Person
Poole, Richard
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Biography and Research Interest
I am currently in the fourth year of a Ph.D. at University College London with Steve Wilson. I hold a B.Sc., First Class in Biology with European Studies (French) from the University of Sussex and I am researching into the upstream regulators of Eph/ephrin signalling and the control of segmentation during zebrafish development.
The upstream regulators of ephrin-B2a and ephrin-B2b:
In zebrafish, as in all vertebrates, development requires the formation of a metameric body plan along the anterior-posterior (A/P) axis. In the embryo, this is most evident in the appearance of segmentally arranged somites1. We have been studying the role of Eph receptor tyrosine kinases and their ligands the Ephrins in somitogenesis. ephA4 and ephrinB2a have a segmental expression pattern in the PSM and intact Eph/ephrin signalling is required for somite furrow formation2. The experimental evidence to date suggests that establishment of A/P interfaces within the PSM is a prerequisite to somite boundary formation.
It is becoming increasingly clear that the elaboration of a segmental production of somites is controlled by a clock and wavefront type mechanism requiring Notch signalling and cycling her1 expression in the PSM 1. This mechanism is likely also to be responsible for the restriction of gene expression into A or P compartments of the presumptive somite. However the molecular nature of the link between the genes that establish A/P patterning and the expression of EphA4 and ephrinB2a is unknown.
We would like to find direct upstream regulators of genes with restricted A and P expression such as EphA4 and ephrinB2a. One approach to achieve this has been to identify novel cDNAs expressed within the PSM. We generated a subtractive library enriched for clones expressed in the PSM. Of 127 clones screened to date 10 clones show specific expression patterns. Two new zebrafish genes from the library are expressed in the PSM. Using mis-expression and morpholino knock-down approaches we find that both genes have a role in mesoderm specification and somitogenesis. Clone 609 appears to be required for correct A:P patterning of the somites downstream of the segmentation clock and may have a role in somite furrow formation and epithelialisation. We find that clone 624 appears to act earlier during mesoderm specification and has a role in the convergent extension movements that occur during zebrafish gastrulation. We are further analysing these and other interesting clones using mis-expression approaches in Eph/ephrin-GFP transgenic lines and using morpholino and transplantation studies.
A second approach has been to try and identify promoter and enhancer elements upstream of ephrinB2a and ephrinB2b. We are now try ing to identify conserved transcription factor binding sites within these elements and to generate transgenic lines expressing GFP under the control of these elements to use as tool to screen for direct upstream regulators.
1. Pourquie, O. Vertebrate somitogenesis. Annu. Rev. Cell Dev. Biol. 17, 311-50 (2001).
2. Durbin, L. et al. Eph signalling is required for segmentation and differentiation of the somites. Genes and Development 12, 3096-3109 (1998).
The upstream regulators of ephrin-B2a and ephrin-B2b:
In zebrafish, as in all vertebrates, development requires the formation of a metameric body plan along the anterior-posterior (A/P) axis. In the embryo, this is most evident in the appearance of segmentally arranged somites1. We have been studying the role of Eph receptor tyrosine kinases and their ligands the Ephrins in somitogenesis. ephA4 and ephrinB2a have a segmental expression pattern in the PSM and intact Eph/ephrin signalling is required for somite furrow formation2. The experimental evidence to date suggests that establishment of A/P interfaces within the PSM is a prerequisite to somite boundary formation.
It is becoming increasingly clear that the elaboration of a segmental production of somites is controlled by a clock and wavefront type mechanism requiring Notch signalling and cycling her1 expression in the PSM 1. This mechanism is likely also to be responsible for the restriction of gene expression into A or P compartments of the presumptive somite. However the molecular nature of the link between the genes that establish A/P patterning and the expression of EphA4 and ephrinB2a is unknown.
We would like to find direct upstream regulators of genes with restricted A and P expression such as EphA4 and ephrinB2a. One approach to achieve this has been to identify novel cDNAs expressed within the PSM. We generated a subtractive library enriched for clones expressed in the PSM. Of 127 clones screened to date 10 clones show specific expression patterns. Two new zebrafish genes from the library are expressed in the PSM. Using mis-expression and morpholino knock-down approaches we find that both genes have a role in mesoderm specification and somitogenesis. Clone 609 appears to be required for correct A:P patterning of the somites downstream of the segmentation clock and may have a role in somite furrow formation and epithelialisation. We find that clone 624 appears to act earlier during mesoderm specification and has a role in the convergent extension movements that occur during zebrafish gastrulation. We are further analysing these and other interesting clones using mis-expression approaches in Eph/ephrin-GFP transgenic lines and using morpholino and transplantation studies.
A second approach has been to try and identify promoter and enhancer elements upstream of ephrinB2a and ephrinB2b. We are now try ing to identify conserved transcription factor binding sites within these elements and to generate transgenic lines expressing GFP under the control of these elements to use as tool to screen for direct upstream regulators.
1. Pourquie, O. Vertebrate somitogenesis. Annu. Rev. Cell Dev. Biol. 17, 311-50 (2001).
2. Durbin, L. et al. Eph signalling is required for segmentation and differentiation of the somites. Genes and Development 12, 3096-3109 (1998).
Non-Zebrafish Publications