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Am J Physiol Heart Circ Physiol
279: H2062–H2067, 2000.
Genetic mapping of quantitative trait loci
influencing left ventricular mass in rats
YASUYUKI TSUJITA,1 NAOHARU IWAI,2 SHINJI TAMAKI,1 YASUYUKI NAKAMURA,1
MASATO NISHIMURA,3 AND MASAHIKO KINOSHITA1
1
First Department of Internal Medicine, Shiga University of Medical Science, Otsu 520-2192;
2
Research Institute, National Cardiovascular Center, Suita 565-8565; and 3Department of Clinical
and Laboratory Medicine, Kyoto Prefectural University of Medicine, Kyoto 602-0841, Japan
Received 19 November 1999; accepted in final form 18 May 2000
sterone synthase (Cyp11b2) (18) gene have been suspected to influence LV mass.
With the use of crosses between hypertensive
strains, between a hypertensive and a normotensive
strain, and between normotensive strains, several
linkage studies have indicated the existence of loci
influencing LV mass independently of blood pressure
(3, 8, 10, 11, 26, 30). Identification of genes contributing to LVH will help in evaluation of a patient’s risk
and provide clues to better therapeutic strategies.
In the present study, we used an animal model,
spontaneously hypertensive rats (SHR/Izm), in an attempt to clarify the quantitative trait loci (QTL) influencing LV mass. With the recent development of rat
and human genetic maps and comparative genetic
maps (35), the present study may provide important
clues to the identification of human genes contributing
to LVH.
METHODS
(LV) mass is a strong independent predictor of cardiovascular morbidity and
mortality (22). Although high blood pressure is the
leading cause of LV hypertrophy (LVH) (9), not all
hypertensive patients develop LVH (32). The correlation between the level of high blood pressure and LV
mass is poor.
Factors other than blood pressure are recognized to
be important in the development of LVH, including
humoral factors such as catecholamine (7, 31) and
ANG II (1, 27), the age at onset of high blood pressure
(12), body size or obesity (21), insulin sensitivity (28),
and genetic background (25, 34). Indeed, variations of
the angiotensin-converting enzyme (14, 29) and aldo-
Experimental animals and genetic crosses. We studied 49
male F2 rats from an intercross of the SHR/Izm and normotensive Lewis rat (LEW/Crj) strains. These strains were
chosen because of the relatively large phenotypic and genotypic differences between them; these provide the contrast
required for informative linkage analysis. The SHR/Izm
strain was obtained from Funabashi Farm (Funabashi, Japan). The LEW/Crj strain was obtained from Charles River
(Atsugi, Japan).
Male SHR/Izm rats were mated with female LEW/Crj rats
to produce F1 rats. Ten F1 male and ten F1 female rats were
intercrossed to produce an F2 population consisting of 49
male rats. Only those litters with 11–15 pups were included
in the present study. All animals were fed standard laboratory rat chow and had ad libitum access to drinking water. A
12:12-h light-dark regimen was maintained throughout the
study. The study protocol was approved by the Ethical Committee of Shiga University of Medical Science.
Determination of phenotypes. Arterial pressure was measured by the direct intra-arterial method in conscious animals at 24 wk of age. Body weight was measured, and the
rats were anesthetized briefly with pentobarbital sodium (50
Address for reprint requests and other correspondence: Y. Tsujita,
First Dept. of Internal Medicine, Shiga University of Medical Science, Tsukinowa Seta, Otsu, Shiga 520-2192, Japan (E-mail:
[email protected]).
The costs of publication of this article were defrayed in part by the
payment of page charges. The article must therefore be hereby
marked ‘‘advertisement’’ in accordance with 18 U.S.C. Section 1734
solely to indicate this fact.
blood pressure; spontaneously hypertensive rats; hypertension; linkage analysis
INCREASED LEFT VENTRICULAR
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Tsujita, Yasuyuki, Naoharu Iwai, Shinji Tamaki, Yasuyuki Nakamura, Masato Nishimura, and Masahiko
Kinoshita. Genetic mapping of quantitative trait loci influencing left ventricular mass in rats. Am J Physiol Heart Circ
Physiol 279: H2062–H2067, 2000.—High blood pressure is
the leading cause of left ventricular hypertrophy (LVH);
however, not all hypertensive patients develop LVH. Genetic
factors are important in the development of LVH. With the
use of F2 male rats from spontaneously hypertensive rats
and Lewis rats, we performed a study to identify the quantitative trait loci (QTL) that influence left ventricular mass
(LVM). Mean arterial pressure (MAP) was measured by the
direct intra-arterial method in conscious animals, and LVM
was determined at 24 wk of age. QTL analysis was done
using 160 microsatellite markers for a genome-wide scan.
Two loci that influenced body weight-adjusted LVM with
logarithm of the odds scores ⬎3.4 were found. One locus on
chromosome 17 influenced LVM independently of MAP. Another locus on chromosome 7 influenced LVM and MAP.
These findings indicate not only the existence of a gene on
chromosome 7 that influences LVM in a manner dependent
on blood pressure but also the existence of a gene on chromosome 17 that influences LVM independently of blood pressure.
GENETICS OF LEFT VENTRICULAR HYPERTROPHY
marker (37, 38). Some other studies (5, 13, 33) that utilized
multiple QTL model mapping have been reported.
The results of the composite interval mapping were recorded as the likelihood ratio statistic. The likelihood ratio
statistic can be converted to a conventional base-10 logarithm of odds (LOD) score by dividing it by 2ln 10 (24). The
threshold values were taken from the guidelines of Lander
and Kruglyak (20), in which the suggestive and significance
thresholds of the dominant/recessive model are 2.0 and 3.4,
respectively, and the suggestive and significance thresholds
of the codominant model are 1.9 and 3.3, respectively.
RESULTS
Characterization of the phenotypes of the LEW/Crj,
SHR/Izm, and F2 rats. Table 1 shows the characterization of the phenotypes of the LEW/Crj, SHR/Izm,
and F2 male rats at 24 wk of age. Significant differences were observed for MAP and LV mass between
male rats of the LEW/Crj and SHR/Izm strains. There
were also differences in body weight between the LEW/
Crj and SHR/Izm strains.
Trait correlations calculated within F2 rats were as
follows. Body weight was positively correlated with LV
mass, with a high correlation coefficient (r ⫽ 0.617, P ⬍
0.0001). MAP was also positively correlated with LV
mass (r ⫽ 0.372, P ⫽ 0.009). Body weight was not
significantly correlated with MAP (r ⫽ 0.019, P ⫽ 0.9).
As described in previous reports (2), a strong linear
relationship between LV mass and body weight (r ⫽
0.617, P ⬍ 0.0001) allowed us to remove the influence
of body weight from LV mass. We tried to remove the
influence of body weight by adjusting LV mass in a
regression with body weight as the covariate. We calculated the predicted LV mass by inputting the body
weight of the LEW/Crj, SHR/Izm, and F2 rats on the
regression line of the F2 rats. The values were expressed as the LV mass index, which was calculated by
dividing LV mass by the predicted LV mass. There
were differences in the LV mass index between the
LEW/Crj and SHR/Izm strains (Table 1). Blood pressure was positively correlated with the LV mass index
(r ⫽ 0.497, P ⫽ 0.0003).
Coverage of the genetic linkage map. Table 2 shows
the genomic coverage of the polymorphic markers. The
selected genetic markers gave an average genome
marker distance of 12.5 cM.
Composite interval mapping. Tables 3 and 4 summarize the analysis of the chromosomal mapping of QTL
that influenced MAP and the LV mass index. Multiple
regression analyses revealed that a pair of loci
Table 1. Characteristics of LEW/Crj, SHR/Izm, and F2 male rats at 24 wk of age
Phenotype
LEW/Crj (n ⫽ 5)
Body wt, g
MAP, mmHg
LVM, mg
LVM/body wt, mg/g
LVM index
417 ⫾ 19*†
112 ⫾ 3*†
697 ⫾ 33*
1.67 ⫾ 0.04*†
0.86 ⫾ 0.02*†
F2 (n ⫽ 49)
354 ⫾ 28
140 ⫾ 13*
722 ⫾ 68*
2.05 ⫾ 0.16*
1.00 ⫾ 0.07*
SHR/Izm (n ⫽ 6)
P (ANOVA)
348 ⫾ 9
174 ⫾ 7
941 ⫾ 22
2.70 ⫾ 0.06
1.32 ⫾ 0.02
⬍0.0001
⬍0.0001
⬍0.0001
⬍0.0001
⬍0.0001
Values are means ⫾ SD; n, number of male rats. MAP, mean arterial pressure; LVM, left ventricular mass. * P ⬍ 0.05 compared with
SHR/Izm, † P ⬍ 0.05 compared with F2 (Tukey’s honestly significant difference).
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mg/kg ip) for insertion of polyethylene catheters (PE-50) into
the right femoral artery. The catheters were passed under
the skin and exposed in the interscapular region, and the rats
were allowed to recover in individual cages with ad libitum
access to food and water. Four days after the operation, mean
arterial pressure (MAP) was recorded for 30 min with continuous sampling after stabilization of blood pressure. Blood
pressure was measured between 2 and 5 P.M. Ventricular
mass was determined by removing the whole heart, excising
the atria, and dissecting the right ventricular wall from the
LV and interventricular septum. Ventricles were blotted dry
of blood before they were weighed.
Genotyping. DNA was isolated from the liver by use of
standard procedures. PCR amplification was used to determine the genotype of the F2 animals at microsatellite loci
that are polymorphic in the LEW/Crj ⫻ SHR/Izm cross. We
used 160 microsatellite markers with an average intermarker distance of 12.5 centimorgans (cM) for a genome-wide
scan. The rat genetic markers used in the present study were
based on a previous report (15) and on information from
Research Genetics (Huntsville, AL).
Linkage and statistical analysis. The linkage map was
constructed using the Map Manager QT version 3.0b28 computer program (23, 24). After the map was constructed, we
localized QTL relative to the position of the microsatellite
markers as follows.
First, simple associations between the genotype at each
locus and phenotypic variables were assessed by using
ANOVA techniques. In addition, a linear regression analysis
was performed using a dominant, recessive, or codominant
genetic model [homozygous for LEW/Crj allele (LL) ⫽ 0,
heterzygous (LS) ⫹ homozygous for SHR/Izm allele (SS) ⫽ 1
(dominant); LL ⫹ LS ⫽ 0, SS ⫽ 1 (recessive); LL ⫽ 0, LS ⫽
1/2, SS ⫽ 1 (codominant)]. Marker loci that gave ANOVA or
regression model F test P ⬍ 0.1 were considered significant.
The second step of analysis involved a stepwise multiple
regression analysis. Only loci that produced P ⬍ 0.1 in the
first step were included in this second analysis.
The third step involved estimation of the approximate
position of individual QTL by use of composite interval mapping (17, 38) or multiple QTL model mapping (16) with the
Map Manager QT computer program. These are based on the
multiple QTL model. Like simple interval mapping, composite interval mapping evaluates the possibility of a target QTL
at multiple analysis points across each intermarker interval.
However, at each point it also includes the effect of one or
more background markers. The inclusion of a background
marker in the analysis helps in one of two ways, depending
on whether the background marker and the target interval
are linked. If they are not linked, inclusion of the background
marker makes the analysis more sensitive to the presence of
QTL in the target interval. If they are linked, inclusion of the
background marker may help separate the target QTL from
other linked QTLs on the distal side of the background
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GENETICS OF LEFT VENTRICULAR HYPERTROPHY
Table 2. Genomic coverage of LEW/Crj and SHR/Izm polymorphic markers
Chromosome
n
% of Chromosome Within 10 cM
of Markers
% of Chromosome Within 20 cM
of Markers
21.6
22.7
30.4
26.8
32.0
23.9
16.3
15.9
39.3
41.9
9.4
12.6
18.2
31.7
44.8
41.9
17.1
44.8
15.9
36.0
25.0
98.6
97.2
87.6
80.0
75.5
91.7
100
100
66.6
61.2
100
92.4
100
57.3
64.1
82.0
100
61.8
100
36.9
89.3
100
100
100
100
86.6
100
100
100
100
77.7
100
100
100
88.0
93.5
100
100
92.4
100
61.2
100
19
9
7
11
7
8
18
11
3
4
5
4
13
3
3
4
17
4
3
2
5
160
Chromosomal distribution, size of the largest gap between neighboring markers, and approximate chromosomal coverage are defined as
the average fraction of the chromosome localized within 10 or 20 centimorgans (cM) of any polymorphic marker. n, Number of markers.
[D7Mgh16 (codominant) and D2Rat15 (dominant)] had
significant effects on MAP (Table 3). The multiple
regression analyses also revealed that two pairs of loci
[the pair D17Rat52 (dominant) and D1Rat84 (recessive) and the pair D7Rat112 (codominant) and
D2Rat15 (dominant)] had significant effects on the LV
mass index (Table 4).
The composite interval mapping revealed two QTLs
for the LV mass index on chromosomes 17 and 7 and
one QTL for MAP on chromosome 7. The QTL for the
Table 3. Loci influencing MAP
Locus
Mode
LL
LS
SS
P
D1Mgh5
D
D
D3Rat46
R
D7Mgh16
C
D7Rat112
C
D7Mgh7
R
D9Rat1
D
142 ⫾ 12
(27)
140 ⫾ 10
(32)
137 ⫾ 11
(23)
141 ⫾ 10
(29)
139 ⫾ 10
(23)
137 ⫾ 11
(22)
144 ⫾ 13
(20)
146 ⫾ 13
(8)
144 ⫾ 13
(11)
147 ⫾ 11
(17)
147 ⫾ 16
(11)
148 ⫾ 15
(14)
149 ⫾ 12
(15)
132 ⫾ 10
(14)
0.0178
D2Rat15
134 ⫾ 12
(14)
132 ⫾ 21
(6)
134 ⫾ 14
(9)
130 ⫾ 7
(9)
133 ⫾ 9
(12)
134 ⫾ 10
(12)
142 ⫾ 12
(14)
D7Mgh16
D2Rat15
(C)
(D)
0.0878
LV mass index on chromosome 17 was determined
using the dominant model with D1Rat84 as a cofactor,
and the QTL for the LV mass index and MAP on
chromosome 7 was determined using the codominant
model with D2Rat15 as a cofactor.
Loci linked to LV mass independent of MAP. The
locus on chromosome 17 was located around D17Rat52
(Fig. 1). The LOD score of the LV mass index at
D17Rat52 was 3.71, which was above the significance
threshold of the dominant model (3.4). The average
value of the LV mass index for rats homozygous for the
SHR/Izm alleles at D17Rat52 was ⬃7% greater than
Table 4. Loci influencing index
Locus
Mode
LL
LS
SS
P
D1Rat84
R
D
D7Rat112
C
D11Mgh3
D
D17Rat52
D
0.98 ⫾ 0.06
(20)
1.02 ⫾ 0.07
(32)
1.00 ⫾ 0.07
(23)
1.01 ⫾ 0.08
(24)
1.02 ⫾ 0.07
(23)
1.04 ⫾ 0.07
(15)
0.99 ⫾ 0.08
(11)
1.04 ⫾ 0.07
(14)
1.02 ⫾ 0.07
(12)
1.02 ⫾ 0.07
(12)
0.0156
D2Rat15
0.98 ⫾ 0.08
(14)
0.94 ⫾ 0.07
(6)
0.94 ⫾ 0.05
(12)
0.96 ⫾ 0.06
(13)
0.95 ⫾ 0.06
(14)
0.0025
0.006
0.0047
0.0005
0.0061
Coefficient
P
21.1
14.9
⬍0.0001
0.003
Values are means ⫾ SD in mmHg of number of animals in parentheses. Locus, marker locus name; mode, mode of inheritance [dominant (D), codominant (C), recessive (R)]; LL, homozygous for LEW/
Crj allele; LS, heterozygous; SS, homozygous for SHR/Izm allele.
Result obtained by multiple regression analysis is also shown: r ⫽
0.577, intercept ⫽ 116.1, P ⬍ 0.0001.
D17Rat52
D1Rat84
D7Rat112
D2Rat15
(D)
(R)
(C)
(D)
0.0222
0.0019
0.0284
0.0016
Coefficient
P
0.076
0.06
0.108
0.091
0.0003
0.0031
⬍0.0001
0.0011
Values are means ⫾ SD of number of animals in parentheses.
Results obtained by multiple regression analysis are also shown:
r ⫽ 0.578, intercept ⫽ 0.927, P ⬍ 0.0001 for D17Rat52 and
D1Rat84 and r ⫽ 0.622, intercept ⫽ 0.864, P ⬍ 0.0001 for
D7Rat112 and D2Rat15.
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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
X
Total
Maximum Distance Between
Adjacent Markers, cM
GENETICS OF LEFT VENTRICULAR HYPERTROPHY
that for rats homozygous for the LEW/Crj alleles (Fig.
2). The LV mass index of heterozygous rats was similar
to that of rats homozygous for the SHR/Izm alleles,
suggesting a dominant mode of inheritance for the
increased LV mass at this locus. The LOD score of
MAP at D17Rat52 was 0.41 (Fig. 1), which was not
above the significance threshold of the dominant
model. There were no significant differences in MAP
among rats grouped according to genotype at the
D17Rat52 locus (Fig. 2). The LOD score of the LV mass
at D17Rat52 was 2.41 in the dominant model (data not
shown), which was above the suggestive threshold of
the dominant model (2.0); however, it was not above
the significance threshold of the dominant model. The
Fig. 3. Multipoint LOD scores curve for QTLs across the entire
chromosome 7. Thin curve, MAP; thick curve, LVM index. Both
phenotypes were calculated with a codominant mode of genetic
model. Dotted horizontal line, LOD threshold for suggestive linkage
(1.9); solid horizontal line, LOD threshold for significant linkage (3.3)
in codominant model as defined by Lander and Kruglyak (20).
Cyp11b1, steroid 11␤-hydroxylase; Cyp11b2, aldosterone synthase;
Has2, hyaluronan synthase 2; Ifng, interferon-␥; Lyz, lysozyme.
LOD score of body weight at D17Rat52 was 0 in the
dominant model (data not shown). The three groups
defined by genotype at the D17Rat52 locus showed no
differences in body weight (Fig. 2).
Locus linked to LV mass and MAP. We found another locus on chromosome 7 linked to the LV mass
index and MAP (Fig. 3). The locus for the LV mass
index was located at D7Rat112. The LOD score of the
LV mass index at the locus was 3.45, which was above
the significance threshold of the codominant model
(3.3). Rats homozygous for the SHR/Izm alleles at the
D7Rat112 locus had an LV mass index ⬃11% greater
than that of rats homozygous for the LEW/Crj alleles
Fig. 2. Phenotypes of F2 rats according to genotypes at D17Rat52. LL, homozygous rats for the LEW/Crj allele
(n ⫽ 14); LS, heterozygous rats (n ⫽
23); SS, homozygous rats for the SHR/
Izm allele (n ⫽ 12); BW, body weight;
MAP, mean arterial pressure. *P ⬍
0.05 (by ANOVA). Values are means ⫾
SE.
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Fig. 1. Multipoint logarithm of odds (LOD) scores curve for quantitative trail loci (QTLs) across the entire chromosome 17. Thin curve,
mean arterial pressure (MAP); thick curve, left ventricular (LV)
mass (LVM) index. Both phenotypes were calculated with a dominant mode of genetic model. Dotted horizontal line, LOD threshold
for suggestive linkage (2.0); solid horizontal line, LOD threshold for
significant linkage (3.4) in dominant model as defined by Lander and
Kruglyak (20). Drd1a, dopamine 1A receptor; Gad2, glutamic acid
decarboxylase 2.
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GENETICS OF LEFT VENTRICULAR HYPERTROPHY
Fig. 4. Phenotypes of F2 rats according to genotypes [LL (n ⫽ 12), LS (n ⫽
23), and SS (n ⫽ 14)] at D7Rat112.
*P ⬍ 0.05 (by ANOVA). Values are
means ⫾ SE.
DISCUSSION
We found a locus that influenced the LV mass index
independent of MAP on rat chromosome 17. The locus
was located around D17Rat52. D17Rat52 was near
17qter. Pravenec et al. (26) reported that, in recombinant inbred strains derived from SHR and normotensive Brown-Norway rats, the marker of dopamine 1A
receptor (Drd1a) on chromosome 17 showed a strong
correlation with LV heart weight, but not with blood
pressure. However, the marker for Drd1a was located
on 17p14, which is far from 17qter. The gene for glutamic acid decarboxylase 2 (Gad2) is located near
D17Rat52 (35). Glutamic acid decarboxylase catalyzes
the synthesis of ␥-aminobutyric acid from glutamic
acid. The relevance of this gene to the phenotypic
variance in LV mass is not clear. There is little information on genes near the locus around D17Rat52.
Yagil et al. (36) reported the existence of a QTL for
blood pressure at a locus around D17Mgh5 in their
study that used female F2 rats derived from saltsensitive Sabra hypertension-prone and salt-resistant
Sabra hypertension-resistant rats. The QTL was also
reported in the cross of the Dahl salt-sensitive and
Lewis rats (4). However, we could not confirm this
locus in our study.
The locus that influenced MAP and the LV mass
index on chromosome 7 was near D7Rat112. The genes
for lysozyme (Lyz), interferon-␥ (Ifng), and hyaluronan
synthase 2 (Has2) are located near D7Rat112 (35). The
relevance of these genes to the phenotypic variance in
LV mass and blood pressure is not clear. Garrett et al.
(6) reported a locus that influenced heart weight and
blood pressure around D7Mit5 in a cross of Dahl saltsensitive and Lewis strains. This locus is near those for
steroid 11␤-hydroxylase (Cyp11b1) and aldosterone
synthase (Cyp11b2). In their study, the Lewis allele
was associated with higher blood pressure and increased heart weight. On the other hand, in the congenic and interval mapping studies with Dahl saltsensitive and Dahl salt-resistant strains, the Dahl saltsensitive rat Cyp11b allele was associated with higher
blood pressure and increased heart weight than was
the Dahl salt-resistant rat Cyp11b allele (2). Considering these conflicting findings, we cannot conclude that
Cyp11b1 or Cyp11b2 was the gene responsible for blood
pressure and LV mass QTL. However, the ratio of
aldosterone to plasma renin activity of the SHR/Izm
strain was significantly higher than that of the LEW/
Crj strain in our study: 28.6 ⫾ 4.4 versus 60.0 ⫾ 12.2
pg 䡠 ml⫺1 䡠 ng⫺1 䡠 ml⫺1 䡠 h⫺1 (P ⬍ 0.05). Thus Cyp11b2
might be a candidate gene for causing high blood pressure and LVH in the SHR/Izm model.
Although some other loci have been reported previously, they were not detected as QTL for blood pressure
in the present study. For example, the renin locus was
reported to be associated with blood pressure variation
in an F2 population derived from SHR and Lewis rats
(19). However, this locus was not identified as a QTL
for blood pressure in the present study. This might be
due to strain differences or the relatively small number
of rats analyzed in the present study.
In conclusion, our findings indicate not only the
existence of a gene on chromosome 7 that influences LV
mass in a manner dependent on blood pressure but
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(Fig. 4). The value of the LV mass index of heterozygous rats at this locus was intermediate between the
LV mass indexes of the homozygous rats, suggesting
that the mode of inheritance is codominant. This locus
was linked to MAP, with an LOD score of 3.95 (Fig. 3),
which was higher than the significance threshold of the
codominant model (3.3). There were also significant
differences in MAP between rats homozygous for the
SHR/Izm allele and those homozygous for the LEW/Crj
allele at the D7Rat112 locus, with higher values in
those homozygous for the SHR/Izm allele (Fig. 4). The
LOD score of LV mass at the locus between D7Rat112
and D7Rat20 was 3.39 in the codominant model (data
not show), which was above the significance threshold
of the codominant model. The LOD score of body
weight was 0.85 in the recessive model (data not
shown), which was not above the significance threshold
of the recessive model (3.4).
GENETICS OF LEFT VENTRICULAR HYPERTROPHY
also the existence of a gene on chromosome 17 that
influences LV mass independently of blood pressure.
20.
REFERENCES
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
ously hypertensive rat with an increase in blood pressure. J Clin
Invest 85: 1328–1332, 1990.
Lander E and Kruglyak L. Genetic dissection of complex
traits: guidelines for interpreting and reporting linkage results.
Nat Genet 11: 241–247, 1995.
Levy D, Anderson KM, Savage DD, Kannel WB, Christiansen JC, and Castelli WP. Echocardiographically detected
left ventricular hypertrophy: prevalence and risk factors. The
Framingham Heart Study. Ann Intern Med 108: 7–13, 1988.
Levy D, Garrison RJ, Savage DD, Kannel WB, and Castelli
WP. Prognostic implications of echocardiographically determined left ventricular mass in the Framingham Heart Study.
N Engl J Med 322: 1561–1566, 1990.
Manly KF. A Macintosh program for storage and analysis of experimental genetic mapping data. Mamm Genome 4: 303–313, 1993.
Manly KF and Olson JM. Overview of QTL mapping software
and introduction to map manager QT. Mamm Genome 10: 327–
334, 1999.
Post WS, Larson MG, Myers RH, Galderisi M, and Levy D.
Heritability of left ventricular mass: the Framingham Heart
Study. Hypertension 30: 1025–1028, 1997.
Pravenec M, Gauguier D, Schott JJ, Buard J, Kren V, Bila
V, Szpirer C, Szpirer J, Wang JM, Huang H, Lezin ES,
Spence MA, Flodman P, Printz M, Lathrop GM, Vergnaud
G, and Kurtz TW. Mapping of quantitative trait loci for blood
pressure and cardiac mass in the rat by genome scanning of
recombinant inbred strains. J Clin Invest 96: 1973–1978, 1995.
Sadoshima J, Xu Y, Slayter HS, and Izumo S. Autocrine
release of angiotensin II mediates stretch-induced hypertrophy
of cardiac myocytes in vitro. Cell 75: 977–984, 1993.
Sasson Z, Rasooly Y, Bhesania T, and Rasooly I. Insulin
resistance is an important determinant of left ventricular mass
in the obese. Circulation 88: 1431–1436, 1993.
Schunkert H, Hense HW, Holmer SR, Stender M, Perz S,
Keil U, Lorell BH, and Riegger GA. Association between a
deletion polymorphism of the angiotensin-converting-enzyme
gene and left ventricular hypertrophy. N Engl J Med 330: 1634–
1638, 1994.
Sebkhi A, Zhao L, Lu L, Haley CS, Nunez DJ, and Wilkins
MR. Genetic determination of cardiac mass in normotensive rats:
results from an F344⫻WKY cross. Hypertension 33: 949–953, 1999.
Simpson P. Norepinephrine-stimulated hypertrophy of cultured rat myocardial cells is an alpha1-adrenergic response.
J Clin Invest 72: 732–738, 1983.
Tingleff J, Munch M, Jakobsen TJ, Torp-Pedersen C, Olsen ME, Jensen KH, Jorgensen T, and Kirchoff M. Prevalence of left ventricular hypertrophy in a hypertensive population. Eur Heart J 17: 143–149, 1996.
Van Der Schaar W, Alonso-Blanco C, Leon-Kloosterziel
KM, Jansen RC, van Ooijen JW, and Koornneef M. QTL
analysis of seed dormancy in Arabidopsis using recombinant
inbred lines and MQM mapping. Heredity 79: 190–200, 1997.
Verhaaren HA, Schieken RM, Mosteller M, Hewitt JK,
Eaves LJ, and Nance WE. Bivariate genetic analysis of left
ventricular mass and weight in pubertal twins (the Medical
College of Virginia twin study). Am J Cardiol 68: 661–668, 1991.
Watanabe TK, Bihoreau MT, McCarthy LC, Kiguwa SL,
Hishigaki H, Tsuji A, Browne J, Yamasaki Y, MizoguchiMiyakita A, Oga K, Ono T, Okuno S, Kanemoto N, Takahashi E, Tomita K, Hayashi H, Adachi M, Webber C, Davis
M, Kiel S, Knights C, Smith A, Critcher R, Miller J,
Thangarajah T, Day PJR, Hudson JR, Irie Y, Takagi T,
Nakamura Y, Goodfellow PN, Lathrop GM, Tanigami A,
and James MR. A radiation hybrid map of the rat genome
containing 5,255 markers. Nat Genet 22: 27–36, 1999.
Yagil C, Sapojnikov M, Kreutz R, Katni G, Lindpaintner K,
Ganten D, and Yagil Y. Salt susceptibility maps to chromosomes 1 and 17 with sex specificity in the Sabra rat model of
hypertension. Hypertension 31: 119–124, 1998.
Zeng ZB. Precision mapping of quantitative trait loci. Genetics
136: 1457–1468, 1994.
Zeng ZB. Theoretical basis for separation of multiple linked
gene effects in mapping quantitative trait loci. Proc Natl Acad
Sci USA 90: 10972–10976, 1993.
Downloaded from http://ajpheart.physiology.org/ by 10.220.32.247 on June 17, 2017
1. Baker KM and Aceto JF. Angiotensin II stimulation of protein
synthesis and cell growth in chick heart cells. Am J Physiol
Heart Circ Physiol 259: H610–H618, 1990.
2. Cicila GT, Dukhanina OI, Kurtz TW, Walder R, Garrett
MR, Dene H, and Rapp JP. Blood pressure and survival of a
chromosome 7 congenic strain bred from Dahl rats. Mamm
Genome 8: 896–902, 1997.
3. Clark JS, Jeffs B, Davidson AO, Lee WK, Anderson NH,
Bihoreau MT, Brosnan MJ, Devlin AM, Kelman AW, Lindpaintner K, and Dominiczak AF. Quantitative trait loci in
genetically hypertensive rats. Possible sex specificity. Hypertension 28: 898–906, 1996.
4. Deng AY, Dene H, Pravenec M, and Rapp JP. Genetic
mapping of two new blood pressure quantitative trait loci in the
rat by genotyping endothelin system genes. J Clin Invest 93:
2701–2709, 1994.
5. Fijneman RJ, de Vries SS, Jansen RC, and Demant P.
Complex interactions of new quantitative trait loci, Sluc1, Sluc2,
Sluc3, and Sluc4, that influence the susceptibility to lung cancer
in the mouse. Nat Genet 14: 465–467, 1996.
6. Garrett MR, Dene H, Walder R, Zhang QY, Cicila GT,
Assadnia S, Deng AY, and Rapp JP. Genome scan and congenic strains for blood pressure QTL using Dahl salt-sensitive
rats. Genome Res 8: 711–723, 1998.
7. Gordon AL, Inchiosa MA Jr, and Lehr D. Isoproterenolinduced cardiomegaly: assessment of myocardial protein content, actomyosin ATPase and heart rate. J Mol Cell Cardiol 4:
543–557, 1972.
8. Hamet P, Kaiser MA, Sun Y, Page V, Vincent M, Kren V,
Pravenec M, Kunes J, Tremblay J, and Samani NJ. HSP27
locus cosegregates with left ventricular mass independently of
blood pressure. Hypertension 28: 1112–1117, 1996.
9. Harrap SB, Dominiczak AF, Fraser R, Lever AF, Morton
JJ, Foy CJ, and Watt GC. Plasma angiotensin II, predisposition to hypertension, and left ventricular size in healthy young
adults. Circulation 93: 1148–1154, 1996.
10. Harris EL, Phelan EL, Thompson CM, Millar JA, and
Grigor MR. Heart mass and blood pressure have separate
genetic determinants in the New Zealand genetically hypertensive (GH) rat. J Hypertens 13: 397–404, 1995.
11. Innes BA, McLaughlin MG, Kapuscinski MK, Jacob HJ, and
Harrap SB. Independent genetic susceptibility to cardiac hypertrophy in inherited hypertension. Hypertension 31: 741–746, 1998.
12. Isoyama S, Wei JY, Izumo S, Fort P, Schoen FJ, and
Grossman W. Effect of age on the development of cardiac
hypertrophy produced by aortic constriction in the rat. Circ Res
61: 337–345, 1987.
13. Iwai N, Kinoshita M, and Shimoike H. Chromosomal mapping of quantitative trait loci that influence renal hemodynamic
functions. Circulation 100: 1923–1929, 1999.
14. Iwai N, Ohmichi N, Nakamura Y, and Kinoshita M. DD
genotype of the angiotensin-converting enzyme gene is a risk
factor for left ventricular hypertrophy. Circulation 90: 2622–
2628, 1994.
15. Jacob HJ, Brown DM, Bunker RK, Daly MJ, Dzau VJ, Goodman A, Koike G, Kren V, Kurtz T, Lernmark A, Levan G, Mao
Y, Pettersson A, Pravenec M, Simon JS, Szpirer C, Szpirer J,
Trolliet MR, Winer ES, and Lander ES. A genetic linkage map
of the laboratory rat, Rattus norvegicus. Nat Genet 9: 63–69, 1995.
16. Jansen RC. Interval mapping of multiple quantitative trait loci.
Genetics 135: 205–211, 1993.
17. Jiang C and Zeng ZB. Multiple trait analysis of genetic mapping for quantitative trait loci. Genetics 140: 1111–1127, 1995.
18. Kupari M, Hautanen A, Lankinen L, Koskinen P, Virolainen
J, Nikkila H, and White PC. Associations between human aldosterone synthase (CYP11B2) gene polymorphisms and left ventricular size, mass, and function. Circulation 97: 569–575, 1998.
19. Kurtz TW, Simonet L, Kabra PM, Wolfe S, Chan L, and
Hjelle BL. Cosegregation of the renin allele of the spontane-
H2067