Skip to main content




October 11, 2013
CONTACT: K.E. Schwab

Researchers examine alligator embryos

SLIPPERY ROCK, Pa. - For Slippery Rock University biology Professor Susan Rehorek the work is done on a tiny scale, but could have very large rewards.

Rehorek, who joined the SRU faculty in 2000, is slicing and dicing alligator embryos on the cellular level as part of her studies on the evolution of the face. The overall concept is to help determine whether or not humans follow the same pattern of development as other animals.

The research is being conducted with Timothy Smith, professor in SRU's School of Physical Therapy, and Abigail Progar, a biology major from Gardners studying in the cytotechnology track.

Rehorek said students who gain experience in histology, the study of how cells interact, by working with her and Smith find they then have very marketable skills that make them highly sought-after as histotechnologists in the job market following graduation.

She said, the CAVE - Comparative Atlas of Vertebrate Embryology - project the SRU researchers are working on is designed "to provide the diverse research community of vertebrate biology with a common resource and to be a complement to the Virtual Human Embryo database, by naming anatomical structures across different species."

"The CAVE project will ultimately pave the way for addressing major problems and gaps in the developmental understanding," she said.

"It will make a crucial contribution to, and complement, existing atlases and databases because it will involve the efforts of some of the comparative anatomists currently working on both the development and adult morphology of both the hard and soft tissues of all the major vertebrate groups, from lampreys to humans," she said.

The research project involves embryology, a combination of anatomy and developmental biology, and provides profound insights into evolutionary biology and how organisms are related and ultimately into human evolution, variations and diseases, she said.

"We are ultimately proposing to establish a website that will provide these diverse research communities with a central resource on the developmental anatomy of key vertebrate species that will allow researchers to compare the development of different species and ultimately to extrapolate the results of developmental and experimental studies to the understanding of vertebrate evolution and ontogeny in general and of human evolution, development and medicine in particular," Rehorek said.

"There is already a considerable body of literature on model organisms such as zebrafish [Danio], frogs [Xenopus], chicken [Gallus] and mice [Mus]. However comparisons of these distantly related groups of related organisms are insufficient, hampering our ability to illuminate the nature of evolutionary transitions across the Vertebrates," she said

In seeking funding, Rehorek said her grant proposal was twofold in that it aimed to produce alligator and procure lemur [Microcebus], serial histological slides in several embryonic and fetal stages.

"The embryonic lab slides are being digitally photographed and the images will be aligned, stacked and used to generate 3D reconstructions, and we will examine some of these stacks, focusing primarily on our area of expertise - specific structures of the facial region - and develop descriptions of the development of this region," she said.

Working with Smith, the researchers have begun preparing the digitized models, which can be viewed in a wide-variety of ways, including rotation, dissection, by region or layer, or even put in motion.

The project is not unlike the recent thin slicing of an entire human cadaver top-to-bottom and side-to-side with the resulting slides then stacked and animated to allow medical students, and others, working with a computer program to better see and understand exactly how the various body parts are interconnected and work together anatomically.

"Now that we have the full genomes, the gene map, for humans, chimpanzees, orangutans, mice and other vertebrate taxa, and will soon have full genomes for representatives of most major groups of vertebrates, we need to know more detail about not only the bone, but also the soft tissues such as glands, ducts and muscles in the anatomical structures of relevant members of these groups," she said.

"We also need information for adults and earlier developmental stages, in order to understand the links between genotype, which shows which genes are present, phenotype, which physical characteristics are observed, and ontogeny, the developmental processes of an individual organism," Rehorek said.

The National Science Foundation-funded Phenoscape project, an example of one of several new projects addressing these links, is creating a knowledge database that integrates evolutionary phenotypes for vertebrate characters with genetic data from three vertebrate model organisms, she said.

"The Phenoscape project has been very successful and has paved the way for further similar projects. In fact, despite the progress and the new techniques and elegant methods that are now being used in the fields of developmental biology and comparative anatomy, there is clearly a huge disparity between the knowledge about hard vs. soft tissues - the anatomical structures at the microscopic level - and about model organisms vs. non-model organisms. Such a mismatch is in large part due to theoretical and historical reasons, rather than to a setback for not having the necessary methods/techniques to address this in a more adequate way," she said.

SRU's collaborators in the initial aspect of the CAVE project include Rui Diogo, an expert in comparative myology/muscles, at Howard University; John Cork, biophysicist and CO-PI for the Virtual Human Embryo project at Louisiana State University; and Jayc Sedlmayr, an expert in comparative neurovasculature dealing with nerves and blood vessels of vertebrates, at Louisiana State University.

Rehorek's earlier research work, conducted from 2006 to 2011, involved a similar project examining development of rabbit faces.

Slippery Rock University is Pennsylvania's premier public residential university. Slippery Rock University provides students with a comprehensive learning experience that intentionally combines academic instruction with enhanced educational and learning opportunities that make a positive difference in their lives.