FOXP2 Expression in Rodent, Rhesus Monkey, and Human Brainstem

The FOXP2 gene encodes a transcription factor responsible for the development of neural structures involved in vocalization in vertebrates. Animal models have proven critical in the study of FOXP2 gene expression, although a comparative interspecies analysis of brainstem structures is understudied. This study evaluates the expression of FOXP2 protein within the brainstem of rats, rhesus monkeys, and humans.

Brainstems of one rat, two rhesus monkeys, and one human were harvested. Immunohistochemistry for FOXP2 was performed, followed by imaging and centroid analysis to identify patterns of expression within the brainstems of the three species. Images were examined with a Nikon Eclipse 80i microscope (Nikon Corporation) in conjunction with Neurolucida software (Version 8; MBF Bioscience) to capture FOXP2 protein in the three-dimensional brainstem landscape in monkeys and rodents. The 50-μm slices chosen for centroid analysis contained the dorsolateral pons and the dorsal medulla, areas that may play a role in FOXP2-related oromotor dyspraxia.

Similarities were observed in the pattern of FOXP2-positive cells and centroids across species, showing a wide distribution of centroids rostrally and medial convergence of centroids caudally. This pattern exhibited rostrolateral-to-caudomedial tapering in both the pons and the medulla. Neural structures crucial for speech exhibited strong FOXP2 staining, including the gigantocellular, parvocellular, and intermediate medullary reticular nuclei, as well as the medullary respiratory columns, the NTS, and the Bötzinger and preBötzinger complexes.

Respiratory pattern generators in the dorsolateral pons and medulla, which house critical premotor neurons for language generation, show similar FOXP2 protein expression across the rat, rhesus monkey, and human. As FOXP2 protein expression is conserved across multiple species, animal models may be valuable resources in studying FOXP2-related disorders, including dyspraxia.