Warren Johnson, Ph.D.
Staff Scientist
[Biography] [Research] [Recent Publications]
{E-Mail
Address} johnsonw@ncifcrf.gov
Research:
My current research encompasses several areas and disciplines, but focuses in general on the evolution of a variety of molecular genetic markers and the use of these to study evolutionary patterns in natural populations. These populations provide the opportunity to study the dynamics of molecular genetic change in different settings and under different selective pressures. In addition, they provide the means for testing theoretical models and the context for interpreting patterns observed in other species, including humans. Several broad areas of research are listed below.
EVOLUTIONARY RELATIONSHIPS AMONG CHEMOKINE RECEPTORS
Chemokine-receptor genes have been implicated in the progression of a wide variety of diseases, including those associated with HIV infection. I have been studying the evolutionary relationships among these receptors in humans, mouse and primate species and have been characterizing patterns of nucleotide and amino acid sequence divergence. Results from this work will aid in understanding the changing functional roles of these genes. I am currently extending this work to other species, particularly those within the felid family.
INTROGRESSION OF MITOCHONDRIAL DNA INTO THE NUCLEAR GENOME
Copies of mitochondrial gene segments have been found in the nuclear genome of many species. We are studying the occurrence of this phenomenon in a common ancestor of the cat species of the genus Pathera, and are describing the resulting patterns in the five extant species, the African lion, leopard, jaguar, tiger, and snow leopard. Results from this work will provide further evidence for the mechanism behind this phenomenon, will provide insights into factors affecting genomic organization, and will aid in our understanding of the evolutionary relationships among these cat species. Improved understanding of the evolutionary history of these species will greatly aid interpretation of the results of several other research efforts in the laboratory.
PATTERNS OF MOLECULAR GENETIC EVOLUTION IN NATURAL POPULATIONS
A variety of molecular genetic markers, including mtDNA and nuclear sequence variation and microsatellite size variations are being used to describe the evolutionary history of natural populations and to discern historic and contemporary processes affecting patterns of molecular genetic variation. These studies are currently focusing on several different felid, canid, and camelid species. We are also developing unique ways to study these natural populations, including the development of methods to extract and utilize genetic material from hair and feces. These studies are closely tied to other research efforts in the laboratory on the evolutionary role of infectious diseases in natural populations.