Dmrt genes participate in the development of Cajal‐Retzius cells derived from the cortical hem in the telencephalon

Background During development, Cajal‐Retzius (CR) cells are the first generated and essential pioneering neurons that control neuronal migration and arealization in the mammalian cortex. CR cells are derived from specific regions within the telencephalon, that is, the pallial septum in the rostromedial cortex, the pallial‐subpallial boundary, and the cortical hem (CH) in the caudomedial cortex. However, the molecular mechanism underlying the generation of CR cell subtypes in distinct regions of origin is poorly understood. Results We found that double‐sex and mab‐3 related transcription factor (Dmrt) genes, that is, Dmrta1 and Dmrt3, were expressed in the progenitor domains that produce CR cells. The number of CH‐derived CR cells was severely decreased in Dmrt3 mutants, especially in Dmrta1 and Dmrt3 double mutants. The reduced production of the CR cells was consistent with the developmental impairment of the CH structures in the medial telencephalon from which the CR cells are produced. Conclusion Dmrta1 and Dmrt3 cooperatively regulate patterning of the CH structure and production of the CR cells from the CH during cortical development. Key Findings Dmrta1 and Dmrt3 (double‐sex and mab‐3 related transcription factor) are expressed in the progenitor domains that produce Cajal‐Retzius (CR) cells. The number of CR cells, derived from the cortical hem (CH), is severely decreased in Dmrt3 mutants, especially in Dmrta1 and Dmrt3 double mutants. The reduced production of the CR cells in Dmrt mutants is consistent with the developmental impairment of the CH structures from which the CR cells are produced.