Fig. 4

Embryonic expression of the six collagen IV ? chains in zebrafish. (A) RT-PCR products for the zebrafish type IV collagen ? chains at the indicated developmental stages (top band) range in size from 666 to 704 bp. The ?-actin control band is shown below. Three expression patterns are noted: developmentally unrestricted (?1 and ?2 chains); postgastrulation (?5 and ?6 chains); and late-onset expression (?3 and ?4 chains). Expression before 6 h postfertilization (hpf) stage is maternal. (B) Cartoon schematic of NC1 heterohexamer of ?1 and ?2 NC1 chains (PDB 5NAX). Black arrow shows viewpoint for C. (C) Bottom-up view of the heterotrimer. The inset is a close-up view of salt bridges that help form the heterotrimer interface. In the ?1 and ?2 chains, a glutamate (E1592 in ?1 and E1633 in ?2) forms a salt bridge with a basic residue (R1481 in ?1 and K1525 in ?2). (D) In situ hybridization for zebrafish ?1 and ?2 chains at 26 hpf and 36 hpf. (E) In situ hybridization for zebrafish ?3 and ?4 chains at 26 hpf, dorsal and lateral views. The ?3 and ?4 chain are localized in the developing brain (b), with ?4 chain also detected in the otic vesicle (o). hpf, hours postfertilization, MBT, mid-blastula transition.