β-catenin Initiates Tooth Neogenesis in Adult Rodent Incisors

β-catenin signaling is required for embryonic tooth morphogenesis and promotes continuous tooth development when activated in embryos. To determine whether activation of this pathway in the adult oral cavity could promote tooth development, we induced mutation of epithelial β-catenin to a stabilized form in adult mice. This caused increased proliferation of the incisor tooth cervical loop, outpouching of incisor epithelium, abnormal morphology of the epithelial-mesenchymal junction, and enhanced expression of genes associated with embryonic tooth development. Ectopic dental-like structures were formed from the incisor region following implantation into immunodeficient mice. Thus, forced activation of β-catenin signaling can initiate an embryonic-like program of tooth development in adult rodent incisor teeth

Seed parent breeding efficiency of three diverse cytoplasmic-nuclear male-sterility systems in pearl millet

Pearl millet (Pennisetum glaucum (L.) R. Br.) hybrids, grown widely in India and to some extent in the US, are all based on an A1 CMS source, leaving the pearl millet hybrids vulnerable to potential disease or insect pest epidemics. A comparison of this CMS system with two additional CMS systems (A4 and A5) in the present study based on isonuclear A-lines (seed parents) and their isonuclear hybrids showed that A-lines with the A4 cytoplasm had much fewer pollen shedders and much reduced selfed seed set in visually assessed non-shedding plants as compared to those with the A1 cytoplasm. A-lines with the A5 cytoplasm had neither any pollen shedders nor did they set any seed when selfed. This showed that the A5 CMS system imparts complete and most stable male sterility, followed by the A4 and A1 CMS systems. The frequency of maintainers, averaged across a diverse range of 26 populations, was highest for the A5 CMS system (98%), followed by the A4 (59%) and the A1 (34%) system indicating the greatest prospects for genetic diversiWcation of A-lines lies with the A5 cytoplasm, and the least with the A1 cytoplasm. Mean grain yield of hybrids with the A1 cytoplasm was 5% more than the A4-system hybrids, while there was no diVerence between the mean grain yield of hybrids based on A1 and A5 CMS systems. Based on these results, it is suggested that seed parents breeding eYciency will be the greatest with the A5 CMS system, followed by the A4 CMS system, and least with the currently commercial A1 CMS system

Evaluation and identification of promising pearl millet germplasm for grain and fodder traits

Results are presented of experiments aiming to evaluate and characterize available germplasm lines, landraces and core collection lines of pearl millet and to exploit genetic variability so as to identify promising germplasm lines for metric traits for utilization in different breeding programmes and develop early and high-yielding potential hybrids/open-pollinated cultivars for grain and fodder in drier areas of India. The materials consisted of 2375 germplasm accessions, 180 landraces and 504 core collection lines. The germplasm lines and landraces were evaluated during the 2006 rainy season in Mandor, Jodhpur, Rajasthan, India. The accessions were sown in 22 blocks. Each block consisted of 120 accessions and 4 controls (J 2405, J 2340, NMP 24 and PP 29). The pearl millet core collection was also evaluated during the 2006 rainy season at 3 locations, i.e. AICPMIP, Mandor, Jodhpur; Agricultural Research Station, Rajasthan Agricultural University, Durgapura, Jaipur, Rajasthan; and Millet Research Station, Junagadh Agricultural University, Jamnagar, Gujarat. The core collection accessions were accommodated in 19 blocks. Each block consisted of 27 test accessions and 3 controls, namely IP 17862 (ICTP 8203), IP 22281 (Raj 171) (grain type) and IP 3616 (fodder type). After every 9 test accessions, one of the 3 controls was sown. Observations were recorded on morphological/metric traits, i.e. vigour, days to 50% flowering, days to maturity, plant height, productive tillers per plant, total tillers per plant, nodes per plant, sheath length, blade length and width, panicle exsertion, length, thickness and density, bristle length, 1000-grain weight, grain yield, grain yield potential, green fodder yield, green fodder yield potential, and overall plant aspect

Elongated Polyproline Motifs Facilitate Enamel Evolution through Matrix Subunit Compaction

How does proline-repeat motif length in the proteins of teeth and bones relate to the evolution of vertebrates? Counterintuitively, longer repeat stretches are associated with smaller aggregated subunits within a supramolecular matrix, resulting in enhanced crystal length in mammalian versus amphibian tooth enamel

Neural Crest Lineage Segregation: a Blueprint for Periodontal Regeneration

During the recent decade, the periodontal attachment apparatus has become one of the premier areas of the body for the development of novel tissue-engineering strategies. In the present review, we describe a developmental biology approach to characterize current concepts in periodontal regeneration and to discuss strategies for future applications in periodontal therapies. To decipher the developmental make-up of the periodontal region, we have followed the path of the migratory neural crest, since it gives rise to periodontal progenitor tissues, which in turn are subjected to the influence of diverse craniofacial extracellular matrices and peptide growth factors. Based on this developmental perspective, we have conducted a systematic analysis of the factors, progenitor cells, and matrices used in current periodontal tissue-engineering approaches. We propose that the developmental history of a tissue is a highly instructive design template for the discovery of novel bioengineering tools and approaches

Ameloblastin Inhibits Cranial Suture Closure by Modulating Msx2 Expression and Proliferation

Deformities of cranial sutures such as craniosynostosis and enlarged parietal foramina greatly impact human development and quality of life. Here we have examined the role of the extracellular matrix protein ameloblastin (Ambn), a recent addition to the family of non-collagenous extracellular bone matrix proteins, in craniofacial bone development and suture formation. Using RT-PCR, western blot and immunohistochemistry, Ambn was localized in mouse calvarial bone and adjacent condensed mesenchyme. Five-fold Ambn overexpression in a K14-driven transgenic mouse model resulted in delayed posterior frontal suture fusion and incomplete suture closure. Moreover, Ambn overexpressor skulls weighed 13.2% less, their interfrontal bones were 35.3% thinner, and the width between frontal bones plus interfrontal suture was 14.3% wider. Ambn overexpressing mice also featured reduced cell proliferation in suture blastemas and in mesenchymal cells from posterior frontal sutures. There was a more than 2-fold reduction of Msx2 in Ambn overexpressing calvariae and suture mesenchymal cells, and this effect was inversely proportionate to the level of Ambn overexpression in different cell lines. The reduction of Msx2 expression as a result of Ambn overexpression was further enhanced in the presence of the MEK/ERK pathway inhibitor O126. Finally, Ambn overexpression significantly reduced Msx2 down-stream target gene expression levels, including osteogenic transcription factors Runx2 and Osx, the bone matrix proteins Ibsp, ColI, Ocn and Opn, and the cell cycle-related gene CcnD1. Together, these data suggest that Ambn plays a crucial role in the regulation of cranial bone growth and suture closure via Msx 2 suppression and proliferation inhibition