Distinct expression patterns for type II topoisomerases IIA and IIB in the early foetal XXXX telencephalon.

@entity1 @entity5255 @entity550 @entity26443 @entity2438 @entity6484 @entity161 @entity7457 @entity14583
@entity14583 and @entity5255 are type II topoisomerase enzymes that have important but distinct roles in DNA replication and RNA transcription. Recently, @entity5255 has been implicated in the transcription of long genes in particular that play crucial roles in neural development and are susceptible to mutations contributing to neurodevelopmental conditions such as @entity2438 and @entity161 . This study maps their expression in the early foetal @entity1 telencephalon between 9 and 12 post-conceptional weeks. @entity14583 immunoreactivity was restricted to cell nuclei of the @entity550 (GE), including the ventricular zone and subventricular zone (SVZ) closely matching expression of the proliferation marker KI67. Comparison with sections immunolabelled for @entity7457 , a medial GE (MGE) marker, and @entity6484 , a cortical progenitor cell and lateral GE (LGE) marker, revealed that @entity14583 -expressing cells were more abundant in MGE than the LGE. In the cortex, @entity5255 is expressed in cell nuclei in both proliferative (SVZ) and post-mitotic compartments (intermediate zone and cortical plate) as revealed by comparison with immunostaining for @entity6484 and the post-mitotic neuron marker @entity26443 . However, co-expression with KI67 was rare. In the GE, @entity5255 was also expressed by proliferative and post-mitotic compartments. In situ hybridisation studies confirmed these patterns of expression, except that @entity14583 mRNA is restricted to cells in the G2/M phase of division. Thus, during early development, @entity14583 is likely to have a role in cell proliferation, whereas @entity5255 is expressed in post-mitotic cells and may be important in controlling expression of long genes even at this early stage.
