Allelic diversity in MCAD deficiency: the biochemical classification of 54 variants identified during 5 years of ACADM sequencing

All exons are not created equal-exon vulnerability determines the effect of exonic mutations on splicing

It is now widely accepted that aberrant splicing of constitutive exons is often caused by mutations affecting cis-acting splicing regulatory elements (SREs), but there is a misconception that all exons have an equal dependency on SREs and thus a similar vulnerability to aberrant splicing. We demonstrate that some exons are more likely to be affected by exonic splicing mutations (ESMs) due to an inherent vulnerability, which is context dependent and influenced by the strength of exon definition. We have developed VulExMap, a tool which is based on empirical data that can designate whether a constitutive exon is vulnerable. Using VulExMap, we find that only 25% of all exons can be categorized as vulnerable, whereas two-thirds of 359 previously reported ESMs in 75 disease genes are located in vulnerable exons. Because VulExMap analysis is based on empirical data on splicing of exons in their endogenous context, it includes all features important in determining the vulnerability. We believe that VulExMap will be an important tool when assessing the effect of exonic mutations by pinpointing whether they are located in exons vulnerable to ESMs.

Liver transcriptome analysis reveal the metabolic and apoptotic responses of Trachinotus ovatus under acute cold stress

Trachinotus ovatus is an economically important fish and has been recommended as a high-quality aquaculture fish breed for the high-quality development of sea ranches in the South China Sea. However, T. ovatus shows intolerance to low temperature, greatly limiting the extension of farming scale, reducing production efficiency in winter, and increasing farming risks. In this study, liver transcriptome analysis was investigated in T. ovatus under acute low temperature conditions (20 and 15 °C) using RNA sequencing (RNA-Seq) technology. Inter-groups differential expression analysis and trend analysis screened 1219 DEGs and four significant profiles (profiles 0, 3, 4, and 7), respectively. GO enrichment analysis showed that these DEGs were mainly related to metabolic process and cell growth and death process. KEGG enrichment analysis found that DEGs were mainly associated with lipid metabolism, carbohydrate metabolism, and cell growth and death, such as gluconeogenesis, glycolysis, fatty acid oxidation, cholesterol biosynthesis, p53 signaling pathway, cell cycle arrest, and apoptotic cell death. Moreover, protein-protein interaction networks identified two hub genes (FOS and JUNB) and some important genes related to metabolic process and cell growth and death process, that corresponding to enrichment analysis. Overall, gluconeogenesis, lipid mobilization, and fatty acid oxidation in metabolic process and cell cycle arrest and apoptotic cell death in cell growth and death process were enhanced, while glycolysis, liver glycogen synthesis and cholesterol biosynthesis in metabolic process were inhibited. The enhancement or attenuatment of metabolic process and cell growth and death process is conducive to maintain energy balance, normal fluidity of cell membrane, normal physiological functions of liver cell, enhancing the tolerance of T. ovatus to cold stress. These results suggested that metabolic process and cell growth and death process play important roles in response to acute cold stress in the liver of T. ovatus. Gene expreesion level analysis showed that acute cold stress at 15 °C was identified as a critical temperature point for T. ovatus in term of cellular metabolism alteration and apoptosis inducement, and rewarming intervention should be timely implemented above 15 °C. Our study can provide theoretical support for breeding cold-tolerant cultivars of T. ovatus, which is contributed to high-quality productions fish production.

Case report: Diagnosis of a patient with Sifrim-Hitz-Weiss syndrome, development and epileptic encephalopathy-14, and medium chain acyl-CoA dehydrogenase deficiency

Background

It is generally recognized that genetic metabolic disorders can result in neurological symptoms such as seizures, developmental delay, and intellectual disability. Heterogeneous clinical presentations make the diagnosis challenging.

Case presentation

In this case report, we present a unique and complex genetic disorder observed in a female patient who exhibited three pathogenic gene variants in the KCNT1, ACADM, and CHD4 genes. The convergence of these variants resulted in a multifaceted clinical presentation characterized by severe seizures of combined focal and generalized onset, metabolic dysfunction, and neurodevelopmental abnormalities. The identification and functional characterization of these gene variants shed light on the intricate interplay between these genes and the patient's phenotype. EEG revealed an epileptiform abnormality which presented in the inter-ictal period from the left frontal-central area and in the ictal period from the left mid-temporal area. The brain MRI revealed volume loss in the posterior periventricular area and parietal parenchyma, myelin destruction with no sign of hypoxic involvement, and left dominant enlargement of the lateral ventricles secondary to loss of central parenchyma. The patient was diagnosed through exome sequencing with Sifrim-Hitz-Weiss syndrome, development and epileptic encephalopathy-14, and medium-chain acyl-CoA dehydrogenase deficiency. An antiseizure medication regimen with valproic acid, levetiracetam, phenobarbital, and clonazepam was initiated. However, this led to only partial control of the seizures.

Conclusion

Clinical follow-up of the patient will further define the clinical spectrum of KCNT1, ACADM, and CHD4 gene variants. It will also determine the long-term efficacy of the treatment of seizures and the development of precision medicine for epilepsy syndromes due to gain-of-function variants. Special emphasis should be put on the role and importance of large-scale genomic testing in understanding and diagnosing complex phenotypes and atypical epileptic syndromes.

Untargeted Metabolomics Identifies Biomarkers for MCADD Neonates in Dried Blood Spots

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most common inherited mitochondrial metabolic disease of fatty acid β-oxidation, especially in newborns. MCADD is clinically diagnosed using Newborn Bloodspot Screening (NBS) and genetic testing. Still, these methods have limitations, such as false negatives or positives in NBS and the variants of uncertain significance in genetic testing. Thus, complementary diagnostic approaches for MCADD are needed. Recently, untargeted metabolomics has been proposed as a diagnostic approach for inherited metabolic diseases (IMDs) due to its ability to detect a wide range of metabolic alterations. We performed an untargeted metabolic profiling of dried blood spots (DBS) from MCADD newborns (n = 14) and healthy controls (n = 14) to discover potential metabolic biomarkers/pathways associated with MCADD. Extracted metabolites from DBS samples were analyzed using UPLC-QToF-MS for untargeted metabolomics analyses. Multivariate and univariate analyses were used to analyze the metabolomics data, and pathway and biomarker analyses were also performed on the significantly identified endogenous metabolites. The MCADD newborns had 1034 significantly dysregulated metabolites compared to healthy newborns (moderated t-test, no correction, p-value ≤ 0.05, FC 1.5). A total of 23 endogenous metabolites were up-regulated, while 84 endogenous metabolites were down-regulated. Pathway analyses showed phenylalanine, tyrosine, and tryptophan biosynthesis as the most affected pathways. Potential metabolic biomarkers for MCADD were PGP (a21:0/PG/F1alpha) and glutathione, with an area under the curve (AUC) of 0.949 and 0.898, respectively. PGP (a21:0/PG/F1alpha) was the first oxidized lipid in the top 15 biomarker list affected by MCADD. Additionally, glutathione was chosen to indicate oxidative stress events that could happen during fatty acid oxidation defects. Our findings suggest that MCADD newborns may have oxidative stress events as signs of the disease. However, further validations of these biomarkers are needed in future studies to ensure their accuracy and reliability as complementary markers with established MCADD markers for clinical diagnosis.

Free carnitine concentrations and biochemical parameters in medium-chain acyl-CoA dehydrogenase deficiency: Genotype-phenotype correlation

Biallelic variants in the ACADM gene cause medium-chain acyl-CoA dehydrogenase deficiency (MCADD). This study reports on differences in the occurrence of secondary free carnitine (C0) deficiency and different biochemical phenotypes related to genotype and age in 109 MCADD patients followed-up at a single tertiary care center during 22 years. C0 deficiency occurred earlier and more frequently in c.985A>G homozygotes (genotype A) compared to c.985A>G compound heterozygotes (genotype B) and individuals carrying variants other than c.985A>G and c.199C>T (genotype D) (median age 4.2 vs. 6.6 years; p < 0.001). No patient carrying c.199C>T (genotype C) developed C0 deficiency. A daily dosage of 20-40 mg/kg carnitine was sufficient to maintain normal C0 concentrations. Compared to genotype A as reference group, octanoylcarnitine (C8) was significantly lower in genotypes B and C, whereas C0 was significantly higher by 8.28 μmol/L in genotype C (p < 0.05). In conclusion, C0 deficiency is mainly found in patients with pathogenic genotypes associated with high concentrations of presumably toxic acylcarnitines, while individuals carrying the variant c.199C>T are spared and show consistently mild biochemical phenotypes into adulthood. Low-dose carnitine supplementation maintains normal C0 concentrations. However, future studies need to evaluate clinical benefits on acute and chronic manifestations of MCADD.

Medium-chain Acyl-COA dehydrogenase deficiency: Pathogenesis, diagnosis, and treatment

INTRODUCTION

Medium-Chain Acyl-CoA Dehydrogenase Deficiency (MCADD) is the most common inherited metabolic disorder of β-oxidation. Patients with MCADD present with hypoketotic hypoglycemia, which may quickly progress to lethargy, coma, and death. Prognosis for MCADD patients is highly promising once a diagnosis has been established, though management strategies may vary depending on the severity of illness and the presence of comorbidities.

METHODS AND RESULTS

Given the rapid developments in the world of gene therapy and implementation of newborn screening for inherited metabolic disorders, the provision of concise and contemporary knowledge of MCADD is essential for clinicians to effectively manage patients. Thus, this review aims to consolidate current information for physicians on the pathogenesis, diagnostic tools, and treatment options for MCADD patients.

CONCLUSION

MCADD is a commonly inherited metabolic disease with serious implications for health outcomes, particularly in children, that may be successfully managed with proper intervention.

Analysis of gene mutations of Medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD) by next-generation sequencing in Henan, China

BACKGROUND

Medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD) is a rare inherited metabolic disorder of fatty acid β-oxidation and one of the most common inborn errors of metabolism. The incidence of MCADD varies among regions and ethnic groups. To date, few cases of MCADD have been documented in China.

OBJECTIVE

The present study aimed to find out the novel genetic pathogenic variants in the Chinese patients and evaluate the detection rate of the disease of high-frequency ACADM pathogenic variants in different regions of China.

METHODS

6 cases of MCADD were screened by tandem mass spectrometric (MS/MS) among 245 054 newborns. We performed next-generation sequencing on 6 families of infants with MCADD. We used the REVEL method to predict the protein function of the detected missense variants and used SPDBV 4.10 to predict the protein 3D structure model. We identified pathogenic variants of ACADM gene in 6 cases of MCADD, and then assessed these variants through Sanger sequencing and association analysis.

RESULTS

The incidence of neonatal MCADD was 1/40,842 in Henan province. Among the 6 patients, five cases were compound heterozygous variants, one case was homozygous variants. DNA sequencing revealed 4 known (c.449_452del, c.1085G>A, c.1229T>C, c.589A>G) and 3 novel mutations (c.849+5_849+8del, c.427A>G, c.1181C>T) in the ACADM gene. Mutation c.1085G>A (p.G362E) was most frequent among Henan people and shows obvious differences between North and South of China.

CONCLUSION

MCADD is relatively rare in China, and c.1085G>A (p.G362E) is a common mutation in Henan population. Our findings, especially novel variants, will help improve the understanding of the genetic background and have facilitated clinical diagnosis and genetic counseling for the affected families.

A Novel Prognostic Signature for Survival Prediction and Immune Implication Based on SARS-CoV-2–Related Genes in Kidney Renal Clear Cell Carcinoma

Kidney renal clear cell carcinoma (KIRC) is a common aggressive malignancy of the urinary system. COVID-19, a highly infectious and severe disease caused by SARS-CoV-2, has become a significant challenge for global public health. Cancer patients have been reported to be more vulnerable to SARS-CoV-2 infection and have a higher risk for serious complications than the general population. However, the correlation between KIRC and COVID-19 remains incompletely elucidated. In this study, we comprehensively investigated the expression and prognostic significance of 333 SARS-CoV-2 infection–related genes in KIRC using the TCGA dataset and identified 31 SARS-CoV-2–related differently expressed genes between KIRC and normal renal tissues. Based on these genes, we constructed and validated a 5-gene prognostic signature (including ACADM, CENPF, KDELC1, PLOD2, and TRMT1) to distinguish low- and high-risk KIRC patients of poor survival in TCGA and E-MTAB-1980 cohorts. Gene set enrichment analysis (GSEA) showed that some inflammatory/immune-related pathways were significantly enriched in the high-risk group. The ESTIMATE analysis indicated that patients in the high-risk group had higher stromal and immune cell scores, therefore lower tumor purity. Moreover, they presented higher proportions of macrophages M0, regulatory T cells (Tregs), and T follicular helper cells and higher expression of immune checkpoints CTLA-4, LAG-3, TIGIT, and PDCD1 than low-risk patients. Besides, we also developed a nomogram to expand clinical applicability, which exhibits excellent predictive accuracy for survival. In conclusion, we identified a novel prognostic signature and nomogram based on SARS-CoV-2–related genes as reliable prognostic predictors for KIRC patients and provided potential therapeutic targets for KIRC and COVID-19.

Vulnerable exons, like ACADM exon 5, are highly dependent on maintaining a correct balance between splicing enhancers and silencers

It is now widely accepted that aberrant splicing of constitutive exons is often caused by mutations affecting cis-acting splicing regulatory elements, but there is a misconception that all exons have an equal dependency on splicing regulatory elements and thus a similar susceptibility to aberrant splicing. We investigated exonic mutations in ACADM exon 5 to experimentally examine their effect on splicing and found that 7 out of 11 tested mutations affected exon inclusion, demonstrating that this constitutive exon is particularly vulnerable to exonic splicing mutations. Employing ACADM exon 5 and 6 as models, we demonstrate that the balance between splicing enhancers and silencers, flanking intron length, and flanking splice site strength are important factors that determine exon definition and splicing efficiency of the exon in question. Our study shows that two constitutive exons in ACADM have different inherent vulnerabilities to exonic splicing mutations. This suggests that in silico prediction of potential pathogenic effects on splicing from exonic mutations may be improved by also considering the inherent vulnerability of the exon. Moreover, we show that single nucleotide polymorphism that affect either of two different exonic splicing silencers, located far apart in exon 5, all protect against both immediately flanking and more distant exonic splicing mutations.

Integrated Analysis of Liver Transcriptome, miRNA, and Proteome of Chinese Indigenous Breed Ningxiang Pig in Three Developmental Stages Uncovers Significant miRNA-mRNA-Protein Networks in Lipid Metabolism

Liver is an important metabolic organ of mammals. During each transitional period of life, liver metabolism is programmed by a complex molecular regulatory system for multiple physiological functions, many pathways of which are regulated by hormones and cytokines, nuclear receptors, and transcription factors. To gain a comprehensive and unbiased molecular understanding of liver growth and development in Ningxiang pigs, we analyzed the mRNA, microRNA (miRNA), and proteomes of the livers of Ningxiang pigs during lactation, nursery, and fattening periods. A total of 22,411 genes (19,653 known mRNAs and 2758 novel mRNAs), 1122 miRNAs (384 known miRNAs and 738 novel miRNAs), and 1123 unique proteins with medium and high abundance were identified by high-throughput sequencing and mass spectrometry. We show that the differences in transcriptional, post-transcriptional, or protein levels were readily identified by comparing different time periods, providing evidence that functional changes that may occur during liver development are widespread. In addition, we found many overlapping differentially expressed genes (DEGs)/differentially expressed miRNAs (DEMs)/differentially expressed proteins (DEPs) related to glycolipid metabolism in any group comparison. These overlapping DEGs/DEMs/DGPs may play an important role in functional transformation during liver development. Short Time-series Expression Miner (STEM) analysis revealed multiple expression patterns of mRNA, miRNA, and protein in the liver. Furthermore, several diverse key Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, including immune defense, glycolipid metabolism, protein transport and uptake, and cell proliferation and development, were identified by combined analysis of DEGs and DGPs. A number of predicted miRNA–mRNA–protein pairs were found and validated by qRT-PCR and parallel reaction monitoring (PRM) assays. The results provide new and important information about the genetic breeding of Ningxiang pigs, which represents a foundation for further understanding the molecular regulatory mechanisms of dynamic development of liver tissue, functional transformation, and lipid metabolism.

Genotype and residual enzyme activity in medium-chain acyl-CoA dehydrogenase (MCAD) deficiency: Are predictions possible?

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most common defect of mitochondrial β-oxidation. Confirmation diagnostics after newborn screening (NBS) can be performed either by enzyme testing and/or by sequencing of the ACADM gene. Here, we report the results from enzyme testing in lymphocytes with gene variants from molecular analysis of the ACADM gene and with the initial acylcarnitine concentrations in the NBS sample. From April 2013 to August 2019, in 388 individuals with characteristic acylcarnitine profiles suggestive of MCADD the octanoyl-CoA-oxidation was measured in lymphocytes. In those individuals with residual activities <50%, molecular genetic analysis of the ACADM gene was performed. In 50% of the samples (195/388), MCADD with a residual activity ranging from 0% to 30% was confirmed. Forty-five percent of the samples (172/388) showed a residual activity >35% excluding MCADD. In the remaining 21 individuals, MCAD residual activity ranged from 30% to 35%. The latter group comprised both heterozygous carriers and individuals carrying two gene variants on different alleles. Twenty new variants could be identified and functionally classified based on their effect on enzyme function. C6 and C8 acylcarnitine species in NBS correlated with MCAD activity and disease severity. MCADD was only confirmed in half of the cases referred suggesting a higher false positive rate than expected. Measurement of the enzyme function in lymphocytes allowed fast confirmation diagnostics and clear determination of the pathogenicity of new gene variants. There is a clear correlation between genotype and enzyme function underlining the reproducibility of the functional measurement in vitro.

Medium-chain acyl CoA dehydrogenase protects mitochondria from lipid peroxidation in glioblastoma

Glioblastoma (GBM) is highly resistant to chemo- and immune-based therapies and targeted inhibitors. To identify novel drug targets, we screened orthotopically implanted, patient-derived glioblastoma sphere-forming cells (GSCs) using an RNAi library to probe essential tumor cell metabolic programs. This identified high dependence on mitochondrial fatty acid metabolism. We focused on medium-chain acyl-CoA dehydrogenase (MCAD), which oxidizes medium-chain fatty acids (MCFAs), due to its consistently high score and high expression among models and upregulation in GBM compared to normal brain. Beyond the expected energetics impairment, MCAD depletion in primary GBM models induced an irreversible cascade of detrimental metabolic effects characterized by accumulation of unmetabolized MCFAs, which induced lipid peroxidation and oxidative stress, irreversible mitochondrial damage, and apoptosis. Our data uncover a novel protective role for MCAD to clear lipid molecules that may cause lethal cell damage, suggesting that therapeutic targeting of MCFA catabolism could exploit a key metabolic feature of GBM.

Clinical, Biochemical, and Molecular Analyses of Medium-Chain Acyl-CoA Dehydrogenase Deficiency in Chinese Patients

Objective

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is a rare inherited metabolic disorder of fatty acid β-oxidation. The present study aimed to evaluate clinical and biochemical manifestations, and the mutation spectrum of this disorder in a large cohort of Chinese patients.

Methods

A total of 24 patients were enrolled, and blood acylcarnitine and urinary organic acid levels were measured by tandem mass spectrometry and gas chromatography–mass spectrometry (GC–MS), respectively. Mutations in the ACADM gene were detected by Sanger or next-generation sequencing. Clinical progression, acylcarnitine spectra, and mutations were analyzed and described in detail.

Results

Among the 24 patients, six cases were diagnosed because of disease onset with symptoms such as vomiting, diarrhea, convulsion, and hypoglycemia; 18 patients without symptoms were diagnosed by newborn screening (NBS). All patients who accepted treatment after diagnosis developed normal intelligence and physique. The concentrations of octanoylcarnitine, the octanoylcarnitine/decanoylcarnitine ratio, and the octanoylcarnitine/acetylcarnitine ratio in the blood and urinary dicarboxylic acid concentrations were consistently elevated. Blood biomarkers failed to decrease after treatment. DNA sequencing revealed seven known and 17 novel mutations in the ACADM gene of patients. Mutation p.T150Rfs^∗4 was most frequent, followed by p.R31C, p.F103Y, p.I223T, p.G362E, and c.387+1delG.

Conclusion

Despite biochemical abnormalities, medium-chain acyl-CoA dehydrogenase deficiency showed relatively mild clinical phenotypes with low mortality and optimistic prognoses in China. NBS is crucial for early diagnosis, treatment, and prognosis.

Proteomic Analysis Reveals the Effect of Trichostatin A and Bone Marrow-Derived Dendritic Cells on the Fatty Acid Metabolism of NIH3T3 Cells under Oxygen-Glucose Deprivation Conditions

Fibroblasts mediate acute wound healing and long-term tissue remodeling with scarring after tissue injury. Following myocardial infarction (MI), necrotized cardiomyocytes become replaced by secreted extracellular matrix proteins produced by fibroblasts. Dendritic cells (DCs) can migrate from the bone marrow to the infarct areas and infarct border areas to mediate collagen accumulation after MI. Trichostatin A (TSA) is known to regulate apoptosis and proliferation in fibroblasts and affect the functions of DCs under oxygen-glucose deprivation (OGD) conditions. In this study, we used label-free quantitative proteomics to investigate the effects of TSA and bone marrow-derived dendritic cells (BMDCs) on NIH3T3 fibroblasts under OGD conditions. The results showed that the fatty acid degradation pathway was significantly upregulated in NIH3T3 cells under OGD conditions and that the fatty acid synthesis pathway was significantly downregulated in NIH3T3 cells treated with conditioned media (CM) from BMDCs treated with TSA under OGD conditions [BMDCs-CM(TSA)]. In addition, BMDCs-CM(TSA) significantly decreased the levels of triglycerides and free fatty acids and mediated fatty acid metabolism-related proteins in NIH3T3 cells under OGD conditions. In summary, this proteomics analysis showed that TSA and BMDCs affect fatty acid metabolism in NIH3T3 cells under OGD conditions.

A nationwide retrospective observational study of population newborn screening for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in the Netherlands

To evaluate the Dutch newborn screening (NBS) for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency since 2007, a nationwide retrospective, observational study was performed of clinical, laboratory and epidemiological parameters of patients with MCAD deficiency born between 2007 and 2015. Severe MCAD deficiency was defined by ACADM genotypes associated with clinical ascertainment, or variant ACADM genotypes with a residual MCAD enzyme activity <10%. Mild MCAD deficiency was defined by variant ACADM genotypes with a residual MCAD enzyme activity ≥10%. The prevalence of MCAD deficiency was 1/8300 (95% CI: 1/7300-1/9600). Sensitivity of the Dutch NBS was 99% and specificity ~100%, with a positive predictive value of 86%. Thirteen newborns with MCAD deficiency suffered from neonatal symptoms, three of them died. Of the 189 identified neonates, 24% had mild MCAD deficiency. The acylcarnitine ratio octanoylcarnitine (C8)/decanoylcarnitine (C10) was superior to C8 in discriminating between mild and severe cases and more stable in the first days of life. NBS for MCAD deficiency has a high sensitivity, specificity, and positive predictive value. In the absence of a golden standard to confirm the diagnosis, the combination of acylcarnitine (ratios), molecular and enzymatic studies allows risk stratification. To improve evaluation of NBS protocols and clinical guidelines, additional use of acylcarnitine ratios and multivariate pattern-recognition software may be reappraised in the Dutch situation. Prospective recording of NBS and follow-up data is warranted covering the entire health care chain of preventive and curative medicine.

[Medium-chain acyl-CoA dehydrogenase enhances invasion and metastasis ability of breast cancer cells]

OBJECTIVE

To investigate the effect of medium-chain acyl-CoA dehydrogenase (ACADM) on invasion and metastasis of breast cancer cells and explore the underlying mechanism.

METHODS

A large cancer genome database was used to analyze the expression of ACADM in breast cancer tissues and normal tissues. The proliferation, migration and invasion of cultured breast cancer MCF-7 and T47D cells with ACADM overexpression or ACADM silencing were evaluated using MTT proliferation assay, EdU assay, Transwell chamber assay, and Boyden invasion assay; Western blotting was used to detect the protein expressions of the related pathway in the cells. In nude mouse models of tail vein metastasis of MCF-7 cells with or without ACADM overexpression, the tumor growth and tumor histopathology were observed using HE staining.

RESULTS

Analysis of the Oncomine sample set showed a significantly higher expression level of ACADM in breast cancer tissues than in normal breast tissues (P &lt; 0.05). Overexpression of ACADM obviously enhanced the migration and invasion abilities and promoted the epithelial-mesenchymal transition (EMT) of cultured MCF-7 and T47D cells; conversely, silencing of ACADM significantly suppressed the migration and invasion of the breast cancer cells. In the nude mouse models, ACADM overexpression in MCF-7 cells significantly enhanced their in vivo migration and invasion abilities.

CONCLUSIONS

ACADM can promote the EMT process of breast cancer cells and improve the migration and invasion ability. ACADM is an oncogene in breast cancer.

Screening of MCAD deficiency in Japan: 16years' experience of enzymatic and genetic evaluation

BACKGROUND

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a representative disorder of fatty acid oxidation and is one of the most prevalent inborn errors of metabolism among Caucasian populations. In Japan, however, it was as late as 2000 when the first patient was found, and enzymatic and genetic evaluation of MCAD deficiency began.

METHODS

We measured octanoyl-CoA dehydrogenase activity in lymphocytes of symptomatic children and newborn screening (NBS)-positive subjects who showed elevated levels of C8-acylcarnitine in blood. The results were further confirmed by direct sequencing of the ACADM gene.

RESULTS

The disease was diagnosed in 9 out of 18 symptomatic children. The affected patients showed residual activities from 0% to 3% of the normal average value, except for one patient with 10% activity. Concerning 50 NBS-positive subjects, 18 with enzymatic activities around 10% or lower and 14 with activities ranging from 13% to 30% were judged to be affected patients, and biallelic variants were detected in most of the cases tested. Newborns with higher enzymatic activities were estimated to be heterozygous carriers or healthy subjects, though biallelic variants were detected in 5 of them. Genetic analysis detected 22 kinds of variant alleles. The most prevalent was c.449_452delCTGA (p.T150Rfs), which was followed by c.50G>A (p.R17H), c.1085G>A (p.G362E), c.157C>T (p.R53C), and c.843A>T (p.R281S); these five variants accounted for approximately 60% of all the alleles examined.

CONCLUSION

Our study has revealed the unique genetic backgrounds of MCAD deficiency among Japanese, based on the largest series of non-Caucasian cases. A continuous spectrum of severity was also observed in our series of NBS-positive cases, suggesting that it is essential for every nation and ethnic group to accumulate its own information on gene variants, together with their enzymatic evaluation, in order to establish an efficient NBS system for MCAD deficiency.

Reassessment of Genomic Sequence Variation to Harmonize Interpretation for Personalized Medicine

Accurate interpretation of DNA sequence variation is a prerequisite for implementing personalized medicine. Discrepancies in interpretation between testing laboratories impede the effective use of genetic test results in clinical medicine. To better understand the underpinnings of these discrepancies, we quantified differences in variant classification internally over time and those between our diagnostic laboratory and other laboratories and resources. We assessed the factors that contribute to these discrepancies and those that facilitate their resolution. Our process resolved 72% of nearly 300 discrepancies between pairs of laboratories to within a one-step classification difference and identified key sources of data that facilitate changes in variant interpretation. The identification and harmonization of variant discrepancies will maximize the clinical use of genetic information; these processes will be fostered by the accumulation of additional population data as well as the sharing of data between diagnostic laboratories.

221 newborn-screened neonates with medium-chain acyl-coenzyme A dehydrogenase deficiency: Findings from the Inborn Errors of Metabolism Collaborative

INTRODUCTION

There is limited understanding of relationships between genotype, phenotype and other conditions contributing to health in neonates with medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD) identified through newborn screening.

METHODS

Retrospective analysis of comprehensive data from a cohort of 221 newborn-screened subjects identified as affected with MCADD in the Inborn Errors of Metabolism - Information System (IBEM-IS), a long term follow-up database of the Inborn Errors of Metabolism Collaborative, was performed.

RESULTS

The average age at notification of first newborn screen results to primary care or metabolic providers was 7.45days. The average octanoylcarnitine (C8) value on first newborn screen was 11.2μmol/L (median 8.6, range 0.36-43.91). A higher C8 level correlated with an earlier first subspecialty visit. Subjects with low birth weight had significantly lower C8 values. Significantly higher C8 values were found in symptomatic newborns, in newborns with abnormal lab testing in addition to newborn screening and/or diagnostic tests, and in subjects homozygous for the c.985A>G ACADM gene mutation or compound heterozygous for the c.985A>G mutation and deletions or other known highly deleterious mutations. Subjects with neonatal symptoms, or neonatal abnormal labs, or neonatal triggers were more likely to have at least one copy of the severe c.985A>G ACADM gene mutation. C8 and genotype category were significant predictors of the likelihood of having neonatal symptoms. Neonates with select triggers were more likely to have symptoms and laboratory abnormalities.

CONCLUSIONS

This collaborative study is the first in the United States to describe health associations of a large cohort of newborn-screened neonates identified as affected with MCADD. The IBEM-IS has utility as a platform to better understand the characteristics of individuals with newborn-screened conditions and their follow-up interactions with the health system.

Intermediate MCAD Deficiency Associated with a Novel Mutation of the ACADM Gene: c.1052C>T

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is an autosomal recessive disorder that leads to a defect in fatty acid oxidation. ACADM is the only candidate gene causing MCAD deficiency. A single nucleotide change, c.985A>G, occurring at exon 11 of the ACADM gene, is the most prevalent mutation. In this study, we report a Caucasian family with multiple MCADD individuals. DNA sequence analysis of the ACADM gene performed in this family revealed that two family members showing mild MCADD symptoms share the same novel change in exon 11, c.1052C>T, resulting in a threonine-to-isoleucine change. The replacement is a nonconservative amino acid change that occurs in the C-terminal all-alpha domain of the MCAD protein. Here we report the finding of a novel missense mutation, c.1052C>T (p.Thr326Ile), in the ACADM gene. To our knowledge, c.1052C>T has not been previously reported in the literature or in any of the current databases we utilize. We hypothesize that this particular mutation in combination with p.Lys304Glu results in an intermediate clinical phenotype of MCADD.

Medium-chain acyl-CoA dehydrogenase deficiency associated with a novel splice mutation in the ACADM gene missed by newborn screening

Background

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common disorder of mitochondrial fatty acid β-oxidation and a target disease of newborn screening in many countries.

Case presentation

We report on two siblings with mild MCAD deficiency associated with a novel splice site mutation in the ACADM gene. The younger sibling was detected by newborn screening, while the older sister was missed, but diagnosed later on by genetic family testing. Both children were found to be compound heterozygous for the common c.985A > G (p.K329E) mutation and a novel splice site mutation, c.600-18G > A, in the ACADM gene. To determine the biological consequence of the c.600-18G > A mutation putative missplicing was investigated at RNA level in granulocytes and monocytes of one of the patients. The splice site mutation was shown to lead to partial missplicing of the ACADM pre-mRNA. Of three detected transcripts two result in truncated, non-functional MCAD proteins as reflected by the reduced octanoyl-CoA oxidation rate in both patients. In one patient a decrease of the octanoyl-CoA oxidation rate was found during a febrile infection indicating that missplicing may be temperature-sensitive.

Conclusions

Our data indicate that the c.600-18G > A variant activates a cryptic splice site, which competes with the natural splice site. Due to only partial missplicing sufficient functional MCAD protein remains to result in mild MCADD that may be missed by newborn screening.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-015-0199-5) contains supplementary material, which is available to authorized users.

Medium-Chain Acyl-CoA Dehydrogenase Deficiency: Evaluation of Genotype-Phenotype Correlation in Patients Detected by Newborn Screening

BACKGROUND

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is included in many newborn screening programmes worldwide. In addition to the prevalent mutation c.985A>G in the ACADM gene, potentially mild mutations like c.199T>C are frequently found in screening cohorts. There is ongoing discussion whether this mutation is associated with a clinical phenotype.

METHODS

In 37 MCADD patients detected by newborn screening, biochemical phenotype (octanoylcarnitine (C8), ratios of C8 to acetylcarnitine (C2), decanoylcarnitine (C10) and dodecanoylcarnitine (C12) at screening and confirmation) and clinical phenotype (inpatient emergency treatment, metabolic decompensations, clinical assessments, psychometric tests) were assessed in relation to genotype.

RESULTS

16 patients were homozygous for c.985A>G (group 1), 11 compound heterozygous for c.199T>C and c.985A>G/another mutation (group 2) and 7 compound heterozygous for c.985A>G and mutations other than c.199T>C (group 3) and 3 carried neither c.985A>G nor c.199T>C but other known homozygous mutations (group 4). At screening C8/C2 and C8/C10, at confirmation C8/C2, C8/C10 and C8/C12 differed significantly between patients compound heterozygous for c.199T>C (group 2) and other genotypes. C8, C10 and C8/C2 at screening were strongly associated with time of sampling in groups 1 + 3 + 4, but not in group 2. Clinical phenotype did not differ between genotypes. Two patients compound heterozygous for c.199T>C and a severe mutation showed neonatal decompensation with hypoglycaemia.

CONCLUSION

Biochemical phenotype differs between MCADD patients compound heterozygous for c.199T>C with a severe mutation and other genotypes. In patients detected by newborn screening, clinical phenotype does not differ between genotypes following uniform treatment recommendations. Neonatal decompensation can also occur in patients with the presumably mild mutation c.199T>C prior to diagnosis.

Functional studies of 18 heterologously expressed medium-chain acyl-CoA dehydrogenase (MCAD) variants

Medium-chain acyl-coenzyme-A dehydrogenase (MCAD) catalyzes the first step of mitochondrial beta-oxidation for medium-chain acyl-CoAs. Mutations in the ACADM gene cause MCAD deficiency presenting with life-threatening symptoms during catabolism. Since fatty-acid-oxidation disorders are part of newborn screening (NBS), many novel mutations with unknown clinical relevance have been identified in asymptomatic newborns. Eighteen of these mutations were separately cloned into the human ACADM gene, heterologously overexpressed in Escherichia coli and functionally characterized by using different substrates, molecular chaperones, and measured at different temperatures. In addition, they were mapped to the three-dimensional MCAD structure, and cross-link experiments were performed. This study identified variants that only moderately affect the MCAD protein in vitro, such as Y42H, E18K, and R6H, in contrast to the remaining 15 mutants. These three mutants display residual octanoyl-CoA oxidation activities in the range of 22 % to 47 %, are as temperature sensitive as the wild type, and reach 100 % activity with molecular chaperone co-overexpression. Projection into the three-dimensional protein structure gave some indication as to possible reasons for decreased enzyme activities. Additionally, six of the eight novel mutations, functionally characterized for the first time, showed severely reduced residual activities < 5 % despite high expression levels. These studies are of relevance because they classify novel mutants in vitro on the basis of their corresponding functional effects. This basic knowledge should be taken into consideration for individual management after NBS.

Differential Expression of PPARγ, FASN, and ACADM Genes in Various Adipose Tissues and Longissimus dorsi Muscle from Yanbian Yellow Cattle and Yan Yellow Cattle

The objective of this study was to investigate the correlation between cattle breeds and deposit of adipose tissues in different positions and the gene expressions of peroxisome proliferator-activated receptor gamma (PPARγ), fatty acid synthase (FASN), and Acyl-CoA dehydrogenase (ACADM), which are associated with lipid metabolism and are valuable for understanding the physiology in fat depot and meat quality. Yanbian yellow cattle and Yan yellow cattle reared under the same conditions display different fat proportions in the carcass. To understand this difference, the expression of PPARγ, FASN, and ACADM in different adipose tissues and longissimus dorsi muscle (LD) in these two breeds were analyzed using the Real-time quantitative polymerase chain reaction method (qRT-PCR). The result showed that PPARγ gene expression was significantly higher in adipose tissue than in LD in both breeds. PPARγ expression was also higher in abdominal fat, in perirenal fat than in the subcutaneous fat (p<0.05) in Yanbian yellow cattle, and was significantly higher in subcutaneous fat in Yan yellow cattle than that in Yanbian yellow cattle. On the other hand, FASN mRNA expression levels in subcutaneous fat and abdominal fat in Yan yellow cattle were significantly higher than that in Yanbian yellow cattle. Interestingly, ACADM gene shows greater fold changes in LD than in adipose tissues in Yan yellow cattle. Furthermore, the expressions of these three genes in lung, colon, kidney, liver and heart of Yanbian yellow cattle and Yan yellow cattle were also investigated. The results showed that the highest expression levels of PPARγ and FASN genes were detected in the lung in both breeds. The expression of ACADM gene in kidney and liver were higher than that in other organs in Yanbian yellow cattle, the comparison was not statistically significant in Yan yellow cattle.

The domain-specific and temperature-dependent protein misfolding phenotype of variant medium-chain acyl-CoA dehydrogenase

The implementation of expanded newborn screening programs reduced mortality and morbidity in medium-chain acyl-CoA dehydrogenase deficiency (MCADD) caused by mutations in the ACADM gene. However, the disease is still potentially fatal. Missense induced MCADD is a protein misfolding disease with a molecular loss-of-function phenotype. Here we established a comprehensive experimental setup to analyze the structural consequences of eight ACADM missense mutations (p.Ala52Val, p.Tyr67His, p.Tyr158His, p.Arg206Cys, p.Asp266Gly, p.Lys329Glu, p.Arg334Lys, p.Arg413Ser) identified after newborn screening and linked the corresponding protein misfolding phenotype to the site of side-chain replacement with respect to the domain. With fever being the crucial risk factor for metabolic decompensation of patients with MCADD, special emphasis was put on the analysis of structural and functional derangements related to thermal stress. Based on protein conformation, thermal stability and kinetic stability, the molecular phenotype in MCADD depends on the structural region that is affected by missense-induced conformational changes with the central β-domain being particularly prone to structural derangement and destabilization. Since systematic classification of conformational derangements induced by ACADM mutations may be a helpful tool in assessing the clinical risk of patients, we scored the misfolding phenotype of the variants in comparison to p.Lys329Glu (K304E), the classical severe mutation, and p.Tyr67His (Y42H), discussed to be mild. Experiments assessing the impact of thermal stress revealed that mutations in the ACADM gene lower the temperature threshold at which MCAD loss-of-function occurs. Consequently, increased temperature as it occurs during intercurrent infections, significantly increases the risk of further conformational derangement and loss of function of the MCAD enzyme explaining the life-threatening clinical courses observed during fever episodes. Early and aggressive antipyretic treatment thus may be life-saving in patients suffering from MCADD.

Newborn screening for medium-chain acyl-CoA dehydrogenase deficiency: regional experience and high incidence of carnitine deficiency

Background

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most common inherited defect in the mitochondrial fatty acid oxidation pathway, resulting in significant morbidity and mortality in undiagnosed patients.

Newborn screening (NBS) has considerably improved MCADD outcome, but the risk of complication remains in some patients. The aim of this study was to evaluate the relationship between genotype, biochemical parameters and clinical data at diagnosis and during follow-up, in order to optimize monitoring of these patients.

Methods

We carried out a multicenter study in southwest Europe, of MCADD patients detected by NBS. Evaluated NBS data included free carnitine (C0) and the acylcarnitines C8, C10, C10:1 together with C8/C2 and C8/C10 ratios, clinical presentation parameters and genotype, in 45 patients. Follow-up data included C0 levels, duration of carnitine supplementation and occurrence of metabolic crises.

Results

C8/C2 ratio and C8 were the most accurate biomarkers of MCADD in NBS. We found a high number of patients homozygous for the prevalent c.985A > G mutation (75%). Moreover, in these patients C8, C8/C10 and C8/C2 were higher than in patients with other genotypes, while median value of C0 was significantly lower (23 μmol/L vs 36 μmol/L).

The average follow-up period was 43 months. To keep carnitine levels within the normal range, carnitine supplementation was required in 82% of patients, and for a longer period in patients homozygotes for the c.985A>G mutation than in patients with other genotypes (average 31 vs 18 months). Even with treatment, median C0 levels remained lower in homozygous patients than in those with other genotypes (14 μmol/L vs 22 μmol/L).

Two patients died and another three suffered a metabolic crisis, all of whom were homozygous for the c.985 A>G mutation.

Conclusions

Our data show a direct association between homozygosity for c.985A>G and lower carnitine values at diagnosis, and a higher dose of carnitine supplementation for maintenance within the normal range. This study contributes to a better understanding of the relationship between genotype and phenotype in newborn patients with MCADD detected through screening which could be useful in improving follow-up strategies and clinical outcome.

Functional effects of different medium-chain acyl-CoA dehydrogenase genotypes and identification of asymptomatic variants

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency (OMIM 201450) is the most common inherited disorder of fatty acid metabolism presenting with hypoglycaemia, hepatopathy and Reye-like symptoms during catabolism. In the past, the majority of patients carried the prevalent c.985A>G mutation in the ACADM gene. Since the introduction of newborn screening many other mutations with unknown clinical relevance have been identified in asymptomatic newborns. In order to identify functional effects of these mutant genotypes we correlated residual MCAD (OMIM 607008) activities as measured by octanoyl-CoA oxidation in lymphocytes with both genotype and relevant medical reports in 65 newborns harbouring mutant alleles. We identified true disease-causing mutations with residual activities of 0 to 20%. In individuals carrying the c.199T>C or c.127G>A mutation on one allele, residual activities were much higher and in the range of heterozygotes (31%-60%). Therefore, both mutations cannot clearly be associated with a clinical phenotype. This demonstrates a correlation between the octanoyl-CoA oxidation rate in lymphocytes and the clinical outcome. With newborn screening, the natural course of disease is difficult to assess. The octanoyl-CoA oxidation rate, therefore, allows a risk assessment at birth and the identification of new ACADM genotypes associated with asymptomatic disease variants.

MCAD deficiency in Denmark

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most common defect of fatty acid oxidation. Many countries have introduced newborn screening for MCADD, because characteristic acylcarnitines can easily be identified in filter paper blood spot samples by tandem mass spectrometry (MS/MS), because MCADD is a frequent disease, and because of the success of early treatment initiated before clinical symptoms have emerged. In Denmark we have screened 519,350 newborns for MCADD by MS/MS and identified 58 affected babies. The diagnosis of MCADD was confirmed in all 58 newborns by mutation analysis. This gives an incidence of MCADD detected by newborn screening in Denmark of 1/8954. In sharp contrast to this we found that the incidence of clinically presenting MCADD in Denmark in the 10 year period preceding introduction of MS/MS-based screening was only 1 in 39,691. This means that four times more newborns with MCADD are detected by screening than what is expected based on the number of children presenting clinically in an unscreened population. The mutation spectrum in the newborns detected by screening is different from that observed in clinically presenting patients with a much lower proportion of newborns being homozygous for the prevalent disease-causing c.985A>G mutation. A significant number of the newborns have genotypes with mutations that have not been observed in patients detected clinically. Some of these mutations, like c.199T>C and c.127G>A, are always associated with a milder biochemical phenotype and may cause a milder form of MCADD with a relatively low risk of disease manifestation, thereby explaining part of the discrepancy between the frequency of clinically manifested MCADD and the frequency of MCADD determined by screening. In addition, our data suggest that some of this discrepancy can be explained by a reduced penetrance of the c.985A>G mutation, with perhaps only 50% of c.985A>G homozygotes presenting with disease manifestations. Interestingly, we also report that the observed number of newborns identified by screening who are homozygous for the c.985A>G mutation is twice that predicted from the estimated carrier frequency. We therefore redetermined the carrier frequency in a new sample of 1946 blood spots using a new assay, but this only confirmed that the c.985A>G carrier frequency in Denmark is approximately 1/105. We conclude that MCADD is much more frequent than expected, has a reduced penetrance and that rapid genotyping using the initial blood spot sample is important for correct diagnosis and counseling.

Risk stratification by residual enzyme activity after newborn screening for medium-chain acyl-CoA dehyrogenase deficiency: data from a cohort study

Background

Since the introduction of medium-chain acyl coenzyme A dehydrogenase (MCAD) deficiency in population newborn bloodspot screening (NBS) programs, subjects have been identified with variant ACADM (gene encoding MCAD enzyme) genotypes that have never been identified in clinically ascertained patients. It could be hypothesised that residual MCAD enzyme activity can contribute in risk stratification of subjects with variant ACADM genotypes.

Methods

We performed a retrospective cohort study of all patients identified upon population NBS for MCAD deficiency in the Netherlands between 2007–2010. Clinical, molecular, and enzymatic data were integrated.

Results

Eighty-four patients from 76 families were identified. Twenty-two percent of the subjects had a variant ACADM genotype. In patients with classical ACADM genotypes, residual MCAD enzyme activity was significantly lower (median 0%, range 0-8%) when compared to subjects with variant ACADM genotypes (range 0-63%; 4 cases with 0%, remainder 20-63%). Patients with (fatal) neonatal presentations before diagnosis displayed residual MCAD enzyme activities <1%. After diagnosis and initiation of treatment, residual MCAD enzyme activities <10% were associated with an increased risk of hypoglycaemia and carnitine supplementation. The prevalence of MCAD deficiency upon screening was 1/8,750 (95% CI 1/7,210–1/11,130).

Conclusions

Determination of residual MCAD enzyme activity improves our understanding of variant ACADM genotypes and may contribute to risk stratification. Subjects with variant ACADM genotypes and residual MCAD enzyme activities <10% should be considered to have the same risks as patients with classical ACADM genotypes. Parental instructions and an emergency regimen will remain principles of the treatment in any type of MCAD deficiency, as the effect of intercurrent illness on residual MCAD enzyme activity remains uncertain. There are, however, arguments in favour of abandoning the general advice to avoid prolonged fasting in subjects with variant ACADM genotypes and >10% residual MCAD enzyme activity.

VLCAD enzyme activity determinations in newborns identified by screening: a valuable tool for risk assessment

Tandem mass spectrometry-based newborn screening correctly identifies individuals with very long-chain acyl-CoA dehydrogenase deficiency (VLCADD). However, a great number of healthy individuals present with identical acylcarnitine profiles during catabolism in the first three days of life. We routinely perform an enzyme activity assay as confirmation analysis in newborns identified by screening. Whereas VLCAD residual activities of less than 10% are clearly diagnostic and indicate patients at risk of clinical disease, the clinical relevance of higher residual activities is unclear. In this study we assess the molecular basis in 34 individuals with residual activities of 10-50%. We identify two pathogenic mutations in patients that result in residual activities as high as 22%, while individuals with residual activities of 25-50% either present with a heterozygous or no mutation in the VLCAD gene. In addition, confirmed heterozygous parents present with residual activities as low as 32%.In conclusion, we identify individuals with 2 pathogenic mutations and those with only one heterozygous mutation in the residual activity range of 20-30%. Whereas heterozygosity is generally regarded as clinically irrelevant, identification of 2 VLCAD mutations leads to precautions in the management of the children. Based on our data we anticipate that individuals with a residual enzyme activity >20% present with a biochemical phenotype but likely remain asymptomatic throughout life. Studies in greater patient numbers are needed to correlate residual activities >10% with the genotype and the outcome.

Expanded newborn screening: articulating the ontology of diseases with bridging work in the clinic

Population screening follows the logic of secondary prevention: a population is screened to detect disease early and to initiate treatment before symptoms emerge. However, not all population screening is justifiable under all circumstances. In this article, we unpack Wilson and Jungner's requirement that knowledge about the natural history of a disease must be 'adequate' for screening to proceed. We argue that any prior understanding of disease is inevitably found to be insufficient once population screening is instituted. Drawing upon ethnographic observations of clinical consultations and staff meetings conducted in a California regional clinical centre for metabolic-genetic disorders, we introduce the notion of bridging work to draw attention to the collective activities of the genetics team to revise the ontological nature of conditions unsettled by population-based newborn screening. Bridging work refers to the many activities required to reconcile the promise of technologies with the realities of their implementation. We illustrate how clinicians bridge the gap between what was known about a disease prior to screening and anomalous screening results, leading to an ontological transformation of disease categories.

[Medium-chain acyl-CoA-dehydrogenase (MCAD) deficiency: French consensus for neonatal screening, diagnosis, and management]

MCAD deficiency is the most common fatty acid oxidation disorder, with the prevalence varying from 1/10,000 to 1/27,000 in the countries adjacent to France. As the High Authority for Health has recently proposed including MCAD deficiency in the panel of diseases neonatally screened for in France, a consensus was written for the management of MCAD deficiency diagnosed either clinically or by neonatal screening. Patients may present acutely with hyperammonemia, hypoglycemia, encephalopathy, and hepatomegaly, mainly after a prolonged fast of intercurrent infection. Sudden death related to heartbeat disorders may also occur. The diagnosis of MCAD deficiency is suspected on the plasma acylcarnitine and/or the urinary organic acid profile. The diagnosis is confirmed by molecular biology and the enzymatic activity for patients who are not homozygous for the main mutation c.985A>G. However, some MCAD-deficient individuals may remain asymptomatic throughout life. The mainstay of treatment consists in avoiding prolonged fast and prescribing l-carnitine for patients who exhibit a deficiency in plasma carnitine. This management has radically modified the natural history of MCAD deficiency. This consensus will allow homogeneous management of these patients once the neonatal screening of MCAD deficiency has been introduced in France.

Newborn screening for medium chain acyl-CoA dehydrogenase deficiency in England: prevalence, predictive value and test validity based on 1.5 million screened babies

BACKGROUND

Medium chain acyl-CoA dehydrogenase deficiency (MCADD) is a rare, life-threatening condition. Early diagnosis by screening asymptomatic newborns may improve outcome, but the benefit to newborns identified with variants not encountered clinically is uncertain.

OBJECTIVE

To estimate, overall and by ethnic group: screen-positive prevalence and predictive value (PPV); MCADD prevalence; proportion MCADD variants detected of predicted definite or uncertain clinical importance.

SETTING

All births in areas of high ethnic minority prevalence in England.

METHODS

Prospective multicentre pilot screening service; testing at age five to eight days; standardized screening, diagnostic and management protocols; independent expert review of screen-positive cases to assign MCADD diagnosis and predicted clinical importance (definite or uncertain).

RESULTS

Approximately 1.5 million babies (79% white; 10% Asian) were screened. MCADD was confirmed in 147 of 190 babies with a positive screening result (screen-positive prevalence: 1.20 per 10,000; MCADD prevalence: 0.94 per 10,000; PPV 77% [95% CI 71-83]), comprising 103 (70%) with MCADD variants of definite clinical importance (95 white [95%]; 2 Asian [2%]) and 44 (30%) with variants of uncertain clinical importance (29 white [67%]; 12 Asian [28%]).

CONCLUSION

One baby in every 10,000 born in England is diagnosed with MCADD by newborn screening; around 60 babies each year. While the majority of MCADD variants detected are predicted to be of definite clinical importance, this varies according to ethnic group, with variants of uncertain importance most commonly found in Asian babies. These findings provide support for MCADD screening but highlight the need to take account of the ethnic diversity of the population tested at implementation.

Clinical validation of cutoff target ranges in newborn screening of metabolic disorders by tandem mass spectrometry: a worldwide collaborative project

PURPOSE

To achieve clinical validation of cutoff values for newborn screening by tandem mass spectrometry through a worldwide collaborative effort.

METHODS

Cumulative percentiles of amino acids and acylcarnitines in dried blood spots of approximately 25–30 million normal newborns and 10,742 deidentified true positive cases are compared to assign clinical significance, which is achieved when the median of a disorder range is, and usually markedly outside, either the 99th or the 1st percentile of the normal population. The cutoff target ranges of analytes and ratios are then defined as the interval between selected percentiles of the two populations. When overlaps occur, adjustments are made to maximize sensitivity and specificity taking all available factors into consideration.

RESULTS

As of December 1, 2010, 130 sites in 45 countries have uploaded a total of 25,114 percentile data points, 565,232 analyte results of true positive cases with 64 conditions, and 5,341 cutoff values. The average rate of submission of true positive cases between December 1, 2008, and December 1, 2010, was 5.1 cases/day. This cumulative evidence generated 91 high and 23 low cutoff target ranges. The overall proportion of cutoff values within the respective target range was 42% (2,269/5,341).

CONCLUSION

An unprecedented level of cooperation and collaboration has allowed the objective definition of cutoff target ranges for 114 markers to be applied to newborn screening of rare metabolic disorders.

Relevance of expanded neonatal screening of medium-chain acyl co-a dehydrogenase deficiency: outcome of a decade in galicia (Spain)

Neonatal screening of medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is of major importance due to the significant morbidity and mortality in undiagnosed patients. MCADD screening has been performed routinely in Galicia since July 2000, and until now 199,943 newborns have been screened. We identified 11 cases of MCADD, which gives an incidence of 1/18,134. During this period, no false negative screens have been detected. At diagnosis, all identified newborns were asymptomatic. Our data showed that octanoylcarnitine (C8) and C8/C10 ratio are the best markers for screening of MCADD. C8 was increased in all patients and C8/C10 was increased in all but one patient.The common mutation, c.985A > G, was found in homozygosity in seven newborns and in compound heterozygosity in three, while one patient did not carry the common mutation at all. In addition, two novel mutations c.245G > C (p.W82S) and c.542A > G (p.D181G) were identified. Ten of the 11 identified newborns did not experience any episodes of decompensation. The patient with the highest level of medium chain acylcarnitines at diagnosis, who was homozygous for the c.985A > G mutation, died at the age of 2 years due to a severe infection.This is the first report of the results from neonatal screening for MCADD in Spain. Our data provide further evidence of the benefits of MCADD screening and contribute to better understanding of this disease.

New technologies extend the scope of newborn blood-spot screening, but old problems remain unresolved

The potential of newborn blood-spot screening is expanding rapidly with the development of new analytical techniques and treatment methods. At the same time, some existing programmes, particularly that for congenital hypothyroidism, are coming under scrutiny because of suspicion that they are being shaped by analytical performance rather than evidence of clinical need. Screening policy varies greatly from country to country.

CONCLUSION

  Ethical and political considerations may sometimes override formal scientific decision models.

The first three years of screening for medium chain acyl-CoA dehydrogenase deficiency (MCADD) by newborn screening ontario

Background

Medium chain acyl-CoA dehydrogenase deficiency (MCADD) is a disorder of mitochondrial fatty acid oxidation and is one of the most common inborn errors of metabolism. Identification of MCADD via newborn screening permits the introduction of interventions that can significantly reduce associated morbidity and mortality. This study reports on the first three years of newborn screening for MCADD in Ontario, Canada.

Methods

Newborn Screening Ontario began screening for MCADD in April 2006, by quantification of acylcarnitines (primarily octanoylcarnitine, C8) in dried blood spots using tandem mass spectrometry. Babies with positive screening results were referred to physicians at one of five regional Newborn Screening Treatment Centres, who were responsible for diagnostic evaluation and follow-up care.

Results

From April 2006 through March 2009, approximately 439 000 infants were screened for MCADD in Ontario. Seventy-four infants screened positive, with a median C8 level of 0.68 uM (range 0.33-30.41 uM). Thirty-one of the screen positive infants have been confirmed to have MCADD, while 36 have been confirmed to be unaffected. Screening C8 levels were higher among infants with MCADD (median 8.93 uM) compared to those with false positive results (median 0.47 uM). Molecular testing was available for 29 confirmed cases of MCADD, 15 of whom were homozygous for the common c.985A > G mutation. Infants homozygous for the common mutation tended to have higher C8 levels (median 12.13 uM) relative to compound heterozygotes for c.985A > G and a second detectable mutation (median 2.01 uM). Eight confirmed mutation carriers were identified among infants in the false positive group. The positive predictive value of a screen positive for MCADD was 46%. The estimated birth prevalence of MCADD in Ontario is approximately 1 in 14 000.

Conclusions

The birth prevalence of MCADD and positive predictive value of the screening test were similar to those identified by other newborn screening programs internationally. We observed some evidence of correlation between genotype and biochemical phenotype (C8 levels), and between C8 screening levels and eventual diagnosis. Current research priorities include further examining the relationships among genotype, biochemical phenotype, and clinical phenotype, with the ultimate goal of improving clinical risk prediction in order to provide tailored disease management advice and genetic counselling to families.