Lymph vessels find a hairy niche.

Lymphatic vessels play important roles in coordinating fluid homeostasis and local immune responses of the tissues they reside in. A new study shows that in addition, lymphatic vessels of the skin are intimately associated with hair follicles and control HF development, cycling, and organization.

Dominant de novo DSP mutations cause erythrokeratodermia-cardiomyopathy syndrome.

Disorders of keratinization (DOK) show marked genotypic and phenotypic heterogeneity. In most cases, disease is primarily cutaneous, and further clinical evaluation is therefore rarely pursued. We have identified subjects with a novel DOK featuring erythrokeratodermia and initially-asymptomatic, progressive, potentially fatal cardiomyopathy, a finding not previously associated with erythrokeratodermia. We show that de novo missense mutations clustered tightly within a single spectrin repeat of DSP cause this novel cardio-cutaneous disorder, which we term erythrokeratodermia-cardiomyopathy (EKC) syndrome. We demonstrate that DSP mutations in our EKC syndrome subjects affect localization of desmosomal proteins and connexin 43 in the skin, and result in desmosome aggregation, widening of intercellular spaces, and lipid secretory defects. DSP encodes desmoplakin, a primary component of desmosomes, intercellular adhesion junctions most abundant in the epidermis and heart. Though mutations in DSP are known to cause other disorders, our cohort features the unique clinical finding of severe whole-body erythrokeratodermia, with distinct effects on localization of desmosomal proteins and connexin 43. These findings add a severe, previously undescribed syndrome featuring erythrokeratodermia and cardiomyopathy to the spectrum of disease caused by mutation in DSP, and identify a specific region of the protein critical to the pathobiology of EKC syndrome and to DSP function in the heart and skin.

Plakophilin-2 loss promotes TGF-ß1/p38 MAPK-dependent fibrotic gene expression in cardiomyocytes.

Members of the desmosome protein family are integral components of the cardiac area composita, a mixed junctional complex responsible for electromechanical coupling between cardiomyocytes. In this study, we provide evidence that loss of the desmosomal armadillo protein Plakophilin-2 (PKP2) in cardiomyocytes elevates transforming growth factor ß1 (TGF-ß1) and p38 mitogen-activated protein kinase (MAPK) signaling, which together coordinate a transcriptional program that results in increased expression of profibrotic genes. Importantly, we demonstrate that expression of Desmoplakin (DP) is lost upon PKP2 knockdown and that restoration of DP expression rescues the activation of this TGF-ß1/p38 MAPK transcriptional cascade. Tissues from PKP2 heterozygous and DP conditional knockout mouse models also exhibit elevated TGF-ß1/p38 MAPK signaling and induction of fibrotic gene expression in vivo. These data therefore identify PKP2 and DP as central players in coordination of desmosome-dependent TGF-ß1/p38 MAPK signaling in cardiomyocytes, pathways known to play a role in different types of cardiac disease, such as arrhythmogenic or hypertrophic cardiomyopathy.