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<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.

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Title page, table of contents and summary only. The complete thesis in print form is available from the University of Adelaide Library. / The Acidic Rich family of RS Domain proteins (ARRS) is defined by both the presence and arrangement of conserved domains within 2 family members. Conserved regions include an RS domain, zinc finger domain, RNA binding motif and a C terminal acidic rich region. Two conserved motifs within the RRM of ARRS proteins have been defined that are not found in the RRM of other RNA binding proteins. Peri implantation stem cell 1 (pscl), the founding member of this family, was originally identified as a developmental marker differentially expressed between the Inner Cell Mass and primitive ectoderm of the mammalian embryo. Psc1 RNA is differentially up-regulated in the post gastrulation embryo and the adult, with high mRNA levels in lung, brain and kidney, and low level expression in other tissues. Comparative analysis of Psc1 to RS domain proteins known to function in mRNA processing, such as SC35 and ASF/SF2, has shown it colocalises to characteristic nuclear speckles. However, in contrast to SR proteins, Pscl localises to additional regions in the nucleus, not containing SR proteins, and to punctate regions in the cytoplasm termed cytospeckles. Further, in the absence of transcription, Psc 1 localises to regions in the nucleus which exclude nuclear speckles. Finally, unlike SC35 and ASF/SF2, which move rapidly in and out of nuclear speckles, FRAP assays show Psc1 is tethered within the nucleus. Analysis of Psc1 domain contribution to subcellular localisation and mobility shows the RRM to be both necessary and sufficient for Psc 1 cytospeckle localisation and is responsible for the nuclear tethering of Pscl. The RS domain of Pscl acts as a nuclear localisation signal and contributes to nuclear speckle localisation. The C terminal of Psc I localises with microtubules and is proposed to mediate Psc 1 cytoskeletal association. The expression of the Drosophila acidic rich RS domain protein (NP609976) is developmentally regulated in the same manner as Pscl, it has a nuclear localisation profile identical to Psc 1 and also localises to speckles in the cytoplasm, all of which support a conserved evolutionary role for Pscl and the ARRS protein family in mRNA processing and trafficking both in the nucleus and in the cytoplasm. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1236604 / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2006

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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.

Hybridization is thought to have played an important role in human evolution, with hybridizing groups having significant differences in soft tissue trait variation. Ectodermal trait variation is of interest because primate hybrids show increased atypical non-metric dental and cranial trait variation thought to be the result of interactions between parental genomes which have diverged for ectodermal trait development (including hair and tooth development). There were also differences between hybridizing hominin groups for limb measurements which have changed significantly throughout human evolution. Here a mouse model is used to look at the effect of hybridization on coat morphology and long bone length. Using standardized photographs, the differences in mean RGB values for the dorsal and ventral coat were used to determine whether the hybrids were different from their parents for pelage colour of different regions of the body, dorsal ventral colour contrast, and levels of variation in coat colour. The sample is composed of parents from one specific and three sub-specific crosses, as well as F1, F2 and first generation backcrossed (B1) hybrids. Long bone measurements of the forelimbs and hind-limbs were collected from micro-CT scans of the sub-specific F1 hybrids and their parents. Previous data have shown that hybridization can have variable morphological outcomes: hybrids can look like one of the parents, they can be intermediate, or they can have extreme traits outside of the range of variation of the parents. Our results indicate that morphological outcomes for coat colour in F1 hybrids depends on factors such as genetic distance. However, the genetic background of one of the strains used for this experiment might contribute the transgressive phenotype of some of the F1 hybrids. Hybrid morphology also changes in subsequent generations (F2 and B1) as new recombinants formed, with transgressive coat colour phenotypes sometimes appearing even if they are not present in the F1 hybrid groups. Phenotypes produced in F1 hybrids are also seen in subsequent generations of hybrids. All sub-specific F1 hybrids were transgressive for long bone length. Compared to parental groups hybrids have a different relationship between the long bones of the forelimb (ratio of humerus to ulna). This is in line with previous data from primate hybrids, that shows that changes in the relationships between different regions of the body occurs in hybrids producing novel phenotypes. The inter-membral indexes are not significantly different from one of the parents for two of the crosses. This data shows that hybridization can produce novel pelage phenotypes over multiple generations. There were many transitions in hair/skin morphology during human evolution and these tissue groups were and are under a great deal of selective pressure due to their direct interaction with the environment. Thus, understanding how these traits are impacted by hybridization will be important for disentangling how hybridization affected our evolutionary trajectory and ability to occupy new regions of the world. Post cranial data, indicates that F1 hominin hybrids might have longer limbs in relation to parental populations, more work needs to be done on the post cranial remains of posited hominin hybrids as well as pedigreed mammalian hybrids to determine if this is a pattern which can be used to identify hybrids in the fossil record.