Both houses of the U.S. Congress are jointly grappling with legislation already passed last month by the Senate titled "The Partial-Birth Abortion Ban Act."

Pro-choice organizations, notably the American Civil Liberties Union (ACLU), denounce this bill as an entering wedge for the threatened reversal of Roe v. Wade, which protects the right of a women to elect an abortion. It also leads to cloning of humans, anti-abortionists warn. ACLU promises to sue Congress over the legislation.

The Congressional lawgivers can spare themselves the trouble.

So implies an opinion voiced by developmental cell biologist Gerald Schatten, who directs the University of Pittsburgh Development Center. Schatten told readers of the current Science, dated April 11, 2003, "The charlatans who have claimed cloning humans have never understood enough cell or developmental biology to succeed."

Schatten's denunciation sums up an accompanying Science commentary headed, "Nuclear transfer: Misguided chromosomes foil primate cloning." This editorial reviews a one-page article in Science titled "Molecular correlates of primate nuclear transfer failures." Schatten is its senior author, and Calvin Simerly its first author and associate professor of obstetrics, gynecology and reproductive sciences at Pittsburgh.

"The overall message of this story," Simerly told BioWorld Today, "is that current methods being employed in this reproductive field to clone animals, like Dolly the sheep or mice, don't work in nonhuman primates - in monkeys. The specific mechanisms that we discovered," he continued, "are related to the very first steps of the cloning process. This is called enucleation, the process where the spindle, along with the chromosomes - the egg's DNA - is actually removed out of the egg prior to introduction of a somatic cell. And that initial step removes vital proteins needed by that somatic cell to successfully complete first division. We think the implications," Simerly added, "are that cloning in humans, or in any primate, is going to be far more difficult than we originally believed. That is, reproductive cloning is probably going to be impossible, using current technology."

Primate Replication Impossible Now, Later Maybe

Schatten's brief paper starts off by noting, "Somatic cell nuclear transfer in nonhuman primates could accelerate medical research by contributing identical animals for research, and clarifying embryonic stem cell potentials. Although rhesus embryos begin development after embryonic cell nuclear transfer [ECNT], there has only been one report of rhesus births after ECNT, and that event has not been replicated."

"Embryonic stem cell culturing," Schatten told BioWorld Today, "aims at one of two objectives: reproduction or therapy. Fundamental flaws in embryonic development," he opined, "may make therapeutic cloning of nonhuman primates difficult, and reproductive cloning of primates - nonhuman and human alike - impossible.

"As we reported in Science," he continued, "we observed basic molecular obstacles that block normal cell development despite our using four different techniques of nuclear transfer. In therapeutic cloning," Schatten explained, "limited cell division is induced in an unfertilized egg cell to produce embryonic stem cells. In reproductive cloning, an egg cell with a donor nucleus is implanted into a living surrogate female in an attempt to achieve a successful pregnancy. The chromosomes do not split properly," he pointed out. "From the very first cell division, development is inappropriate in vital ways."

In the current study, the co-authors used known methods of nuclear transfer on 716 eggs retrieved from female rhesus macaques. Although 33 embryos were transferred into surrogate mothers after initial cell division, no pregnancies resulted. The team used antibodies to tag the cell proteins and DNA so that they could track progress. "When cells divide," Simerly observed, "very basic things are supposed to happen, and they just don't happen.

"Primate cloning efforts may be fundamentally limited by the dividing cell's failure to divvy its genetic material properly," Simerly explained, "and it now appears that the problem lies with the formation of a cell structure called the spindle. During cell division, the chromosomes duplicate themselves and then line up along the spindle, which helps pull the opposite ends of the cell apart."

Simerly and his co-authors transferred the nuclei of rhesus monkey cell types into enucleated (emptied) eggs. Although cell division proceeded, two key proteins required for spindle pole assembly were missing. The chromosomes did not line up properly, and the resulting embryos lacked the correct chromosome number.

The Science editorial was authored by the journal's staff writer, Gretchen Vogel, who noted, "When governments around the world debate how to prevent human reproductive cloning, it seems that nature has put a few hurdles of its own in the way. Unpublished date from this and other groups suggest that the same problems confronting rhesus monkeys may also thwart attempts to clone humans."

Wannabe Human-Baby Cloners Can't Succeed

"There are potential ways around the new-found obstacles," Schatten predicted, "but for now groups that made controversial claims that they would use the techniques that produced Dolly to create human babies are unlikely to succeed. It is almost as if someone drew a sharp line between old-world primates - which include people - and other animals."

"Primate nuclear transfer," the article concluded, "appears to be challenged by stricter molecular requirements for mitotic spindle assembly, than in other mammals. In cattle, the somatic centrosome is transferred during nuclear transfer, whereas mice rely on the oocyte's maternal centrosome. With current approaches, nuclear transfer to produce embryonic stem cells in nonhuman primates may prove difficult - and reproductive cloning unachievable."

"The area we would like to pursue next," Simerly said, "is to perfect cloning in nonhuman primates. We are totally against reproductive cloning in humans. We think it is unethical, unsafe and should be outlawed. However, we believe that clonal propagation in monkeys is very important for two reasons. First, to determine if embryonic stem cells are safe and effective for treating diseases like diabetes, Parkinson's, breast cancer, Alzheimer's and blindness or whatever. Second," he concluded, "because identical monkeys - our closest animal cousins - can help us solve medical problems more adequately than mice."