Molecular regulation of neuroblast migration in the postnatal brain and intracellular trafficking of Diacylglycerol lipase

Student thesis: Doctoral ThesisDoctor of Philosophy


During development and after birth neural stem cells in the subventricular zone (SVZ) generate neuroblasts that migrate along the rostral migratory stream (RMS) to populate the olfactory bulb (OB) with neurons. Multiple factors promote neuroblast migration, but the contribution that many of these make to guidance within the intact RMS is not known. In the first part of this present
study we have characterised in detail how endocannabinoid (eCB), fibroblast growth factor receptor (FGFR) and brain-derived neurotrophic factor (BDNF) signalling regulate motility and guidance, and also determined whether any of these receptors operate in a regionally restricted manner. We used in vivo electroporation in postnatal mice to fluorescently label neuroblasts,
followed by live cell imaging to detail their migratory properties. Cannabinoid receptor antagonists rendered neuroblasts less mobile, and when they did move guidance was lost. Similar results were obtained when eCB synthesis was blocked with diacylglycerol lipase (DAGL, enzymes that are responsible for the synthesis of the eCB receptor ligand 2-AG) inhibitor. Importantly eCB
function is required for directed migration at both ends of the RMS. Likewise, inhibition of BDNF signalling disrupted motility and guidance in a similar manner along the entire RMS. In contrast, altering FGFR signalling inhibits motility and perturbs guidance, but only at the beginning of the stream. Inhibition of FGFR signalling in vivo also reduces the length of the leading process on migratory neuroblasts in a graded manner along the RMS.

In the second part of this study we focus on the intracellular trafficking of DAGLs. Apart from their function in neuroblast migration as shown above, DAGLs are also involved in axonal growth, guidance and synaptic signalling. We developed a new construct which allows the surface labelling of DAGLα. By expressing this construct in neurons, we found DAGLα co-localizes with
Homer, a postsynaptic marker. An antibody feeding assay revealed that DAGLα undergoes constitutive endocytosis in cultured hippocampal neurons and COS-7 cells. Detailed studies showed that DAGLα co-localizes with early endosome markers and undergoes recycling in COS- 7 cells. This constitutive endocytosis and recycling of the enzyme is likely to be responsible for the distinct localization pattern of DAGLα in neurons.

In summary, these results describe the important role of eCB, FGFR and BDNF signalling in neuroblast migration in the postnatal brain. Also it is the first time it has been shown that DAGLα undergoes constitutive endocytosis and recycling inside of the cell.
Date of Award2015
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorPatrick Doherty (Supervisor) & Giovanna Lalli (Supervisor)

Cite this