Knocking out the homeobox gene Msx2 effects the development of the immune system

Proper development of the immune system is critical for defense against infection. Complex signaling occurs during immune system development and changes in this signaling can have adverse effects ranging from immunodeficiency to cancer. Lymphoid Enhancer Factor (Lef-1) is an important regulator of immune system development. Msx2 is known to be regulated by the transcription factor Lef-1 in many tissues during development and expression of Msx2 in lymphocytes has recently been reported. We therefore believe Msx2 may be a regulator of lymphocyte development. To determine possible functions for the expression of this regulatory gene in lymphocytes, we looked at the immune system of Msx2 knockout mice. Wright-Giemsa staining was performed to numerically compare leukocyte populations. We found that in the knockout mice the ratio of neutrophils to lymphocytes increased compared to the wild-type mice. To measure any changes in lymphocytes in the knockout mice, CD-19, Thy-1, and CD-5 cells were fluorescently tagged and the quantity of these cells was obtained. CD- 19 and Thy-1 cells showed no numerical differences in the knockout mouse, while CD- 5 cells were decreased. This finding suggests that fewer B-1a cells are produced in mice lacking the Msx2 gene. Thus, the Msx2 gene may play a role in the development of the immune system, specifically in regulating lymphocyte development.