title: Long QT syndrome-associated mutations in intrauterine fetal death.
abstract: OBJECTIVE
  Intrauterine fetal death or stillbirth occurs in approximately 1 out of every 160 pregnancies and accounts for 50% of all perinatal deaths. Postmortem evaluation fails to elucidate an underlying cause in many cases. Long QT syndrome (LQTS) may contribute to this problem.
  
  
  OBJECTIVE
  To determine the spectrum and prevalence of mutations in the 3 most common LQTS susceptible genes (KCNQ1, KCNH2, and SCN5A) for a cohort of unexplained cases.
  
  
  METHODS
  In this case series, retrospective postmortem genetic testing was conducted on a convenience sample of 91 unexplained intrauterine fetal deaths (mean [SD] estimated gestational age at fetal death, 26.3 [8.7] weeks) that were collected from 2006-2012 by the Mayo Clinic, Rochester, Minnesota, or the Fondazione IRCCS Policlinico San Matteo, Pavia, Italy. More than 1300 ostensibly healthy individuals served as controls. In addition, publicly available exome databases were assessed for the general population frequency of identified genetic variants.
  
  
  METHODS
  Comprehensive mutational analyses of KCNQ1 (KV7.1, LQTS type 1), KCNH2 (HERG/KV11.1, LQTS type 2), and SCN5A (NaV1.5, LQTS type 3) were performed using denaturing high-performance liquid chromatography and direct DNA sequencing on genomic DNA extracted from decedent tissue. Functional analyses of novel mutations were performed using heterologous expression and patch-clamp recording.
  
  
  RESULTS
  The 3 putative LQTS susceptibility missense mutations (KCNQ1, p.A283T; KCNQ1, p.R397W; and KCNH2 [1b], p.R25W), with a heterozygous frequency of less than 0.05% in more than 10 000 publicly available exomes and absent in more than 1000 ethnically similar control patients, were discovered in 3 intrauterine fetal deaths (3.3% [95% CI, 0.68%-9.3%]). Both KV7.1-A283T (16-week male) and KV7.1-R397W (16-week female) mutations were associated with marked KV7.1 loss-of-function consistent with in utero LQTS type 1, whereas the HERG1b-R25W mutation (33.2-week male) exhibited a loss of function consistent with in utero LQTS type 2. In addition, 5 intrauterine fetal deaths hosted SCN5A rare nonsynonymous genetic variants (p.T220I, p.R1193Q, involving 2 cases, and p.P2006A, involving 2 cases) that conferred in vitro electrophysiological characteristics consistent with potentially proarrhythmic phenotypes.
  
  
  CONCLUSIONS
  In this molecular genetic evaluation of 91 cases of intrauterine fetal death, missense mutations associated with LQTS susceptibility were discovered in 3 cases (3.3%) and overall, genetic variants leading to dysfunctional LQTS-associated ion channels in vitro were discovered in 8 cases (8.8%). These preliminary findings may provide insights into mechanisms of some cases of stillbirth.
authors.affiliation: Department of Molecular Medicine, University of Pavia, and Molecular Cardiology Laboratory, Fondazione IRRCCS Policlinico S Matteo, Pavia, Italy.
authors.forename: Lia
authors.initials: L
authors.lastname: Crotti
authors.forename: David J
authors.initials: DJ
authors.lastname: Tester
authors.forename: Wendy M
authors.initials: WM
authors.lastname: White
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Bartos
authors.forename: Roberto
authors.initials: R
authors.lastname: Insolia
authors.forename: Alessandra
authors.initials: A
authors.lastname: Besana
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Kunic
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Will
authors.forename: Ellyn J
authors.initials: EJ
authors.lastname: Velasco
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Bair
authors.forename: Alice
authors.initials: A
authors.lastname: Ghidoni
authors.forename: Irene
authors.initials: I
authors.lastname: Cetin
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Van Dyke
authors.forename: Myra J
authors.initials: MJ
authors.lastname: Wick
authors.forename: Brian
authors.initials: B
authors.lastname: Brost
authors.forename: Brian P
authors.initials: BP
authors.lastname: Delisle
authors.forename: Fabio
authors.initials: F
authors.lastname: Facchinetti
authors.forename: Alfred L
authors.initials: AL
authors.lastname: George
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Schwartz
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ackerman
mesh_terms: D001344:Autopsy; D004252:DNA Mutational Analysis; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics / Q000378:metabolism; D005260:Female; D005313:Fetal Death / Q000235:genetics*; D005333:Fetus / Q000503:physiopathology; D015870:Gene Expression; D006801:Humans; D007231:Infant, Newborn; D051657:KCNQ1 Potassium Channel / Q000235:genetics / Q000378:metabolism; D008133:Long QT Syndrome / Q000235:genetics*; D008297:Male; D020125:Mutation, Missense; D009206:Myocardium / Q000378:metabolism; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000235:genetics / Q000378:metabolism; D012189:Retrospective Studies
chemical_list: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D051657:KCNQ1 Potassium Channel; D062554:NAV1.5 Voltage-Gated Sodium Channel; C568320:SCN5A protein, human