Part II: Planarian Stem Cells
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|iBiology Archives: Alejandro Sánchez Alvarado iBioSeminar (2007)|
Planarians are free-living flatworms best known for their amazing ability to regenerate. They also “shrink”, by losing cells, during starvation. In his first lecture, Dr. Sánchez Alvarado discusses the intrinsic problems of scale and proportion that face planarians during growth and regeneration. How do these organisms increase and decrease their cell number without perturbing the functionality of the different tissues? How do they regenerate a specific organ and how does it integrate and function properly? By performing an RNAi screen of the planarian pharynx, Sánchez Alvarado and his lab were able to identify genes required for different steps in these complex processes.
In his second video, Sánchez Alvarado focuses on planarian stem cells called neoblasts. By identifying genetic markers for each stage of stem cell differentiation (pre, early, late and terminal differentiation), Sánchez Alvarado’s lab was able to show that neoblasts are truly totipotent, giving rise to all cell types. Surprisingly, they also demonstrated for the first time that planarian neoblasts undergo acentriolar mitosis, a process previously known to occur only during meiotic cell division in animals.
Scientists, influenced by grants and resources, are focusing their studies on a small number of model organisms. Sánchez Alvarado argues that the diverse array of understudied organisms could provide us with insights into previously unknown biological processes. By comparing excretory pathways, Sánchez Alvarado has demonstrated extensive similarities between vertebrate kidneys and planarian protonephridia. In fact, mutations that cause human polycystic kidney disease induce similar pathologies in planarians. These findings reflect on the ability of non-traditional model organisms to provide insight into biology and human disease.
Dr. Alejandro Sánchez Alvarado is an Investigator at the Stowers Institute for Medical Research in Kansas City, MO and the Howard Hughes Medical Institute. He is also co-director of the summer course on embryology at the Marine Biological Laboratory in Woods Hole, MA.
Sánchez Alvarado moved from Venezuela and received his Bachelor’s degree in Molecular Biology and Chemistry from Vanderbilt University and his Ph.D. in Pharmacology and Cell Biophysics from the University of Cincinnati School of Medicine. In 1994, he joined the laboratory of Dr. Donald D. Brown at the Carnegie Institution of Washington, Department of Embryology as a postdoctoral fellow and in 1995 was appointed Staff Associate. It was during this period that Sánchez Alvarado began to explore systems in which to molecularly dissect the problem of regeneration. From 2002-2011, Sánchez Alvarado was a faculty member in the Department of Neurobiology and Anatomy at the University of Utah School of Medicine. Today his lab uses planarians to explore the processes that govern regeneration. He is interested in the molecular mechanisms by which this organism keeps the integrity of its different tissues during the process of regeneration and growth.
Sánchez Alvarado was the recipient of a Merit Award from the National Institutes of Health and the E.E. Just Award from the American Society for Cell Biology and he was a Kavli Fellow of the National Science Foundation. Sánchez Alvarado was elected to the American Academy of Arts and Sciences in 2015.
- Alejandro Sánchez Alvarado’s iBioEducation: Staying Young
- Peter Reddien's iBioEducation: Regeneration
Carolyn E. Adler and Alejandro Sánchez Alvarado (2015). Types or States? Cellular Dynamics and Regenerative Potential. Trends in Cell Biology, 25: 687–696. http://www.ncbi.nlm.nih.gov/pubmed/26437587
Carolyn E. Adler, Chris W. Seidel, Sean McKinney and Alejandro Sánchez Alvarado (2014). Selective amputation of the pharynx identifies a FoxA-dependent regeneration program in planaria. eLife 3. http://www.ncbi.nlm.nih.gov/pubmed/24737865
Hanh Thi-Kim Vu, Jochen C. Rink, Sean A. McKinney, Melainia McClain, Naharajan Lakshmanaperumal, Richard Alexander and Alejandro Sánchez Alvarado (2015). Stem cells and fluid flow drive cyst formation in an invertebrate excretory organ. eLife 4. http://www.ncbi.nlm.nih.gov/pubmed/26057828
Alejandro Sánchez Alvarado and Shinya Yamanaka (2014). Rethinking differentiation: stem cells, regeneration, and plasticity. Cell, 157:110-9. http://www.ncbi.nlm.nih.gov/pubmed/24679530