in them. We generated an adult hypomorphic model of PA in Pcca(-) mice using a transgene bearing an A138T mutant of the human PCCA protein. Pcca(-/-)(A138T) mice have 2% of wild-type PCC activity, survive to adulthood, and have elevations in propionyl-carnitine, methylcitrate, glycine, alanine, lysine, ammonia, and markers associated with cardiomyopathy similar to those in patients with PA. This adult model allowed gene therapy testing by intravenous injection with adenovirus serotype 5 (Ad5) and adeno-associated virus 2/8 (AAV8) vectors. Ad5-mediated more rapid increases in PCCA protein and propionyl-CoA carboxylase (PCC) activity in the liver than AAV8 and both vectors reduced propionylcarnitine and methylcitrate levels. Phenotypic correction was transient with first generation Ad whereas AAV8-mediated long-lasting effects. These data suggest that this PA model may be a useful platform for optimizing systemic intravenous therapies for PA.

A vector-host system to fingerprint virus tropism.

Reporter genes are important tools for assessing vector pharmacology in vivo. Although useful, current systems are limited by (1) the need to generate a new vector for each different reporter, (2) the inability to package reporter genes in small vectors, and (3) variations in reporter gene feedback due to variations in cell-to-cell vector copy number. To circumvent these problems, we have used Cre recombinase as a "cat's paw" to activate reporter genes embedded in transgenic mice. The small Cre gene was introduced into self-complementary adeno-associated viral (scAAV) vectors with limited packaging capacity. Injection of scAAV-Cre vectors into mice with loxP-inactivated luciferase enabled in vivo imaging distributions comparable to the signal observed after AAV-luciferase injection. When injected into mT/mG mice, AAV-Cre converted ubiquitous expression of red fluorescent protein (RFP) to green fluorescent protein (GFP) expression only where the vectors transduced cells. Injection into F(1) hybrid luciferase and mT/mG mice enabled simultaneous three-reporter tracking. This system was able to discriminate cell-specific transduction in all organs tested, with particular usefulness for detecting AAV serotype-specific transduction in the liver, kidney, and muscle. Given that F(1) mice bear exactly one copy of luciferase and one copy of RFP-GFP, each reporter gene is either "on" or "off" in a cell. The Cre system therefore provides a unique quantum method to quantify vector delivery that can be applied when vector capacity is limited.