SINGLE-NUCLEOTIDE POLYMORPHISMS IN EXONIC
AND PROMOTER REGIONS OF TRANSCRIPTION
FACTORS OF SECOND HEART FIELD ASSOCIATED
WITH SPORADIC CONGENITAL CARDIAC ANOMALIES
Wang E, Fan X, Nie Y, Zheng Z, Hu S,
*Corresponding Author: Shengshou Hu M. D., Cardiac Surgery Department, Fuwai Hospital, Chinese
Academy of Medical Sciences, Peking Union Medical College, Xicheng District, Beijing, 100037,
China, Tel & Fax: 86-010-88322325 E-mail: shengshouh@sina.cn
page: 39
|
|
DISCUSSION
SNPs located in exon or promoter regions play important
roles in CHD development. Our previous study
revealed that polymorphisms located in the exons and
promoters of growth factors influence the risk of CHD
(15). We then revealed that the minor alleles in the intronic
SNPs in the transcription factors regulating the second
heart field increased the risk of CHD (14). In this study, we
evaluated the associations between polymorphisms in the
exons and promoters of the second heart field and CHD.
Mutations in SMYD1 (16), MEF2C (11), GATA5 (17),
and TBX20 (10) were found to be critical for the transcriptional
regulation of gene expression for CHD development.
Mutations in the exons of these genes can inactivate
an allele or cause gene dysfunction by interfering with
DNA interactions. In this study, we found ten SNPs located
in the exons and promoters of SMYD1, MEF2C, GATA5,
and TBX20 which regulate SHF development and were
significantly associated with CHD. The minor alleles of
two SNPs, GATA5: rs6061243 G>C and TBX20: rs336283
A>G, were significantly associated with an increased risk
of CHD. Additionally, the minor alleles of the remaining
SNPs increased the risk of different CHD types.
SHF regulation involves numerous signaling and transcriptional
cascades. The ISL1-GATA-MEF2C pathway
plays an important and central role in the transcription factor
network of SHF. When heart looping occurs, Mef2c transcripts
are robustly expressed in the outflow tract and right
ventricle and are less abundant in the left ventricle and atria
(18). Mouse embryos lacking Mef2c exhibit severe defects
of the outflow tract and hypoplasia of the right ventricle
(19). These observations imply a crucial role for MEF2C
in the transcription factor networks regulating myoblast differentiation in SHFs. There were two SNPs located in
the promoter region of MEF2C that were associated with
CHD in this study (15). The minor G allele of MEF2C:
rs80043958 A>G exhibited an increased risk of VSD, ASD,
and PDA, while the G allele of MEF2C: rs304154 A>G
only increased TOF risk. The bioinformatic analysis suggested
that both SNPs cause promoter loss in MEF2C,
which might disrupt binding with other transcription factors
and influence MEF2C transcription. Subsequent luciferase
assays showed that the minor G allele of rs304154 could
either decrease the transcription level of MEF2C alone
or influence its transcription level in combination with
FOXC1, GATA1, or FOXC1+GATA1. Although we did
not find that the G allele of rs80043958 influenced the
transcriptional level of MEF2C when the HLTF interacted
with a promoter containing rs80043958. The minor G allele
increased the transcription level of MEF2C.
Epigenetic factors may also be involved in cardiac
morphogenesis. The disturbance of the chromatin remodeling
protein Smyd1 in mice results in a phenotype with a
decreased right ventricle and dysplasia of the left ventricle
(20). There have been few reports of SMYD1 mutations
associated with CHD. One study revealed that one de
novo exonic mutation in SMYD1 was associated with hypertrophic
cardiomyopathy (12). In the present study, we
found that both identified SNPs of SMYD1 were located
in the exon. The minor G allele of SMYD1: rs2919881
A>G (p.I253I) increased the risk of PA or PS with IVS.
The minor G allele of SMYD1: rs1542088 T>G (p.R131R)
increased the risk of simple CHD. Both SNPs are synonymous
variants. There is a SET domain in Smyd1 that
has methyltransferase activity and histone deacetylase
(HDAC) activity, which can represses genes (20). p.I253I
is located in the ET domain of SMYD1, which is a pivotal
SET domain that functions as the primary catalytic
domain. p.R131R is located in the SET-I domain, which
contributes to the binding of cofactors with substrates and
protein stability (21). Therefore, we could infer that the
p.I253I variant might influence methyltransferase activity,
while p.R131R could interfere with cofactor and substrate
binding with SMYD1.
Three GATA factors, GATA 4, 5, and 6, were expressed
in the heart in a partially overlapping way. GATA transcription
factors are key regulators of cardiac development.
In contrast to GATA 4 and 6, GATA 5 expression
is more restricted to endocardial cushions in the outflow
tract during cardiac development. Laforest et al. found that
Gata4+/−Gata5+/− and Gata5+/−Gata6+/− double heterozygous
mice die in the embryonic or perinatal periods
due to dysplasia of the OFT, including double outlet right
ventricle (DORV) and VSD. These studies reveal the existence
of important genetic interactions between GATA5 and
the other two Gata factors in outflow tract morphogenesis
(22). Later studies in humans revealed GATA5 mutations
associated with VSD, aortic bicuspid, DORV, and TOF
(13, 23-25). In our study, the minor A allele of GATA5:
rs41305803 G>A (p.D203D) increased the risk of RVOTO,
which is an outflow tract malformation. The minor C allele
of GATA5: rs6587239 T>C (p.K284K) increased the
risk of simple CHD. Subjects carrying GATA5 rs6061243
(p.S327S) GC presented a 4.31-fold increase in the risk of
CHD. These results were similar to previous studies and
suggest that subtle alterations in the activity of the GATA5
factor might cause CHD in humans.
TBX20 is critical for heart chamber formation, especially
the outflow tract and right ventricle, which are
the anterior derivatives of the SHF (26). Targeted disruption
of TBX20 leads to unlooped and severely hypoplastic
myocardial tubes in mice (27). Incomplete knockdown of
TBX20 results in severely compromised valve formation,
hypoplastic right ventricle, and persistent truncus arteriosus
(9). In cardiac development, TBX20 functions as a
dosage-dependent moderator (9). Either loss- or gain-offunction
in TBX20 results in abnormal heart development
(28). TBX20 mutations are associated with VSD, ASD,
TOF, DORV, persistent truncus arteriosus (PTA), and adult
dilated cardiomyopathy in humans (29, 30). Mutations in
either the exon or promoter regions of TBX20 can lead to
CHD (10). This study revealed that TBX20: rs336283 A>G
in the promoter increased the risk of CHD, while TBX20:
rs336284 A>G (p.S13S) in an exon increased the risk of
SV. Further luciferase assays showed that the G allele of
rs336284 decreased the transcription level of TBX20, even
with the interaction with ZFX.
Limitations are still present in this study. First, the
small sample size limited the persuasiveness. A large number
of CHD patients and healthy controls for genotyping
will be included in our next study. Second, the mechanisms
of these ten SNPs affecting the risk of CHD still require
further investigation. The knock-in mouse model must be
built in order to explore the mechanism by which these
SNPs affect CHD formation at the genetic and molecular
biological levels.
In this study, the associations of exonic and promoter
SNPs in SHF transcription factors with an increased risk
of CHD were evaluated. This results suggest that SNPs in
SHF exon and promoter regions play roles in the pathogenesis
of CHD.
Conflict of interest: none
Authors’ contributions: Enshi Wang and Shengshou
Hu: Conceived of study. Enshi Wang and Xuesong Fan:
Performed research. Enshi Wang, Yu Nie, Zhe Zheng: Analyzed data. Enshi Wang wrote the paper; Shengshou
Hu: Supervision. Enshi Wang, Xuesong Fan: Validation.
Shengshou Hu: Writing-Reviewing and Editing.
Acknowledgements: This work was supported by
the National Natural Science Foundation of China (Grants
no. 81400242, 81430006, and 81441010) and the National
Basic Research Development Program in China (Program
973: 2010CB529505).
|
|
|
|
 |
Number 27
VOL. 27 (2), 2024 |
Number 27
VOL. 27 (1), 2024 |
Number 26
Number 26 VOL. 26(2), 2023 All in one |
Number 26
VOL. 26(2), 2023 |
Number 26
VOL. 26, 2023 Supplement |
Number 26
VOL. 26(1), 2023 |
Number 25
VOL. 25(2), 2022 |
Number 25
VOL. 25 (1), 2022 |
Number 24
VOL. 24(2), 2021 |
Number 24
VOL. 24(1), 2021 |
Number 23
VOL. 23(2), 2020 |
Number 22
VOL. 22(2), 2019 |
Number 22
VOL. 22(1), 2019 |
Number 22
VOL. 22, 2019 Supplement |
Number 21
VOL. 21(2), 2018 |
Number 21
VOL. 21 (1), 2018 |
Number 21
VOL. 21, 2018 Supplement |
Number 20
VOL. 20 (2), 2017 |
Number 20
VOL. 20 (1), 2017 |
Number 19
VOL. 19 (2), 2016 |
Number 19
VOL. 19 (1), 2016 |
Number 18
VOL. 18 (2), 2015 |
Number 18
VOL. 18 (1), 2015 |
Number 17
VOL. 17 (2), 2014 |
Number 17
VOL. 17 (1), 2014 |
Number 16
VOL. 16 (2), 2013 |
Number 16
VOL. 16 (1), 2013 |
Number 15
VOL. 15 (2), 2012 |
Number 15
VOL. 15, 2012 Supplement |
Number 15
Vol. 15 (1), 2012 |
Number 14
14 - Vol. 14 (2), 2011 |
Number 14
The 9th Balkan Congress of Medical Genetics |
Number 14
14 - Vol. 14 (1), 2011 |
Number 13
Vol. 13 (2), 2010 |
Number 13
Vol.13 (1), 2010 |
Number 12
Vol.12 (2), 2009 |
Number 12
Vol.12 (1), 2009 |
Number 11
Vol.11 (2),2008 |
Number 11
Vol.11 (1),2008 |
Number 10
Vol.10 (2), 2007 |
Number 10
10 (1),2007 |
Number 9
1&2, 2006 |
Number 9
3&4, 2006 |
Number 8
1&2, 2005 |
Number 8
3&4, 2004 |
Number 7
1&2, 2004 |
Number 6
3&4, 2003 |
Number 6
1&2, 2003 |
Number 5
3&4, 2002 |
Number 5
1&2, 2002 |
Number 4
Vol.3 (4), 2000 |
Number 4
Vol.2 (4), 1999 |
Number 4
Vol.1 (4), 1998 |
Number 4
3&4, 2001 |
Number 4
1&2, 2001 |
Number 3
Vol.3 (3), 2000 |
Number 3
Vol.2 (3), 1999 |
Number 3
Vol.1 (3), 1998 |
Number 2
Vol.3(2), 2000 |
Number 2
Vol.1 (2), 1998 |
Number 2
Vol.2 (2), 1999 |
Number 1
Vol.3 (1), 2000 |
Number 1
Vol.2 (1), 1999 |
Number 1
Vol.1 (1), 1998 |
|
|
