Lhx2 Regulates Distinct Dendritic Architecture of Pyramidal Neurons across Primary Sensory Areas

Distinct neocortical regions subserve different sensory functions, yet the cellular features that distinguish neurons across cortical areas remain poorly understood. Layer (L)2/3 pyramidal neurons (PyNs) are generated at similar developmental times throughout the cortex, but whether their morphological and functional properties are shaped by areal identity programs is unclear. Here, we compared L2/3 PyNs in mouse primary somatosensory (S1) and primary visual (V1) cortices (both male and female). We observed pronounced areal differences where V1 neurons exhibited smaller and less complex dendritic arbors and displayed increased intrinsic excitability relative to their counterparts in S1. These differences were present in both juvenile and adult stages, indicating that they emerge early and persist over time. Given prior evidence implicating the transcription factor LHX2 in dendritic arborization, we tested its contribution to these differences. Loss of Lhx2 in E15.5 V1 progenitors did not alter neuronal morphology in V1, in contrast to our previous findings in S1. We found that E15.5 progenitors display lower levels of LHX2 protein in V1 than in S1; therefore, we overexpressed Lhx2 in V1 progenitors and found increased dendritic branching complexity in V1 L2/3 PyNs. Together, these findings identify LHX2 as a molecular regulator that contributes to area-specific structural differentiation of L2/3 PyNs. Our results show that PyNs arising from different regions of the dorsal pallium diverge in morphology and physiology according to the cortical area, suggesting that regionally patterned transcriptional programs help establish functional specialization across the neocortex.