A novel mutation in the COL12A1 gene

COL12A1 Gene Variant and a Review of the Literature: A Case Report of Ullrich Congenital Muscular Dystrophy

Introduction

Mutations in collagen type IV-associated genes lead to Ullrich congenital muscular dystrophy (UCMD) and Bethlem myopathy (BM). COL12A1 gene mutations have rarely been reported in patients with UCMD- and BM-like disorders not involving COL6 mutations. UCMD-2 results from homozygous mutations in the COL12A1 gene on the long arm of chromosome 6. Pathogenic variants in COL12A1 result in a rare congenital connective tissue/myopathy overlap syndrome under the heading of myopathic Ehlers-Danlos syndrome. COL12A1 dominant pathogenic variants have been rarely reported, and the phenotypic spectrum has not yet been identified.

Case Presentation

We describe a female patient aged 2 years and 10 months exhibiting a milder phenotype who presented due to pronounced joint hyperlaxity, frequent falls, and skin lesions. Genetic analysis revealed a homozygous c.8903C>T (p.Pro2968Leu) missense variant that had previously been described but concerning which there had been no clinical report, in the COL12A1 gene.

Discussion/Conclusion

This report is presented in order to raise awareness of rare mutations in the COL12A1 gene that affect muscle and connective tissue and to add to the literature in defining the phenotypic spectrum.

The coordinated activities of collagen VI and XII in maintenance of tissue structure, function and repair: evidence for a physical interaction

Collagen VI and collagen XII are structurally complex collagens of the extracellular matrix (ECM). Like all collagens, type VI and XII both possess triple-helical components that facilitate participation in the ECM network, but collagen VI and XII are distinct from the more abundant fibrillar collagens in that they also possess arrays of structurally globular modules with the capacity to propagate signaling to attached cells. Cell attachment to collagen VI and XII is known to regulate protective, proliferative or developmental processes through a variety of mechanisms, but a growing body of genetic and biochemical evidence suggests that at least some of these phenomena may be potentiated through mechanisms that require coordinated interaction between the two collagens. For example, genetic studies in humans have identified forms of myopathic Ehlers-Danlos syndrome with overlapping phenotypes that result from mutations in either collagen VI or XII, and biochemical and cell-based studies have identified accessory molecules that could form bridging interactions between the two collagens. However, the demonstration of a direct or ternary structural interaction between collagen VI or XII has not yet been reported. This Hypothesis and Theory review article examines the evidence that supports the existence of a functional complex between type VI and XII collagen in the ECM and discusses potential biological implications.

Homozygous splice site variant affecting the first von Willebrand factor A domain of COL12A1 in a patient with myopathic Ehlers-Danlos syndrome

Myopathic Ehlers-Danlos syndrome (mEDS) is a subtype of EDS that is caused by abnormalities in COL12A1. Up-to-date, 24 patients from 15 families with mEDS have been reported, with 14 families showing inheritance in an autosomal dominant manner and one family in an autosomal recessive manner. We encountered an additional patient with autosomal recessive mEDS. The patient is a 47-year-old Japanese man, born to consanguineous parents with no related features of mEDS. After birth, he presented with hypotonia, weak spontaneous movements, scoliosis, and torticollis. He had soft palms but no skin hyperextensibility or fragility. Progressive scoliosis, undescended testes, and muscular torticollis required surgery. During adulthood, he worked normally and had no physical concerns. Clinical exome analysis revealed a novel homozygous variant in COL12A1 (NM_004370.6:c.395-1G > A) at the splice acceptor site of exon 6, leading to in-frame skipping of exon 6. The patient was diagnosed with mEDS. The milder manifestations in the current patient compared with previously reported patients with mEDS might be related to the site of the variant. The variant is located in the genomic region encoding the first von Willebrand factor A domain, which affects only the long isoform of collagen XII, in contrast to the variants in previously reported mEDS patients that affected both the long and short isoforms. Further studies are needed to delineate comprehensive genotype-phenotype correlation of the disorder.

Collagen XII mediated cellular and extracellular mechanisms in development, regeneration, and disease

Collagen XII, a fibril-associated collagen with interrupted triple helices (FACIT), influences fibrillogenesis in numerous tissues. In addition to this extracellular function, collagen XII also directly regulates cellular function. Collagen XII is widely expressed in connective tissues, particularly tendons, ligaments, and the periodontium and periosteum, where it is enriched in the pericellular regions. Mutations in the collagen XII gene cause myopathic Ehlers-Danlos syndrome (mEDS), an early-onset disease characterized by overlapping connective tissue abnormalities and muscle weakness. Patients with mEDS exhibit delayed motor development, muscle weakness, joint laxity, hypermobility, joint contractures, and abnormal wound healing. A mEDS mouse model was generated by deletion of the Col12a1 gene, resulting in skeletal and muscle abnormalities with disorganized tissue structures and altered mechanical properties. Extracellularly, collagen XII interacts with collagen I fibrils and regulates collagen fibril spacing and assembly during fibrillogenesis. Evidence for the binding of collagen XII to other EDS-related molecules (e.g., decorin and tenascin X) suggests that disruption of ECM molecular interactions is one of the causes of connective tissue pathology in mEDS. Collagen XII also has been shown to influence cell behavior, such as cell shape and cell-cell communication, by providing physical connection between adjacent cells during tissue development and regeneration. The focus of this review is on the functions of collagen XII in development, regeneration, and disease.

Ehlers-Danlos: A Literature Review and Case Report in a Colombian Woman with Multiple Comorbidities

Ehlers-Danlos syndromes (EDS) are a heterogeneous group of genetically transmitted connective tissue disorders that directly affect collagen synthesis, with a broad range of symptoms. Case presentation: This study presents a clinical case of a Colombian woman with myopathic EDS and multiple comorbidities taking 40 years of medical history to make the right diagnosis. This article also presents a review of the current literature on EDS, not only to remind the syndrome but also to help the clinician correctly identify symptoms of this diverse syndrome. Conclusion: A multidisciplinary approach to the diagnosis of the patient, including clinical and molecular analysis, and neuropsychological and psychological assessment, is important to improve the treatment choice and the outcome prediction of the patients.

COL12A1 Single Nucleotide Polymorphisms rs240736 and rs970547 Are Not Associated with Temporomandibular Joint Disc Displacement without Reduction

Temporomandibular disorders (TMDs) may affect up to 25% of the population, with almost 70% of these TMD cases developing malpositioning of the disc over time in what is known as internal derangement (ID). Despite significant efforts, the molecular mechanism underlying disease progression is not yet very well known. In this study, the role of COL12A1 rs970547 and rs240736 polymorphisms as potential genetic factors regulating ID was investigated. The study included 124 Caucasian patients of both sexes after disc displacement without reduction (DDwoR) in either one or two temporomandibular joints (TMJs), either of which meet the criteria for this condition. All patients underwent clinical examination and 3D digital imaging. The COL12A1 rs970547 and rs240736 polymorphisms were evaluated. There were no statistically significant differences in the chi-square test between the study group and healthy controls. The examined COL12A1 rs240736 and rs970547 polymorphisms do not contribute to DDwoR in Polish Caucasians.

A local regulatory network in the testis mediated by laminin and collagen fragments that supports spermatogenesis

It is almost five decades since the discovery of the hypothalamic-pituitary-testicular axis. This refers to the hormonal axis that connects the hypothalamus, pituitary gland and testes, which in turn, regulates the production of spermatozoa through spermatogenesis in the seminiferous tubules, and testosterone through steroidogenesis by Leydig cells in the interstitium, of the testes. Emerging evidence has demonstrated the presence of a regulatory network across the seminiferous epithelium utilizing bioactive molecules produced locally at specific domains of the epithelium. Studies have shown that biologically active fragments are produced from structural laminin and collagen chains in the basement membrane. Additionally, bioactive peptides are also produced locally in non-basement membrane laminin chains at the Sertoli-spermatid interface known as apical ectoplasmic specialization (apical ES, a testis-specific actin-based anchoring junction type). These bioactive peptides are derived from structural laminins and/or collagens at the corresponding sites through proteolytic cleavage by matrix metalloproteinases (MMPs). They in turn serve as autocrine and/or paracrine factors to modulate and coordinate cellular events across the epithelium by linking the apical and basal compartments, the apical and basal ES, the blood-testis barrier (BTB), and the basement membrane of the tunica propria. The cellular events supported by these bioactive peptides/fragments include the release of spermatozoa at spermiation, remodeling of the immunological barrier to facilitate the transport of preleptotene spermatocytes across the BTB, and the transport of haploid spermatids across the epithelium to support spermiogenesis. In this review, we critically evaluate these findings. Our goal is to identify research areas that deserve attentions in future years. The proposed research also provides the much needed understanding on the biology of spermatogenesis supported by a local network of regulatory biomolecules.