Temporal Patterning of Neural Progenitors in Drosophila - Current Topics in Developmental Biology - page 90

to examine how the expression dynamics of the temporal genes leads to epi-
genetic changes and thus regulates NB competence, and eventually
determines the end of neurogenesis. Such studies are relevant for the devel-
opment of cell replacement therapies using stem cells to treat various
diseases.
Another big challenge is to elucidate how the temporal and spatial iden-
tity of NBs, as well as the Notch-dependent binary fate choices, are inte-
grated to generate specific neuron fates.
Finally, how the temporal sequence evolved is a great question for evo-
lutionary developmental neurobiologists. An interesting observation is that
the Hb Cas temporal sequence in VNC NBs mimics the

anterior to posterior spatial distribution of Hb

! Kr ! Pdm !

! ! !

Cas expres-
sion domains at cellular blastoderm in the embryo ( Isshiki et al., 2001 ).
Whether they use the same regulatory logic is not known. The Hth

Kr Pdm

!

Ey regulatory cascades have not
been described in other contexts. Evolutionary studies might provide clues
as to how this powerful mechanism has evolved to pattern neural precursors
to generate neural diversity.

Klu ! Ey ! Slp ! D ! Tll or D ! Grh !

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