Maternal expression of Crk^HMJ22995 under the control of Scer\GAL4^{VP16.mat.αTub67C} leads to some embryonic lethality; a few embryos exhibit morphological defects, from denticle belt deletion or fusion, ventral or dorsal holes, or pattern disruption; a minority of lethal embryos shows defective germband retraction. By stage 15, embryos show substantial and highly prevalent CNS defects, with most cases showing severe nervous system patterning disruption, and others showing milder axon patterning defects (inappropriate midline crossing of axons as well as loss of commissural or longitudinal axons in some segment); most embryos with strong CNS defects also have strong defects in the overlying epidermis (ranging from epidermal holes to strong disruptions to the epidermal pattern).