Fig. 4. Expression of ZLAP2 isoforms during zebrafish development. (A,B) Northern blot analysis of the ZLAP2 expression. Total RNA of D. rerio embryos at the eight-cell stage (lane 1), early blastula (3 hpf, lane 2), late blastula (4.5 hpf, lane 3), late gastrula (7.5 hpf, lane 4), one-somite stage (10 hpf, lane 5), at the age of 24 hours (24 h embryo, lane 6) and 48 hours (48 h embryo, lane 7) were hybridized with in vitro synthesized [³²P]-labeled RNA complementary to ZLAP2 mRNAs. (A) A sequence exclusively present in the ZLAP2 mRNA (nucleotides 642-942 of ZLAP2) or (B) a probe complementary to the complete ZLAP2 mRNA were used for hybridization. The hybridized mRNAs have estimated sizes of 3600 (3.6), 2800 (2.8), 2600 (2.6), 1900 (1.9) and 1600 (1.6) nucleotides. (C) Total proteins of nine developmental stages were separated by SDS-PAGE (11% acrylamide) and immunoblotted with ZLAP2-serum1. In each lane, total proteins of 2.5 embryos were loaded. The developmental stage is specified on top of each lane. Expression of ZLAP2ß and was first seen in the late gastrula (lane 4), and ZLAP2 was only detectable in minor amounts in embryos aged 36 hours (36 h embryo; lane 9). The apparent different mobilities of ZLAP2 in some lanes is caused by abundant yolk proteins that have slightly lower mobilities than ZLAP2. (D) Total proteins of seven developmental stages identical to those in lanes 1-7 of (A) were separated by SDS-PAGE (11% acrylamide) and immunoblotted with lamin antibody X155 reacting in zebrafish with lamin B2. In each lane, total proteins of 2.5 embryos were loaded. Lamin B2 is first detectable in the late gastrula (lane 4). Molecular masses of reference proteins (in kDa) are marked (C,D).