Parathyroid hormone-related peptide (PTHrP) is abundantly expressed throughout the gestational tissues and has multiple roles in fetal development. The importance of PTHrP in embryonic growth and survival is emphasised by the retarded growth and peri-natal lethality of the PTHrP knockout mouse. PTHrP is a regulator of cell survival, proliferation and differentiation in a number of tissues and organs. However, its effects in the development and function of the placenta are yet to be fully defined. Therefore, the PTHrP knockout mouse was used to examine the morphological development and function of the placenta in the absence of fetal PTHrP gene expression. Embryos that were wild-type (WT), heterozygous (HZ) and null (NL) for the PTHrP allele were used for comparison. PTHrP expression was undetectable in the trophoblast cells of the NL placenta, with the HZ placenta exhibiting an intermediate phenotype. Placental development did occur in the absence of fetal PTHrP, although morphological abnormalities were apparent in the junctional zone and labyrinth zone at embryonic day (E)18. The NL placenta was frequently interrupted by large spaces and contained highly misshapen canals, which may reflect altered cellular and cell-matrix interactions. The area of the junctional zone on HZ and NL placental sections was reduced at E14 and E16, as was the area of the labyrinth zone of the NL placenta at E14 and E18. In culture, NL trophoblast cells had a lowered capacity for proliferation and survival. Elevated apoptosis was also observed in the HZ and NL placenta in vivo at E16 and E18, as judged by increased staining for the apoptotic marker, cleaved caspase-3. This effect was less pronounced in the HZ placenta. Evidence of increased insulin-like growth factor 2 (Igf2) expression was observed in the HZ and NL placenta at E14 and E16, which may have been a compensatory response to preserve some aspects of placental function in a PTHrP-deficient environment. Despite a reduced area of junctional and labyrinth zones on NL placental sections, no differences in placental weight was observed at any gestational age examined, which may indicate differences exist in the composition of the NL placenta. Fetal weight was lower in NL than WT fetuses at E16 and E18, whereas fetal weight in the HZ group was unaltered at these gestational ages. This suggests that the NL placenta had a more profoundly reduced capacity to support fetal growth. System A amino acid transport was significantly reduced in the NL placenta at E18, perhaps contributing to decreased NL fetal weight. Glycogen content of the NL placenta was reduced compared to WT at E12 and E14, but raised at E18, which may have been a compensatory mechanism to support fetal growth. In conclusion, PTHrP influences the morphological differentiation of the mouse placenta, trophoblast cell survival, nutrient transport and extraembryonic energy storage. PTHrP is an important regulator of placental development and function, which has associative effects on fetal growth and development.

Development in Bihar

No description available.

Thesis (Ph. D.)--Cornell University, May, 2008. / Vita. Includes bibliographical references.

No description available.

No description available.

No description available.

Origin and development

The traditional view of the genome is based on the dogma that genetic information flows from DNA to RNA to protein. Genes have essentially been synonymous with proteins, with RNA viewed primarily as an intermediate template for protein translation. Intriguingly, only ~2% of the human genome encodes proteins, and the number of protein-coding genes (~20,000) is similar between humans and the simple nematode worm.I have been involved with the analysis of a large-scale transcriptome study, intiated by the RIKEN Genomic Sciences Centre in Japan. As part of this work, it was discovered that the genome carries instructions for tens of thousands of “non protein-coding RNAs” (ncRNAs)(please refer to Appendix A to view the original articles that appeared in Science). The significance of these ncRNAs remains a matter of intense interest and debate. Some have argued that these ncRNAs are simply transcriptional noise, while others have suggested that they comprise a critical regulatory system, which directs the complex patterns of gene expression that underlie differentiation and development.To investigate this further, I have conducted a series of studies that explore the expression and evolution of ncRNAs in mammals. Firstly, I established a comprehensive, on-line database of ncRNAs. This collection provides information on more than twenty thousand ncRNAs, and has proven a valuable resource for ncRNA studies. Secondly, I have systematically analyzed the conservation of known functional ncRNA subsets. I found that small ncRNAs (microRNAs and snoRNAs) were well-conserved similar to protein-coding sequences, whereas longer functional ncRNAs were not. These results indicate that long ncRNAs are evolving more rapidly than other functional genomic elements, and suggest that many of the recently-discovered ncRNAs – most of which are long and of unknown significance – might still be functional, despite having poor sequence conservation. Thirdly, I have shown that many ncRNAs are derived from genuine transcripts, whose expression appears regulated in a biologically-relevant manner. Fourthly, I helped develop a computational strategy to identify extremely large ncRNAs and discovered >60 novel candidates, several of which were characterized experimentally. Prior to this work, only a handful of extremely large ncRNAs had been previously described, and these play critical roles in processes such as genomic imprinting and X chromosome inactivation. This study represented the first systematic discovery of extremely large ncRNAs. Finally, I designed custom microarrays and profiled ncRNA expression across the development of CD8+ T cells. CD8+ T cells serve an important role in immunity by killing virus-infected and tumour cells, and transit through a series of functionally-distinct developmental stages. I found that ~200 novel ncRNAs are dynamically expressed during CD8+ T cell development.Taken together, my findings indicate that ncRNAs are a major, regulated output of the mammalian genome, and are consistent with the notion that ncRNAs represent an important, previously-unrecognised biological control system.

<i>Trichinella spiralis</i> is a parasitic nematode of mammalian skeletal muscle.  Its life cycle includes two stages where developmental progression appears to be inhibited until a specific host niche is encountered.  The newborn larva, released within the host intestine depends upon entry to skeletal muscle for continued development.  The muscle larva encapsulates within skeletal muscle and further reproductive development is dependent upon ingestion by a new host.  Developmental arrest has been extensively characterised in <i>Caenorhabditis</i> <i>elegans</i>, where an alternative L3 larva, the dauer larva, is formed in response to environmental conditions refractive to continued reproductive development.  Using the wealth of genetic information regarding <i>C. elegans</i> dauer formation, putative periods of arrest were examined in <i>T. spiralis.</i> TGF-<span lang=EN-GB style='font-family:Symbol'>b-like and insulin-like signalling pathways are critical mediators of <i>C. elegans </i>dauer formation.  A <i>T. spiralis</i> TGF-<span lang=EN-GB style='font-family: Symbol'>b-ligand was identified and designated <i>ts-tll-1</i>.  Sequencing and analysis revealed <i>ts-tll-1</i> to be similar to vertebrate bone morphogenetic proteins and <i>C. elegans </i>DBL-1, is involved in body size regulation.  EST mining identified putative type I and II TGF-<span lang=EN-GB style='font-family:Symbol'>b receptors and a subtilsin-like proprotein convertase, suggesting conservation of TGF-<span lang=EN-GB style='font-family:Symbol'>b-like signalling in <i>T. spiralis.  </i>A partial <i>Trichinella </i>gene encoding an orthologue of the <i>C. elegans</i> insulin-like, tyrosine kinase receptor, DAF-2, was identified by degenerate PCR and designated <i>ts-tkr.  ts-tkr</i> is most similar to <i>C. elegans daf-2</i> within the highly conserved tyrosine kinase domain.  Two alternative transcripts of <i>ts-tkr</i> were identified by 3’ RACE, which differed in their 3’ UTRs.  Semi-quantitative RT-PCR analysis suggested <i>ts-tkr </i>expression was greatest in adult worms, implying a role in promoting reproductive development. Semi-quantitative RT-PCR was also to assess the expression of selected housekeeping and ES protein encoding genes during the <i>T. spiralis </i>life cycle.  While transcription in the <i>C. elegans</i> dauer is depressed, there was no obvious transcriptional repression in <i>Trichinella</i> newborn or muscle larva.