Biomedical Engineering Reference
In-Depth Information
nevertheless inadequate to supply the needs of the research
community. The development of highly derived specific
pathogen free (SPF) colonies of rhesus macaques has
increased the importance of genetically managing these
colonies to maintain optimal levels of genetic heterogeneity
by maximizing
eventually replace rhesus macaques as the preferred
nonhuman primate model (
Bowden and Smith, 1992
).
Between 1995 and 2005, approximately 90% of the
151 653 macaques imported to the USA were longtail
macaques (
AESOP-Project, 2006
), and the number
continues to rise. Colonies of longtail macaques, albeit
small ones, are maintained at six of the eight NPRCs and at
many other breeding facilities throughout the USA that also
breed rhesus macaques for use in biomedical research. The
different origins represented at these breeding facilities are
Indonesia, Malaysia, Philippines, Mauritius and, increas-
ingly, Indochina (Vietnam, Cambodia, and Laos), which
comprise approximately 65% of all longtail macaques
imported during the period of time cited above. While some
longtail macaques are exported directly to the USA from
their countries of origin, more than half, primarily of
Indochinese origin, are exported to China, where longtail
macaques are not indigenous (
Zhang et al., 1991
), an
important fact that is not always appreciated by the
biomedical research community, then sold to breeding and
research facilities in the USA and elsewhere. The exact
origin of such animals can never be known with certainty
without genetic testing.
Caution should be exercised when using animals with
undocumented origins, because some breeders, such as
those in China, mix animals of different countries of origin
in their breeding stock and export them as unmixed
animals. Due to widespread paraphyly in the fascicularis
group of macaque species, some populations of different
species are genetically more similar to each other than
either is to its own conspecifics (
Smith and McDonough,
2005
), and this paraphyly can influence their suitability for
use as an animal model. At least some of the paraphyly is
due to natural inter-species hybridization where overlap
occurs, or has occurred in the past, in the ranges of rhesus
and longtail macaques, such as in Indochina (
Hamada et al.,
2006
), the principal source of longtail macaques exported
from China. This range overlap was probably much more
extensive during the last two Pleistocene glacial maxima,
around 150 000 and 20 000 years ago, which led to exten-
sive introgression of genes of Chinese rhesus macaques
into Indochinese longtail macaques. Such introgressive
hybridization has caused an underappreciated level of
reticulation during the evolution of primates (
Arnold and
Meyer, 2006
) that problemitizes systematic studies based
on either morphological or molecular evidence. It is
important to assess the incidence and significance of
ancient natural hybridization that has already occurred
between rhesus and longtail macaques in Indochina vis `
vis their use as animals models and to consider the extent
and patterns of genetic differences among regional pop-
ulations of both species.
These two taxa, which share approximately 93% of
their genomes in common with humans (
Gibbs et al., 2007
),
random breeding
and minimizing
inbreeding and genetic subdivision.
The severe shortage of rhesus macaques as subjects for
biomedical research prompted the establishment of
national centers for breeding Indian-origin rhesus
macaques in the USA (
Goodwin and Augistin, 1975; NIH,
1978; Held, 1980
). After their exportation from India
ceased in 1978, China became the principal supplier of
additional rhesus macaques to these centers and, thus,
domestic-bred rhesus macaques represent both countries of
origin with only negligible contributions from rhesus
macaques from other countries (
Kyes et al., 2006
). In
addition to the rhesus colonies at the NIH and at each of the
eight (the New England, Oregon, California, Yerkes,
Wisconsin, Southwest, Washington, and Tulane) National
Primate Research Centers (NPRCs) funded by the NIH,
large free-ranging colonies of rhesus macaques are main-
tained on Cayo Santiago and at Sabana Seco, Puerto Rico,
and captive colonies are maintained at numerous privately
supported breeding facilities including those at the Perrine
Primate Center of the University of Miami, the New Iberia
Primate Research Center of the University of Louisiana,
Lafayette, the Michale E. Keeling Center for Comparative
Medicine and Research of the University of Texas in Bas-
trop, the Wake Forrest Primate Research Center, Covance's
Primate Breeding Center in Alice, Texas, the Mannheimer
Foundation in Homestead, Florida, Primate Products in
Immokalee, Florida and Alpha Genesis, Inc. on Morgan
Island (formerly from La Parguero, Puerto Rica), and near
Yemassee, South Carolina (formerly, Laboratory Animal
Breeders Services, of Virginia). Owing to the severe
shortages of rhesus macaques for biomedical research, the
Office of AIDS Research (OAR) of NIH and the NCRR
have recommended both the expansion of existing rhesus
macaque breeding colonies and the identification and
development of alternative animal models based on other
primate species (
WDRMBMR, 2003
).
The popularity of the rhesus macaque as an animal
model is followed, increasingly closely, by its sister taxon
in the fascicularis group of macaque species, the longtail
macaque (M. fascicularis), also known as the crab-eating or
cynomolgus macaque. Longtail macaques are smaller in
size and easier and more economical to maintain than
rhesus macaques (
Sano et al., 2006
). Their smaller size,
lower cost, ready availability, lower aggressiveness (hence
greater ease of handling), close genetic relationship to
rhesus macaques, and nonseasonal breeding pattern
provide advantages to their breeding and use as animal
models
compared to rhesus macaques. They may
