††† Welcome to the laboratory of
†††† Charles A. Lessman, Ph.D.
Department of Biological Sciences
††††††††††† Our lab is currently interested in zebrafish ovarian physiology. We are especially focused on final oocyte maturation that produces the fertilizable egg. The oocyte-egg transition is necessary for subsequent fertilization and development of the embryo. The process of oogenesis begins with the proliferation of oogonial stem cells and ends with oocyte maturation. Thus our lab is trying to understand how the female gamete is produced and the underlying physiological processes that lead to the fully developed female gamete or egg cell.
††††††††††† We have developed a new technique called Computer-Aided Meiotic Maturation Assay (CAMMA) that uses computer-controlled transparency scanners to automatically image large arrays of zebrafish oocytes during the final maturation process. An example is shown below: (click on link)
Interested in a graduate degree?
Graduate Assistantships & tuition waivers are available to qualified graduate students
The overall process of oocyte maturation and egg activation is shown in this figure (at left):
The germinal vesicle (cell nucleus, GV) is seen as the darker circle in the interior of the oocyte. After steroid treatment (progestogen) the GV moves (GVM) to the animal pole (site of micropyle or sperm entry site) and undergoes breakdown or dissolution (GVD). Also during maturation cytoplasm, relatively yolk-free, accumulates at the animal pole. It is at this time that ovulation or shedding of the follicular wall occurs. After the egg is oviposited and fertilized, the blastodisc continues to enlarge, cortical alveoli are exocytosed and the perivitelline space forms.
We are also interested in how the oocyte-egg-embryo transitions occur and how the major cell components, such as the cytoskeleton are affected. We are focused on the tubulins, a major component of the cytoskeleton, including gamma tubulin. Microtubules are very important cell constituents that play a myriad of roles in the typical cell. How does the oocyte, that lacks a well defined centrosome, organize its microtubules and how is the centrosome reinstated by the sperm at fertilization?
At left is a 4-8 cell zebrafish embryo, green indicates gamma tubulin. Red is DAPI staining. Yolk tends to stain non-specifically, but between the linear arrays of gamma tubulin, the nuclei stain red.
A blastula stage zebrafish embryo shows gamma tubulin enrichment at the centrosomes (green) on either side of each nucleus (red). Soluble gamma tubulin remains high during cleavage stages.
cytoskeletal system of interest is the actin myofilaments
responsible for embryonic motility. We have discovered a motility mutant we
have named Dead Elvis (del) that shows a paralyzed
phenotype (i.e., doesnít shake, rattle or roll and we ARE in
Click below to see del vs wt viewed thru a microscope