• Hongjun Shi, Annabelle Enriquez, Melissa Rapadas, Ella M M A Martin, Roni Wang, Julie Moreau, Chai K Lim, Justin O Szot, Eddie Ip, James N Hughes, Kotaro Sugimoto, David T Humphreys, Aideen M McInerney-Leo, Paul J Leo, Ghassan J Maghzal, Jake Halliday, Janine Smith, Alison Colley, Paul R Mark, Felicity Collins, David O Sillence, David S Winlaw, Joshua W K Ho, Gilles J Guillemin, Matthew A Brown, Kazu Kikuchi, Paul Q Thomas, Roland Stocker, Eleni Giannoulatou, Gavin Chapman, Emma L Duncan, Duncan B Sparrow, and Sally L Dunwoodie.
• From the Divisions of Developmental and Stem Cell Biology (H.S., A.E., M.R., E.M.M.A.M., R.W., J.M., J.O.S., E.I., K.S., J.H., K.K., G.C., D.B.S., S.L.D.), Vascular Biology (G.J.M., R.S.), and Molecular, Structural, and Computational Biology (D.T.H., J.W.K.H., E.G.), Victor Chang Cardiac Research Institute, the Faculties of Medicine and Science, University of New South Wales (H.S., A.E., J.O.S., E.I., D.T.H., G.J.M., J.W.K.H., K.K., R.S., E.G., G.C., D.B.S., S.L.D.), Liverpool Hospital, Department of Clinical Genetics (A.E., A.C.), the Department of Clinical Genetics (A.E., J.S., F.C., D.O.S.) and the Heart Centre for Children (D.S.W.), Children's Hospital at Westmead, the Discipline of Genetic Medicine (A.E., J.S., F.C., D.O.S.) and the Medical School (D.S.W.), University of Sydney, and the Faculty of Medicine and Health Sciences, Macquarie University (C.K.L., G.J.G.) - all in Sydney, the School of Biological Sciences, University of Adelaide, Adelaide, SA (J.N.H., P.Q.T.), and the Institute of Health and Biomedical Innovation, Queensland University of Technology (A.M.M.-L., P.J.L., M.A.B., E.L.D.), the Translational Research Institute (A.M.M.-L., P.J.L., M.A.B., E.L.D.), the Department of Endocrinology, Royal Brisbane and Women's Hospital (E.L.D.), and the University of Queensland School of Medicine (E.L.D.), Brisbane - all in Australia; and Spectrum Health Medical Group, Medical Genetics, Grand Rapids, MI (P.R.M.).
• N. Engl. J. Med. 2017 Aug 10; 377 (6): 544552544-552.

BackgroundCongenital malformations can be manifested as combinations of phenotypes that co-occur more often than expected by chance. In many such cases, it has proved difficult to identify a genetic cause. We sought the genetic cause of cardiac, vertebral, and renal defects, among others, in unrelated patients.MethodsWe used genomic sequencing to identify potentially pathogenic gene variants in families in which a person had multiple congenital malformations. We tested the function of the variant by using assays of in vitro enzyme activity and by quantifying metabolites in patient plasma. We engineered mouse models with similar variants using the CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9 system.ResultsVariants were identified in two genes that encode enzymes of the kynurenine pathway, 3-hydroxyanthranilic acid 3,4-dioxygenase (HAAO) and kynureninase (KYNU). Three patients carried homozygous variants predicting loss-of-function changes in the HAAO or KYNU proteins (HAAO p.D162*, HAAO p.W186*, or KYNU p.V57Efs*21). Another patient carried heterozygous KYNU variants (p.Y156* and p.F349Kfs*4). The mutant enzymes had greatly reduced activity in vitro. Nicotinamide adenine dinucleotide (NAD) is synthesized de novo from tryptophan through the kynurenine pathway. The patients had reduced levels of circulating NAD. Defects similar to those in the patients developed in the embryos of Haao-null or Kynu-null mice owing to NAD deficiency. In null mice, the prevention of NAD deficiency during gestation averted defects.ConclusionsDisruption of NAD synthesis caused a deficiency of NAD and congenital malformations in humans and mice. Niacin supplementation during gestation prevented the malformations in mice. (Funded by the National Health and Medical Research Council of Australia and others.).

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