Genomics - Weekly Calendar

Sergey Kryazhimskiy, Harvard, Epistasis and adaptation in yeast
Populations adapt when they encounter new environments, but our ability to predict the course and rate of adaptation are quite limited. A major complication is that we do not know how one mutation might influence the fitness effects of other mutations. In other words, we do not know the structure of epistasis among beneficial mutations. I will describe an experiment that reveals an interesting statistical structure in how adaptive mutations affect each other and discuss the implications of these findings for our ability to predict evolutionary outcomes.
Joseph Henry Room, Jadwin Hall  ·  12:00 p.m.– 1:00 p.m.

Shamil Sunyaev, Harvard Med Sch, Human germ line and somatic mutation rates: evolution, biology and statistical genetics
http://genetics.bwh.harvard.edu/genetics/labs/Sunyaev/index.html

Sequencing technology enabled systematic identification of de novo germ line mutations and somatic mutations in cancer. Mutation rate appears to be variable along the human genome. Replication timing, chromatin accessibility and negative selection maintaining hypermutable sequence contexts all contribute to the mutation rate heterogeneity. The data on somatic mutations suggest that Global Genome Repair (GGR) system is responsible for the dependence of mutation rate on chromatin accessibility. Two evolutionary models may potentially explain the origin of mutation rate heterogeneity. The heterogeneity of mutation rate along the human genome has important consequences for evolutionary genomics and for statistical genetics approaches based on recurrent mutations.

Carl Icahn Lab 101  ·  4:15 p.m.– 5:15 p.m.

Aravinthan Samuel, Harvard FAS, How worms wiggle
http://worms.physics.harvard.edu/

Directed locomotion requires coordinated motor activity throughout an animal’s body. The nematode C. elegans, with only 302 neurons, offers an opportunity to understand how locomotion is organized by an entire motor system. We discovered that the mechanism that organizes undulatory locomotion in C. elegans is a novel form of sensory feedback within the motor circuit. Stretch-sensory feedback simply compels each body segment to bend in the same direction and shortly after the bending of the adjacent anterior segment. Remarkably, the entire sensorimotor loop operates is contained within a single (particularly sophisticated) type of neuron. We used microfluidics, optogenetics, calcium imaging, and modeling to show how stretch-sensory feedback is integrated into the motor circuit and how it explains the propagation of undulatory waves from head to tail. Our results point to a new framework for the organization of swimming and crawling gaits in worm undulatory locomotion.

Carl Icahn Lab 101  ·  4:30 p.m.– 5:30 p.m.