Nucleation and growth of microtubules from gamma-tubulin-functionalized gold surfaces.

Microtubules are protein filaments that are emerging as potential building blocks in manufacturing nanoscale structures and systems such as interconnecting nanowires. Future development in using microtubules necessitates a control of their nucleation and growth. We report the controlled nucleation and growth of microtubules from functionalized gold on a hydrophilic oxidized silicon wafer.

Collagen type VI expression during cardiac development and in human fetuses with trisomy 21.

The role played by specific extracellular matrix molecules in normal endocardial cushion differentiation into valves and septa remains to be established. In this respect, type collagen VI is of particular interest because genes encoding the alpha1 and alpha2 chains are located on chromosome 21, and defects involving the atrioventricular (AV) cushions are frequent in trisomy 21. Collagen VI expression was studied in normal human embryonic and fetal hearts (5-18 weeks of development) and compared by immunohistochemistry with results from fetuses (10-16 weeks of development) with trisomy 21.

Beta 1 integrin activation mediates adhesive differences between trisomy 21 and non-trisomic fibroblasts on type VI collagen.

Trisomy 21 (Down syndrome) is a common genetic condition with a high incidence of congenital heart defects (CHD), particularly those involving abnormal development of the embryonic atrioventricular (AV) canal. Type VI collagen (Col VI) is expressed in the developing AV canal extracellular matrix, and has been associated with trisomy 21 AV canal defects in human genetic studies. Although the molecular mechanisms linking Col VI and trisomy 21 AV canal defects are not well understood, a computer model predicts increased cell adhesiveness is responsible for these CHD.

The type III connecting segment of fibronectin contains an aspartic acid residue that regulates the rate of binding to integrin alpha 4 beta 1.

The type III connecting segment (IIICS) within fibronectin is the major binding site for the integrin alpha 4 beta 1. Most integrin ligands have an essential acidic residue within their integrin binding site, in IIICS this residue is hypothesized to be the aspartic acid at position 21. Alanine scanning mutagenesis was used to determine the amino acid residues within the intact IIICS domain required for interaction with alpha 4 beta 1.

Hypocotyl expression and light downregulation of the soybean tubulin gene, tubB1.

The tubB1 beta-tubulin gene of Glycine max (previously named s beta 1) is highly expressed only in rapidly elongating regions of etiolated seedling hypocotyls and this expression is strongly downregulated when the seedlings are exposed to light. Primer extension demonstrated that the gene was transcribed in these tissues and contained two sites of transcriptional initiation. To determine the mechanism regulating tubB1 expression, a chimeric reporter gene was constructed by fusing 5' upstream regions of tubB1 to a promoterless beta-glucuronidase (GUS) gene and these constructs were introduced into protoplasts by electroporation.

Limited expression of a diverged beta-tubulin gene during soybean (Glycine max [L.] Merr.) development.

We examined the developmental expression of a diverged soybean beta-tubulin gene (designated sb-1), which had been cloned and sequenced previously. A probe specific for the sb-1 gene was constructed from the 3' transcribed untranslated sequence. As a control, a more general probe for beta-tubulin genes and their transcripts was constructed from a highly conserved region of the third exon of another soybean beta-tubulin gene, sb-2.