title: Significance of ACADM mutations identified through newborn screening of MCAD deficiency in Japan.
abstract: BACKGROUND
  Since the first case was detected in 2000, there has been a remarkable increase in Japanese patients diagnosed with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. Genetic analysis has revealed a spectrum of mutations that is quite different from those observed in Caucasian populations. In 2014, Japan initiated nationwide newborn screening (NBS) for MCAD using tandem mass spectrometry (MS/MS). It is an urgent issue to assess the risk of acute metabolic decompensation from the respective novel mutations found thus far.
  
  
  METHODS
  To evaluate the pathogenic effect of each mutation, we established a eukaryotic cell expression system and prepared 11 mutant proteins identified in five symptomatic patients and eight MS/MS-NBS-positive newborns, as well as two common Caucasian mutations, p.K329E (c.985G>A) and p.Y67H (c.157C>T) for comparison.
  
  
  RESULTS
  The expression of four mutant proteins (p.Q45R, p.P92L, p.P128X and p.Y397N) were severely impaired, whereas the others expressed normally, as did p.K329E and p.Y67H. Based on their dehydrogenase activities toward n-octanoyl-CoA, we determined three mutations (p.R53C, p.R281S and p.G362E) to be disease-causing, two mutations having (p.R17H and p.M274V) to be of marginal risk, and two mutations (p.K271E and p.I416T) as benign. Their allele-specific activities were as a whole in accordance with those estimated from the results of measurement in peripheral blood mononuclear cells.
  
  
  CONCLUSIONS
  As most of the mutations detected in the Japanese population are unique, prudent genetic and enzymatic analysis is essential to precisely evaluate the latent risk of clinical onset for screening-positive newborns.
authors.affiliation: Department of Pediatrics, National Hospital Organization Kure Medical Center, Kure 737-0023, Japan; Department of Pediatrics, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Hara
authors.affiliation: Department of Pediatrics, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan. Electronic address: isleofmaple@me.com.
authors.forename: Go
authors.initials: G
authors.lastname: Tajima
authors.affiliation: Department of Pediatrics, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okada
authors.affiliation: Department of Pediatrics, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
authors.forename: Miyuki
authors.initials: M
authors.lastname: Tsumura
authors.affiliation: Department of Pediatrics, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
authors.forename: Reiko
authors.initials: R
authors.lastname: Kagawa
authors.affiliation: Shirao Clinic of Pediatrics and Pediatric Allergy, Department of Pediatrics, Hiroshima 734-0023, Japan.
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Shirao
authors.affiliation: Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8553, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ohno
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Fukuoka University, Fukuoka 814-0180, Japan.
authors.forename: Shin'ichiro
authors.initials: S
authors.lastname: Yasunaga
authors.affiliation: Department of Food and Nutrition, Beppu University, Ooita 874-0501, Japan.
authors.forename: Motoaki
authors.initials: M
authors.lastname: Ohtsubo
authors.affiliation: Department of Pediatrics, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan.
authors.forename: Ikue
authors.initials: I
authors.lastname: Hata
authors.affiliation: Nursing House for Severe Motor and Intellectual Disabilities SUZUGAMINE, Hiroshima 731-5122, Japan.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Sakura
authors.affiliation: Department of Health Science, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Shigematsu
authors.affiliation: Department of Stem Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8553, Japan. Electronic address: takihara@hiroshima-u.ac.jp.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Takihara
authors.affiliation: Department of Pediatrics, Hiroshima University Graduate School of Biomedical & Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Kobayashi
mesh_terms: D042964:Acyl-CoA Dehydrogenase / Q000172:deficiency* / Q000235:genetics* / Q000378:metabolism*; D044466:Asian People / Q000235:genetics; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007564:Japan; D008052:Lipid Metabolism, Inborn Errors / Q000175:diagnosis* / Q000208:ethnology / Q000235:genetics; D008297:Male; D009154:Mutation; D015997:Neonatal Screening / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*; D044465:White People / Q000235:genetics
chemical_list: D042964:Acyl-CoA Dehydrogenase
keywords: Allele-specific expression; Enzyme activity; Japanese; MCAD deficiency; Newborn screening; Novel mutation