FANCD2 protein is expressed in proliferating cells of human tissues that are cancer-prone in Fanconi anaemia

Fanconi anaemia (FA) is an inherited form of progressive pancytopenia associated with developmental defects, chromosomal instability, and Cancer predisposition. At least seven distinct FA proteins function in concert to protect the genome, a key step being the activation of FANCD2 by mono-ubiquitination. This paper reports an immunohistochemical analysis of FANCD2 expression in normal human tissue. The highest expression was observed in maturing spermatocytes and fetal oocytes (consistent with a role for FANCD2 in meiosis) and in germinal centre cells of the spleen, tonsil, and lymph nodes (consistent with a role in proliferation). FANCD2 expression was also seen in tissues predisposed to Cancer development in FA patients: haematopoietic cells, especially in the fetus, and squamous cell epithelia, particularly in the head and neck region and uterine cervix. FANCD2 expression was also occasionally seen in the breast and Fallopian tube epithelium, the respiratory epithelium of the trachea, and the exocrine cells of the pancreas, indicating that these tissues may also be cancer-prone in FA. FANCD2 expression is frequently expressed in proliferating cells as demonstrated by Ki-67 immunofluorescence double staining, consistent with a function of FANCD2 in DNA replication.