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… Continue Reading