Novel FHL1 mutation variant identified in a patient with nonobstructive hypertrophic cardiomyopathy and myopathy - a case report

New Clinical Phenotype in a Child Presenting With an FHL1 Mutation

There is a range of phenotypes associated with pathogenic variants in the FHL1 gene, including X-linked dominant scapuloperoneal myopathy, X-linked myopathy with postural muscle atrophy, reducing body myopathy, Emery-Dreifuss muscular dystrophy, rigid-spine syndrome, and hypertrophic cardiomyopathy. This gene encodes the four-and-a-half LIM domain protein 1 which is highly expressed in skeletal and cardiac muscle. The function of this protein includes influencing cellular architecture, myoblast differentiation, mechanotransduction, and skeletal muscle fiber size. We report a case of a 6-year-old boy with a novel FHL1 gene mutation who presented to the neuromuscular clinic for evaluation of stiffness, joint contractures, and mild proximal weakness. Symptoms first noted in the newborn period have been slowly progressive. The child's presentation has not been described before and represents a new clinical phenotype within the spectrum of FHL1-related disorders.

Pathogenic genes and clinical prognosis in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an autosomal dominant inherited cardiomyopathy characterized by left ventricular hypertrophy. It is one of the chief causes of sudden cardiac death in younger people and athletes. Molecular-genetic studies have confirmed that the vast majority of HCM is caused by mutations in genes encoding sarcomere proteins. HCM has a relatively wide phenotypic heterogeneity, varying from asymptomatic to sudden cardiac death, because of the many different mutations and pathogenic genes underlying it. Many studies have explored the clinical symptoms and prognosis of HCM, emphasizing the importance of genotype in evaluating patient prognosis and guiding the clinical management of HCM. To elaborate the main pathogenic genes and phenotypic prognosis in HCM to promote a better understanding of this genetic disease. Retrospective analysis of literature to evaluate the association between underlying gene mutations and clinical phenotypes in HCM patients. As sequencing technology advances, the pathogenic gene mutation spectrum and phenotypic characteristics of HCM are gradually becoming clearer. HCM is a widespread inherited disease with a highly variable clinical phenotype. The precise mechanisms linking known pathogenic gene mutations and the clinical course of this heterogeneous condition remain elusive.

The FHL1 myopathy spectrum revisited: a literature review and report of two new patients

Objectives

Mutations in the FHL1 gene have been associated with a diverse spectrum of X-linked diseases affecting skeletal and cardiac muscle. Six clinically distinct human myopathies can be recognized, including reducing body myopathy (RBM), X-linked dominant scapuloperoneal myopathy (SPM), X-linked myopathy with postural muscle atrophy (XMPMA), rigid spine syndrome (RSS), hypertrophic cardiomyopathy (HCM) and type 6 Emery- Dreifuss muscular dystrophy (EDMD). The core features of all described FHL1opathies are mostly scapuloperoneal muscle weakness, rigid spine, cardiac involvement, and cytoplasmic bodies in the muscle biopsy.

Methods

We systematically reviewed the medical literature between the years 2000 and 2024 regarding the phenotype and genotype description of FHL1-associated myopathies.

Results

Here, we report two novel patients presenting with an X-linked myopathy with postural muscle atrophy (XMPMA) caused by the c.672 C > G FHL1 gene mutation.

Conclusion

When encountering these features in a patient, one may consider screening for an FHL1 mutation. The course ranges from a severe fatal course with early onset to very mild features with late onset. Once a dystrophinopathy has been excluded, increased CK values in male subjects with possible X-linked inheritance should always trigger FHL1 gene screening.

Kinome and phosphoproteome reprogramming underlies the aberrant immune responses in critically ill COVID-19 patients

SARS-CoV-2 infection triggers extensive host immune reactions, leading to severe diseases in certain individuals. However, the molecular basis underlying the excessive yet non-productive immune responses in severe COVID-19 remains incompletely understood. In this study, we conducted a comprehensive analysis of the peripheral blood mononuclear cell (PBMC) proteome and phosphoproteome in sepsis patients positive or negative for SARS-CoV-2 infection, as well as healthy subjects, using quantitative mass spectrometry. Our findings demonstrate dynamic changes in the COVID-19 PBMC proteome and phosphoproteome during disease progression, with distinctive protein or phosphoprotein signatures capable of distinguishing longitudinal disease states. Furthermore, SARS-CoV-2 infection induces a global reprogramming of the kinome and phosphoproteome, resulting in defective adaptive immune response mediated by the B and T lymphocytes, compromised innate immune responses involving the SIGLEC and SLAM family of immunoreceptors, and excessive cytokine-JAK-STAT signaling. In addition to uncovering host proteome and phosphoproteome aberrations caused by SARS-CoV-2, our work recapitulates several reported therapeutic targets for COVID-19 and identified numerous new candidates, including the kinases PKG1, CK2, ROCK1/2, GRK2, SYK, JAK2/3, TYK2, DNA-PK, PKCδ, and the cytokine IL-12.

Next-Generation Sequencing Gene Panels in Inheritable Cardiomyopathies and Channelopathies: Prevalence of Pathogenic Variants and Variants of Unknown Significance in Uncommon Genes

The diffusion of next-generation sequencing (NGS)-based approaches allows for the identification of pathogenic mutations of cardiomyopathies and channelopathies in more than 200 different genes. Since genes considered uncommon for a clinical phenotype are also now included in molecular testing, the detection rate of disease-causing variants has increased. Here, we report the prevalence of genetic variants detected by using a NGS custom panel in a cohort of 133 patients with inherited cardiomyopathies (n = 77) or channelopathies (n = 56). We identified 82 variants, of which 50 (61%) were identified in genes without a strong or definitive evidence of disease association according to the NIH-funded Clinical Genome Resource (ClinGen; "uncommon genes"). Among these, 35 (70%) were variants of unknown significance (VUSs), 13 (26%) were pathogenic (P) or likely pathogenic (LP) mutations, and 2 (4%) benign (B) or likely benign (LB) variants according to American College of Medical Genetics (ACMG) classifications. These data reinforce the need for the screening of uncommon genes in order to increase the diagnostic sensitivity of the genetic testing of inherited cardiomyopathies and channelopathies by allowing for the identification of mutations in genes that are not usually explored due to a currently poor association with the clinical phenotype.

Three novel FHL1 Variants cause a mild Phenotype of Emery-Dreifuss Muscular Dystrophy

Emery-Dreifuss muscular dystrophy (EDMD) is a hereditary muscle disease, characterized by the clinical triade of early-onset joint contractures, progressive muscle weakness and cardiac involvement. Pathogenic variants in FHL1 can cause a rare X-linked recessive form of EDMD, type 6. We report three men with novel variants in FHL1 leading to EDMD6. Onset of muscle symptoms was in late adulthood and muscle weakness was not prominent in either of the patients. All patients had hypertrophic cardiomyopathy and one of them also had cardiac arrhythmias. Western blot performed on muscle biopsies from two of the patients showed no FHL1 protein expression. We predict that the variant in the third patient also leads to absence of FHL1 protein. Complete loss of all FHL1 isoforms combined with mild muscle involvement supports the hypothesis that loss of all FHL1 isoforms is more benign than the cytotoxic effects of expressed FHL1 protein with pathogenic missense variants. This article is protected by copyright. All rights reserved.

Understanding the molecular basis of cardiomyopathy

Inherited cardiomyopathies are a major cause of mortality and morbidity worldwide and can be caused by mutations in a wide range of proteins located in different cellular compartments. The present review is based on Dr. Ju Chen's 2021 Robert M. Berne Distinguished Lectureship of the American Physiological Society Cardiovascular Section, in which he provided an overview of the current knowledge on the cardiomyopathy-associated proteins that have been studied in his laboratory. The review provides a general summary of the proteins in different compartments of cardiomyocytes associated with cardiomyopathies, with specific focus on the proteins that have been studied in Dr. Chen's laboratory.

Yield of Rare Variants Detected by Targeted Next-Generation Sequencing in a Cohort of Romanian Index Patients with Hypertrophic Cardiomyopathy

BACKGROUND

The aim of this study was to explore the rare variants in a cohort of Romanian index cases with hypertrophic cardiomyopathy (HCM).

METHODS

Forty-five unrelated probands with HCM were screened by targeted next generation sequencing (NGS) of 47 core and emerging genes connected with HCM.

RESULTS

We identified 95 variants with allele frequency < 0.1% in population databases. MYBPC3 and TTN had the largest number of rare variants (17 variants each). A definite genetic etiology was found in 6 probands (13.3%), while inconclusive results due to either known or novel variants were established in 31 cases (68.9%). All disease-causing variants were detected in sarcomeric genes (MYBPC3 and MYH7 with two cases each, and one case in TNNI3 and TPM1 respectively). Multiple variants were detected in 27 subjects (60%), but no proband carried more than one causal variant. Of note, almost half of the rare variants were novel.

CONCLUSIONS

Herein we reported for the first time the rare variants identified in core and putative genes associated with HCM in a cohort of Romanian unrelated adult patients. The clinical significance of most detected variants is yet to be established, additional studies based on segregation analysis being required for definite classification.