Identification of gene mutations in six Chinese patients with maple syrup urine disease.

Background: Maple syrup urine disease (MSUD) is a rare autosomal recessive amino acid metabolic disease. This study is to identify the pathogenic genetic factors of six cases of MUSD and evaluates the application value of high-throughput sequencing technology in the early diagnosis of MUSD. Methods: Clinical examination was carried out for patients and used blood tandem mass spectrometry (MS/MS), urine gas chromatography-mass spectrometry (GC/MS), and the application of high-throughput sequencing technology for detection. Validate candidate mutations by polymerase chain reaction (PCR)-Sanger sequencing technology. Bioinformatics software analyzed the variants' pathogenicity. Using Swiss PDB Viewer software to predict the effect of mutation on the structure of BCKDHA and BCKDHB proteins. Result: A total of six MSUD patients were diagnosed, including four males and two females. Nine variants were found in three genes of six MSUD families by high-throughput sequencing, including four missense mutations: c.659C>T(p.A220V), c.818C>T(p.T273I), c.1134C>G(p.D378E), and c.1006G>A(p.G336S); two non-sense mutations: c.1291C>T(p.R431*) and c.331C>T(p.R111*); three deletion mutations: c.550delT (p.S184Pfs*46), c.718delC (p.P240Lfs*14), and c.795delG (p.N266Tfs*64). Sanger sequencing's results were consistent with the high-throughput sequencing. The bioinformatics software revealed that the mutations were harmful, and the prediction results of Swiss PDB Viewer suggest that variation affects protein conformation. Conclusion: This study identified nine pathogenic variants in the BCKDHA, BCKDHB, and DBT genes in six MSUD families, including two novel pathogenic variants in the BCKDHB gene, which enriched the genetic mutational spectrum of the disease. High-throughput sequencing is essential for the MSUD's differential diagnosis, early treatment, and prenatal diagnosis.

Identification and molecular analysis of 11 cases of the PTS gene variants associated with tetrahydrobiopterin deficiency.

Background: Tetrahydrobiopterin deficiency (BH4D) is a rare autosomal recessive amino acid metabolic disease that belongs to a kind of hyperphenylalaninemia (HPA), and 6-pyruvyltetrahydrotrexate synthase (PTPS) deficiency is the most common type of BH4D. This study investigates the clinical and genetic characteristics of 11 PTPS deficiency cases in the Beijing area, identifies the genetic pathogenic factors, and evaluates the value of high-throughput sequencing in the precise diagnosis of PTPS deficiency. Methods: The Beijing Neonatal Disease Screening Center diagnosed patients with HPA. The study used phenylalanine (Phe) in blood, the ratio of Phe to Thr, urotrexate spectrum analysis, erythrocyte dihydrotrexate reductase (DHPR) activity determination, and high-throughput sequencing as methods. Bioinformatics software analyzed the variants' pathogenicity and used RT-PCR to identify deep intron variants' pathogenicity. Result: Among 635 cases with HPA, 38 cases were diagnosed with BH4D, of which the incidence in HPA was 5.98%. Nine kinds of PTS gene variants were detected, including seven missense variants, one splicing variant, and one deletion variant. The splicing variant c.84-291A>G had three splicing results in vivo: normal length, 79bp pseudoexon insertion, and exon 3 skipping. Bioinformatics and Sanger sequencing were performed to verify the identified variants. Conclusion: High-throughput sequencing is a helpful tool for clinical diagnosis and differential diagnosis of BH4D. This study confirms that c.84-291A>G is the hot spot variant of PTPS deficiency, and it is the first reported variant with a new splicing pattern in vivo. A novel deletion variant c.84_163del (p.Lys29Cysfs∗9) was found to enrich the genetic variant spectrum of the disease.

Clinical characteristics and related gene mutations of infants with short-chain acyl-CoA dehydrogenase deficiency by neonatal screening in Beijing.

OBJECTIVE: To investigate the clinical characteristics of infants with short-chain acyl-CoA dehydrogenase deficiency (SCADD) and related gene mutations in Beijing. METHODS: The acylcarnitine levels in the blood samples of 100 603 neonates in Beijing during August 2014 and March 2022 were measured by tandem mass spectrometry (MS/MS). The suspected SCADD neonates were rechecked by MS/MS, urine gas chromatography-mass spectrometry (GC/MS) and next-generation sequencing (NGS) for diagnosis. The clinical, biochemical and gene mutation characteristics of infants with SCADD were analyzed; the growth and intellectual development of these patients were observed regularly. RESULTS: Among 100 603 live births, the elevated C4 concentration or elevated C4/C3 ratio were detected in the initial screening from 196 neonates, and 131 were recalled. Five cases of SCADD were diagnosed with an incidence rate of 4.97/100 000 (1/20 121). There was no significant abnormality in clinical manifestations, however, the blood butyrylcarnitine (C4) level and the ratio of C4 to propionylcarnitine (C3) were raised in all diagnosed cases. Urinary organic acids were analyzed in 4 cases, all of whom had increased ethyl malonate acid levels. Seven mutations were detected in the ACADS gene, all of which were known missense mutations. One patient had homozygous mutation, and the others showed compound heterozygous mutations. No clinical symptoms were observed, and the physical and intellectual development was normal in all patients at a median age of 33 (4-40) months during follow-up. CONCLUSIONS: The incidence rate of SCADD was 1/20 121 in Beijing. Neonates with early diagnosis and without clinical symptoms usually have good prognosis.

Clinical characteristics and genetics analysis for the ITD of congenital hypothyroidism.

OBJECTIVES: Iodide transport defect (ITD) is one of the principal causes of congenital hypothyroidism (CH) and its primary molecular mechanism is a mutation of the sodium/iodide symporter (NIS) gene. This study aims to analyse the clinical characteristics and genetic mutations of ITD. METHODS: The participants were a pair of siblings diagnosed with congenital hypothyroidism. Inductively coupled plasma mass spectrometry was used to determine the concentration of salivary iodine and serum iodine and to calculate their ratio. At the same time, next-generation sequencing (NGS) was applied to detect all exons of congenital hypothyroidism-related genes. All suspicious variants were further validated in the patients and their parents by PCR and Sanger sequencing. RESULTS: Both patients were conclusively diagnosed with thyroid iodine transport defect (ITD). NGS identified two variants of the NIS gene in the siblings: c.1021G>A (p.Gly341Arg) with paternal origin and c.1330-2A>C with maternal origin. Both of these variants have not been reported to date. They are predicted to be pathogenic based on these clinical symptoms and comprehensive software analysis. CONCLUSIONS: This is the first reported family study of congenital hypothyroidism with SLC5A5 mutation in China. Next-generation sequencing technology is an effective means of studying the genetics of congenital hypothyroidism. The therapeutic effect of potassium iodide needs to be further evaluated.

Circular RNA circCTNNA1 promotes colorectal cancer progression by sponging miR-149-5p and regulating FOXM1 expression.

Circular RNAs (circRNAs) are an emerging class of non-coding RNAs, identified to participate in multiple malignancies. Nevertheless, the clinical significance, biological function, and regulatory mechanisms of circRNAs in colon cancer (CC) remain largely unclear. In this study, the circRNA expression profile in CC and matched normal tissues was analyzed using circRNA microarrays. A novel circRNA, circCTNNA1, was significantly upregulated in CC, and its level was associated with advanced tumor-node-metastasis stage and poor prognosis of patients with CC. Functional experiments, including Cell Counting Kit-8, colony formation, 5-ethynyl-2'-deoxyuridine, transwell, wound healing, flow cytometric analysis, and in vivo tumorigenesis assay were then performed to investigate the oncogenic role of circCTNNA1. The results revealed that circCTNNA1 promoted CC cell proliferation, migration, and invasion in vitro and in vivo. Mechanistically, RNA pull-down, RNA immunoprecipitation, dual-luciferase reporter assays, and fluorescent in situ hybridization were performed to unveil that circCTNNA1 can serve as a competing endogenous RNA of miR-149-5p to counteract the suppressive effect of miR-149-5p on downstream target Forkhead Box M1 (FOXM1). In summary, our study demonstrated that circCTNNA1 facilitated CC proliferation and invasion via the circCTNNA1/miR-149-5p/FOXM1 axis, and it might function as a novel diagnostic or therapeutic target for patients with CC.

Inborn errors of metabolism detectable by tandem mass spectrometry in Beijing.

Background Individual inborn errors of metabolism (IEMs) are rare disorders. Expanded newborn screening for IEMs by tandem mass spectrometry (TMS) is an efficient approach for early diagnosis. Here we provide the newborn screening program for the application of this approach (between July 2014 and March 2019) to the identification of newborns in Beijing at risk of developing a potentially fatal disease. Methods The amino acids and acylcarnitines in dried blood spots were analyzed by TMS. Diagnoses of newborns with elevated metabolites were confirmed by gas chromatography-mass spectrometry, biochemical studies, and genetic analysis. Results Among the healthy newborns, 16 metabolic disorder cases were confirmed, giving a total birth prevalence of 1:3666 live births. Organic acidemia (OA) was the most common (9/16 patients; 56%), and methylmalonic acidemia was the most frequently observed OA (7/9 patients; 89%). Five infants were diagnosed with methylmalonic acidemia with homocystinuria type CblC, two with isolated methylmalonic acidemia, one with propionic acidemia, and one with isovaleric acidemia. Four patients (4/16, 25%) were diagnosed with hyperphenylalaninemia. One suffered with medium-chain acyl CoA dehydrogenase deficiency, one with carnitine uptake deficiency, and one with citrin deficiency. Eleven cases underwent genetic analysis. Seventeen mutations in eight IEM-associated genes were identified in 11 confirmed cases. Symptoms were already present within 2 days after birth in 44% (7/16) cases. The infant with propionic acidemia died at 7 days after birth. The other cases received timely diagnosis and treatment, and most of them grew well. Conclusions The results illustrate challenges encountered in disease management highlighting the importance of newborn screening for inherited metabolic disorders, which is not yet nationally available in our country. Regional newborn screening programs will provide a better estimation of the incidence of IEM.

A pilot study on newborn screening for congenital adrenal hyperplasia in Beijing.

Background A provisionary screening programme for 21-hydroxylase deficiency (21-OHD) was initiated in Beijing in 2014. The aim of this study was to investigate the incidence and the associated clinical characteristics of neonatal congenital adrenal hyperplasia (CAH) in Beijing and to provide evidence-based guidance for its application in CAH screening. Methods Live birth newborns (n=44,360) were screened for CAH in Beijing from July 2014 to April 2018. The levels of 17-hydroxyprogesterone (17-OHP) in the blood were estimated using the time-resolved fluoroimmunoassay. Neonates with a positive result and a level >30 nmol/L of 17-OHP were called for a retest. CAH was diagnosed based on further laboratory findings combined with clinical signs, such as weight loss, feeding difficulties, skin pigmentation, and atypical genitalia. Through a review of medical records, the clinical findings including molecular data were reported. Results Of the 44,360 neonates screened, 280 cases were deemed positive. Of these, 203 neonates were recalled for further tests and six patients (three boys and three girls) were diagnosed with CAH. Five cases of classic salt-wasting and one case of simple virilising 21-OHD were identified. The incidence of CAH in Beijing was 1:7393. The most frequent 21-OHD mutation was c.293-13C/A>G. Conclusions The incidence of CAH in Beijing was higher than the national average. The results support the need for neonatal CAH screening in Beijing. This pilot study demonstrates the clinical characteristics of 21-OHD through newborn screening. Early detection and treatment through neonatal screening may reduce mortality rates and optimise developmental outcomes.

Whole-exome sequencing as a powerful tool for identifying genetic causes in a patient with POLG-related disorders and phenylketonuria.

OBJECTIVE: This study's aim was to identify the genetic causes in a patient with phenylketonuria and hearing loss, liver disease, developmental and mental retardation, hypotonia, and external ophthalmoplegia. METHODS: Whole-exome sequencing and Sanger sequencing analysis were used to determine the genetic causes of manifestations in a young boy with hearing loss, liver disease, develop-mental and mental retardation, hypotonia, and external ophthalmoplegia. RESULTS: We found that the child harbored polymerase gamma ( POLG) compound heterozygous mutations, c.2617G>A (p.E873K) and c.3550G>A (p.D1184N), and phenylalanine hydroxylase ( PAH) compound heterozygous mutations, c.721C>T (p.R241C) and c.728G>A (p.R243Q). Among them, the POLG p.E873K mutation is a novel mutation and is not present in the Exome Aggregation Consortium database, Genome Aggregation database, and 1000 Genomes database. The two heterozygous mutations were each inherited from both of the child's parents. This finding suggested that the phenotype and the genotype were segregated. CONCLUSION: Using whole-exome sequencing, we not only identified PAH mutations causing phenylketonuria, but also identified the genetic cause of the mitochondrial disease and found a novel POLG mutation. Our findings could be useful in helping future parents obtain healthy embryos through assisted reproductive technology.

[Follow up and gene mutation analysis in cases suspected as 3-methylcrotonyl-coenzyme A carboxylase deficiency by neonatal screening].

OBJECTIVE: 3-Methylcrotonyl-coenzyme A carboxylase deficiency (MCCD) is an autosomal recessive inborn error of leucine catabolism. The cases suspected as MCCD detected by neonatal screening are not rare. The aim of the study was to investigate the clinical outcomes in cases suspected as MCCD by neonatal screening. The second aim was to investigate the mutation spectrum of MCC gene in Chinese population and hotspot mutation. METHOD: Forty-two cases (male 33, female 9) , who had higher blood 3-hydroxy-isovalerylcarnitine (C5-OH) levels(cut-off <0.6 µmol/L) detected by neonatal screening using MS/MS, were recruited to this study during Sept.2011 to Mar.2013. The C5-OH concentrations were [0.84 (0.61-20.15) µmol/L] in 42 cases at the screening recall. Five cases were firstly diagnosed as maternal MCCD, 6 cases as benign MCCD and 31 cases were suspected as MCCD. To follow up the height, weight, mental development, blood C5-OH concentrations and urinary 3-methylcrotonyl-glycine (3-MCG) and 3-hydroxy isovalerate (3-HIVA) in order to investigate the clinical outcome. The MCCC1 and MCCC2 gene mutation were analyzed for some cases. The novel gene variants were evaluated, and the influence of novel missense variants on the protein structure and function were predicted by PolyPhen-2, SIFT, UniProt and PDB software. RESULT: (1) Forty-two cases had no symptoms, their physical and mental development were normal in the last visit at the median ages of 29 months, the oldest age of follow up was nearly 9 years. (2) Gene mutation analysis was performed for 29 cases with informed consent signed by parents.Fourteen different mutations were identified in 19 cases. The mutations in MCCC1 gene accounted for 86%, the most common mutation was c.ins1680A, (accounted for 40%). Nine kinds of novel variant were detected including 211AG>CC/p.Q74P, c.295G>A/p.G99S, c.764A>C/p.H255P, c.964G>A/p. E322K, c.1331G>A/p.R444H, c.1124delT, c.39_58del20, c.1518delG, c.639+2T>A.Other 3 kinds of mutation in MCCC1 gene and 2 kinds of mutation in MCCC2 gene have been reported previously; the amino acid of mutant positions of five kinds of novel missense variant are almost highly conserved. These missense variants were predicted to cause change of human MCC protein side chain structure by changing hydrogen bonding, size of amino acid residue and electric charge, and predicted to damage the protein function possibly according to PolyPhen-2 and PDB analysis. So these novel variants may be disease-causing mutations. No mutation were detected in 10 cases. (3) Blood concentrations of C5-OH when screening, recall and end of follow-up in maternal MCCD was 3.50 (1.63-11.43), 1.84 (1.00-9.30), 0.27 (0.26-5.81) µmol/L. There was a significant downward trend.In contrast, benign MCCD group was 8.20 (3.60-9.60), 9.67 (3.88-20.15), 23.0 (5.87-49.10) µmol/L.It showed a rising trend. Children's urinary 3-MCG of benign MCCD group was found abnormally elevated in 4 cases (100%) when they were recalled. CONCLUSION: A certain number of cases with MCCD or suspected as MCCD in this study had no symptoms and normal physical and mental development after follow-up to oldest age of nearly 9 years. The mutation in MCCC1 gene is common, nine novel mutations were found, c.ins1680A may be a hotspot mutation in Chinese population. The urinary GC/MS analysis and blood MS/MS analysis for mother should be routinely performed for all cases with high blood C5-OH level detected by neonatal screening.

[Clinical and mutational features of maternal 3-methylcrotonyl coenzyme deficiency].

OBJECTIVE: To report on 5 patients with maternal 3-methylcrotonyl coenzyme A carboxylase deficiency (MCCD) and to confirm the clinical diagnosis through mutation analysis. METHODS: Five neonates with higher blood 3-hydroxy isovalerylcarnitine (C5-OH) concentration detected upon newborn screening with tandem mass spectrometry and their mothers were recruited. Urinary organic acids were analyzed with gas chromatography mass spectrometry. Gene mutation and protein function analysis were performed by PCR direct sequencing and PolyPhen-2 software. RESULTS: Higher blood C5-OH concentrations (5.11-21.77 µmol/L) and abnormal 3-hydroxy isovalerate and 3-methylcrotonyl glycine in urine were detected in the five asymptomatic mothers, who were diagnosed as benign MCCD. Higher C5-OH concentration was also detected in their neonates by tandem mass spectrometry, which had gradually decreased to normal levels in three neonates. Four new variations, i.e., c.ins1680A(25%), c.203C > T (p.A68V), c.572T > C (p.L191P) and c.639+5G > T were detected in the MCCC1 gene, in addition with 2 mutations [c.1406G > T (p.R469L, novel variation) and c.592C > T (p.Q198X)]. The novel variations were predicted to have affected protein structure and function. CONCLUSION: For neonates with higher C5-OH concentration detected upon neonatal screening, their mothers should be also tested to rule out MCCD. Mutations in MCCC1 gene are quite common.