Development and application of linkage analysis in genetic diagnosis of familial hypertrophic cardiomyopathy

Presurgical Nasoalveolar Molding in a 4-day-old Infant with Unilateral Cleft Lip, Alveolus, and Palate Deformity

Introduction

A four day old male infant was referred to our department. Infant’s mother complained of an opening over lip and difficulty in feeding and desires to get it corrected. On clinical examination patient showed complete unilateral cleft lip, alveolus and palate deformity towards the left side.

Methods

On the initial visit, lip taping using 1/4inch 3M Steri-strip was applied and instructions were given to parents about lip taping, and advised to continue lip taping for 2 weeks. Initial impressions were taken to fabricate the Presurgical nasoalveolar molding appliance. Intraoral molding plate was made to approximate the maxillary segments. Nasal stent was added to correct the nose deformity. Presurgical impressions were made.

Results

Under this pre surgical treatment, the cleft alveolus reduced in size from 13mm to 3mm at the alveolar ridge and palate, respectively. The nasal wing was lifted considerably.

Conclusion

Pre-surgical nasoalveolar moulding helped to reduce the cleft gap, improve the arch form, approximate lip segments and distinctly improve the morphology of the nose by correcting flattened nasal wings. This aforementioned correction not only enabled better aesthetic results after surgery but also reduced tissues tension and scar formation post-surgery.

Setting up Multiplex Panels for Genetic Testing of Familial Hypertrophic Cardiomyopathy Based on Linkage Analysis

BACKGROUND

Familial hypertrophic cardiomyopathy (HCM) is caused by mutations in genes encoding cardiac sarcomere proteins. Nowadays genetic testing of HCM plays an important role in clinical practice by contributing to the diagnosis, prognosis, and screening of high-risk individuals. The aim of this study was developing a reliable testing strategy for HCM based on linkage analysis and appropriate for Iranian population.

METHODS

Six panels of four microsatellite markers surrounding MYH7, MYBPC3, TNNT2, TNNI3, TPM1, and MYL2 genes (24 markers in total) were selected for multiplex PCR and fragment length analysis. Characteristics of markers and informativeness of the panels were evaluated in 50 unrelated Iranians. The efficacy of the strategy was verified in a family with HCM.

RESULTS

All markers were highly polymorphic. The panels were informative in 96-100% of samples. Multipoint linkage analysis excluded the linkage between the disease and all six genes by obtaining maximum LOD score ≤-2.

CONCLUSION

This study suggests a reliable genetic testing method based on linkage analysis between 6 sarcomere genes and familial HCM. It could be applied for diagnostic, predictive, or screening testing in clinical setting.

Genetic and phenotypic characterization of mutations in myosin-binding protein C (MYBPC3) in 81 families with familial hypertrophic cardiomyopathy: total or partial haploinsufficiency

Mutations in the MYBPC3 gene, encoding the sarcomere protein myosin-binding protein C, are among the most frequent causes of autosomal dominant familial hypertrophic cardiomyopathy (FHC). We studied the frequency, type, and pathogenetic mechanism of MYBPC3 mutations in an unselected cohort of 81 FHC families, consecutively enrolled at a tertiary referral center. Nine mutations, six of which were novel, were found in 10 (12.3%) of the families using single-strand conformation polymorphism and DNA sequencing. A frameshift mutation in exon 2 clearly suggests that haploinsufficiency is a pathogenetic mechanism in FHC. In addition, splice site mutations in exon 6 and intron 31, a deletion in exon 13, and a nonsense mutation in exon 25, all lead to premature termination codons, most likely causing loss of function and haploinsufficiency. Furthermore, there were two missense mutations (D228N and A833 T) and one in-frame deletion (DeltaLys813). A considerable intrafamilial variation in phenotypic expression of MYBPC3-based FHC was noted, and we suggest that mutations influencing stability of mRNA could play a role in the variable penetrance and expressivity of the disease, perhaps via partial haploinsuffciency.

Variable clinical manifestation of a novel missense mutation in the alpha-tropomyosin (TPM1) gene in familial hypertrophic cardiomyopathy

OBJECTIVES

This study was initiated to identify the disease-causing genetic defect in a family with hypertrophic cardiomyopathy (HCM) and high incidence of sudden death.

BACKGROUND

Familial hypertropic cardiomyopathy (FHC) is an autosomal dominant transmitted disorder that is genetically and clinically heterogeneous. Mutations in 11 genes have been associated with the pathogenesis of the disease.

METHODS

We studied a large FHC family, first by linkage analysis, to identify the gene involved, and subsequently screened the gene, encoding alpha-tropomyosin (TPM1), for mutations by using single-strand conformation polymorphism and sequencing analysis.

RESULTS

Twelve family members presented clinical features of HCM, five of whom died at young age, while others had only mild clinical features. Marker analysis showed linkage for the TPM1 gene on chromosome 15q22 (maximal logarithm of the odds score is 5.16, theta = 0); subsequently, a novel missense mutation (Glu62Gln) was identified.

CONCLUSIONS

The novel mutation identified in TPM1 is associated with the clinical features of cardiac hypertrophy in all but one genetically affected member of this large family. The clinical data suggest a malignant phenotype at young age with a variable clinical manifestation and penetrance at older age. The Glu62Gln mutation is the sixth TPM1 mutation identified as the cause of FHC, indicating that mutations in this gene are very rare. This is the first reported amino acid substitution at the f-position within the coiled-coil structure of the tropomyosin protein.

Idiopathic restrictive cardiomyopathy is part of the clinical expression of cardiac troponin I mutations

Restrictive cardiomyopathy (RCM) is an uncommon heart muscle disorder characterized by impaired filling of the ventricles with reduced volume in the presence of normal or near normal wall thickness and systolic function. The disease may be associated with systemic disease but is most often idiopathic. We recognized a large family in which individuals were affected by either idiopathic RCM or hypertrophic cardiomyopathy (HCM). Linkage analysis to selected sarcomeric contractile protein genes identified cardiac troponin I (TNNI3) as the likely disease gene. Subsequent mutation analysis revealed a novel missense mutation, which cosegregated with the disease in the family (lod score: 4.8). To determine if idiopathic RCM is part of the clinical expression of TNNI3 mutations, genetic investigations of the gene were performed in an additional nine unrelated RCM patients with restrictive filling patterns, bi-atrial dilatation, normal systolic function, and normal wall thickness. TNNI3 mutations were identified in six of these nine RCM patients. Two of the mutations identified in young individuals were de novo mutations. All mutations appeared in conserved and functionally important domains of the gene. This article was published online in advance of the print edition. The date of publication is available from the JCI website, http://www.jci.org.