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Fig. 3 Knockdown of ß4GalT5 results in dorsalization. (A) Lateral views of 2-somite control-injected and ß4GalT5MO-injected embryos. The morphant phenotype is manifested by an elongation of the anteroposterior axis. (B) 26-somite embryo injected with control morpholinos, lateral view. (C) When ß4GalT5MO-injected embryos reach the 26-somite stage, the mature ß4GalT5MO phenotype is observed (lateral and dorsal views). (Class 3) 5 ng of ß4GalT5 morpholino results in mild dorsalization manifested by a slight tail coil. This phenotype is similar to the pgy phenotype reported by Mullins et al. (Mullins et al., 1996) and correlates with their Class 3. (Class 4) 10 ng of morpholino produces a more significant coiling of the tail, as well as dorsalization within the anterior regions of the embryo, and embryos are considered moderately dorsalized, similar to the snh phenotype representing Class 4 of Mullins et al. (Mullins et al., 1996). (Class 5) Injection of 15-20 ng of ß4GalT5 morpholino produces the most severe dorsalization, which appears similar to that seen in the swr mutant. (D) Lateral view of 26-somite embryo injected with ß4GalT5MO3 and mRNA encoding full-length ß4GalT5. These embryos were essentially wild type in appearance. (E) In situ hybridization of pax2a in the otic vesicle of 26-somite control embryo; asterisks indicate the paired otoliths, which are absent in an equivalently staged ß4GalT5MO embryo.