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L-2-HGA IN STAFFORDSHIRE BULL TERRIERS
Submitted for publication by Roger Pugh (UK)
L-2-HGA (L-2-hydroxyglutaric aciduria) in Staffordshire Bull
Terriers is a neurometabolic disorder characterized by elevated
levels of L-2-hydroxyglutaric acid in urine, plasma and
cerebrospinal fluid.
L-2-HGA affects the
central nervous system, with clinical signs usually apparent between
6 months and one year (although they can appear later). Symptoms
include epileptic seizures, “wobbly” gait, tremors, muscle stiffness
as a result of exercise or excitement and altered behaviour.
The mutation, or
change to the structure of the gene, probably occurred spontaneously
in a single dog but once in the population has been inherited from
generations to generation like any other gene. The disorder shows
an autosomal recessive mode of inheritance: two copies of the
defective gene (one inherited from each parent) have to be present
for a dog to be affected by the disease. Individuals with one copy
of the defective gene and one copy of the normal gene – called
carriers – show no symptoms but can pass the defective gene onto
their offspring. When two apparently healthy carriers are crossed,
25% (on average) of the offspring will be affected by the disease,
25% will be clear and the remaining 50% will themselves be carriers.
The mutation
responsible for the disease has recently been identified at the
Animal Health Trust. Using the information from this research, we
have developed a DNA test for the disease. This test not only
diagnoses dogs affected with this disease but can also detect those
dogs which are carriers, displaying no symptoms of the disease but
able to produce affected pups. Carriers could not be detected by
the tests previously available which involved either a blood or
urine test detecting elevated levels of L-2-hydroxyglutarate or
magnetic resonance imaging. Under most circumstances, there will be
a much greater number of carriers than affected animals in a
population. It is important to eliminate such carriers from a
breeding population since they represent a hidden reservoir of the
disease that can produce affected dogs at any time.
The test is
available now and information on submitting samples is given below.
Breeders will be sent results identifying their dog as belonging to
one of three categories:
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CLEAR: |
The dog has
2 copies of the normal gene and will neither develop
L-2-HGA, nor pass a copy of the L-2-HGA gene to any of its
offspring.
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CARRIER: |
The dog has
one copy of the normal gene and one copy of the mutant gene
that causes L-2-HGA. It will not develop L-2-HGA but will
pass on the L-2-HGA gene to 50% (on average) of its
offspring.
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AFFECTED: |
The dog has
two copies of the L-2-HGA mutation and is affected with
L-2-HGA. It will develop L-2-HGA at some stage during its
lifetime, assuming it lives to an appropriate age. |
Carriers can still be bred to clear dogs. On average, 50% of such a
litter will be clear and 50% carriers; there can be no affected pups
produced from such a mating. Pups which will be used for breeding
can themselves be DNA tested to determine whether they are clear or
carriers. |
Vind asb aangeheg meer informasie oor die L2HGA
en HC toetse asook die toets aanvraag vorm.
Die prosedure werk soos volg:
Sodra die teler gereed is om die honde te laat
toets, kan ek ‘n koerier reël om die bloedmonster by die
veearts
te kom oplaai (koste is op die informasie dokument aangedui). Al
wat ek nodig het is die veearts
se fisiese adres, kontak nommer,
‘n kontak persoon en die datum en beraamde tyd (oggend of middag)
wanneer die monsters opgelaai moet word. Die aanvraag vorm
(request form) moet asb vir elke hond wat
getoets moet word
ingevul word en die veearts wat die bloedmonster neem moet dit
ook asb teken. Die
vorm kan saam met die bloedmonster met die
koerier gestuur word, of die teler kan dit faks of scan en
e-
pos. Indien die teler die monsters hier wil kom aflaai of ‘n
ander koerier wil gebruik, is hulle ook meer as
welkom.
Sodra ons die monster ontvang het, begin ons met
die analises en ons waarborg dat die resultate binne 10
werksdae
gereed sal wees, maar gewoonlik is dit binne 3 – 5 dae gereed.
Die resultate word direk na die
teler per e-pos gestuur.
Ek het die resultaat verslag wat ons vir Penny
gegenereer het ook hier aangeheg as ‘n voorbeeld van hoe
ons
verslae lyk. Ons sit die werklike resultate wat ons vir die hond
genereer ook in dat, indien die teler ‘n
tweede opinie by enige
genetikus wil kry, hulle dit kan doen. Indien jy wil hê dat ek
die grafiek in meer detail
vir jou moet verduidelik sal ek dit
met graagte doen!
Moet asb nie huiwer om my te kontak indien jy
enige verdere informasie benodig nie!
Groete,
Henriëtte van der Zwan
Animal Geneticist
Inqaba Biotechnical
Industries (Pty) Ltd
Cell: 082 859 2229
Tel: 012 343 5829
Fax: 012 343 0287
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