INFERTILITY RELATED TO X-TRISOMY IN A LABRADOR
RETRIEVER BITCH
Vol. 58 (4) 2003
Goldschmidt, B., Paulino, F.O., Souza, L.M. and Gomes, H.F.
Veterinary School, Fluminense Federal University, Vital Brasil Filho Street, no 64, Niteró
Janeiro,
Brasil, CEP: 24230-340.
Abstract
A 2-year-old Labrador Retriever bitch, was admitted to the Veterinary Clinical Service becau
anoestrus. A chromosome investigation was performed using the lymphocyte culture method.
copies of the X chromosome were identified in all the cells analysed. Besides the primary anoe
chronic dermatitis was observed and abnormal behavior as coprophagy of cat and dog excrem
species with X-trisomy, either normal females or females with reproductive problems are involv
phenotypic and clinical effects of X-trisomy are discussed.
Introduction
Aneuploidy is due to non-disjunction of single chromosomes at cell division.
It is known to occur both in meiosis and mitosis, and the resulting primary
products are trisomy (2n+1) and monosomy (2n-1). Postnatal occurrence of
sex chromosome aneuploidy appears more commonly than autosomal
aneuploidy. Its survival is due to the dosage compensation mechanism,
which tends to maintain the amount of active chromatin at a constant level
(4). Several cases of aneuploidy have been reported in dogs, and
cytogenetic investigations of intersex dogs have revealed cases of XXY
trisomy and X monosomy (5,6,7,8), but until now only two cases of X trisomy
were described in dogs(2,3).
The aim of this study was to examine cytogenetical findings with causes of
reproductive failures in dogs.
Materials and Methods
A 2-year-old, Labrador Retriever breed bitch was submitted to the
veterinary clinic to investigate its anoestrus. The bitch was normal
phenotype, including external reproductive organs. Five ml of blood was
collected and used for lymphocyte culture as previously described (1), but
slightly modified for domestic animals in order to obtain preparations for the
cytogenetic study.
A swab of cells from the buccal mucosa was smeared on a microscope
slide for Barr chromatin study after staining with crystal violet (9)
Results and Discussion
On external examination normal vulva with perfectly formed lips were
found. The chromosome analysis showed 79 chromosomes in all thirty
spreads, including an extra X chromosome (figure 1). The buccal mucosa
smears showed nuclei with two Barr bodies, indicating that the extra
chromosome was an X. (figure 2). Therefore, the karyotype was designated
as 79,XXX.
This abnormality is relatively
frequent in humans, but a high
proportion of women with X trisomy
are fertile (10).
In cattle, X trisomy has been widely
described (11, 12, 13, 14) and in
horses, eight cases of trisomy have
been described (15,16, 17). A case of
X-trisomy in the mouse was also
reported (18) associated with infertility,
due to small ovaries containing only
primordial and primary follicles.
In dogs, only two cases have been
reported with X trisomy; one
associated with gonadal disgenesis (2)
and, the second described in a 5years-old mixed breed bitch, that was
infertile and with a congenital absence
of some premolar and molar teeth (3).
Other than extra X inativation, the X Figure 1 - Metaphase presenting three X chromosomes
arrows
trisomy cell lineage may produce a
failure in the organogenesis of the
ovarian tissue correlated with anestrus
and inibition of germ cells to be
meiotic.
The phenotypic effects of the
chromosome aberrations range from
those which cause considerable
reductions in fertility to those which are
statistically demonstrable only when
extensive numbers of aberration
carriers are investigated. Those
causing considerable fertility reduction
do not usually present any risk since
they are eliminated fairly quickly by
artificial selection. It is necessary to
identify and select the carriers of
chromosome abnormalities to achieve
a correct diagnosis of reproductive
problems.
Figure 2 - The arrows indicate two Barr bodies represe
inactivated X chromosomes in the trisomic bitch.
LINKS TO OTHER ARTICLES IN THIS ISSUE
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