Clinical utility gene card for: acrodermatitis enteropathica - update 2015

[Recurrent systemic sporadic rash for 10 years in a girl aged 11 years]

A girl, aged 11 years, was admitted due to recurrent rash on the whole body and mucosa for 10 years, and typical rash was erythema at the perioral region, hand-foot joints, vulva, and perianal region, with blisters, erosions, and ulcers on the erythema. The girl was improved after zinc supplementation. Her younger brother had similar rash and medical history. The histopathological examination showed epidermal parakeratosis with mild hyperkeratosis, severe spongiform edema of the stratum corneum, significant proliferation of acanthocytes, and vacuolation of keratinocytes. The genetic testing revealed that both the girl and her younger brother had a homozygous mutation of c.1456(exon9)delG in the SLC39A4 gene, and thus the girl was diagnosed with acrodermatitis enteropathica. It is concluded that for children with recurrent rash on the limbs and at the perioral region, genetic testing should be performed as early as possible to make a confirmed diagnosis, and a sufficient dose of zinc supplementation should be given, while the levels of trace elements such as blood zinc should be regularly monitored.

Mechanistic Impact of Zinc Deficiency in Human Development

Zinc (Zn) deficiency in humans is an emerging global health issue affecting approximately two billion people across the globe. The situation prevails due to the intake of Zn deficient grains and vegetables worldwide. Clinical identification of Zn deficiency in humans remains problematic because the symptoms do not appear until impair the vital organs, such as the gastrointestinal track, central nervous system, immune system, skeletal, and nervous system. Lower Zn body levels are also responsible for multiple physiological disorders, such as apoptosis, organs destruction, DNA injuries, and oxidative damage to the cellular components through reactive oxygen species (ROS). The oxidative damage causes chronic inflammation lead toward several chronic diseases, such as heart diseases, cancers, alcohol-related malady, muscular contraction, and neuro-pathogenesis. The present review focused on the physiological and growth-related changes in humans under Zn deficient conditions, mechanisms adopted by the human body under Zn deficiency for the proper functioning of the body systems, and the importance of nutritional and nutraceutical approaches to overcome Zn deficiency in humans and concluded that the biofortified food is the best source of Zn as compared to the chemical supplementation to avoid their negative impacts on human.

An extracellular histidine-containing motif in the zinc transporter ZIP4 plays a role in zinc sensing and zinc-induced endocytosis in mammalian cells

Zinc is an essential trace element that serves as a cofactor for enzymes in critical biochemical processes and also plays a structural role in numerous proteins. Zinc transporter ZIP4 (ZIP4) is a zinc importer required for dietary zinc uptake in the intestine and other cell types. Studies in cultured cells have reported that zinc stimulates the endocytosis of plasma membrane-localized ZIP4 protein, resulting in reduced cellular zinc uptake. Thus, zinc-regulated trafficking of ZIP4 is a key means for regulating cellular zinc homeostasis, but the underlying mechanisms are not well understood. In this study, we used mutational analysis, immunoblotting, HEK293 cells, and immunofluorescence microscopy to identify a histidine-containing motif (³⁹⁸HTH) in the first extracellular loop that is required for high sensitivity to low zinc concentrations in a zinc-induced endocytic response of mouse ZIP4 (mZIP4). Moreover, using synthetic peptides with selective substitutions and truncated mZIP4 variants, we provide evidence that histidine residues in this motif coordinate a zinc ion in mZIP4 homodimers at the plasma membrane. These findings suggest that ³⁹⁸HTH is an important zinc-sensing motif for eliciting high-affinity zinc-stimulated endocytosis of mZIP4 and provide insight into cellular mechanisms for regulating cellular zinc homeostasis in mammalian cells.