This chapter focuses on mouse homeo box gene organization and expression. The process of embryogenesis in any organism can be thought of as a progressive expression of information that subdivides the embryo into ever finer units of determination. In Drosophila this process can be roughly divided into three steps: (1) the maternal establishment of the anteroposterior and dorsoventral coordinates of the embryo, (2) the segmentation of the embryo, and (3) the assignment of identities to each of the segments. The genetic analysis of each of these processes has proceeded more or less independently. Two known clusters of genes that contain homeo boxes of the Antennapedia class have been mapped in the mouse. Homeo box sequences homologous to the engrailed class have also been found in mouse. One locus designated En-1 has been mapped to within several centimorgans of the murine morphogenetic locus Dominant hemimelia on chromosome 1. A second engrailed-like homeo box designated En-2 has been mapped to mouse chromosome 5 in close linkage with hammertoe and hemimelic extra toes. Homeo box genes are expressed in a wide variety of tissues, developmental stages, and cell lines.
Bibliographical noteFunding Information:
We would like to acknowledge the participation of Dr. William McGinnis in the work cited from this laboratory. His continuing advice and encouragement IS also greatly appreciated. A.A.F. is the recipient of a Markey Foundation Fellowship. M.F.U. is supported by a Life and Health Insurance Medical Research Fund Scholarship. L.D.B., C.P.H.. and A.F.-S. are supported by N.I.H. predoctoral training grants. A.F. is a National Cancer Cytology Center Post-Doctoral Fellow. M.R. was an N.I.H. postdoctoral trainee. We thank Vincent Salerno for excellent technical assistance and Suzy Pafka for photographic assistance. This work was supported by N.I.H. grant GM09966 to F.H.R.