Organelle and cellular abnormalities associated with hippocampal heterotopia in neonatal doublecortin knockout mice

PLoS One. 2013 Sep 2;8(9):e72622. doi: 10.1371/journal.pone.0072622. eCollection 2013.


Heterotopic or aberrantly positioned cortical neurons are associated with epilepsy and intellectual disability. Various mouse models exist with forms of heterotopia, but the composition and state of cells developing in heterotopic bands has been little studied. Dcx knockout (KO) mice show hippocampal CA3 pyramidal cell lamination abnormalities, appearing from the age of E17.5, and mice suffer from spontaneous epilepsy. The Dcx KO CA3 region is organized in two distinct pyramidal cell layers, resembling a heterotopic situation, and exhibits hyperexcitability. Here, we characterized the abnormally organized cells in postnatal mouse brains. Electron microscopy confirmed that the Dcx KO CA3 layers at postnatal day (P) 0 are distinct and separated by an intermediate layer devoid of neuronal somata. We found that organization and cytoplasm content of pyramidal neurons in each layer were altered compared to wild type (WT) cells. Less regular nuclei and differences in mitochondria and Golgi apparatuses were identified. Each Dcx KO CA3 layer at P0 contained pyramidal neurons but also other closely apposed cells, displaying different morphologies. Quantitative PCR and immunodetections revealed increased numbers of oligodendrocyte precursor cells (OPCs) and interneurons in close proximity to Dcx KO pyramidal cells. Immunohistochemistry experiments also showed that caspase-3 dependent cell death was increased in the CA1 and CA3 regions of Dcx KO hippocampi at P2. Thus, unsuspected ultrastructural abnormalities and cellular heterogeneity may lead to abnormal neuronal function and survival in this model, which together may contribute to the development of hyperexcitability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / metabolism*
  • Brain / pathology*
  • Brain / ultrastructure
  • CA1 Region, Hippocampal / metabolism
  • CA1 Region, Hippocampal / pathology
  • CA1 Region, Hippocampal / ultrastructure
  • CA3 Region, Hippocampal / metabolism
  • CA3 Region, Hippocampal / pathology
  • CA3 Region, Hippocampal / ultrastructure
  • Caspase 3 / metabolism
  • Doublecortin Domain Proteins
  • Doublecortin Protein
  • Female
  • Golgi Apparatus / metabolism
  • Golgi Apparatus / pathology
  • Golgi Apparatus / ultrastructure
  • Hippocampus / metabolism*
  • Hippocampus / pathology*
  • Immunohistochemistry
  • In Situ Hybridization
  • Male
  • Mice
  • Mice, Knockout
  • Microscopy, Electron
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism*
  • Mitochondria / metabolism
  • Mitochondria / pathology
  • Mitochondria / ultrastructure
  • Neuropeptides / genetics
  • Neuropeptides / metabolism*


  • Dcx protein, mouse
  • Doublecortin Domain Proteins
  • Doublecortin Protein
  • Microtubule-Associated Proteins
  • Neuropeptides
  • Caspase 3

Grants and funding

The authors thank the Inserm Avenir program, the French Agence National de la Recherche (ANR-08-MNP-013), the Bettencourt Schueller Foundation and the Jérôme Lejeune Foundation for grant support to FF, and Paris 6 and An-Najah universities for support to RKN. The authors thank the Ile de France region through the Neuropole (Nerf) for support of EBJ and animal house facilities, and the FRC Rotary for confocal microscope equipment. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.