Presenter 5: Manuela D Alessandro. University of Strasbourg, France

Presenter 5: Manuela D’Alessandro. University of Strasbourg, France

Dr. Manuela D'Alessandro comes from Italy, she studied in Bologna where she gained her PhD after one year spent in Canada. She is now working as a postdoctoral researcher in Strasbourg at the IGBMC in the lab. of J. Laporte whose lab main topic is the study of Centronuclear myopathy (CNM).

There are 3 forms of CNM: X-linked, Autosomal (Dominant and Recessive). CNM are characterized by muscle weakness and typical skeletal muscle biopsies showing small rounded fibers and nuclei located at the center of the cell, while in control muscles the nuclei are located at the periphery of the cell. Each organism is made of cells, each cell hosts a nucleus and finally chromosomes are inside the nucleus. Chromosomes are made of a long filament of DNA containing all the genetic information to build the full human body. Indeed the DNA contains the information to make proteins. Our hair, our nails, our skin, our blood, our enzymes and hormones are proteins; indeed, our bodies contain some ten thousand to fifty thousand kinds of proteins. Mutations in the DNA sequence can produce mutation in the protein structure and this can affect their function. This event can lead to disease state.

Several proteins are mutated in CNM and include: myotubularin, amphyphisin and dynamin. These proteins are located at least in part at the cell membranes, inserted in the lipid bilayer, which is the external envelope that contains the cell. The goal of the study is to understand how mutations in proteins located on cell membranes can affect the position of the nucleus inside the cell. To achieve this target Dr. Manuela D’Alessandro is using the fact that most of the human genes are also found in model organisms used in research laboratories, and her experimental approaches include biochemical and genetic experiments.

Among the different model organism available in research (dogs, mice, fishes, flies, nematodes) she is using C. elegans: transparent nematode (roundworm) of the soil, about 1 mm in length. The use of worms presents different advantages: they are easy to grow, not pathogenic and have a short lifecycle. In addition, these animals are self-fertilising and they can be kept alive frozen. Worms are suitable to all the experiments usually done in the laboratories. Even if worms appear very different from human, they both share 50% of their genes. It is possible to introduce fluorescent markers in the worms to highlights membranes and nucleus enabling clear assessment of the defects of nuclei positioning. To date, three Nobel prizes in Physiology, Medicine and Chemistry have been awarded to researchers using C. elegans.

The most important is that all the CNM genes are present in worms and that worm mutants are also available for the three CNM proteins. In worms, mutations in CNM proteins cause nuclear misplacement, alike in patient muscles. This defect can be quantified and characterized by using CLEM (Correlative Light Electron Microscopy). This technique is used to correlate the defects observed in the animal with the ultra-structural component in its cells.

Pharmacological tests are long-term targets of the funded project: molecules effective on nematodes (molecules that are able to rescue the nuclear mis-positioning ) will be validated in our mice CNM models; this might open the way to develop drugs effective in CNM patients.

Q1: How to select drugs for tests? A1: Commonly scientists use ‘kits’ which contain molecules synthesized by chemical companies. Those molecules will be given to the worms, nuclei positioning will be monitored with different microscopy techniques, and the drugs that give satisfaction will be then tested on mice to confirm their efficacy