Senators Sam Brownback (R-KS) and Mary Landrieu (D-LA) have introduced the Human-Animal Hybrid Prohibition Act of 2009 to the Senate on July 9.  Along with 20 cosponsors the two Senators have set out what they think will be sensible guidelines for human-animal hybrids. From Brownback’s blog:

“The issue is that when you make changes in the germ-line, such changes are passed along to one’s offspring. You could make a change now that could be passed along through the gene-pool for the rest of humanity. We do not know what the full effect of this could be, and it could be disastrous.

Ugh, I hate when people pull out the disaster around the corner speech.  Sam has no clue about how this works but he does represent a decent amount of thought in the US.

As a preface to what I think about the bill I am putting my belief out there that I don’t really think there is anything special about humans versus other animals.  We’ve all trecked the same course of time to reach this evolutionary phase.

I’ll first note that chimeras have been around for a while in biomedical research.  It is of a great advantage to be able to express human cells and tissues inside our closest relatives, the mammals (a humanster makes an anemia drug for us). No ethics committee in the world will let you purposely give someone parkinson’s, diabetes, or cancer. But the attraction to this approach from medical researchers is that you can give a mouse any disease you want.  By placing human tissues in mice and simulating a disease of that tissue researchers can more highly characterize the cell biology, biochemistry, and treatments of the disease.

The questions of developmental biology are many and deep, even with human embryonic stem cells (hESCs) we can only coax the formation of the 3 germinal layers with no axial morphogenesis.  Early human development remains as a bastion of unanswered questions, from the general morphological changes to genetic structure and expression.  Some scientists have started to tackle this these questions by integrating hESCs in mouse blastocysts like Daylon James from The Rockefeller University.

A  majority of embryonic chimeras generated from morula aggregation showed localization of hESCs (green in panels K, M, and N) to host ICM with retention of Oct-3/4  (red in K–N) and absence of Cdx2 (blue in panels K, L, and N).

A majority of embryonic chimeras generated from morula aggregation showed localization of hESCs (green in panels K, M, and N) to host ICM with retention of Oct-3/4 (red in K–N) and absence of Cdx2 (blue in panels K, L, and N).

The real question comes for most people when you start engineering a mouse brain with most or all of its neurons that are human, maybe before the architecture of the brain is even laid down.  Granted neurons aren’t even half of the cells in the brain but I could see how this may cause hesitance on the part of people wondering if this is a now sentient mouse.  I don’t know if there is an answer out there about that issue but I would wager a lot of money that you would have a mouse brain expressing human neurons and functioning like a mouse brain.

The language of the bill itself will have to be carefully looked at and I worry about any legislation that lays down rules for the direction of science.  It is hard to decide what the face of biomedical research will look like in 25 years, what techniques and new biological tools will we have?  Will it be possible to express whole human systems in a primate and study heart disease on human hearts?  Is a monkey with a human heart a monkey, a human, or a human/monkey hybrid?  Is a person with pig heart valve a human, pig, or a human/pig hybrid?

I am afraid that these questions are hard to answer and handcuffing exploration by the legislature will only silence discussion on how to ethically conduct these experiments and preserve the stature of the human species.  In the future the techniques will be innovative and able to manipulate DNA and hybrid questions with much more certainty but we have to at least leave the market open to exploration and discussion.

I guess in the end my view of life and the connectedness of all species will most likely knock me out of contention for ethicist on this issue.  It is just very hard for me to agree that a monkey and a slug are more closely associated (both ‘animals’) than humans and monkeys.

I know I didn’t discuss the bill much itself but I will have to do more research on the direction of such studies and look at the wording more carefully because honestly it isn’t very clear.