Figure 1.

Loss of function mutations in SJ genes result in embryonic lethality with defects in head involution and dorsal closure. DIC photomicrographs (A–F, H–L) and a brightfield photomicrograph (G) of cuticle preparations of w¹¹¹⁸ (A and J), Cont^ex956 (B and F), Tsf2^KG01571 (C), Nrx-IV⁴³⁰⁴ (D), Nrg¹⁷ (E and G–I), Mcr¹ (K), and kune^c309 (L). Anterior is to the left and dorsal is up or facing. Defects in dorsal closure are indicated by cuticular scabs or holes on the dorsal surface (asterisks in B–D), whereas defects in head involution vary from completely uninvoluted head structures (arrows in E and F), to incomplete head involution where head skeletal structures are compressed anteriorly (arrow in K), to underdeveloped head skeleton (arrow in L points to a head skeleton lacking most of the dorsal and ventral processes). A number of embryos showed an “Empty Cuticle” phenotype (G), that when devitellinized varied from having a thin cuticle barely capable of holding the embryo together (H), to little or no cuticle resulting in disorganized mass of cells (I). Note the cuticle has separated from the epidermis in all of the mutant animals (small black arrows), but not in the w¹¹¹⁸ animals. Scale bars = 100 μm in A–F, H, and I, 60 μm in G, and 50 μm in J–L.