Cloning and expression analysis of cadherin7 in the central nervous system of the embryonic zebrafish.

Cadherin cell adhesion molecules exhibit unique expression patterns during development of the vertebrate central nervous system. In this study, we obtained a full-length cDNA of a novel zebrafish cadherin using reverse transcriptase-polymerase chain reaction (RT-PCR) and 5' and 3' rapid amplification of cDNA ends (RACE). The deduced amino acid sequence of this molecule is most similar to the published amino acid sequences of chicken and mammalian cadherin7 (Cdh7), a member of the type II cadherin subfamily. cadherin7 message (cdh7) expression in embryonic zebrafish was studied using in situ hybridization and RT-PCR methods. cdh7 expression begins at about 12h postfertilization (hpf) in a small patch in the anterior neural keel, and along the midline of the posterior neural keel. By 24 hpf, cdh7 expression in the brain shows a distinct segmental pattern that reflects the neuromeric organization of the brain, while its expression domain in the spinal cord is continuous, but confined to the middle region of the spinal cord. As development proceeds, cdh7 expression is detected in more regions of the brain, including the major visual structures in the fore- and midbrains, while its expression domain in the hindbrain becomes more restricted, and its expression in the spinal cord becomes undetectable. cdh7 expression becomes reduced in 3-day old embryos. Our results show that cdh7 expression in the zebrafish developing central nervous system is both spatially and temporally regulated.

The translational apparatus of Tortula ruralis: polysomal retention of transcripts encoding the ribosomal proteins RPS14, RPS16 and RPL23 in desiccated and rehydrated gametophytes.

Tortula ruralis (Syntrichia ruralis) is an important model system for the study of plant vegetative desiccation tolerance. One of the most intriguing aspects of desiccation-tolerant plants is the maintenance of key cellular components in stable and viable forms in the desiccated state, particularly those related to the translational apparatus (i.e. ribosomes and ribosomal RNAs). This study investigated the third integral component of the translational apparatus, the ribosomal proteins. Three T. ruralis cDNAs encoding predicted polypeptides with significant similarity to ribosomal proteins were isolated from a cDNA expression library derived from the polysomal, messenger ribonucleoprotein particle (mRNP) fraction of desiccated gametophytes; Rps14 and Rps16 encode the small-subunit ribosomal proteins RPS14 and RPS16, respectively, and Rpl23 encodes the large-subunit ribosomal protein RPL23. RPS14, RPS16 and RPL23, the deduced polypeptides, have predicted molecular masses of 14.4 kDa, 16.2 kDa and 14.9 kDa and predicted pI's of 11.08, 10.34 and 10. 67, respectively. Phylogenetic analysis of the deduced amino acid sequences demonstrated that each of the T. ruralis proteins is most similar to ribosomal proteins from higher plants even though RPS14 and RPL23 show high divergence from their other plant counterparts. RNA blot hybridizations of RNAs present within the polysomal mRNP fraction (i.e. the 100 Kxg pellet) demonstrated that Rps14, Rps16 and Rpl23 are expressed in moss gametophytes during a desiccation-rehydration cycle and, according to the prior cDNA classification scheme in T. ruralis, are constitutive clones. These findings clearly demonstrated that Rps14, Rps16 and Rpl23 transcripts are retained within the polysomal fractions of desiccated gametophytes.