The Immunomodulatory Role of Microbiota in Rheumatic Heart Disease: What Do We Know and What Can We Learn from Other Rheumatic Diseases?

Rheumatic heart disease (RHD) represents a serious cardiac sequela of acute rheumatic fever, occurring in 30-45% of patients. RHD is multifactorial, with a strong familial predisposition and known environmental risk factors that drive loss of immunological tolerance. The gut and oral microbiome have recently been implicated in the pathogenesis of RHD. Disruption of the delicate balance of the microbiome, or dysbiosis, is thought to lead to autoimmune responses through several different mechanisms including molecular mimicry, epitope spreading, and bystander activation. However, data on the microbiomes of RHD patients are scarce. Therefore, in this comprehensive review, we explore the various dimensions of the intricate relationship between the microbiome and the immune system in RHD and other rheumatic diseases to explore the potential effect of microbiota on RHD and opportunities for diagnosis and treatment.

A novel homozygous TPM1 mutation in familial pediatric hypertrophic cardiomyopathy and in silico screening of potential targeting drugs

OBJECTIVE

Familial hypertrophic cardiomyopathy (HCM) is the most common genetic cardiac disease. While sarcomeric gene mutations explain many HCM cases, the genetic basis of about half of HCM cases remains elusive. Here we aimed to identify the gene causing HCM in a non-consanguineous Saudi Arabian family with affected family members and a history of sudden death. The impact of the identified mutation on protein structure and potential drug targets were evaluated in silico.

MATERIALS AND METHODS

Triplets (two HCM subjects and one patent ductus arteriosus (PDA) case) and unaffected parents were screened by targeted next-generation sequencing (NGS) for 181 candidate cardiomyopathy genes. In silico structural and functional analyses, including protein modeling, structure prediction, drug screening, drug binding, and dynamic simulations were performed to explore the potential pathogenicity of the variant and to identify candidate drugs.

RESULTS

A homozygous missense mutation in exon 1 of TMP1 (assembly GRCh37-chr15: 63340781; G>A) was identified in the triplets [two HCM and one patent ductus arteriosus (PDA)] that substituted glycine for arginine at codon 3 (p.Gly3Arg). The parents were heterozygous for the variant. The mutation was predicted to cause a significant and deleterious change in the TPM1 protein structure that slightly affected drug binding, stability, and conformation. In addition, we identified several putative TPM1-targeting drugs through structure-based in silico screening.

CONCLUSIONS

TPM1 mutations are a common cause of HCM and other congenital heart defects. To date, TPM1 has not been associated with isolated PDA; to our knowledge, this is the first report of the homozygous missense variation p.Gly3Arg in TPM1 associated with familial autosomal recessive pediatric HCM and PDA. The identified candidate TPM1 inhibitors warrant further prospective investigation.

Next-generation sequencing identifies a homozygous mutation in ACADVL associated with pediatric familial dilated cardiomyopathy

OBJECTIVE

Pediatric familial dilated cardiomyopathy (DCM) is a rare and severe heart disease. The genetics of familial DCM are complex and include over 100 known disease-causing genes, but many causative genes are unknown. We aimed to identify the causative gene for DCM in a consanguineous Saudi Arabian family with affected family members and a history of sudden death.

PATIENTS AND METHODS

Affected (two children) and unaffected (one sibling and the mother) family members were screened by next-generation sequencing (NGS) for 181 candidate DCM genes and underwent metabolic screening. Fifty-seven clinically annotated controls and 46 DCM cases were then tested for the identified mutation. In silico structural and functional analyses including protein modeling, structure prediction and dynamic simulations were performed.

RESULTS

A homozygous missense mutation in exon 15 of the acyl-CoA dehydrogenase very long chain gene (ACADVL; chr17:7127303; G>A) was identified in affected subjects that substituted histidine for arginine at codon 450 (p.R450H). The variant was heterozygous in the mother and unaffected sister. The mutation was absent in 57 clinically annotated controls and 48 pediatric DCM cases. The mutation was predicted to cause a significant and deleterious change in the ACADVL protein structure that affected drug binding, stability, and conformation. Metabolic screening confirmed VLCAD deficiency in affected individuals.

CONCLUSIONS

The ACADVL R450H mutation is an uncommon cause of the DCM phenotype that appears to be autosomal recessive. Targeted NGS is useful for identifying the causative mutation(s) in familial DCM of unknown genetic cause.

The Polymorphism at the microRNA-155 Binding Site in the AGTR1 Gene is not Significantly Associated with Rheumatic Heart Disease in Saudi Arabia Population

BACKGROUND

Rheumatic Heart Disease (RHD) remains a major cause of cardiovascular diseases and the most devastating effects are shown on children and young adults. RHD is caused due to the interaction between microbial, environmental, immunologic, and genetic factors. The Renin- Angiotensin Aldosterone System (RAAS) has been strongly implicated as the susceptibility pathway in the pathogenesis of the cardiovascular disease.

OBJECTIVE

The present study investigated the modulating effect of Angiotensin II type 1 receptor (AGTR1) 1166A>C polymorphism on the RHD and its clinical features in Saudi Arabia.

METHODS

AGTR1 1166A>C polymorphism was genotyped in 96 echocardiographically confirmed RHD patients and 142 ethnically matched controls by the TaqMan allelic discrimination method.

RESULTS

Genotype distribution of the AGTR1 1166A>C polymorphism was not significantly different between RHD and control groups. Furthermore, AGTR1 1166A>C genotypes are not associated with the clinical features of RHD. These data support that there was no evidence for an association between AGTR1 1166A>C polymorphism and RHD in Saudi Arabia.

CONCLUSION

To the best of our knowledge, this is the first study that has investigated the possible association between AGTR1 1166A>C polymorphism and susceptibility to RHD and its clinical features. Even though the AGTR1 gene, 1166A>C (rs5186), was reported to be associated with hypertension, left ventricular hypertrophy and coronary heart disease. The present study did not find any association between AGTR1 1166A>C polymorphism and RHD in Saudi Arabia. Further studies are needed to confirm our findings.

Digenic Inheritance of LAMA4 and MYH7 Mutations in Patient with Infantile Dilated Cardiomyopathy

Background and objectives: Dilated cardiomyopathy (DCM) is a rare cardiac disease characterised by left ventricular enlargement, reduced left ventricular contractility, and impaired systolic function. Childhood DCM is clinically and genetically heterogenous and associated with mutations in over 100 genes. The aim of this study was to identify novel variations associated with infantile DCM. Materials and Methods: Targeted next generation sequencing (NGS) of 181 cardiomyopathy-related genes was performed in three unrelated consanguineous families from Saudi Arabia. Variants were confirmed and their frequency established in 50 known DCM cases and 80 clinically annotated healthy controls. Results: The three index cases presented between 7 and 10 months of age with severe DCM. In Family A, there was digenic inheritance of two heterozygous variants: a novel variant in LAMA4 (c.3925G > A, p.Asp1309Asn) and a known DCM mutation in MYH7 (c.2770G > A; p.Glu924Lys). The LAMA4 p.Asp1309Asn variant was predicted to be likely pathogenic according to international guidelines. The other two families had no identifiable potentially deleterious variants. Conclusions: Inheritance of two genetic variants may have a synergistic or dose effect to cause severe DCM. We report of a novel p.Asp1309Asn variation associated with DCM. Targeted NGS is useful in the molecular diagnosis of DCM and to guide whole-family management and counselling.

A novel splice-site mutation in the ASPM gene underlies autosomal recessive primary microcephaly

BACKGROUND

Autosomal recessive primary microcephaly (MCPH) is a clinically and genetically heterogeneous disorder. Patients with MCPH exhibit reduced occipito-frontal head circumference and non-progressive intellectual disability. To date, 17 genes have been known as an underlying cause of MCPH in humans. ASPM (abnormal spindle-like, microcephaly associated) is the most commonly mutated MCPH gene.

OBJECTIVE

Identify the genetic defect underlying MCPH in a Saudi family.

DESIGN

A cross-sectional clinical genetic study of a Saudi family.

SETTING

Madinah Maternity and Children Hospital and Centre for Genetics and Inherited Diseases, Taibah University.

PATIENTS AND METHODS

A molecular analysis was carried out on DNA samples from 10 individuals of a Saudi family segregating MCPH. DNA was isolated from the peripheral blood of 10 individuals, including 2 patients, and whole exome sequencing was performed using the Nextera Rapid Capture kit and NextSeq500 instrument. VariantStudio was used to filter and prioritize variants.

MAIN OUTCOME MEASURE(S)

Detection of mutation in the ASPM gene in a family segregating autoso- mal recessive primary microcephaly.

RESULTS

A novel homozygous splice-site variant (c.3742-1G > C) in the ASPM gene was identified. The variant is predicted to have an effect on splicing. Human Splice Finder, an in silico tool, predicted skipping of exon 16 due to this variant.

CONCLUSION

Skipping of exon 16 may change the order and number of IQ motifs in the ASPM protein leading to typical MCPH phenotype.

LIMITATIONS

Single family study.

LGMD2D syndrome: the importance of clinical and molecular genetics in patient and family management. Case Report

We report the case of a seven-year-old female from a consanguineous Saudi family with autosomal recessive limb girdle muscular dystrophy type 2D (LGMD2D) most likely caused by a rare SGCA mutation. Histopathological and molecular investigations resulted in the discovery of a homozygous mutation (c.226 C>T (p.L76 F)) in exon 3 of SGCA in the patient. The parents and one sibling were heterozygous carriers, but the mutation was not otherwise detected in 80 ethnic controls from the same geographic area. In silico analysis revealed that the mutation resulted in a functional leucine to phenylalanine alteration that was deleterious to the protein structure. This is only the second reported case of the p.L76F mutation in LGMD, and highlights that molecular genetics analysis is essential to deliver the most appropriate management to the patient and offer the family genetic counseling.

Impact of MIF Gene Promoter Variations on Risk of Rheumatic Heart Disease and Its Age of Onset in Saudi Arabian Patients

Although macrophage migration inhibitory factor (MIF) has consistently been shown to be an important immune modulator, data on the association between MIF promoter variations and the risk of developing rheumatic heart disease (RHD) remain inconclusive. RHD is an important complication of streptococcal infections in the Middle East, not least in Saudi Arabia, and identifying risk markers is an important priority. Therefore, we investigated the association between two functional MIF promoter variations and RHD susceptibility and severity in Saudi patients: the MIF-173G > C substitution (rs755622) and the MIF-794 CATT5-8 tetranucleotide repeat (rs5844572). Three hundred twenty-six individuals (124 RHD patients and 202 age-, sex-, and ethnically matched healthy controls) were genotyped using allelic discrimination and fragment analysis. Data were analyzed with respect to disease susceptibility, severity, sex, and age of onset. There was a significantly lower frequency of 173C allele carriage in RHD patients compared to controls [odds ratio (OR) = 0.47; 95% confidence intervals (CIs) = 0.28-0.77; p = 0.003]. Interestingly, the 173C allele was associated with late disease onset (p = 0.001). The 794 5-repeat allele was associated with decreased RHD risk (OR = 0.56; 95% CIs = 0.38-0.82; p = 0.003). In contrast, the 794 6-repeat allele was associated with increased risk of RHD (OR = 1.7; 95% CIs = 1.2-2.5; p = 0.002). MIF promoter variations appear to have a dual role in RHD, with 173C allele non-carriers at higher risk of developing RHD at a younger age. These results require further validation in larger multi-ethnic cohorts, and functional studies are necessary to understand the underlying molecular mechanisms driving the at-risk phenotype.

The MTHFR C677T polymorphism is associated with mitral valve rheumatic heart disease

OBJECTIVE

Rheumatic heart disease (RHD) is a serious complication of rheumatic fever (RF). Plasma homocysteine (Hcy) levels are increased in RHD patients. MTHFR catalyzes the irreversible conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate and plays a vital role in Hcy metabolism. We hypothesize that the MTHFR C677T polymorphism is associated with a risk of RHD.

PATIENTS AND METHODS

Eighty-six patients with RHD and 130 matched controls without a history of RHD were eligible for the study. The diagnosis of RHD was made according to modified Jones' criteria and echocardiography. Using echocardiography, RHD patients were further divided into mitral valve lesion (MVL) and combined valve lesion (CVL) groups. MTHFR C677T polymorphisms were genotyped by DNA sequencing. The chi-squared test was used to evaluate differences in genotypes.

RESULTS

Control genotypes were in Hardy-Weinberg equilibrium. The C677T homozygous genotype (OR = 4.09; 95% CIs 1.16-14.44; p = 0.020) and recessive model (TT vs. CC+CT; OR = 4.05; 95% CIs 1.17-14.04; p = 0.019) were significantly associated with MVL RHD.

CONCLUSIONS

This is the first study to investigate the association between the MTHFR C677T polymorphism and risk of RHD. The MTHFR C677T polymorphism is associated with RHD in patients with MVLs, perhaps via an Hcy-mediated cytokine effect.

Angiotensin-converting enzyme gene insertion deletion (ACE I/D) polymorphism in Saudi children with congenital heart disease

OBJECTIVE

Congenital heart diseases (CHDs) are the leading cause of infant deaths worldwide. Angiotensin-converting enzyme (ACE) gene I/D polymorphism is associated with many cardiovascular diseases. The precise relationship between this polymorphism and CHDs is not clear. The aim of this work is to determine the normal distribution of I/D polymorphism in Saudi citizens and to test for any association between this polymorphism and CHDs in Saudi children.

PATIENTS AND METHODS

Ninety-six CHD cases and 145 controls were included in this study. DNA was isolated from their peripheral blood, and then ACE I/D gene polymorphism was assayed by polymerase chain reaction (PCR).

RESULTS

There was no significant difference among the frequencies of the DD, DI and II genotypes in patients and controls [39 (41%), 64 (44%), 48 (51%) and 62 (43%), 7 (7%), 19 (13%)] respectively (p-value = 0.3 and OR (95% CI) = 0.3). There was no significant difference between D allele (DD+DI) and II genotype distribution among patients and controls [p-value = 0.2 & OR (95% CI) = 1.9 (0.8-4.7)]. Moreover, there was no difference between I allele (II+DI) and DD frequency [p-value = 0.8 & OR = 0.9, CI = 0.5-1.5].

CONCLUSIONS

ACE I/D gene polymorphism is not associated with CHDs in Saudi children. Further large-scale studies are necessary to establish our findings.

Angiotensin-converting enzyme gene insertion/deletion polymorphism in Saudi patients with rheumatic heart disease

OBJECTIVES

To investigate the association between angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism and rheumatic heart disease (RHD) in Saudi patients.

METHODS

A case-control study was conducted in Saudi RHD patients. Genomic DNA was isolated from 99 RHD patients attending the Pediatric Cardiology Clinic at the Maternity and Children Hospital, Al-Madinah, Saudi Arabia from March 2013 to June 2014, and from 145 age- and gender-matched controls. Patient clinical records were reviewed to report major and minor modified Jones' criteria for diagnosis. The diagnosis was confirmed by echocardiography. The ACE I/D polymorphism was identified by polymerase chain reaction.

RESULTS

A significant difference in ACE D allele carriage (DD+ID) distribution between RHD cases and controls was identified (p=0.02, odds ratio = 3.6, 95% confidence interval: 1.2-10.8). The D allele carriage was significantly associated with development of mitral valve lesions alone (p=0.03).

CONCLUSION

The ACE I/D polymorphism is associated with an increased risk of RHD in the Saudi population. Further studies are needed to confirm our findings and to understand the molecular mechanisms underlying this association.

Kawasaki disease in Western Saudi Arabia

OBJECTIVE

To describe our experience on Kawasaki disease in the Madinah region, Kingdom of Saudi Arabia (KSA).

METHODS

This is a retrospective hospital based study. The study was conducted in Maternity and Children Hospital, Madinah, Kingdom of Saudi Arabia during January 2007 to January 2010. The study included 51 patients' records as suspected cases of Kawasaki disease. The study was approved by the Ethical Committee.

RESULTS

Twenty-four patients were proven to have Kawasaki disease in this study. The mean age of the patients at diagnosis was 3.1+/-2.4 years. Most patients were younger than 5 years (83.3%). The male to female ratio was 1.7:1. Diagnosis was made 8.1+/-3.3 days after start of fever with a range from 4-15 days. All patients received intravenous immunoglobulin (IVIG) with 2 requiring another dose of IVIG. Echocardiography was performed 10.1+/-3.9 days from onset of fever with a range of 4-20 days. The duration of hospital stay was 7.9+/-5.8 days with a range from 3-25 days. Three patients had coronary artery abnormalities and still have coronary artery dilatation at last follow-up appointment.

CONCLUSION

A high index of suspicion is mandatory for early diagnosis of Kawasaki disease as delayed diagnosis may lead to coronary lesions. A national awareness program on Kawasaki disease is recommended.