title: Left-Right Asymmetry of Maturation Rates in Human Embryonic Neural Development.
abstract: Left-right asymmetry is a fundamental organizing feature of the human brain, and neuropsychiatric disorders such as schizophrenia sometimes involve alterations of brain asymmetry. As early as 8 weeks postconception, the majority of human fetuses move their right arms more than their left arms, but because nerve fiber tracts are still descending from the forebrain at this stage, spinal-muscular asymmetries are likely to play an important developmental role.
  
  
  
  We used RNA sequencing to measure gene expression levels in the left and right spinal cords, and the left and right hindbrains, of 18 postmortem human embryos aged 4 to 8 weeks postconception. Genes showing embryonic lateralization were tested for an enrichment of signals in genome-wide association data for schizophrenia.
  
  
  
  The left side of the embryonic spinal cord was found to mature faster than the right side. Both sides transitioned from transcriptional profiles associated with cell division and proliferation at earlier stages to neuronal differentiation and function at later stages, but the two sides were not in synchrony (p = 2.2 E-161). The hindbrain showed a left-right mirrored pattern compared with the spinal cord, consistent with the well-known crossing over of function between these two structures. Genes that showed lateralization in the embryonic spinal cord were enriched for association signals with schizophrenia (p = 4.3 E-05).
  
  
  
  These are the earliest stage left-right differences of human neural development ever reported. Disruption of the lateralized developmental program may play a role in the genetic susceptibility to schizophrenia.
authors.affiliation: Language and Genetics Department, Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands.
authors.forename: Carolien G F
authors.initials: CGF
authors.lastname: de Kovel
authors.affiliation: Institute of Genetic Medicine, Newcastle, United Kingdom.
authors.forename: Steven
authors.initials: S
authors.lastname: Lisgo
authors.affiliation: Language and Genetics Department, Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands.
authors.forename: Guy
authors.initials: G
authors.lastname: Karlebach
authors.affiliation: Beijing Genomics Institute-Shenzhen, Shenzhen, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Ju
authors.affiliation: Beijing Genomics Institute-Shenzhen, Shenzhen, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Cheng
authors.affiliation: Language and Genetics Department, Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands; Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands.
authors.forename: Simon E
authors.initials: SE
authors.lastname: Fisher
authors.affiliation: Language and Genetics Department, Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands; Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands. Electronic address: clyde.francks@mpi.nl.
authors.forename: Clyde
authors.initials: C
authors.lastname: Francks
mesh_terms: D007839:Functional Laterality; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D055106:Genome-Wide Association Study; D006801:Humans; D012249:Rhombencephalon / Q000196:embryology* / Q000378:metabolism* / Q000473:pathology; D012559:Schizophrenia / Q000235:genetics / Q000378:metabolism; D013116:Spinal Cord / Q000196:embryology* / Q000378:metabolism* / Q000473:pathology
keywords: Development; Gene expression; Hindbrain; Lateralization; Maturation rate; Schizophrenia; Spinal cord