P 306. Role of Cdk5rap2 in Neocortical Development
30 October 2018 (online)
Background: Homozygous mutations in the cyclin-dependent kinase 5 regulatory subunit-associated protein 2 gene CDK5RAP2 cause autosomal recessive primary microcephaly (MCPH) type 3 in humans. MCPH is characterized by severe microcephaly at birth and intellectual disability. Cdk5rap2 is a centrosomal protein highly expressed in the neural progenitor pool. It has functions in cleavage plane orientation of apical neuronal progenitors, maintenance of the centriole engagement and cohesion, microtubule organizing function, and proper spindle formation
Aims: The main goal of this study is to understand the role of Cdk5rap2 in maintaining the neural stem cell pool and therefore normal brain size
Question: How defects in Cdk5rap2 functions affect neurogenesis and lead to an increase in apoptosis resulting in a thinner cerebral cortex
Methods: To assess the population level cell cycle in Cdk5rap2 mutant or Hertwig’s anemia mice (an/an), we used a cumulative pulse labeling of heterozygous (an/+) pregnant mice with S-phase thymidine analogs 5-iodo-20-deoxyuridine (IddU) and 5-bromo-20-deoxyuridine (BrdU, interval 90 minutes). Thirty minutes after the second pulse, the E11.5 embryos were collected, fixed in 4% paraformaldehyde overnight at 4°C, dehydrated in ethanol series, and embedded in paraffin. Selected sections were then immunostained for Iddu/Brdu incorporation and apoptotic cell markers Caspase3.
Results: We detected a decrease in the relative number of exclusively Iddu positive germ cells which left the cell cycle and a downward shift in the accumulation peak of the S-labeled progenitor nuclei after 30 minutes of Brdu incorporation in an/an. This was accompanied by a gradual increase in the Caspase3+ apoptotic cells toward the pial surface of the cerebral wall.
Conclusion: Here, we report a potential role of Cdk5rap2 in controlling neuronal progenitor’s cell cycle progression and interkinetic nuclear migration in Cdk5rap2 mutant mice.