title: X-linked macrocytic dyserythropoietic anemia in females with an ALAS2 mutation.
abstract: Macrocytic anemia with abnormal erythropoiesis is a common feature of megaloblastic anemias, congenital dyserythropoietic anemias, and myelodysplastic syndromes. Here, we characterized a family with multiple female individuals who have macrocytic anemia. The proband was noted to have dyserythropoiesis and iron overload. After an extensive diagnostic evaluation that did not provide insight into the cause of the disease, whole-exome sequencing of multiple family members revealed the presence of a mutation in the X chromosomal gene ALAS2, which encodes 5'-aminolevulinate synthase 2, in the affected females. We determined that this mutation (Y365C) impairs binding of the essential cofactor pyridoxal 5'-phosphate to ALAS2, resulting in destabilization of the enzyme and consequent loss of function. X inactivation was not highly skewed in wbc from the affected individuals. In contrast, and consistent with the severity of the ALAS2 mutation, there was a complete skewing toward expression of the WT allele in mRNA from reticulocytes that could be recapitulated in primary erythroid cultures. Together, the results of the X inactivation and mRNA studies illustrate how this X-linked dominant mutation in ALAS2 can perturb normal erythropoiesis through cell-nonautonomous effects. Moreover, our findings highlight the value of whole-exome sequencing in diagnostically challenging cases for the identification of disease etiology and extension of the known phenotypic spectrum of disease.
authors.forename: Vijay G
authors.initials: VG
authors.lastname: Sankaran
authors.forename: Jacob C
authors.initials: JC
authors.lastname: Ulirsch
authors.forename: Vassili
authors.initials: V
authors.lastname: Tchaikovskii
authors.forename: Leif S
authors.initials: LS
authors.lastname: Ludwig
authors.forename: Aoi
authors.initials: A
authors.lastname: Wakabayashi
authors.forename: Senkottuvelan
authors.initials: S
authors.lastname: Kadirvel
authors.forename: R Coleman
authors.initials: RC
authors.lastname: Lindsley
authors.forename: Rafael
authors.initials: R
authors.lastname: Bejar
authors.forename: Jiahai
authors.initials: J
authors.lastname: Shi
authors.forename: Scott B
authors.initials: SB
authors.lastname: Lovitch
authors.forename: David F
authors.initials: DF
authors.lastname: Bishop
authors.forename: David P
authors.initials: DP
authors.lastname: Steensma
mesh_terms: D000624:5-Aminolevulinate Synthetase / Q000235:genetics* / Q000378:metabolism; D000328:Adult; D000742:Anemia, Dyserythropoietic, Congenital / Q000235:genetics*; D000748:Anemia, Macrocytic / Q000235:genetics*; D002478:Cells, Cultured; D004920:Erythropoiesis / Q000235:genetics*; D059472:Exome / Q000235:genetics; D005260:Female; D005799:Genes, Dominant; D050172:Genes, X-Linked; D040181:Genetic Diseases, X-Linked / Q000097:blood / Q000235:genetics*; D006470:Hemorrhage / Q000209:etiology; D006801:Humans; D019190:Iron Overload / Q000209:etiology; D008297:Male; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D017354:Point Mutation; D011247:Pregnancy; D011250:Pregnancy Complications, Hematologic / Q000235:genetics; D011485:Protein Binding; D011487:Protein Conformation; D011644:Puerperal Disorders / Q000209:etiology; D011732:Pyridoxal Phosphate / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D012156:Reticulocytes / Q000378:metabolism; D049951:X Chromosome Inactivation
chemical_list: D012333:RNA, Messenger; D011732:Pyridoxal Phosphate; D000624:5-Aminolevulinate Synthetase; C480079:ALAS2 protein, human