Both Drosophila ZFH proteins are expressed in the nervous system. For more information about these neurons see Islet , Engrailed and Huckebein . Loss of zfh- 1 function results in various degrees of local errors in mesodermal cell fate or positioning. The ventral-oblique and the dorsal muscles are usually the most severely affected. There are a variety of errors in segregation of muscle precursors.
Mutants have missing muscles, misplaced muscles, and nuclei within a muscle are disorganized.
The foregut and hindgut appear normal, but the midgut, structured by expression of zfh-1 in the visceral mesoderm , is abnormal. Constrictions start to form but rarely complete the subdivision of the yolk, and the elongation and narrowing of the gut occurs in a partial and very uneven fashion. Other defects are seen in the heart, gonads and pole cells. Of great interest is the expression of ZFH-1 in head mesoderm. Here the gene's expression does not require twist or snail , both of which are required for visceral and somatic mesoderm expression of ZFH-1.