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Association of A31P and A74T Polymorphisms in the Myosin Binding
Protein C3 Gene and Hypertrophic Cardiomyopathy in Maine Coon
and Other Breed Cats
G. Wess, C. Schinner, K. Weber, H. Ku
¨chenhoff, and K. Hartmann
Background: Hypertrophic cardiomyopathy (HCM) is an inherited autosomal dominant trait in cats. The A31P single
nucleotide polymorphism (SNP) in the myosin binding protein C 3 gene is thought to be the causative mutation in Maine Coon
cats. Additionally, the A74T SNP is offered as a genetic test for HCM.
Objectives: To evaluate the genetic association between the above-mentioned SNPs and phenotypes.
Animals: Eighty-three Maine Coon cats and 68 cats of other breeds.
Methods: The study was performed prospectively. Cats were phenotyped as healthy or HCM with echocardiography.
Taqman genotyping assays were used for genotyping; results were confirmed by sequencing analysis.
Results: A31P was found in 18/83 (22%) Maine Coon cats. Fifteen of 18 Maine Coons (83%) with the A31P mutation were
healthy on echocardiographic examination (mean age 65 months). A74T was present in 28/79 (35%) of Maine Coons and in 42/
68 (62%) of other cat breeds. Twenty-two of 28 (79%) of Maine Coons and 21/42 (62%) of other breed cats with the A74T
mutation were healthy at a mean age of 72 months and 91 months, respectively. Of 12 Maine Coons with HCM, 9 (75%) were
genotype-negative for A31P and 6 (50%) for A74T. Allele frequencies did not differ significantly (P5.47) between phenotype
groups. None of the evaluated genetic tests was able to provide useful predictive information of disease outcome.
Conclusions and Clinical Importance: The value of currently available genetic tests is low in the cats of this study. The mu-
tations analyzed appear to have a low penetrance, and even homozygote cats can remain healthy.
Key words: Animals; Carrier proteins/genetics; Genetic tests; HCM.
Hypertrophic cardiomyopathy (HCM) is the most
common familial genetic heart disease in humans,
affecting one in 500 individuals.
1,2
In 60% of cases it
is inherited as an autosomal dominant trait, while ex-
hibiting an enormous phenotypic and genotypic hetero-
geneity. De novo mutations are also considered to be a
cause of sporadic HCM.
3,4
For many years, HCM in
humans has been suspected of being a genetic disease of
the sarcomere. To date, 4450 different mutations con-
sidered responsible for familial HCM have been
identified within 13 sarcomere- and myofilament-related
genes.
5–7
HCM is the most common cardiac disease in cats. Au-
tosomal dominant inheritance with a heterogeneous
disease outcome has been documented in a family of
Maine Coon cats.
8,9
One point mutations in the cardiac
myosin binding protein C 3 (MYBPC3) gene (A31P)
leading to amino acid changes in the protein occur in
Maine Coon cats with HCM and one point mutation in
the same gene (R820W) is thought to cause the same dis-
ease in Ragdoll cats.
9,10
Another single nucleotide
polymorphisms (SNP) (A74T) of the MVBPC3 has been
suspected to cause HCM in Maine Coon cats.
a
Several
commercial laboratories currently provide genetic tests
for the above-mentioned mutations. The A31P mutation
is present in about 34% of all Maine Coon cats world-
wide, although studies evaluating the relationship
between genotype and clinical outcome are lacking.
11
The goal of this study, therefore, was to evaluate the ge-
netic association of A31P and A74T SNPs with the
phenotype of HCM in Maine Coon cats in Germany.
Clinical validation (sensitivity, specificity) of both genetic
tests was assessed as well. In addition, the presence of the
2 above-named SNPs was evaluated in other breeds
besides Maine Coon cats.
Materials and Methods
Animals
Eighty-three Maine Coon cats and 68 cats of various other
breeds (Norwegian Forest cats, Persian cats, Domestic Shorthair
cats) were included in this prospective study over a period of 2 years
(August 2005–August 2007). All cats were from owners living in
From the Clinic of Small Animal Medicine (Wess, Schinner, Weber,
Hartmann), and the Statistical Consulting Unit (Ku
¨chenhoff), Lud-
wig-Maximilians-University, Munich, Germany. Parts of this study
havebeenpresentedpreviouslyattheACVIMmeeting2008inSan
Antonio.
Corresponding author: Gerhard Wess, DVM, Dipl. ACVIM (Car-
diology), Dipl. ECVIM-CA (Cardiology and Internal Medicine),
Clinic of Small Animal Internal Medicine, Ludwig-Maximilians-
University, Veterinaerstr. 13, 80539 Munich, Germany. e-mail:
gwess@lmu.de.
Submitted September 5, 2009; Revised February 5, 2010;
Accepted March 1, 2010.
Copyright r2010 by the American College of Veterinary Internal
Medicine
10.1111/j.1939-1676.2010.0514.x
Abbreviations:
CV coefficient of variation
HCM hypertrophic cardiomyopathy
IVS interventricular septum
IVSd interventricular septum at end-diastole
LV left ventricular
LVPW left ventricular posterior wall
LVPWd left ventricular posterior wall at end-diastole
MYBPC3 myosin binding protein C 3
PCR polymerase chain reaction
SNPs single nucleotide polymorphisms
TDI tissue Doppler imaging
J Vet Intern Med 2010;24:527–532
Germany, Switzerland, or Austria and patients presented to the
cardiology service of the Clinic of Small Animal Medicine or cats
participating in an HCM screening program. Pedigree sheets and
Internet databases were used to determine the origin of the Maine
Coon cats. The majority of the Maine Coon cats originated from
Germany (n 558) and Austria (n 511), and 8 cats were from the
United States, 3 from Switzerland, and 2 from Canada and Den-
mark each. Looking at the parents level of these cats, 48.2% (n 5
80) were from Germany, 21.1% (n 535) came from United States,
8.4% (n 514) were from Austria, 6.0% (n 520) from Canada,
3.6% (n 56) from Italy, 3.0% (n 55) from Denmark, 3.0% (n 55)
from Switzerland; 3 cats were from United Kingdom, 2 from Po-
land, 2 from France, 2 from the Netherlands, and 1 from Spain.
Cats were classified into 2 breed groups: ‘‘Maine Coon’’ and ‘‘other
breeds.’’ They were then further classified into the groups ‘‘healthy’’
or ‘‘HCM’’ according to echocardiographic phenotype results. In
the control group, female and male cats had to be a minimum age of
36 and 24 months, respectively, based on the fact that HCM can
usually be detected echocardiographically by this age in affected
cats.
8
Cats were considered genotype-positive for A31P or A74T if
at least 1 mutated allele was detected. Cats displaying only the wild-
type allele were considered genotype negative.
Phenotyping
Cats were prospectively phenotyped by clinical examination and
echocardiography. Animals with other diseases causing ventricular
concentric hypertrophy were excluded from the study. All echocar-
diographic studies were performed by 1 experienced examiner
(G.W.), with an ultrasound unit equipped with a 5.5–7.5 MHz
phased-array transducer with continuous ECG monitoring and
echocardiographic loops were stored digitally.
b
Ultrasound exam-
inations were performed without sedation in gently restrained cats
in lateral recumbency. Standard echocardiographic views were ob-
tained in right and left lateral recumbency.
12
End-diastolic
measurements of left ventricular (LV) wall thickness were per-
formed with two-dimensional echocardiography in the right
parasternal short-axis view at the level of the papillary muscles,
and in the right parasternal long-axis view in the basal and mid-
ventricular myocardial segments of the left ventricular posterior
wall at end-diastole (LVPWd) and the interventricular septum at
end-diastole (IVSd). HCM was defined as regional or generalized
hypertrophy with a diastolic wall thickness 6 mm of the LVPWd
or of the IVSd. At least 3 measurements were performed in each of
the myocardial segment described above of the left ventricular pos-
terior wall (LVPW) and interventricular septum (IVS) and the
mean value of at least 3 measurements of the thickest segment was
calculated. Hyperthyroidism and hypertension were excluded as
secondary causes of hypertrophy by measurement of basal serum
T4 concentration and blood pressure by Doppler technique.
c
Blood
pressure was considered normal if systolic blood pressure was
o150 mmHg. Healthy genotype-positive cats were re-examined
after 1 year. In addition, cats with equivocal measurements (only
prominent papillary muscle, or wall thickness between 5.5 and
6.0 mm) were excluded from the study if ultrasound findings
remained equivocal after 1 year. Measurement reliability was
determined for systolic and diastolic LV chamber diameter and
for diastolic wall thickness of the LVPW and IVS. Ten echocardio-
grams were randomly selected to be subjected to 3 repeated
analyses within 1 week by 1 investigator (G.W.) to determine
intraobserver measurement variability. The investigator was un-
aware of the results of the prior echocardiographic analyses.
Genotyping
For genotyping, DNA was extracted from peripheral blood
leucocytes with the QIAamp DNA Mini Kit.
d,13
The quantity of
DNA was assessed by photometric measurement. A 250-bp frag-
ment of the feline MYBPC3 gene including both polymorphic sites
was amplified by polymerase chain reaction (PCR) from 4 cats with
known A31P SNP genotype to confirm the feline sequence. Ampli-
fication primers were obtained from a commercial laboratory.
e
The
forward primer was 50-AGT CTC AGC CTT CAG CAA GAA
GCC-30, and the reverse primer 5 0-GGT CAA ACT TGA CCT
TGG AGG AGC C-30.
Standard PCR amplification was carried out with the HotS-
tarTaq PCR Master Mix
f
according to the manufacturer’s
instructions,
14
with 30 cycles on an Eppendorf thermal cycler, using
601C as annealing temperature. The PCR product was visualized by
gel electrophoresis and purified with the MinElute PCR Purification
Kit
g
according to the manufacturer’s instructions.
15
The PCR prod-
uct was sequenced by a commercial laboratory
d
performing a single
read of each sample with forward and reverse primers. Using this
sequence as a template, TaqMan Genotyping Assays for the A31P
and A74T SNPs were produced by a commercial Assay-by-Design-
Service.
h
These assays use a primer pair and allele-specific minor
groove binding probes with either VIC or 6-FAM as fluorescent
reporter dye. For allelic discrimination of the A31P SNP, the wild-
type G-allele was labelled with VIC and the mutated C-allele with
6-FAM. For discrimination of the A74T SNP, the wild-type A-allele
was labelled with 6-FAM and the mutated G-allele with VIC.
The allelic discrimination assays were run in 96-well reaction
plates on a 7,500 Real-Time PCR System.
h
12.5 mLof2TaqMan
Universal Master Mix, no AmpErase UNG
h
and 1.25 mL20SNP
Assay Mix
h
were mixed with 11.25 mL DNA, diluted in nuclease-
free water to a final reaction volume of 25 mL. On each plate, no
template controls (reaction mix without DNA) were included as
negative controls. DNA samples from cats with known homo- and
heterozygous genotypes were included as positive controls. Allelic
discrimination analysis was performed by 7,500 SDS software. For
all cases assigned to either the G/C or C/C genotype of the A31P
SNP with the TaqMan assay, standard PCR reactions were per-
formed. PCR products were then sent to a commercial laboratory
d
for sequencing analysis to confirm specificity of the TaqMan assays.
In silico analysis of A31P and A74T amino acid variations in the
MYBPC3 protein.
The possible impact of the SNPs on the protein was evaluated by
PolyPhen.
i
This tool is designed to calculate the likelihood that an
amino acid substitution resulting from a genetic mutation changes
structure and function of a human protein by comparing the allelic
variants with homologous proteins.
16
Statistics
The prevalence of HCM in Maine Coon cats was calculated from
randomly screened Maine Coon cats in the HCM screening pro-
gram. Allele frequencies were calculated for all phenotype groups.
Fisher’s exact test was used to compare allele frequencies of the
phenotype groups ‘‘healthy’’ and ‘‘HCM’’ (Po.05). Odds ratios
for having HCM were generated for all genotype-positives and ho-
mozygotes separately. Clinical validity was evaluated for both
genetic tests by calculating sensitivity and specificity.
17,18
The intra-
observer coefficients of variations (CV) were calculated by a
variance component analysis. The CV were obtained by dividing
the root of the variance error by the mean of the repeated measure-
ments, times 100.
Results
The prevalence of HCM in cats in the present study
was 15% (95% CI 57–22%). The A31P SNP was found
in 22% (n 518) of the Maine Coon cats, but not in any
of the other breeds. Minor allele frequency was 0.13 for
528 Wess et al
the C-allele. Of the genotype-positive cats, 83% (n 515)
were classified as normal (healthy) on echocardiographic
examination (LVPWd, mean 4.51 mm, range 3.0–
5.5 mm; IVSd mean 4.57 mm, range 3.2–5.4 mm) (Fig 1).
Mean age of genotype-positive cats with healthy pheno-
type was 65 months (range 24–146 months). Two of these
cats were homozygous (C/C) for the A31P SNP (58 and
64 months old). On echocardiographic examination, the
phenotype HCM was found in only 3 cats with the A31P-
SNP mutation. One of these cats was homozygous and 2
cats were heterozygous for the A31P SNP. All heterozy-
gous and homozygous cases (G/C and C/C) identified
with the TaqMan assay were confirmed as heterozygous
G/C and homozygous C/C by sequencing analysis.
Sixty-five Maine Coon cats (78%) were genotype-
negative. Of those cats, 68% (n 556) had a normal
phenotype (mean age 71 months); 9 of the cats (14%) in
this group had HCM. In total, 9/12 phenotype-positive
Maine Coon cats were genotype-negative (75%). The
echocardiographic examination of the phenotype-posi-
tive cats included 8 cats with concentric hypertrophy and
4 cats with regional hypertrophy (LVPWd, mean 7.1 mm,
range 6.1–10.0 mm; IVSd mean 7.0 mm, range 6.2–
8.7 mm).
The A74T SNP was found in 28 (35%) of the Maine
Coon cats studied (Fig 2). Minor allele frequency was
0.22 for the A-allele. Of the genotype-positive Maine
Coons cats, 79% had a ‘‘healthy’’ phenotype (n 522) at
a mean age of 72 months. Four of these cats were homo-
zygous (A/A) for the A74T SNP, and 18 cats (82%) were
heterozygous (G/A). The A74T SNP was identified in
21% (n 56) of Maine Coon cats with HCM, 2 of which
were homozygous and 4 of which were heterozygous for
the mutation.
The A74T SNP was present in 42 (62%) cats of other
breeds (Persian, Norwegian Forest cats, and Domestic
Shorthair cats) and in 26 (38%) other breed cats the SNP
was not found (G/G). Of the 21 ‘‘healthy’’ phenotype
Fig 1. Phenotypes and genotypes of Maine Coon cats with the A31P mutation. G/C represents heterozygous state and C/C the homozygous
state. Age is displayed as mean age of the selected group.
Fig 2. Phenotypes and genotypes of Maine Coon cats with the A74T mutation. G/A represents the heterozygous state and A/A the homo-
zygous state. Age is displayed as mean age of the selected group.
529Genetic Basis for HCM in Cats
cats (mean age 91.4 months), 9 cats were heterozygous
(G/A), 4 cats were homozygous (A/A) for the A74T SNP
alleles, and in 8 cats the SNP was not found (G/G). HCM
was diagnosed in 40/68 cats of other breeds (59%). The
echocardiographic examination of the phenotype-
positive cats included 28 cats with concentric hyper-
trophy and 12 cats with regional hypertrophy (LVPWd,
mean 7.2 mm, range 6.1–9.8 mm; IVSd mean 6.8 mm,
range 6.2–8.9 mm).
Of the 40 cats with HCM (mean age 108 months), 35%
(n 514) were heterozygous and 25% (n 510) were ho-
mozygous for the A74T SNP. The SNP was not found in
40% (n 516) of the HCM cats (G/G). Seven cats were
equivocal on the echocardiographic phenotype (2 were
homozygous, and 3 were heterozygous for the A74T
SNP).
There was no statistically significant difference ob-
served in allele frequencies between cats with HCM and
healthy controls for both SNPs, neither in Maine Coon
cats nor in the other breeds. No statistically significant
association between genotype and HCM was detected
(Table 1).
Sensitivity (25% for A31P; 50% for A74T) was very
low for both genetic tests in the examined population.
None of the genetic tests were able to reliably predict the
echocardiographic phenotype (Tables 2 and 3). Evaluation
of the potential impact of the amino acid substitutions
caused by the A31P and A74T SNPs by PolyPhen did
not suggest damaging effects on the protein. Results of
the echocardiographic repeatability study revealed very
good findings: CV for diastolic LVPW was 3.3%, for
diastolic IVS 2.6%, for diastolic LV diameter 2.0% and
for systolic LV diameter 4.2%.
Discussion
The current study found that a positive test result in
the AP31 SNP or A74T SNP test does not predict that a
cat has echocardiographic changes or that it will develop
HCM later in life, and that a negative AP31 SNP or
A74T SNP test does not determine whether a cat has or
will develop HCM.
HCM is the most common cardiac disease in cats. It is
considered an autosomal dominant disease in humans as
well as in cats. A penetrance of 100% was reported for a
family of inbred Maine Coon cats, with the stillborns
representing lethal homozygotes that died in utero.
8
The
A31P mutation was first detected in this colony of Maine
Coon cats,
9
most of which had echocardiographic evi-
dence of HCM by an age of 24 months in males and 36
months in females.
8
Therefore, only males older than 24
months and females older than 36 months were included
into the healthy control group in the current study. HCM
cats were included in the present study at any age. The
possibility that cats in the control group will develop
HCM later in life cannot be excluded, and follow-ups in
this group are desirable. However, as the mean age of the
cats in the control group of the present study was 65
months, it is unlikely that many cats in this group will
develop HCM later in life.
Two cats with a normal phenotype at an age of 58 and
65 months were homozygous for the AP31 SNP. Maine
Coon cats carrying the homozygous mutation were sus-
pected to represent stillborn cats in the Maine Coon
breeding study, but homozygous cats for the A31P mu-
tation were found to be alive not only in the present
study, but also in the UC Davis Maine Coon colony.
19
Therefore, either the assumption that cats carrying a ho-
mozygous mutation will be stillborn cats is not correct,
or the A31P mutation alone is not the only mutation
causing HCM in Maine Coon cats. At least, the A31P
Table 1. Odds ratios for the A31P and A74T SNPs in
the MYBPC3 gene in Maine Coon cats (MC).
MC Phenotype Genotype 1 Genotype 2 N OR 95% CI
A31P G/G 1G/C C/C 3.14 0.20–5.96
Healthy 69 2 71
HCM 11 1 12
G/G G/C 1C/C 1.24 0.29–5.18
Healthy 56 15 71
HCM 9 3 12
A74T G/G 1G/A A/A 3.15 0.51–9.51
Healthy 63 4 67
HCM 10 2 12
G/G G/A 1A/A 2.04 0.59–7.07
Healthy 45 22 67
HCM 6 6 12
Genotype 1 and Genotype 2 show which combinations of geno-
types were used to calculate the odds ratios. For the A31P SNP G/
C, heterozygous; C/C, homozygous cases and G/G, wildtype; for
A74T G/A, heterozygous; A/A, homozygous cases and G/G, wild-
type.
n, number of animals; OR, odds ratio; CI, confidence interval.
Table 2: Validity of the genetic test for the A31P SNP in
Maine Coon cats.
A31P
Scenario 1
G/C 1C/C 5
Genotype Positive
Scenario 2
C/C 5
Genotype Positive
95% CI 95% CI
Sensitivity 0.25 0.08–0.55 0.08 0.01–0.41
Specificity 0.79 0.68–0.87 0.97 0.89–0.99
Scenario 1, heterozygous (G/C) and homozygotes (C/C) are
counted as genotype positives; Scenario 2, only homozygotes are
counted as genotype positives; 95% CI, 95% confidence interval.
Table 3: Validity of the genetic test for the A74T SNP.
A74T
Scenario 1
G/A 1A/A 5
Genotype Positive
Scenario 2
A/A 5
Genotype Positive
95% CI 95% CI
Sensitivity 0.50 0.24–0.76 0.17 0.04–0.48
Specificity 0.67 0.55–0.73 0.94 0.85–0.98
Scenario 1, heterozygous (A/C) and homozygotes (A/A) are
counted among genotype positives; Scenario 2, homozygotes
are counted among genotype positives; 95% CI, 95% confidence
interval.
530 Wess et al
mutation does not appear to be a prenatal lethal factor,
neither in the present study population nor in the UC
Davis Maine Coon colony and another study evaluating
the A31P mutation in Maine Coon cats.
8,19,20
Never-
theless, in the inbred Maine Coon cat colony, the
A31P mutation appears to be associated with cardiac
changes.
19
A recent study demonstrated that the hetero-
zygous manifestation of the MYBPC3 A31P mutation is
not associated with occurrence of LV hypertrophy and
major myocardial dysfunction in Maine Coon cats.
20
Only inconsistent, minor regional diastolic myocardial
dysfunction were detected in a study using tissue doppler
imaging (TDI) in cats with the A31P mutation. A
reduced diastolic function was identified in only a few
LV wall segments, whereas other segments had normal
TDI values.
20
A diastolic dysfunction detected using TDI
could be an early marker of HCM, but this remains to be
proven in future studies. In the present study, TDI was
not used and therefore we potentially might have missed
early diastolic dysfunction. However, if diastolic dys-
function is truly an early indicator of HCM, than the
diastolic dysfunction should progress to a more obvious
HCM picture over time. The cats in the present study
were almost twice as old compared with the cats in the
TDI study population, in which the inconsistent regional
diastolic dysfunction was reported.
20
Therefore, even if
we would have missed diagnosing a diastolic dysfunc-
tion, the disease should have progressed to a more
obvious HCM picture in the cats of the present study.
As this was not the case, the clinical implication of a po-
tentially missed TDI abnormality seems to be low, with
480% of the cats in the present study still being normal
based on echocardiography at an advanced age.
The A31P mutation might be the cause of HCM in the
Maine Coon cats in the UC Davis breeding colony.
However, it could also only be a marker for an unknown
mutation with pathogenic potential. In the Maine Coon
cats tested in this study, the A31P SNP was not associ-
ated with HCM, which could possibly be because of a
varying genetic background. The analysis of the pedi-
grees revealed that Maine Coon cats used in this study
were from catteries throughout the world, with the ma-
jority of the cats originating from Germany, Austria, the
United States, and Canada. As the Maine Coon breed is
a comparatively young breed founded in the 1960s it is
not surprising that there are still many cats imported
from the United States and Canada and that cats in this
breed have a close genetic relationship. A study evaluat-
ing the prevalence of the A31P mutation found that this
mutation exists in about one third of the Maine Coon
cats throughout the world, and that the prevalence of the
mutation (heterozygous or homozygous) was very simi-
lar among countries of submission.
11
Therefore, the
results of this study could be representative also for other
countries and not only for the selected population. How-
ever, further studies are necessary on this subject.
Basing breeding recommendations for Maine Coon
cats on the A31P or A74T, or both gene tests appears
questionable unless cats that are related to the UC Davis
family are used for breeding. Another reason for the ob-
served variations in field and experimental breeding
conditions could be modifier genes that cause HCM in
combination with the A31P mutation. However, to date
no modifier gene has been identified in cats. In humans,
4400 mutations have been detected in 24 genes encoding
for various forms of HCM.
2,21,22
The other SNP (A74T) suspected to cause HCM in
Maine Coon cats and other breed cats is incompletely
reported, yet the test is already being offered by
commercial laboratories.
a
Therefore, the A74T SNP was
also investigated in this study. As with the A31P muta-
tion, HCM cats negative for the mutation were
identified. Consequently, it appears highly likely that
other or additional mutations causing HCM exist in
Maine Coon cats. Similar to the A31P mutation, 79%
of the Maine Coon cats with a positive gene test were
normal on echo at a mean age of 72 months. Of these
cats, 4 cats were homozygous for the mutation at a mean
age of 88 months. As with the A31P mutation, no statis-
tical difference in the percentage of affected cats was
found between gene test-positive and -negative cats, nor
was a correlation detected between phenotype and geno-
type. In contrast to the A31P mutation, which was
specific for Maine Coon cats, the A74T mutation was
also detected in other breeds (in which also no correla-
tion was present between genotype and phenotype). The
A74T SNP, therefore, appears to be a mutation that is
neither specific for Maine Coon cats nor causes HCM.
An Internet-based software program (Polyphen) from
Harvard University that tries to predict whether a muta-
tion is likely to affect protein function, classifying the
changes as ‘‘benign’’ or ‘‘malignant,’’ was used in this
study. The feline genome was used in the present study as
a reference to let the software predict if the SNPs are sus-
pected to be benign or malignant changes. For both the
A31P and A74T SNP, the program predicted that the
SNP probably are benign changes, which is in contrast to
a previous study that used the human genome and this
explains the different findings.
9
Although this might sup-
port the findings of this study, the results are only
calculations by a software and the value of a computa-
tional method should not be overestimated. Only
functional tests of the mutated protein would be able to
prove this assumption. A limitation of this study is that,
as all cats were client-owned cats, no necropsy was per-
formed on the phenotypically healthy, but positively
tested cats, and therefore no necropsy results could be
compared with the genotype. Another limitation is that
some cats may have been too young for the detection of
disease on echocardiography and may develop HCM la-
ter in life. However, as mentioned earlier, the mean age of
the healthy group of cats was 65 months and, thus, quite
old, so that the likelihood of developing the disease later
on is very low. Certainly, long-term follow-up studies
would help answer this question.
This study proves that other mutations or genetic in-
fluences causing HCM must exist as most cats with HCM
were negative for the AP31 SNP.
Therefore, it can be concluded that:
1. A negative AP31 SNP or A74T SNP test does not de-
termine whether a cat has or will develop HCM, as
531Genetic Basis for HCM in Cats
most of the cats with HCM in this study did not have
either SNP;
2. A positive test result does not implicate that a cat has
echocardiographic changes or that it will develop
HCM later in life, at least in the selected population,
as most of the cats with a positive gene test in this
study did not exhibit echocardiographic changes at a
mean age of 65 months;
3. Breeding decisions or recommendations should not
be based solely on A31P or A74T testing.
Footnotes
a
Nyberg MT, Koch J, Christiansen M. Intra-allelic Genetic Hetero-
genity of Hypertrophic Cardiomyopathy in the Maine Coon Cat.
Hugo Human Genome Meeting HGM2007, Montreal, Canada,
2007; 199 [poster abstract].
b
Vivid 7, GE, Horten, Norway
c
Parks 811-BT, Parks Medical Electronics Inc, Aloha, OR
d
Qiagen, Hilden, Germany
e
Metabion GmbH, Martinsried, Germany
f
HotStarTaq PCR Master Mix, Qiagen
g
MinElute PCR Purification Kit, Qiagen
h
Applied Biosystems, Foster City, CA
i
PolyPhen, Harvard University, Cambridge, MA: http://genetics.
bwh.harvard.edu/pph/index.html
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