Paleocortex is specified in mice in which dorsal telencephalic patterning is severely disrupted

Area of Science:

• Neuroscience
• Developmental Biology
• Genetics

Background:

• Telencephalon patterning involves distinct mechanisms for dorsal and ventral structures.
• Paleocortex specification, particularly its dorsal or ventral origins, remains poorly understood.
• The paleocortex is hypothesized to be a dorsal cortical structure originating from the lateral dorsal telencephalon.

Purpose of the Study:

• To investigate paleocortex specification in the context of disrupted dorsal telencephalic patterning.
• To determine the influence of dorsal signaling centers on paleocortex development.
• To explore the intrinsic developmental timing of paleocortex specification.

Main Methods:

• Analysis of paleocortical marker expression in Lhx2-/-, Gli3-/-, and BF1-/- mutant mice.
• Examination of Wnt and Bmp signaling in relation to the cortical hem in mutant backgrounds.
• In vitro culture assay using isolated lateral telencephalon explants from embryonic day 10.5.

Main Results:

• Paleocortical markers are expressed in Lhx2-/- and Gli3-/- mutants despite severe dorsal patterning defects.
• Paleocortical markers are absent in BF1-/- mutants where the ventral telencephalon is deleted.
• Paleocortical specification is independent of cortical hem signaling levels and occurs in isolated lateral telencephalon explants by embryonic day 10.5.

Conclusions:

• Paleocortex specification can occur independently of major dorsal telencephalic patterning events.
• Ventral telencephalon integrity is crucial for paleocortex specification.
• Intrinsic mechanisms within the lateral telencephalon likely initiate paleocortex specification very early, before embryonic day 10.5.