Transcriptome of chicken (Gallus gallus) bursal M cells

In mammals, a subset of follicle-associated epithelial (FAE) cells, known as M cells, conduct the transcytosis of antigens across the epithelium into the underlying lymphoid tissues. Despite the importance of M cells in the induction of mucosal immunity, our knowledge of chicken M cells and their gene expression profile is limited. We previously revealed that M cells in the FAE of the chicken lung, bursa of Fabricius (bursa), and caecum are visualised based on the expression of CSF1R. Here, we applied RNA-seq analysis on highly enriched CSF1R-expressing bursal M cells to investigate their transcriptome and identify novel chicken M cell-associated genes. Our data show that, like mammalian M cells, chicken bursal M cells also express SOX8, MARCKSL1, TNFAIP2, TNFRSF11B, and PRNP. Immunohistochemical analysis also confirmed the expression of SOX8 in CSF1R-expressing cells in the lung, bursa, and caecum. However, other mammalian M cell-associated genes such as SPIB, GP2, ANAX5, and AIF1 were not represented in the chicken genome. Instead, we show chicken bursal M cells express high levels of related genes such as SPI1, ITGB8, ANAX4, ANXA11, and AIF1L. Whereas our data show that bursal M cells expressed CSF1R-highly, the M cells in the small intestine lacked CSF1R and expressed SOX8. This study offers novel insights into the transcriptome of chicken M cells, revealing that CSF1R expression in these cells is tissue-specific. This finding may suggest the divergence in the development or functionality of chicken M cells.