Analysis of cases of 3-methylcrotonyl CoA carboxylase deficiency (3-MCCD) in the California newborn screening program reported in the state database

Newborn screening for 3-methylcrotonyl-CoA carboxylase deficiency in Zhejiang province, China

BACKGROUND

3-Methylcrotonyl-CoA carboxylase deficiency (3-MCCD) is an autosomal recessive inborn defect of leucine catabolism caused by MCCC1 or MCCC2 variants. 3-MCCD is considered to be a relatively benign disorder with favorable outcome. We report the biochemical, clinical, and molecular features of patients with 3-MCCD.

METHODS

From January 2009 to August 2022, 4,402,587 newborns were screened by tandem mass spectrometry. Newborns with increased C5OH concentrations were recalled for repeated testing, urine organic acid analysis and molecular genetic analysis were performed if the second test was still positive.

RESULTS

A total of 53 patients were diagnosed with 3-MCCD. The estimated incidence of 3-MCCD in Zhejiang Province was 1 in 83,068 newborns. All these 53 patients exhibited increased C5OH concentrations in blood. 94 % (50/53) of the patients had markedly increased urinary 3-hydroxyisovaleric acid and 3-methylcrotonylglycine. All these 53 patients did not present any clinical symptom. Twenty-three of 53 patients had secondary carnitine deficiency. Twenty-eight patients had variants in MCCC1 and 25 had variants in MCCC2. Eleven novel variants were found in MCCC1 and MCCC2. The c.639 + 2 T > A and c.1144-1147delinsTTTT were the most common variant in MCCC1 and MCCC2 gene, respectively.

CONCLUSION

We elucidated the incidence of 3-MCCD in Zhejiang province, China. All patients showed asymptomatic and present normal growth and development during follow-up. Eleven novel MCCC1 and MCCC2 variants were identified, which expanded the variant spectrum.

lncRNA AABR07005593.1 potentiates PM2.5-induced interleukin-6 expression by targeting MCCC1

BACKGROUND

Fine particle pollution, specifically pollution by fine particulate matter (PM_2.5), remains a significant concern in developing countries and plays an important role in the development and progression of respiratory diseases. Increasing evidences have demonstrated that long non-coding RNAs (lncRNAs) may act as vital molecules by binding to specific RNA-binding protein (RBP); however, their relationship with PM_2.5 pollution is largely unexplored.

OBJECTIVE

We investigated the association between lncRNA and respiratory system inflammation caused by PM_2.5.

METHODS

PM_2.5 components were detected by gas chromatography-mass spectrometry (GC-MS), inductively coupled plasma-mass spectrometry (ICP-MS), and ionic chromatography. We established an inflammation model of PM_2.5-induced toxicity in vivo (male and female SD rats, 0, 25, 50 and 100 mg/k PM_2.5, 1, 7 and 14 days, single non-invasive tracheal instillation) and in vitro (rat alveolar macrophage cell line (NR8383), 0, 50, 100, 200, 400 μM PM_2.5 for 24, 48, and 72 h). lncRNA high-throughput sequencing (lncRNA-seq) was used to investigate lncRNA profiles in PM_2.5-treated NR8383 cells, and RNA interference (RNAi) was applied to explore the function of the target lncRNA. The mechanisms associated with specific lncRNAs were explored using comprehensive identification of RNA-binding proteins by mass spectrometry (ChIRP-MS) and western blot.

RESULTS

PM_2.5-treated NR8383 cells and SD rats exhibited respiratory inflammation. lncRNA AABR07005593.1 was a pro-inflammatory factor that regulated IL-6 levels. Mechanistically, ChIRP-MS and western blot analyses revealed that highly expressed lncRNA AABR07005593.1 interacted with MCCC1 to involve in the activation of NF-κB pathway, and ultimately promoted the expression of IL-6.

CONCLUSION

This study demonstrated that PM_2.5 induced inflammation in vivo and in vitro. Furthermore, lncRNA AABR07005593.1 bound to MCCC1 to potentiated IL-6 expression. Therefore, lncRNA AABR07005593.1 may act as a potential biomarker for PM_2.5 inflammation.

3-Methylcrotonyl-CoA carboxylase deficiency newborn screening in a population of 536,008: is routine screening necessary?

Objective To evaluate whether 3-methylcrotonyl-CoA carboxylase deficiency (3-MCCD) should be routinely screened in newborns. Methods Dried blood spots (DBS) were collected and analyzed by tandem mass spectrometry (TMS). Blood samples were collected from infants with positive 3-MCCD results. Targeted sequencing was performed using the extended panel for inherited metabolic diseases to detect 306 genes. The sequencing libraries were quantified and used for massively parallel sequencing on the Illumina HiSeq 2500 platform. Results A total of 536,008 infants underwent newborn screening (NBS) and 14 cases of 3-MCCD were diagnosed. The incidence of 3-MCCD in Jiangsu province was 1:38,286. During the last 3 years of follow-up, none of the subjects with 3-MCCD exhibited obvious clinical symptoms. Only two children had mild feeding difficulties and vomiting. Eleven patients had complex variants of the MCCC1 gene, and three patients had mutations in MCCC2. In total, 17 types of MCCC1 or MCCC2 variants were found, and c.639 + 2t > a was the most common mutation. Conclusions As far as the current results are concerned, 3-MCCD may be benign in Jiangsu province. However, additional investigations and a longer follow-up period are necessary to decide whether NBS of 3-MCCD is necessary or not.

Expanded Newborn Screening for Inborn Errors of Metabolism by Tandem Mass Spectrometry in Suzhou, China: Disease Spectrum, Prevalence, Genetic Characteristics in a Chinese Population

Expanded newborn screening for inborn errors of metabolism (IEMs) by tandem mass spectrometry (MS/MS) could simultaneously analyze more than 40 metabolites and identify about 50 kinds of IEMs. Next generation sequencing (NGS) targeting hundreds of IMEs-associated genes as a follow-up test in expanded newborn screening has been used for genetic analysis of patients. The spectrum, prevalence, and genetic characteristic of IEMs vary dramatically in different populations. To determine the spectrum, prevalence, and gene mutations of IEMs in newborns in Suzhou, China, 401,660 newborns were screened by MS/MS and 138 patients were referred to genetic analysis by NGS. The spectrum of 22 IEMs were observed in Suzhou population of newborns, and the overall incidence (excluding short chain acyl-CoA dehydrogenase deficiency (SCADD) and 3-Methylcrotonyl-CoA carboxylase deficiency (3-MCCD)) was 1/3,163. The prevalence of each IEM ranged from 1/401,660 to 1/19,128, while phenylketonuria (PKU) (1/19,128) and Mild hyperphenylalaninemia (M-HPA) (1/19,128) were the most common IEMs, followed by primary carnitine uptake defect (PCUD) (1/26,777), SCADD (1/28,690), hypermethioninemia (H-MET) (1/30,893), 3-MCCD (1/33,412) and methylmalonic acidemia (MMA) (1/40,166). Moreover, 89 reported mutations and 51 novel mutations in 25 IMEs-associated genes were detected in 138 patients with one of 22 IEMs. Some hotspot mutations were observed for ten IEMs, including PAH gene c.728G > A, c.611A > G, and c.721C > T for Phenylketonuria, PAH gene c.158G > A, c.1238G > C, c.728G > A, and c.1315+6T > A for M-HPA, SLC22A5 gene c.1400C > G, c.51C > G, and c.760C > T for PCUD, ACADS gene c.1031A > G, c.164C > T, and c.1130C > T for SCAD deficiency, MAT1A gene c.791G > A for H-MET, MCCC1 gene c.639+2T > A and c.863A > G for 3-MCCD, MMUT gene c.1663G > A for MMA, SLC25A13 gene c.IVS16ins3Kb and c.852_855delTATG for cittrullinemia II, PTS gene c.259C > T and c.166G > A for Tetrahydrobiopterin deficiency, and ACAD8 gene c.1000C > T and c.286C > A for Isobutyryl coa dehydrogenase deficiency. All these hotspot mutations were reported to be pathogenic or likely pathogenic, except a novel mutation of ACAD8 gene c.286C > A. These mutational hotspots could be potential candidates for gene screening and these novel mutations expanded the mutational spectrum of IEMs. Therefore, our findings could be of value for genetic counseling and genetic diagnosis of IEMs.

Improving the diagnosis of cobalamin and related defects by genomic analysis, plus functional and structural assessment of novel variants

Background

Cellular cobalamin defects are a locus and allelic heterogeneous disorder. The gold standard for coming to genetic diagnoses of cobalamin defects has for some time been gene-by-gene Sanger sequencing of individual DNA fragments. Enzymatic and cellular methods are employed before such sequencing to help in the selection of the gene defects to be sought, but this is time-consuming and laborious. Furthermore some cases remain undiagnosed because no biochemical methods have been available to test for cobalamin absorption and transport defects.

Results

This paper reports the use of massive parallel sequencing of DNA (exome analysis) for the accurate and rapid genetic diagnosis of cobalamin-related defects in a cohort of affected patients. The method was first validated in an initial cohort with different cobalamin defects. Mendelian segregation, the frequency of mutations, and the comprehensive structural and functional analysis of gene variants, identified disease-causing mutations in 12 genes involved in the absorption and synthesis of active cofactors of vitamin B₁₂ (22 cases), and in the non-cobalamin metabolism-related genes ACSF3 (in four biochemically misdiagnosed patients) and SUCLA2 (in one patient with an unusual presentation). We have identified thirteen new variants all classified as pathogenic according to the ACGM recommendation but four were classified as variant likely pathogenic in MUT and SUCLA2. Functional and structural analysis provided evidences to classify them as pathogenic variants.

Conclusions

The present findings suggest that the technology used is sufficiently sensitive and specific, and the results it provides sufficiently reproducible, to recommend its use as a second-tier test after the biochemical detection of cobalamin disorder markers in the first days of life. However, for accurate diagnoses to be made, biochemical and functional tests that allow comprehensive clinical phenotyping are also needed.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0862-y) contains supplementary material, which is available to authorized users.

Follow-up status during the first 5 years of life for metabolic disorders on the federal Recommended Uniform Screening Panel

PURPOSE

To investigate the 5-year follow-up status for newborns diagnosed with metabolic disorders designated as "primary disorders" on the federal Recommended Uniform Screening Panel (RUSP).

METHODS

Follow-up status and demographic characteristics are described for 426 newborns diagnosed with one of 20 primary metabolic disorders on the RUSP between 2005 and 2009. Newborn screening program data were linked to birth certificate data. Follow-up status is described for each year through age 5 and by disorder type. Maternal characteristics of those who stayed in active care were compared with those who did not.

RESULTS

Of 426 diagnosed newborns, by the end of 5 years of follow-up 55.2% stayed in active care, 20.4% became lost to follow-up, 8.7% moved out of state, 6.3% were determined to require no further follow-up, 4.7% refused follow-up, and 4.7% died. Among the initial group of disorders with more than 10 diagnosed cases, phenylketonuria (90%) had the highest percentage of patients still in active care after 5 years. Patients in active care had similar characteristics to patients not in active care when maternal age, race/ethnicity, completed education years, and expected source of payment for delivery were compared.

CONCLUSION

Staying in active care may associate with disorder type but not maternal characteristics.

Neonatal Screening for Inherited Metabolic Diseases in 2016

The scope of newborn screening (NBS) programs is continuously expanding. NBS programs are secondary prevention interventions widely recognized internationally in the "field of Public Health." These interventions are aimed at early detection of asymptomatic children affected by certain diseases, with the objective to establish a definitive diagnosis and apply the proper treatment to prevent further complications and sequelae and ensure a better quality of life. The most significant event in the history of neonatal screening was the discovery of phenylketonuria in 1934. This disease has been the paradigm of inherited metabolic diseases. The next paradigm was the introduction of tandem mass spectrometry in the NBS programs that make possible the simultaneous measurement of several metabolites and consequently, the detection of several diseases in one blood spot and in an unique analysis. We aim to review the current situation of neonatal screening in 2016 worldwide and show scientific evidence of the benefits for some diseases. We will also discuss future challenges. It should be taken into account that any consideration to expand an NBS panel should involve a rigorous process of decision-making that balances benefits against the risks of harm.

Primary and maternal 3-methylcrotonyl-CoA carboxylase deficiency: insights from the Israel newborn screening program

BACKGROUND

3-Methylcrotonyl-CoA carboxylase deficiency (3MCCD) is an inborn error of leucine catabolism. Tandem mass spectrometry newborn screening (NBS) programs worldwide confirmed 3MCCD to be the most common organic aciduria and a relatively benign disorder with favorable outcome. In addition, several asymptomatic 3MCCD mothers were initially identified following abnormal screening of their healthy babies and were appropriately termed maternal 3MCCD.

METHODS

This is a retrospective study that summarizes all the clinical, biochemical, and genetic data collected by questionnaires of all 3MCCD individuals that were identified by the extended Israeli NBS program since its introduction in 2009 including maternal 3MCCD cases.

RESULTS

A total of 36 3MCCD subjects were diagnosed within the 50-month study period; 16 were classified primary and 20 maternal cases. Four additional 3MCCD individuals were identified following sibling screening. All maternal 3MCCD cases were asymptomatic except for one mother who manifested childhood hypotonia. Most of the primary 3MCCD individuals were asymptomatic except for two whose condition was also complicated by severe prematurity. Initial dried blood spot (DBS) free carnitine was significantly lower in neonates born to 3MCCD mothers compared with newborns with primary 3MCCD (p = 0.0009). Most of the mutations identified in the MCCC1 and MCCC2 genes were missense, five of them were novel.

CONCLUSIONS

Maternal 3MCCD is more common than previously thought and its presence may be initially indicated by low DBS free carnitine levels. Our findings provide additional confirmation of the benign nature of 3MCCD and we suggest to exclude this disorder from NBS programs.

A New Approach for Fast Metabolic Diagnostics in CMAMMA

BACKGROUND

The presence of increased urinary concentrations of both methylmalonic acid (MMA) and malonic acid (MA) is assumed to differentiate combined malonic and methylmalonic aciduria (CMAMMA), due to mutations in the ACSF3 gene, from other causes of methylmalonic aciduria (classic MMAemia). Detection of MA in urine, however, is challenging since excretion of MA can be easily missed. The objective of the study was to develop a method for quantification of MA in plasma to allow differentiation between CMAMMA and classic MMAemia.

METHODS

Compound heterozygosity for mutations in the ACSF3 gene was detected in two female siblings using diagnostic exome sequencing. Urine (MMA and MA) was analyzed with GC/MS, while plasma was analyzed with UPLC-MS/MS. MA/MMA ratios were calculated.

RESULTS

Both patients had a severe psychiatric presentation (at the age of 6 years and 5.5 years, respectively) after a viral infection. MA excretion in the patients was only just above the highest control value in several samples. MA concentrations in plasma from the two patients were clearly above the highest value observed in control subjects. However, MA concentrations in plasma from patients with classic MMAemia were also elevated. Additional, calculation of MA/MMA ratio in plasma allowed to fully differentiate between CMAMMA and classic MMAemia.

CONCLUSIONS

Calculating the MA/MMA ratio in plasma allows differentiation between CMAMMA and classic MMAemia. The full clinical spectrum of CMAMMA remains to be delineated.

Is L-Carnitine Supplementation Beneficial in 3-Methylcrotonyl-CoA Carboxylase Deficiency?

BACKGROUND

3-Methylcrotonyl-CoA carboxylase deficiency (3-MCCd) is an autosomal recessive disorder in the catabolism of leucine. In the present study, we investigated the current and prior medical condition of patients with 3-MCCd in the Faroe Islands and their carnitine levels in blood, urine and muscle tissue with and without L-carnitine supplementation to evaluate the current treatment strategy of not recommending L-carnitine supplementation to Faroese 3-MCCd patients.

METHODS

Blood and urine samples and muscle biopsies were collected from patients at inclusion and at 3 months. Eight patients received L-carnitine supplementation when recruited; five did not. Included patients who received supplementation were asked to stop L-carnitine, the others were asked to initiate L-carnitine supplementation during the study. Symptoms were determined by review of hospital medical records and questionnaires answered at baseline and after the intervention.

RESULTS

The prevalence of 3-MCCd in the Faroe Islands was 1:2,400, the highest reported worldwide. All patients were homozygous for the MCCC1 mutation c.1526delG. When not administered L-carnitine, the 3-MCCd patients (n = 13) had low plasma and muscle free carnitine levels, 6.9 (SD 1.4) μmol/L and 785 (SD 301) nmol/g wet weight, respectively. L-Carnitine supplementation increased muscle and plasma carnitine levels to a low-normal range, 25.5 (SD 10.9) μmol/L and 1,827 (SD 523) nmol/g wet weight, p < 0.01, respectively. Seven of the thirteen 3-MCCd subjects suffered from self-reported fatigue with some alleviation after L-carnitine supplementation.

CONCLUSION

3-MCCd is common in the Faroe Islands. Some symptomatic 3-MCCd patients may benefit biochemically and clinically from L-carnitine supplementation, a more general recommendation cannot be given.

Consanguinity and rare mutations outside of MCCC genes underlie nonspecific phenotypes of MCCD

Purpose

3-Methylcrotonyl-CoA carboxylase deficiency (MCCD) is an autosomal recessive disorder of leucine catabolism that has a highly variable clinical phenotype, ranging from acute metabolic acidosis to nonspecific symptoms such as developmental delay, failure to thrive, hemiparesis, muscular hypotonia, and multiple sclerosis. Implementation of newborn screening for MCCD has resulted in broadening the range of phenotypic expression to include asymptomatic adults. The purpose of this study was to identify factors underlying the varying phenotypes of MCCD.

Methods

We performed exome sequencing on DNA from 33 cases and 108 healthy controls. We examined these data for associations between either MCC mutational status, genetic ancestry, or consanguinity and the absence or presence/specificity of clinical symptoms in MCCD cases.

Results

We determined that individuals with nonspecific clinical phenotypes are highly inbred compared with cases that are asymptomatic and healthy controls. For 5 of these 10 individuals, we discovered a homozygous damaging mutation in a disease gene that is likely to underlie their nonspecific clinical phenotypes previously attributed to MCCD.

Conclusion

Our study shows that nonspecific phenotypes attributed to MCCD are associated with consanguinity and are likely not due to mutations in the MCC enzyme but result from rare homozygous mutations in other disease genes.

Biochemical and molecular characteristics of patients with organic acidaemias and urea cycle disorders identified through newborn screening

BACKGROUND

In recent years it has become clear that newborn screening (NBS) programmes using tandem mass spectrometry identify "patients" with "classical" inborn errors of metabolism who are asymptomatic. This observation raises issues regarding medicalization of "non-diseases," potentially unnecessary treatment and unnecessary anxiety to parents.

AIMS

This study aims to identify possible markers that may assist in predicting the need for treatment of infants with "classical" organic acidaemias (OA) and urea cycle disorders (UCD) diagnosed through NBS.

METHODS

Medical records of all patients with classical OA and UCD detected through the Victorian NBS programme from February 2002 to January 2014, or diagnosed clinically between 1990 and January 2002 were retrospectively reviewed.

RESULTS

Neonatal presentation did not always predict the need for on-going strict treatment. Blood concentrations of amino acids and acyl-carnitines and the changes thereof in follow-up samples correlated with severity in citrullinaemia-I, possibly isovaleric acidaemia but not in argininosuccinic aciduria or propionic acidaemia. Some specific mutations correlate with "attenuated" citrullinaemia-I. Gender may affect clinical outcome in propionic acidaemia.

CONCLUSIONS

Changes in blood concentration of certain metabolites (amino acids, acyl-carnitines) in the first weeks of life may be predictive of the need for treatment in some disorders but not in others. Mutation analysis may be predictive in some disorders but whether or not this should be considered as second-tier testing in NBS should be discussed separately.