With improved resolution, tissue-specific molecular markers and precise timing, University of Oregon biologist James A. Weston and colleagues have possibly overturned a long-standing assumption about the origin of embryonic cells that give rise to connective and skeletal tissues that form the base of the skull and facial structures in back-boned creatures from fish to humans.

Weston and co-authors from the Max Planck Institute of Immunology in Germany and the French National Scientific Research Centre at the Curie Institute document their potentially textbook-changing case in an article appearing online this week (May 19-23) ahead of regular publication in the Proceedings of the National Academy of Sciences.

The cells in question, they argue, do not come from a portion of embryonic neural epithelium called the neural crest, as widely believed, but rather from a distinct thin layer of epidermal epithelial cells next to it. “Our results,” Weston said, “could lead to a better understanding of the etiology of craniofacial defects, as well as the evolution of the head that distinguishes vertebrates from other creatures.”

The neural crest was first identified by classical embryologists in the late 19th and early 20th centuries and has been one of the most studied embryonic tissues. Conventional wisdom says that the neural crest gives rise to skeletal and connective tissue of the head and face, as well as a wide diversity of other stem cells that migrate to many places in the vertebrate embryo, where they spawn the cells that create the peripheral nervous system, and pigment cells in skin and hair (or scales and feathers).

The new study is part of research done over 25 years in Weston’s quest to understand early development of the neural crest and explore alternative explanations for sometimes differing findings involving its assumed cell lineages. Weston noted that mutations in mice that adversely affected development of the peripheral nervous system or pigmentation did not affect craniofacial structures, whereas mutations that caused abnormal development of skeletal and connective tissue of the head and face did not alter neural crest-derived pigment or peripheral nervous system cells.

This paradox, he said, led him to wonder if different genetic programs were required to function in distinct embryonic precursors of these tissues. “In our new paper,” he said, “we finally were able to re-examine some of the underlying assumptions that have led to the conventional wisdom about the source of the embryonic cell lineages that give rise to the skeleton and connective tissue of the head and face.”

In the mouse embryo at eight days gestation, Weston and collaborators used high-resolution imaging and immunostaining techniques to identify and track the dispersal of cells known to jump start connective and skeletal tissue development. They were able to see clearly that these cells came from the non-neural layer of cells rather than from the neural crest. The same distinction also exists in chicken embryos during the first few days of gestation, Weston noted. “Looking at the right time is very important,” he said.

Weston argues that this non-neural epithelium is indeed distinct from the neural crest, because its cells contain characteristically different molecules. He and colleagues dispute suggestions that this non-neural structure is simply a sub-domain of the neural crest. “These cells emerge at a different time in development and disperse in the embryo before neural crest cells begin to migrate,” Weston said.

“New technologies let us see cell types more clearly than ever before,” said Weston, a member of the UO’s Institute of Neuroscience. “We previously had discovered that a molecule that marks cell surfaces in the non-neural epithelium reveals a very sharp boundary between this non-neural epithelium and the neural tissue connected to the neural crest. In this study, we took a closer look.”

They located a population of cells in the non-neural epithelium that express other molecules that “do not appear to originate from the neural crest,” said Weston, who retired in 2001 but continued to teach in the College of Arts and Sciences until 2006. He still collaborates in some research with colleagues at the UO and at various labs around the world.

“I think our results have two important messages,” he said. “First, it is important to identify and validate — rather than ignore — assumptions; and second, because we identified an alternative embryonic cell lineage as the source of the head and facial structures, we can now more effectively analyze and understand the molecular-genetic mechanisms that regulate the normal and abnormal development of these structures.”

Researchers from the University of Melbourne, Australia, and the University of Texas, USA, have extracted genes from the extinct Tasmanian tiger (thylacine), inserted it into a mouse and observed a biological function – this is a world first for the use of the DNA of an extinct species to induce a functional response in another living organism.

The results, published in the international scientific journal PLoS ONE this week, showed that the thylacine Col2a1 gene has a similar function in developing cartilage and bone development as the Col2a1 gene does in the mouse.

“This is the first time that DNA from an extinct species has been used to induce a functional response in another living organism,” said Dr Andrew Pask, RD Wright Fellow at the University of Melbourne’s Department of Zoology who led the research.

“As more and more species of animals become extinct, we are continuing to lose critical knowledge of gene function and their potential.”

“Up until now we have only been able to examine gene sequences from extinct animals. This research was developed to go one step further to examine extinct gene function in a whole organism,” he said.

“This research has enormous potential for many applications including the development of new biomedicines and gaining a better understanding of the biology of extinct animals,” said Professor Richard Behringer, Deputy Head of the Department of Molecular Genetics, M.D. Anderson Cancer Center, at the University of Texas, who is the corresponding author on the paper.

The last known Tasmanian tiger died in captivity in the Hobart Zoo in 1936. This enigmatic marsupial carnivore was hunted to extinction in the wild in the early 1900s.

Researchers say fortunately some thylacine pouch young and adult tissues were preserved in alcohol in several museum collections around the world.

The research team used thylacine specimens from Museum Victoria in Melbourne Australia to examine how the thylacine genome functioned.

The research team isolated DNA from 100 year old ethanol fixed specimens. After authenticating this DNA as truly thylacine, it was inserted into mouse embryos and its function examined.

The thylacine DNA was resurrected, showing a function in the developing mouse cartilage, which will later form the bone.

“At a time when extinction rates are increasing at an alarming rate, especially of mammals, this research discovery is critical,” says Professor Marilyn Renfree, Federation Fellow and Laureate Professor in the University of Melbourne’s Department of Zoology, the senior author on the paper.

“For those species that have already become extinct, our method shows that access to their genetic biodiversity may not be completely lost.”

Significant numbers of female high school athletes and non-athletes suffer from one or more components of the female athlete triad, a combination of three conditions that can lead to cardiovascular disease, according to a new study by Medical College of Wisconsin researchers in Milwaukee.

The study results were presented today at the American College of Sports Medicine at Indianapolis, by Anne Z. Hoch, D.O., associate professor of orthopedic surgery and physical medicine and rehabilitation at the Medical College, and director of the Froedtert & Medical College Sports Medicine Program. She is also a member of the Medical College’s Cardiovascular Center.

Dr. Hoch found that 78 percent of female high school athletes and 65 percent of female high school non-athletes display one or more components of the female athlete triad. The triad is a combination of three conditions – low energy availability, menstrual abnormalities and low bone mineral density – that often leads to the same steroid and hormonal profiles as postmenopausal women.

“We are concerned that non athletic girls have some of the same components of the female athlete triad as athletes and are in fact at greater risk for low bone density,” says Dr. Hoch. “These young women are under great pressure to conform to society’s standards of body image. In an effort to lose weight, they are restricting their caloric intake and adapting unhealthy nutrition habits.”

The study, conducted at Froedtert Hospital, examined eighty varsity athletes and eighty non-athletes at an all-girls school in Milwaukee. Ninety-three percent of non-athletes were found to have calcium deficiencies, compared to 74 percent of athletes.

“Most important and alarming is that 30 percent of the non athletes versus 16 percent of athletes were found to have low bone mineral density putting them at greater risk for developing osteoporosis earlier in life,” says Dr. Hoch.

Both groups showed little difference in low energy availability, with 39 percent of non-athletes and 36 percent of athletes reporting this condition. The athletes reported 33 percent more menstrual abnormalities than the non-athletes. Women who have normal periods, and hence normal estrogen levels, are less likely to display changes in the function of the layer of cells that line the interior of blood vessels, called the endothelium.

“Change in endothelial function is the seminal event in cardiovascular disease,” says Dr. Hoch.

Dr. Hoch began her studies in the late 1990s to see if young women who have menstrual abnormalities as a result of participating in intense sports are likely to develop cardiovascular disease similar to that seen in postmenopausal women. She and her colleagues were able to show that young women who had the triad also had early vascular change that is a precursor to cardiovascular disease.

“We not only need to educate athletes about the consequences of the triad, now we must educate all students about the harmful effects of a restrictive diet in the adolescent period,” says Dr. Hoch.

While demand for organic meat and milk is increasing by about 20% per year in the United States, almost all organic grain and forage to support these industries in the mid-Atlantic region is imported from other regions. To meet this demand locally, area farmers need information on expected crop yields and effective management options.

Scientists in the Sustainable Agricultural Systems Laboratory at the USDA-Agricultural Research Service (ARS) Beltsville Agricultural Research Center (BARC) in Maryland have studied the impact of diverse organic cropping systems on crop yields over a ten year period. Results from the study, which was funded by USDA-ARS, were published in the May-June issue of Agronomy Journal.

The researchers collected data on crop yields, nitrogen inputs, weed densities, and crop populations from the USDA-ARS Beltsville Farming Systems Project (FSP), a long-term cropping systems trial with two conventional and three organic systems that was established in 1996. The three organic systems differed in crop rotation length and complexity.

The study revealed that corn and soybean yields in organic systems were, on average, 76 and 82%, respectively, of those in conventional systems in years with normal weather. Winter wheat yields were similar among systems. Corn yields were lower in the organic than in the conventional systems primarily due to lower nitrogen availability in the organic systems, which rely on legume crops and animal manures. Weed competition also contributed to lower corn grain yields in organic systems. For soybean, weed competition alone accounted for differences in yield between organic and conventional systems.

Among organic systems crop rotation length and complexity had a strong impact on corn grain yield. A crop rotation that included corn, soybean, wheat and hay resulted in average corn grain yield 30% greater than in a simple corn-soybean rotation and 10% greater than in a corn-soybean-wheat rotation. Differences were due to increased nitrogen availability and lowered weed competition with increasing crop rotation length and complexity. Crop rotation length and complexity did not affect soybean and wheat yields.

Dr. Michel Cavigelli, lead author of the study, stated, “These research results show that longer, more complex crop rotations can help address the two most important production challenges in organic grain crop production: providing adequate nitrogen for crop needs and decreasing weed competition.” This research should help organic farmers and those considering transitioning to organic farming select crop rotations best suited for the mid-Atlantic region. Since the FSP is one of only a handful of long-term cropping systems trials that includes diverse organic crop rotations, these results will also be of interest to organic farmers and those working with organic farmers nationwide.

Ongoing research at the USDA-ARS Sustainable Agricultural Systems Lab at BARC is designed to increase soil nitrogen availability and decrease weed pressure in organic grain crop rotations.