ABSTRACTS:

TITLE: XENOPUS LIM MOTIF-CONTAINING PROTEIN KINASE, XLIMK1, IS EXPRESSED IN THE DEVELOPING HEAD STRUCTURE OF THE EMBRYO.
AUTHOR: TAKAHASHI T, AOKI S, NAKAMURA T, KOSHIMIZU U, MATSUMOTO K, NAKAMURA
JOURNAL: DEVELOPMENTAL DYNAMICS 1997 Jun;209(2):196-205
ABSTRACT: The LIM double zinc finger motif is found in several developmentally functioning and cytoskeletal proteins, and is considered to be very important for protein-protein interactions. LIM kinase (LIMK) is a novel protein enzyme containing two LIM motifs at the N-terminal, the function of which has yet to be clearly defined. In this study, we cloned a cDNA encoding Xenopus frog counterpart of human LIMK1 gene by PCR mediated cloning, and called it Xlimk1. Xlimk1 is highly homologous to mammalian LIMK1 in each structural domain, particularly in LIM and protein kinase domains.

In Northern blot analysis, two distinct Xlimk1 transcripts of 9.0 Kb and 3.7 Kb were present in early cleavage stages of the embryo. Both mRNA species were subsequently decreased at the gastrula stages. The 9.0 Kb of Xlimk1 mRNA again appeared in late neurula stage, then the expression level gradually increased in later stages of the embryo. Analysis showed the localization of Xlimk1 transcripts in the animal half of the blastula embryo. In post-neurula stages, specific signals for Xlimk1 were found, mostly, in the anterior (head) region of the embryo, including the developing brain, hyoid and branchial arches, and the sensory organs. These results indicate that Xlimk1 may play an important role in neural development and formation of anterior (head) structures in the Xenopus embryo.

KEY WORDS/PHRASES
CYTOSKELETAL PROTEINS
CLEAVAGE STAGES
GASTRULA STAGES
HOMOLOGOUS
NEURULA STAGE
NORTHERN BLOT ANALYSIS
TRANSCRIPTS
ZINC FINGERS

TITLE: CHICK NOGGIN IS EXPRESSED IN THE ORGANIZER AND NEURAL PLATE DURING AXIAL DEVELOPMENT, BUT OFFERS NO EVIDENCE OF INVOLVEMENT IN PRIMARY AXIS FORMATION
AUTHOR: CONNOLLY DJ, PATEL K, COOKE J
JOURNAL: INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 1997 Apr;41(2):389-96
ABSTRACT: We have cloned and examined the early developmental expression of the chick homolog of noggin, a gene originally isolated in the Xenopus frog that can create a top and bottom in a developing gastula. It can also induce neural tissue when expressed experimentally. Chick noggin is expressed at relatively low levels, but at sites equivalent to those seen in amphibian development, namely Hensen's node and the endo- and mesodermal head bud. There is also diffuse expression in the early central nervous system, centered on the ventral midline, and later hindbrain-associated expression.

Since the earlier of these expression sites are consistent with organizer functions suggested by the properties of the protein in Xenopus experiments, we have used recombinant mammalian Noggin protein in tests for developmental disturbance on the early gastrula-staged chick blastomere. These tests detect effects, on chick, of various other secreted proteins that simulate or replicate early developmental signals in Xenopus. We have been unable to observe such effects with a range of Noggin concentrations including those that dramatically effect the Xenopus embryo. To illustrate effects observed in such tests with secreted proteins active on early stages, we show results with the known Xenopus ventralizer Bone Morphogenetic Protein 4 (BMP-4).

KEY WORDS/PHRASES
BLASTOMERE
CLONED
DEVELOPMENTAL EXPRESSION
DEVELOPMENTAL SIGNALS
RECOMBINANT
HOMOLOG

TITLE: MOLECULAR CLONING AND CHARACTERIZATION OF DROSOPHILA GENES ENCODING SMALL GTPASES OF THE RAB AND RHO FAMILIES.
AUTHOR: SASAMURA T, KOBAYASHI T, KOJIMA S, QADOTA H, OHYA Y, MASAI I, HOTTA Y
JOURNAL: MOLECULAR GENES AND GENETICS 1997 May 20;254(5):486-94
ABSTRACT: We have isolated eight genes from Drosophila, small GTPases. They can be classified into three rab family genes (Drab2, Drab5, Drab11) and five rho family genes (Drac1a, Drac1b, Drac3, Dcdc42, DrhoA).

While Drac3 is a novel type of rac gene, others are homologues of known mammalian genes for small GTPases. Northern blot analyses showed that all the genes are expressed throughout all developmental stages from embryo to adult. In situ hybridization to embryos revealed that Drab2, Drac1b, and Drac3 are highly expressed in the nervous system, in the trunk mesoderm, and in the cephalic mesoderm, respectively. We found that Drac3 is expressed in hemocyte precursor cells. In the Drac3 deficiency embryos, the hemocyte precursor cells start to differentiate normally, but never develop into mature hemocytes, indicating that Drac3 is essential for their maturation. The DrhoA and Dcdc42 genes complemented S. cerevisiae rho1 and cdc42 mutations in the same manner as human rhoA and CDC42, respectively. These results suggest functional similarity between Drosophila and mammalian small GTPase genes.

KEY WORDS/PHRASES
GTPASES
HOMOLOGUES
IN SITU HYBRIDIZATION