Here is the final part of my meeting report on the BSDB-BSCB Spring Conference this April in Warwick. In the first part, I covered some of the talks on transcriptional regulation, and in part two I gave a brief overview on recent attempts to decipher large-scale transcription factor networks. In this final part I will touch on several seemingly unrelated subjects, which reflects how difficult it was for us developmental biologists to make choices between some of the parallel sessions: the BSCB’s stem cell sessions and the BSDB’s limb development and “evo-devo” sessions.
In one of the stem cell sessions, Austin Smith (Centre for Stem Cell Research, Cambridge, UK) emphasized the artificial nature of cultured embryonic stem (ES) cells and how the previously empirically determined requirements to maintain these cells do not reflect minimal requirements. Supply of these factors, such as specific sera, might even be counterproductive in maintaining the pluripotent state, since they contain many inductive stimuli. His lab has established that specific inhibition of the MEK/ERK cascade and GSK3 simultaneously is sufficient to provide optimal conditions for ES cell derivation and maintenance from all mouse strains and even from rats.
Kevin Eggan (Harvard University, USA) and his group have succeeded in reprogramming skin cells of patients suffering from either inherited or sporadic instances of Amyotrophic Lateral Sclerosis (ALS) into pluripotent stem cells. They were then able to differentiate these patient-specific induced pluripotent stem (iPS) cells into spinal motor neurons and glia, the cell types affected in the disease. Now they are comparing the behavior of these cells to that of the corresponding cell types generated from skin cells of healthy individuals, attempting to uncover the molecular mechanisms underlying ALS.
Of the limb development session I will only cover Richard Behringer‘s (University of Texas, Houston, USA) talk, since I did a bit of session hopping at that time. He presented their work on forelimb development in the bat, where they identified Paired-related homeobox 1 (Prx1) as a promising candidate underlying limb diversification between mouse and bat. In mice, they replaced the Prx1 enhancer with that of the bat, and observed a significant increase in both the length of the forelimb and the levels of Prx1 mRNA. In the second part of his talk, Behringer described their experiments in which they expressed a human HoxB1-9 transgene in a HoxB1-9 knockout mouse. This resulted in almost complete rescue of the knockout phenotype. Interestingly, the presence of the human transgene had a dominant effect in either wildtype or mutant mice: Only 5 sacral vertebrae rather than 6 formed, which might be the result of a shift of the expression boundary of HOXB9 in human compared to the mouse.
After first making a case for the need of new model organisms by presenting his group’s work on germline formation in the beach hopper Parhyale hawaiensis, Nipam Patel (University of California, Berkeley, USA) described how he has been using Google’s search engine to collect about 3000 examples of mosaic butterfly gynandromorphs, which show regions of both male and female characteristic patterns in the same wing. He observed that these naturally occurring clones do not cross a certain boundary, which is distinct from the boundary separating the classical anterior and posterior compartments defined in Drosophila. They were able to experimentally trace the origin of this unexpected compartment back to embryonic development. This so-called S compartment is also present in Drosophila, albeit in a very thin line. The studies Patel presented demonstrated how much there still is to learn in developmental evolution, and how the usage of unconventional model organisms can unmask unknown processes, which might be more concealed in our traditional systems.
Kristin Tessmar-Raible (University of Vienna, Austria) presented the unusual organism and topic her team works on: They use the annelid worm Platynereis dumerilii to study lunar rhythms, which synchronize spawning in these animals. In a series of experiments using entrainment and expression profiling of candidate genes, they identified the core set of genes of the lunar clock. Interestingly, the circadian and lunar clocks seem to regulate the same subsets of genes. A group of photosensory-neurosecretory cells of the inner medial forebrain of this species has recently been shown to represent the ancient core of vertebrate and invertebrate brains, and Tessmar-Raible’s group is now investigating whether and how these cells are involved in regulating the clocks.
Finally I’d like to mention the BSDB’s Waddington Medal, which is awarded annually at the spring meeting to a developmental biologist for their outstanding research performance and services to the subject community. This year it went to Robin Lovell-Badge (NIMR, London, UK), for his research on sex determination, stem cells and the development of the nervous system. He gave a highly entertaining lecture on the important steps in his life and career, including video coverage from his childhood and pictures of the various cars he has owned over the years.
I thoroughly enjoyed the meeting, especially due to the wide range of subjects it covered. So I’m looking forward to attending next year’s spring meeting, which will be announced here.