Biomedical subjects

Dimitris Bourikas

Publications and source records attributed to Dimitris Bourikas.

5 recordsLinked to original sources

PubMed2006

The short coiled-coil domain-containing protein UNC-69 cooperates with UNC-76 to regulate axonal outgrowth and normal presynaptic organization in Caenorhabditis elegans.

BACKGROUND: The nematode Caenorhabditis elegans has been used extensively to identify the genetic requirements for proper nervous system development and function. Key to this process is the direction of vesicles to the growing axons and dendrites, which is required for growth-cone extension and synapse formation in the developing neurons. The contribution and mechanism of membrane traffic in neuronal development are not fully understood, however. RESULTS: We show that the C. elegans gene unc-69 is required for axon outgrowth, guidance, fasciculation and normal presynaptic organization. We identify UNC-69 as an evolutionarily conserved 108-amino-acid protein with a short coiled-coil domain. UNC-69 interacts physically with UNC-76, mutations in which produce similar defects to loss of unc-69 function. In addition, a weak reduction-of-function allele, unc-69(ju69), preferentially causes mislocalization of the synaptic vesicle marker synaptobrevin. UNC-69 and UNC-76 colocalize as puncta in neuronal processes and cooperate to regulate axon extension and synapse formation. The chicken UNC-69 homolog is highly expressed in the developing central nervous system, and its inactivation by RNA interference leads to axon guidance defects. CONCLUSION: We have identified a novel protein complex, composed of UNC-69 and UNC-76, which promotes axonal growth and normal presynaptic organization in C. elegans. As both proteins are conserved through evolution, we suggest that the mammalian homologs of UNC-69 and UNC-76 (SCOCO and FEZ, respectively) may function similarly.

Animals↗

PubMed2005

Sonic hedgehog guides commissural axons along the longitudinal axis of the spinal cord.

Dorsal commissural axons in the developing spinal cord cross the floor plate, then turn rostrally and grow along the longitudinal axis, close to the floor plate. We used a subtractive hybridization approach to identify guidance cues responsible for the rostral turn in chicken embryos. One of the candidates was the morphogen Sonic hedgehog (Shh). Silencing of the gene SHH (which encodes Shh) by in ovo RNAi during commissural axon navigation demonstrated a repulsive role in post-commissural axon guidance. This effect of Shh was not mediated by Patched (Ptc) and Smoothened (Smo), the receptors that mediate effects of Shh in morphogenesis and commissural axon growth toward the floor plate. Rather, functional in vivo studies showed that the repulsive effect of Shh on postcommissural axons was mediated by Hedgehog interacting protein (Hip).

Age Factors↗

PubMed2003

Modulation of the Na(+)-H(+) antiport activity by adrenaline on erythrocytes from normal and obese individuals.

The effect of adrenaline on normal and obese human Na(+)-H(+) antiport (NHE 1) erythrocyte activity has been studied. Adrenaline increased both intracellular pH (pHi) and Na(+) influx in erythrocyte suspensions. This effect of adrenaline was inhibited by amiloride or EIPA, indicating that adrenaline stimulated NHE 1. Phorbol myristicate ester (PMA), a protein kinase C (PKC) stimulator, increased the activity of NHE 1 whereas calphostin C, a PKC inhibitor, partially inhibited NHE 1 activation induced by adrenaline. The effect of adrenaline to NHE 1 was counteracted by prazocin and by propranolol as well indicating the involvement of both alpha and beta 2 adrenergic receptors. The effect of adrenaline on erythrocyte NHE 1 activity was significantly more profound in obese compared to normal subjects. These data indicate that adrenaline induces an increase of pHi and Na(+) uptake of human erythrocytes through stimulation of NHE 1 activity. The significantly more profound stimulation of NHE 1 activity by adrenaline in obese as compared to normal subjects is discussed.

Amiloride↗

PubMed2003

New tools for gene manipulation in chicken embryos.

Genomics has changed the pace by which genes are analyzed. Rather than looking at genes one by one, gene expression today is studied at the genome level. Unfortunately, the data we get from microarray analysis do not give us any clues about the function of these genes. Functional analyses are still refractory to large-scale, high-throughput studies, particularly in vertebrates. With the development of in ovo RNAi as a tool for specific gene silencing, the chicken embryo has become an efficient in vivo system to study gene function during development. A major advantage of in ovo RNAi is the fact that the knowledge of a cDNA fragment of the gene of interest is sufficient to get loss-of-function phenotypes. Thus, this new approach is a valuable tool for functional genomics.

Animals↗

PubMed2002

Screening for gene function in chicken embryo using RNAi and electroporation.

In the postgenomic era the elucidation of the physiological function of genes has become the rate-limiting step in the quest to understand the development and function of living organisms. Gene functions cannot be determined by high-throughput methods but require analysis in the context of the entire organism. This is particularly true in the developing vertebrate nervous system. Because of its easy accessibility in the egg, the chicken embryo has been the model of choice for developmental in vivo studies. However, its usefulness has been hampered by a lack of methods for genetic manipulation. Here we describe an approach that could compensate for this disadvantage. By combining gene silencing by dsRNA (through RNA interference, RNAi) with in ovo electroporation, we developed an efficient method to induce loss of gene function in vivo during the development of the chicken CNS. This method opens new possibilities for studying gene function not only by gain-of-function but also by loss-of-function approaches and therefore represents a new tool for functional genomics.

Animals↗