Little big fly
In this photo taken by Cristina Morera Albert, of the CMRB, a house fly is observed with a scanning electron microscope (SEM). This type of microscope uses electrons and electromagnetic lenses to “illuminate” a sample allowing visualising the sample in 3D at high magnification.
In this case, we observe the compound eyes of the fly and its thorax, which is divided into three segments: prothorax, mesothorax and metathorax. The thorax is covered by hairs called bristles, which are always arranged in the same place and have a sensory function. One can also see the wings, which protrude from the second segment, with their nerves.
Cristina Eguizabal came from Cambridge, UK, to the CMRB two and a half years ago to try to get male haploid cells (spermatozoids) from human pluripotent stem cells. She uses both human embryonic cells (hES) and induced pluripotent stem cells (iPS). The first are obtained through fertility clinics from unused fertilised embryos. The hES are isolated from the embryos and derived into cell lines at the Stem Cell Bank of the CMRB, on the 4th floor of the PRBB, where Eguizabal is working under the coordination of Anna Veiga. iPS cells, on the other hand, can be derived in vitro from skin cells or cord blood, as was shown recently, although the protocol is not optimal and these cells are not yet safe for clinical use.
Once she has the pluripotent stem cells in culture, Eguizabal tries to find the best conditions to differentiate them into primordial germ cells (PGC), which can then give rise to the spermatozoids or oocytes. What would be the practical applications of this, if it works?
Giving hope to parents
The simplest would be to allow people who are sterile to have children with their genetic characteristics. Currently, a sterile man depends upon anonymous semen donations to have a child. With this technique, a simple skin biopsy could lead to the creation of his own iPS cells, which would be differentiated in vitro into PGCs and which would give rise to sperm with his DNA which could be used in “in vitro fertilisation” (IVF) to have his child.
Another related application would be to allow people to have children free of a genetic disease which they themselves suffer. In this case, the procedure would be the same, but once the iPS cells were obtained, their genetic error would be corrected. This would be possible for well-studied monogenic diseases, caused by a single gene, such as cystic fibrosis or Duchene muscular dystrophy.
Many steps to go
“This won’t be happening for 10 or 15 years”, predicts Eguizabal. “Apart from the step I am working on, the differentiation of the iPS cells into PGCs, of which very little is known, all the other steps in the process need more research. For example, deriving the iPS cells from skin cells needs to become safer, as at the moment one of the genes included in this transformation is an oncogene, which could lead to cancer. The genetic correction of the iPS cells is also something people are working hard on”, continues the researcher. Both of these issues are also studied at the CMRB.
The differentiation of stem cells into sexual gametes, spermatozoids and oocytes, is the most difficult, much more so than getting stem cells to become neurones or cardiovascular cells, according to the Basque biologist. “First of all, the sexual gametes are the only cells that go through meiosis, a type of cell division that implies losing half of your genome. And secondly, their aim is to give rise to a living being, so their genetic and epigenetic information must be 100% correct”, she says. During normal physiology, germ cells suffer a huge epigenetic re-programming: their whole genome is methylated and de-methylated again. Methylation is a reversible modification of the DNA which affects gene expression. And in order to get functional gametes, it is important to reproduce this methylation in vitro. But it is not easy. Eguizabal plans to use molecular techniques such as bisulphite sequencing to check the methylation status of the DNA once she gets the cells she is interested in.
This article was published in the El·lipse publication of the PRBB.
An interview recently published in Ellipse, the monthly magazine of the PRBB.
Hermann Bujard was from 2007 until 2009 the director of the European Molecular Biology Organisation (EMBO), which started 45 years ago with 13 member states and now has now up to 27. Bujard has worked both in academia and in industry, having also been scientific director at Hoffmann La Roche. Now currently working on malaria, he visited the PRBB and told us about his vision of science.
EMBO has played an important role in the development of modern life sciences in Europe. We identify and support postdoctoral fellows and young group leaders around the world, and we organise meetings and publish some journals. We only have an annual budget of only 16 million €, but we offer quality and support to individuals. We have created a network of excellence throughout Europe: if you look at the CV of any high quality life scientist in Europe, at some period in their career they will have been involved with EMBO. And this network leads to many cross-border collaborations.
What is the situation regarding female researchers?
This is a long-standing issue at EMBO, and a difficult one. More than 50% of students are female, while at the senior level women occupy only 15% of the positions. I think the research careers are such that we select against very precious good and original people, not only women but also men. It’s a very tough The competition is very tough, and by the time you get a 5-year position you are 37 and you might want to have a family, but you still have a lot of insecurity and a low salary. In addition you have the publishing pressure. Many women who would be very capable scientists just don’t want to go down this road. And we have to think whether we can afford to lose 50% of our creative brains.
What is the solution?
I think that we should look at the whole career of the person and not only their publications. At the moment, we select people who publish a lot, but they normally do mainstream research. and these usually do research on the main stream. There are researchers that are good and original thinkers and may publish only one paper every two years, but each of them is a seminal piece of work. And yet, we select against them. We are too much success-oriented in the short-term. Instead, we should ask the applicants for their four best papers, read them and decide if the person has good ideas.
What has changed in European science in the last 15 years?
Spain is my favourite country to exemplify that change. 15 years ago people from Spain only applied for fellowships to leave, while today many people apply to come to the new centres of excellence in Madrid or Barcelona, and not only Spaniards, but people from the UK or America. And this is a success of structure: highly valued scientists have introduced a critical mass of people working together in a departmental structure which is very good for small and young independent groups.
For example, what you have established here at the PRBB is very close to how things should work. The founders of the park created a spirit that can be seen in the way people behave. When you select very good group leaders, you get good postdocs, good students. And good people are not shy, they communicate, are open to discussion. I think this atmosphere exists here.
Breaking the difraction barrier
In this pseudocolored image by Gemma Perez from the UPF, we can observe the improvement in resolution of Stimulated Emission Depletion (STED) microscopy (right), compared with confocal microscopy (left).
STED is one of the recently developed super-resolution methods that have broken the diffraction limit in light microscopy, and the CRG/UPF Advanced Light Microscopy Unit has one of the only two STED systems currently available in Spain.
The dots in the image show the distribution of PatL1, a component of Processing Bodies (PB), dynamic cytoplasmatic granules that are conserved among eukaryotes. PBs are too small and sometimes are in too close vicinity to be properly rendered by confocal imaging, which has a maximal resolution of 200 nm. In contrast, STED microscopy, capable of resolving distances of <80 nm, can show more details of their sizes and distribution (bar= 1 µm).