It looks like primates are ruling the science world these days, last week it was famous primate fossil “IDA” made headlines and now Japanese scientists succeeded in generating transgenic primate marmoset . This research might go a long way in use of Marmosets as an alternative disease model to rhesus macaques.Erika Sasaki and her colleagues at the Central Institute for Experimental Animals in Kawasaki injected viral vectors with green fluorescent protein (GFP) into 91 marmoset embryos and successfully shown passing of a transgene a primate to its offspring.Transgenic primate was reported last year ,when scientists in United states generated transgenic monkeys as a model of Huntington’s disease , but in these animals, the gene did not fully integrate into the monkey’s own DNA and was not passed down to their offspring. To be a successful model for human diseases ,this criteria of passing the genes to next generation should be passed. This amazing research of passing the foreign gene to offspring was reported in the May 28 Nature.

What are Primates ?

Primates are members of the taxonomic order Primate, a subgroup of mammals.( If you find your way to primates in tree of life : Go to the web page of Tree of life and then to group Therapsida ,then look for mammals in them and after clicking on it ,will lead you to different mammalians. Primates are part of Eutherians which includes all placental mammals and can be divided into four categories :

1) Platyrrhini ( includes New World Monkeys)
2) Tarsii (Tarsius )
3) Strepsirrhini
4) Catarrhini (Humans, great apes, gibbons, Old World monkeys)

All primates exhibit some important characters : like forward facing eyes , two arms and two legs, rather than four legs, hands and feet (not paws),most species have nails rather than claws, opposable set of digits
and easily visible fingerprints which can be used for individual identification.

What are Marmosets ?

Marmosets are New World monkeys of the genus Callithrix. Most marmosets are about 20 centimetres (7.9 in) long. Relative to other monkeys, they show some apparently primitive features: they have claws rather than nails, and tactile hairs on their wrists.

Marmosets have some advantages over other primates in having relatively small size and are easy to handle. They reach sexual maturity in just over a year and a female can have up to 80 babies (with a short gestation period of 148 days) compared with about 10 for the rhesus macaque. Experts believe that Marmosets will be definitely better as model for human diseases when compared to Mice but they have also some reservations. Some are of the opinion that their brains are too small for positron emission tomography scans and some think lack of knowledge regarding Marmosets can serve a disadvantage when compared to macaque,where a higher brain function research paradigm has been established for things like attention and decision-making. In addition not to forget the problems these Marmoset project researchers will face from bioethicists and animal-rights groups over creating a colony of animals born with a disease.

For long time now transgenic Mice served as models for human disease ,where foreign DNA ( Human gene-mutant or disease causing form) is incorporated into the mouse genome and this helps to study the function of that particular human gene to be studied in living animals rather than in cell culture. Today many mouse models for human diseases are available ,ranging from anaemia and asthma to autism and schizophrenia . However , all human diseases ( Like cystic fibrosis , Alzheimer’s) cannot to be modeled in mice for various biological reasons and here come it is our closest animal relatives ,the non-human primates to rescue.

In the recent work published in Nature , Erika Sasaki and colleagues used viral DNA as a delivery vehicle to introduce the gene for GFP into the DNA of the common marmoset Callithrix jacchus. They show that the gene integrated into the monkey’s DNA and was successfully passed down to their offspring, which were healthy and all expressed the new gene. This work ,which can be considered as milestone on the road to developing the means to investigate these diseases , will definitely go a long way in understanding mechanism of many human diseases and finally finding cure to them.

Journal references:

1. Sasaki et al. Generation of transgenic non-human primates with germline transmission. Nature, 2009; 459 (7246): 523 DOI: 10.1038/nature08090
2. David Cyranoski. Marmoset model takes centre stage. Nature, 2009; 459 (7246): 492 DOI: 10.1038/459492a
3. Gerald Schatten, Shoukhrat Mitalipov. Developmental biology: Transgenic primate offspring. Nature, 2009; 459 (7246): 515 DOI: 10.1038/459515a

Image Credit :
Wikimedia commons

Update :

Some interesting links about Transgenic Mice :

1) Background on Mouse as a Model Organism
2) What is a Transgenic Animal ?

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