{"id":{"repo_id":"oxford-brookes","oai_identifier":"tle:566bc3ea-8840-482f-b3d7-b8fc0e2a173d:d6bd9758-527a-46cd-bfe2-c433766e8fca:1"},"canonical_url":"https://search.dev.ndltd.org/etd/oxford-brookes/tle:566bc3ea-8840-482f-b3d7-b8fc0e2a173d:d6bd9758-527a-46cd-bfe2-c433766e8fca:1","repository":{"repo_id":"oxford-brookes","name":"Oxford Brookes University","base_url":"https://radar.brookes.ac.uk/radar/oai"},"display":{"title":"Developmental dynamics of posterior segment addition in the spider Parasteatoda tepidariorum","abstract":"Segmentation generates repetitive units along the anterior–posterior axis during embryogenesis. It is thought that this modularity facilitated diversification of the body plan, making segmentation an evolutionarily advantageous trait. Arthropods exhibit diverse segmentation modes, ranging from the near-simultaneous formation of segments in Diptera within a syncytium to the sequential addition of segments after cellularisation in most other arthropods. Although the evolution of these mechanisms remains unclear, a set of pair-rule genes (PRGs), regulated by Wnt signalling and the transcription factor Caudal, appear to be central to arthropod segmentation. My project investigated the genetic and cellular regulation of segment addition in an early-branching arthropod, the spider, Parasteatoda tepidariorum. To investigate PRG expression in P. tepidariorum, I analysed Pt-evenskipped (eve), Pt-odd skipped (odd), Pt-hairy (h), Pt-paired (prd), and their duplicates where present. Pt-eve and selected duplicates of Pt-h and Pt-prd exhibited segmentation-relevant expression patterns, whereas no Pt-odd transcripts were detected in the segment addition zone (SAZ). Pairwise in situ comparisons of PRG expression allowed me to assay the PRG register of P. tepidariorum during early and late segmentation, highlighting similarities and differences with other arthropods. To further examine the regulation of segmentation in this spider, I generated polyclonal antibodies against Pt-Cad and Pt-Wnt8, and tested a Pax3/7 antibody from Davis and Patel, which recognises Prd protein across arthropods. The Pt-Cad antibody detected Pt-Cad protein in the SAZ at stage 6, but signal intensity was insufficient for extended analysis. The anti–Pt-Wnt8 antibody did not yield detectable staining. In contrast, the Pax3/7 antibody successfully detected Pt-Prd2 in situ, enabling comparative analysis of Pt-prd2 mRNA and protein expression. Protein distribution was broader than the corresponding mRNA domain, lagging posteriorly. The relative expression of mRNA and protein changed from posterior to anterior during segment formation. The shift suggested that the PRG register using mRNA alone may be misleading, and a comparison of Pt-eve mRNA with Pt-prd2 protein showed Pt-Prd2 protein overlapped with Pt-eve mRNA, prompting a revised interpretation of the PRG register in both early and late segmentation. To gain an unbiased, cellular-resolution view of segmentation, I examined marker genes from three single-cell RNA sequencing (scRNA-seq) clusters annotated previously. Nine genes were assessed and compared to established segmentation markers. Parental RNA interference of Pt-g30822 revealed a striking phenotype: embryos developed grossly enlarged opisthosomas with irregular surfaces and delayed limb-bud formation on the fourth leg-bearing segment, although opisthosomal segmentation proceeded. These results suggest that there are three cell states during opisthosomal segmentation: (1) the SAZ, a posterior segmentation organiser; (2) the segment maturation zone, where segments are defined and initiate patterning and differentiation; and (3) the mesoderm, which has an undetermined role. Overall, my project consolidated P. tepidariorum as a comparative model and advanced our understanding of the genetic and cellular basis of segmentation.","abstract_html":"Segmentation generates repetitive units along the anterior–posterior axis during embryogenesis. It is thought that this modularity facilitated diversification of the body plan, making segmentation an evolutionarily advantageous trait. Arthropods exhibit diverse segmentation modes, ranging from the near-simultaneous formation of segments in Diptera within a syncytium to the sequential addition of segments after cellularisation in most other arthropods. Although the evolution of these mechanisms remains unclear, a set of pair-rule genes (PRGs), regulated by Wnt signalling and the transcription factor Caudal, appear to be central to arthropod segmentation. My project investigated the genetic and cellular regulation of segment addition in an early-branching arthropod, the spider, Parasteatoda tepidariorum. To investigate PRG expression in P. tepidariorum, I analysed Pt-evenskipped (eve), Pt-odd skipped (odd), Pt-hairy (h), Pt-paired (prd), and their duplicates where present. Pt-eve and selected duplicates of Pt-h and Pt-prd exhibited segmentation-relevant expression patterns, whereas no Pt-odd transcripts were detected in the segment addition zone (SAZ). Pairwise in situ comparisons of PRG expression allowed me to assay the PRG register of P. tepidariorum during early and late segmentation, highlighting similarities and differences with other arthropods. To further examine the regulation of segmentation in this spider, I generated polyclonal antibodies against Pt-Cad and Pt-Wnt8, and tested a Pax3/7 antibody from Davis and Patel, which recognises Prd protein across arthropods. The Pt-Cad antibody detected Pt-Cad protein in the SAZ at stage 6, but signal intensity was insufficient for extended analysis. The anti–Pt-Wnt8 antibody did not yield detectable staining. In contrast, the Pax3/7 antibody successfully detected Pt-Prd2 in situ, enabling comparative analysis of Pt-prd2 mRNA and protein expression. Protein distribution was broader than the corresponding mRNA domain, lagging posteriorly. The relative expression of mRNA and protein changed from posterior to anterior during segment formation. The shift suggested that the PRG register using mRNA alone may be misleading, and a comparison of Pt-eve mRNA with Pt-prd2 protein showed Pt-Prd2 protein overlapped with Pt-eve mRNA, prompting a revised interpretation of the PRG register in both early and late segmentation. To gain an unbiased, cellular-resolution view of segmentation, I examined marker genes from three single-cell RNA sequencing (scRNA-seq) clusters annotated previously. Nine genes were assessed and compared to established segmentation markers. Parental RNA interference of Pt-g30822 revealed a striking phenotype: embryos developed grossly enlarged opisthosomas with irregular surfaces and delayed limb-bud formation on the fourth leg-bearing segment, although opisthosomal segmentation proceeded. These results suggest that there are three cell states during opisthosomal segmentation: (1) the SAZ, a posterior segmentation organiser; (2) the segment maturation zone, where segments are defined and initiate patterning and differentiation; and (3) the mesoderm, which has an undetermined role. Overall, my project consolidated P. tepidariorum as a comparative model and advanced our understanding of the genetic and cellular basis of segmentation.","abstract_has_math":false,"creators":["Blakeley, Grace Elizabeth"],"institution":"Oxford Brookes University","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["McGregor, Alistair","Blakeley, Grace"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":null,"date_issued":"","date_published":null,"updated_at":"2026-07-24T03:42:14Z","subjects":[],"languages":["en"],"rights":["All rights reserved"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.24384/wbtg-9c17","outbound_label":"DOI","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["McGregor, Alistair","Blakeley, Grace"]},{"key":"dc:creator","label":"Author","values":["Blakeley, Grace Elizabeth"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:publisher","label":"Institution","values":["Oxford Brookes University"]},{"key":"dc:type","label":"Dc Type","values":["thesis"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["All rights reserved"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://doi.org/10.24384/wbtg-9c17","https://radar.brookes.ac.uk/radar/file/566bc3ea-8840-482f-b3d7-b8fc0e2a173d/1/Blakeley2025PosteriorSegmentAddition.pdf","https://radar.brookes.ac.uk/radar/file/566bc3ea-8840-482f-b3d7-b8fc0e2a173d/1/Grace Blakeley_Declaration Form.pdf"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Segmentation generates repetitive units along the anterior–posterior axis during embryogenesis. It is thought that this modularity facilitated diversification of the body plan, making segmentation an evolutionarily advantageous trait. Arthropods exhibit diverse segmentation modes, ranging from the near-simultaneous formation of segments in Diptera within a syncytium to the sequential addition of segments after cellularisation in most other arthropods. Although the evolution of these mechanisms remains unclear, a set of pair-rule genes (PRGs), regulated by Wnt signalling and the transcription factor Caudal, appear to be central to arthropod segmentation. My project investigated the genetic and cellular regulation of segment addition in an early-branching arthropod, the spider, Parasteatoda tepidariorum. To investigate PRG expression in P. tepidariorum, I analysed Pt-evenskipped (eve), Pt-odd skipped (odd), Pt-hairy (h), Pt-paired (prd), and their duplicates where present. Pt-eve and selected duplicates of Pt-h and Pt-prd exhibited segmentation-relevant expression patterns, whereas no Pt-odd transcripts were detected in the segment addition zone (SAZ). Pairwise in situ comparisons of PRG expression allowed me to assay the PRG register of P. tepidariorum during early and late segmentation, highlighting similarities and differences with other arthropods. To further examine the regulation of segmentation in this spider, I generated polyclonal antibodies against Pt-Cad and Pt-Wnt8, and tested a Pax3/7 antibody from Davis and Patel, which recognises Prd protein across arthropods. The Pt-Cad antibody detected Pt-Cad protein in the SAZ at stage 6, but signal intensity was insufficient for extended analysis. The anti–Pt-Wnt8 antibody did not yield detectable staining. In contrast, the Pax3/7 antibody successfully detected Pt-Prd2 in situ, enabling comparative analysis of Pt-prd2 mRNA and protein expression. Protein distribution was broader than the corresponding mRNA domain, lagging posteriorly. The relative expression of mRNA and protein changed from posterior to anterior during segment formation. The shift suggested that the PRG register using mRNA alone may be misleading, and a comparison of Pt-eve mRNA with Pt-prd2 protein showed Pt-Prd2 protein overlapped with Pt-eve mRNA, prompting a revised interpretation of the PRG register in both early and late segmentation. To gain an unbiased, cellular-resolution view of segmentation, I examined marker genes from three single-cell RNA sequencing (scRNA-seq) clusters annotated previously. Nine genes were assessed and compared to established segmentation markers. Parental RNA interference of Pt-g30822 revealed a striking phenotype: embryos developed grossly enlarged opisthosomas with irregular surfaces and delayed limb-bud formation on the fourth leg-bearing segment, although opisthosomal segmentation proceeded. These results suggest that there are three cell states during opisthosomal segmentation: (1) the SAZ, a posterior segmentation organiser; (2) the segment maturation zone, where segments are defined and initiate patterning and differentiation; and (3) the mesoderm, which has an undetermined role. Overall, my project consolidated P. tepidariorum as a comparative model and advanced our understanding of the genetic and cellular basis of segmentation."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Developmental dynamics of posterior segment addition in the spider Parasteatoda tepidariorum"]}]}],"canonical_facts":{"dc:contributor":["McGregor, Alistair","Blakeley, Grace"],"dc:creator":["Blakeley, Grace Elizabeth"],"dc:description":["Segmentation generates repetitive units along the anterior–posterior axis during embryogenesis. It is thought that this modularity facilitated diversification of the body plan, making segmentation an evolutionarily advantageous trait. Arthropods exhibit diverse segmentation modes, ranging from the near-simultaneous formation of segments in Diptera within a syncytium to the sequential addition of segments after cellularisation in most other arthropods. Although the evolution of these mechanisms remains unclear, a set of pair-rule genes (PRGs), regulated by Wnt signalling and the transcription factor Caudal, appear to be central to arthropod segmentation. My project investigated the genetic and cellular regulation of segment addition in an early-branching arthropod, the spider, Parasteatoda tepidariorum. To investigate PRG expression in P. tepidariorum, I analysed Pt-evenskipped (eve), Pt-odd skipped (odd), Pt-hairy (h), Pt-paired (prd), and their duplicates where present. Pt-eve and selected duplicates of Pt-h and Pt-prd exhibited segmentation-relevant expression patterns, whereas no Pt-odd transcripts were detected in the segment addition zone (SAZ). Pairwise in situ comparisons of PRG expression allowed me to assay the PRG register of P. tepidariorum during early and late segmentation, highlighting similarities and differences with other arthropods. To further examine the regulation of segmentation in this spider, I generated polyclonal antibodies against Pt-Cad and Pt-Wnt8, and tested a Pax3/7 antibody from Davis and Patel, which recognises Prd protein across arthropods. The Pt-Cad antibody detected Pt-Cad protein in the SAZ at stage 6, but signal intensity was insufficient for extended analysis. The anti–Pt-Wnt8 antibody did not yield detectable staining. In contrast, the Pax3/7 antibody successfully detected Pt-Prd2 in situ, enabling comparative analysis of Pt-prd2 mRNA and protein expression. Protein distribution was broader than the corresponding mRNA domain, lagging posteriorly. The relative expression of mRNA and protein changed from posterior to anterior during segment formation. The shift suggested that the PRG register using mRNA alone may be misleading, and a comparison of Pt-eve mRNA with Pt-prd2 protein showed Pt-Prd2 protein overlapped with Pt-eve mRNA, prompting a revised interpretation of the PRG register in both early and late segmentation. To gain an unbiased, cellular-resolution view of segmentation, I examined marker genes from three single-cell RNA sequencing (scRNA-seq) clusters annotated previously. Nine genes were assessed and compared to established segmentation markers. Parental RNA interference of Pt-g30822 revealed a striking phenotype: embryos developed grossly enlarged opisthosomas with irregular surfaces and delayed limb-bud formation on the fourth leg-bearing segment, although opisthosomal segmentation proceeded. These results suggest that there are three cell states during opisthosomal segmentation: (1) the SAZ, a posterior segmentation organiser; (2) the segment maturation zone, where segments are defined and initiate patterning and differentiation; and (3) the mesoderm, which has an undetermined role. Overall, my project consolidated P. tepidariorum as a comparative model and advanced our understanding of the genetic and cellular basis of segmentation."],"dc:format":["application/pdf"],"dc:identifier":["https://doi.org/10.24384/wbtg-9c17","https://radar.brookes.ac.uk/radar/file/566bc3ea-8840-482f-b3d7-b8fc0e2a173d/1/Blakeley2025PosteriorSegmentAddition.pdf","https://radar.brookes.ac.uk/radar/file/566bc3ea-8840-482f-b3d7-b8fc0e2a173d/1/Grace Blakeley_Declaration Form.pdf"],"dc:language":["en"],"dc:publisher":["Oxford Brookes University"],"dc:rights":["All rights reserved"],"dc:title":["Developmental dynamics of posterior segment addition in the spider Parasteatoda tepidariorum"],"dc:type":["thesis"]},"updated_at":"2026-07-24T03:42:14Z"}