THE MOUSE HOMOLOG OF THE REGION-SPECIFIC HOMEOTIC GENE SPALT OF DROSOPHILA IS EXPRESSED IN THE DEVELOPING NERVOUS-SYSTEM AND IN MESODERM-DERIVED STRUCTURES

The region specific homeotic gene spalt (sal) of Drosophila determines the specification of terminal segments. Its mutation leads to an inco mplete transformation of terminal segments into trunk-like segments. T he gene product is a zinc finger protein with a novel structure. We ha ve isolated the mouse homolog of the Drosophila spalt gene (msal). The msal cDNA sequence is similar to its Drosophila counterpart in that i t contains seven C2H2-type zinc finger motifs grouped into three pairs plus a single zinc finger closely linked to the middle pair. The two genes exhibit high sequence similarity in the zinc finger regions and to a lower extent in the putative transactivation domains. We have ana lysed the expression pattern of msal and show that it is expressed in the developing neuroectoderm of the brain, the inner ear and the spina l cord and in urogenital ridge-derived structures such as testis, ovar ies and kidneys. A weaker and transient expression is seen in early em bryos in the branchial arches and in tissues like the notochord, the l imb buds and the heart. Given its role in Drosophila melanogaster and its strong sequence conservation, this expression pattern suggests an important role for msal in the development of the nervous system.