Cajal-Retzius cells in the postnatal hippocampus

Hippocampal Cajal-Retzius cells labeled in a Pde1c-Cre;tdTomato mouse at P30

The hippocampus is a brain structure acknowledged for its role in memory formation, learning and the representation of space. Cajal-Retzius (CR) cells occupy the hippocampus for an extended period during postnatal development, where they play a crucial role in the maturation of this region. To better understand the role of hippocampal CR cells during postnatal development and maturation, we aim to investigate the extent of the hippocampal CR circuit and how these cells contribute to the maturation of the hippocampal region.
Hippocampal CR cells are integrated in the most superficial layer of the hippocampus, but the full extent of this network remains to be uncovered. Previous studies hint at yet to be identified, long-range projections to these cells, possibly from an extrahippocampal origin. Additionally, axonal arborizations of CR cells have been noted to extend into several areas of the hippocampal formation. We aim to further elaborate on this network and map the input and output of hippocampal CR cells. Subsequently, we seek to understand the physiological impact of the mapped inputs and outputs on hippocampal circuit activity.
Furthermore we aim to determine what happens to hippocampal development and function when CR cells are prematurely removed. We discovered that removal of hippocampal CR cells skews the trajectory of morphological development. As morphological alterations are indicative for altered plasticity functions, we will investigate if there is a subsequent behavioral deficit in learning and/or physiological alteration of hippocampal cells. In defining such cell functions during early development, we may lay the groundwork for future investigations into a variety of neurological diseases in which hippocampal dysfunction is considered.

This work has received support from the Research Council of Norway, the Trond Mohn Foundation and the European Commission with a MSCA postdoctoral fellowship (CaRe-Space, to GQ).