Mapping Loci Causing Susceptibility to Anal Atresia in Pigs, Using
a Resource Pedigree
By Tetsuo Hori, Elisabetta Giuffra, Leif Andersson, and Haruo Ohkawa
Tsukuba, Japan; Uppsala, Sweden; and Mito, Japan
Very little information on the genetic
background for anal atresia (anorectal malformations; AA) in
humans has been described. A strikingly similar natural
anomaly occurs in piglets. The authors have used this as an
animal model for various research purposes. The affected
piglets were treated surgically soon after birth, raised, and
used for breeding. The authors have generated a resource
pedigree segregating for this naturally occurring nonsyndro-
mal AA and describe here the ﬁrst attempt to map suscepti-
bility loci by marker analysis.
A pig pedigree with a high incidence of AA has
been established by selective breeding using 3 probands
from the Landrace and Large White breeds. It has been
maintained by intrafamilial crossing for more than 15 years.
A backcross pedigree has now been generated by mating 4
AA females to an unaffected male from the Chinese Meishan
animals were both intercrossed and backcrossed to
affected AA animals. A genome scan was carried out using
, and affected backcross progeny. Ninety-two mi
crosatellite loci were analyzed using ﬂuorescently labelled
primers and an ABI377 sequencer. Linkage analysis was
done with the CRI-MAP 2.4 software.
Crossing affected parents increased the incidence of
abnormalities from 30% to 61.9%. All 39 F
pigs were unaf
fected. In the F
intercross, only 3 of 205 (1.5%) were affected,
whereas 42 of 523 (8.0%) backcross progeny were affected.
The marked difference in the incidence of affected progeny in
intercross and in the backcross indicates the presence
of multiple genes causing AA. The genome scan showed
suggestive evidence for the presence of a susceptibility locus
on pig chromosome 15 (lod score 2.7 for a pig microsatellite
The results clearly show that AA has a oligo-
genic or polygenic background. The genome scan showed
one suggestive locus causing AA on pig chromosome 15.
The long-term goal is to identify causative genes for this
malformation by comparative positional candidate cloning.
This study provides, for the ﬁrst time, linkage mapping of
nonsyndromal anorectal malformations with a polygenic
J Pediatr Surg 36:1370-1374. Copyright
2001 by W.B.
INDEX WORDS: Congenital anal atresia, anorectal anomaly,
polygenic disease, linkage mapping, pig, animal model.
NAL ATRESIA (anorectal anomaly; AA) is a com-
mon disorder in the neonatal surgical practice. AA
most likely has a multifactorial background and is thus
controlled by an unknown number of genes and environ-
mental factors. Thus, the identiﬁcation of the genes
controlling such malformations by family studies in the
human is exceedingly difﬁcult. The aim of this study was
to utilize a pig animal model for mapping genes causing
AA and to gain more basic knowledge on the develop-
mental errors leading to this malformation. The long-
term goal is to use this knowledge for development of
improved therapy for the human patients.
Congenital AA is a fairly common anorectal malfor-
mation affecting 1 in 5,000 live births
in humans. The
spectrum of abnormalities ranges from a simple ectopic
or stenotic anus, to imperforate anus with a ﬁstula to the
distal urinary tract, to complex cloacal abnormalities.
The principal event in anorectal development appears to
be a shift of the dorsal part of the cloaca and the adjacent
gut to the body surface of the tail groove. Regression of
the dorsal part of the cloacal plate forms an essential part
of this process. Agenesis of this part to the membrane
blocks the normal shift of the anorectum to the body
surface with anorectal malformation as the result.
Associated anomalies (such as cardiovascular gastroin-
testinal, vertebral, and genitourinary system anomalies)
are found in more than 60% of infants. Although a
number of syndromes, including VACTERL, Pallister-
Hall, and hereditary sacral agenesis, have been associ-
ated with congenital anorectal malformations, the ge-
From the Department of Pediatric Surgery, University of Tsukuba,
Tsukuba, Japan; the Department of Animal Breeding and Genetics,
Swedish University of Agricultural Sciences, Uppsala Biomedical Cen-
ter, Uppsala, Sweden; and Ibaraki Children’s Hospital, Mito, Japan.
Dr T. Hori and Dr E. Giuffra contributed equally to this work.
This work was supported by the Japanese Ministry of Education and
Science and University of Tsukuba, the Swedish Foundation for Inter-
national Cooperation in Research and Higher Education, the Swedish
Research Council for Forestry and Agriculture, and STINT.
Address reprint requests to Tetsuo Hori, MD, Department of Pedi-
atric Surgery, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba-shi,
Ibaraki-ken, 305-8575, Japan.
Copyright © 2001 by W.B. Saunders Company
Journal of Pediatric Surgery,
Vol 36, No 9 (September), 2001: pp 1370-1374