Ricardo Mallarino

Ricardo Mallarino

Special Seminar

Event Date/Location

February 21, 2017 - 12:30 pm
Schultz Laboratory 107

Speaker

  • Ricardo Mallarino

    Harvard University, Hoekstra Lab

    I graduated from Universidad de los Andes in Bogotá, Colombia with a BSc in Biology. Since my sophomore year, I spent my summers working at the Smithsonian Tropical Research Institute (STRI) in Panamá, where I learned basic molecular biology skills and got exposed to a variety of organisms, ranging from seagrasses to marine bivalves and their associated bacterial endosymbionts. After obtaining my BSc, I spent two more years at STRI working with Chris Jiggins and Biff Bermingham in the molecular systematics and phylogenetics of neotropical butterflies. In 2005, I moved to Cambridge, MA to pursue a Ph.D. at Harvard University with Arkhat Abzhanov. In my dissertation, I investigated the developmental mechanisms responsible for generating the vast range of beak sizes and shapes seen in Darwin’s finches and their close relatives. This research revealed that different avian species have evolved a unique set of patterning instructions that are combined in different ways and proportions to induce multidimensional shifts in beak morphology. After completing my Ph.D., I joined Hopi Hoekstra's lab at Harvard, where I am currently a postdoctoral fellow working on understanding the molecular mechanisms that regulate pigment type (color) and distribution (color pattern).

Topic

Evolution and Development: Developmental Mechanisms of Stripe Formation in Rodents

 Due to their diversity, sophistication, and visual accessibility, mammalian color patterns represent an excellent model in which to investigate the developmental, cellular, and molecular mechanisms by which repetitive morphologic structures develop and evolve. I took advantage of the naturally occurring color pattern of the African striped mice, Rhabdomys pumilio, to investigate the processes responsible for forming periodic stripes, a common pattern in mammals. De novo transcriptomic assembly and analysis of striped mouse skin showed that stripes result from underlying differences in melanocyte maturation, which give rise to spatial variation in hair color. From the many loci involved in this process, the transcription factor Alx3 was identified as a major hierarchical regulator. During striped mouse embryogenesis, patterned expression of Alx3 precedes pigment stripes and acts to directly represses Mitf, a master regulator of melanocyte differentiation. In addition, Alx3 is also differentially expressed in the dorsal stripes of chipmunks, which have independently evolved a similar pattern of dorsal stripes. Together, this work shows that differences in the spatial control of Alx3 expression lead to striped patterns in rodents, revealing both a new factor regulating pigment cells and a previously unappreciated mechanism for modulating hair color, and thereby provide new insight into the ways in which phenotypic novelty evolves.

Audience

Free and open to the university community and the public.

Host

Department of Molecular Biology