Developmental expression pattern and alternative splicing of X. laevis DAZAP1. Western blots of extracts probed with antibodies against xDAZAP1 or tubulin (control), prepared from (A) fully grown oocytes (stage VI), in vitro matured (mature), or unfertilized eggs (egg); or (B) unfertilized eggs or embryos (up to stage 41) according to the tables of Nieuwkoop and Faber (1994). After the 12 initial cleavages following fertilization, zygotic transcription ensues at the mid blastula transition (stage 8) with gastrulation being initiated at stage 10. The neural plate (stage 14) starts to fold at stage 15, with the neural tube being completely closed by stage 21. The tail bud is discernable at stage 24, at which time embryos exhibit response to external stimuli with spontaneous movement beginning at stage 26. By stage 28, the general pattern of the brain is largely established, and by stage 29/30, the tail bud is distinct with 24–25 somites segregated, with segregation reaching the tail. The heart starts beating at stage 33/34 with hatching initiating at stage 35/36, when the length of the tail bud is about three times its breadth. The entire pronephros is functional by stage 37/38, with the mouth breaking through at stage 40 and initial torsion of the intestine and segregation of the primordial germ cells occurring at stage 41. (C) Extracts from stage VI and progesterone matured oocytes were untreated (−) or treated with calf intestinal phosphotase (CIP; +) and analyzed by Western blot using the indicated antibodies. ERK2 is active when phosphorylated (P-ERK). (D) Comparison of the C-terminal region of the long forms of xDAZAP1 and hDAZAP1, with identities shown in black and similarities shown in gray. The newly identified alternative C-terminal exon of xDAZAP1 is underlined, and ERK-phosphorylated threonine residues in hDAZAP1 are indicated by asterisks.
