Health Scan: 'Organizer cells' form embryos

It has been a mystery to mankind how, within the first month of a human pregnancy, this structure turns into an elongated embryo.

By
September 18, 2011 02:46
3 minute read.
Sperm cells surround an embryo

Sperm cells surround an embryo 311. (photo credit: Debbi Morello/Detroit Free Press/MCT)

Biology students, when they begin to study embryos, are usually presented with an image that looks like the inside of a melon, representing a disk-like cluster of cells. But it has been a mystery to mankind how, within the first month of a human pregnancy, this structure turns into an elongated embryo. Now Hebrew University of Jerusalem scientists have explained for the first time how the human embryo acquires this shape: “organizer” cells.

The first significant step towards understanding the issue was made nearly a century ago in experiments conducted by German embryologists Hans Spemann and Hilde Mangold, who, using early newt embryos, identified a group of cells within them which upon transplantation formed a two-headed tadpole. They concluded that the transplanted cells were organizing cells in their vicinity into a typical embryonic shape, and dubbed them “organizer” cells. The two-headed newt embryos possessed both their own organizers and the transplanted ones, both of which organized nearby cells to form a head structure.

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Recently, Hebrew University researchers managed to generate human organizer cells using human embryonic stem cells. The research was conducted by Nadav Sharon, a graduate student under the supervision of Prof. Nissim Benvenisty at the Alexander Silberman Institute of Life Sciences, in collaboration with genetics Prof. Abraham Fainsod at the HU-Hadassah Medical Faculty, and was published in a recent issue of the journal Stem Cells.

Based on the similarity that dominates the initial developmental processes of all vertebrates, the group raised the human cells in conditions that recreated those of early amphibian embryogenesis. Within two days, the human cells started expressing genes characteristic of the organizer cells. To verify that these cells possesed true organizing ability, the researchers repeated Spemann and Mangold’s experiments. But this time human cells rather than those of amphibians were transplanted, into frog embryos.

The midline of an amphibian embryo is marked by a neural tube – a tissue destined to form the embryo’s central nervous system. To the researcher’s complete surprise, some of the frog embryos that were implanted with the human cells were later found to possess not one but two neural tubes – the second also composed of frog cells, proving that the injected human cells organized the cells in their vicinity to acquire a tubular shape.

Shape determination during human embryonic development is a very important process; any error could lead to miscarriage or the birth of a severely defective baby. The identification of the human organizer should allow better understanding of this process, the researchers suggest. In addition, they said, the ability of the human organizer cells to shape a frog neural tube may assist in forming human neural tubes in culture, from which neural cells could be obtained for transplantation into people with spinal damage, though much further research would be required to reach that stage.

INVENTION TO PREVENT CHILDREN FROM OPENING SEAT BELTS

Modern vehicles have special buttons to press that prevent children from rolling down the windows, but there has been nothing until now to foil their urge to open seat belt buckles. Collin Veele, a mechanical engineering major at Michigan Technological University, who consulted with Alex Cotton, a mechanical engineering and economics major at the same school, was first informed of the problem by a babysitter, who told him about a pair of siblings that had been making trouble in the back seat of a car.

“They would undo each other’s seat belts,” the sitter told Veele. Thus began the Buckle Blocker, for which Cotton was named one of the “Top-Ten College Entrepreneurs of 2011” by Entrepreneur Magazine. Together, the students designed the device, which keeps little hands from undoing seat belt buckles in vehicles.

They began with sketches and then progressed to a 3- D model, which enabled them to start showing people what it looked liked and give them a feel for the product.

“We kept revising the design, and now finally we have a functioning, injection-molded prototype,” Cotton said. The result is a lever that slips over the buckle, keeping little hands at bay. Next came fundraising to advance the product to the manufacturing stage. The Michigan Tech students also secured a provisional patent and a trademark on the name. Now, after two years, it’s ready for market, Cotton says.


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