title: Exome Sequencing of SLC30A2 Identifies Novel Loss- and Gain-of-Function Variants Associated with Breast Cell Dysfunction.
abstract: The zinc (Zn) transporter ZnT2 (SLC30A2) is expressed in specialized secretory cells including breast, pancreas and prostate, and imports Zn into mitochondria and vesicles. Mutations in SLC30A2 substantially reduce milk Zn concentration ([Zn]) and cause severe Zn deficiency in exclusively breastfed infants. Recent studies show that ZnT2-null mice have low milk [Zn], in addition to profound defects in mammary gland function during lactation. Here, we used breast milk [Zn] to identify novel non-synonymous ZnT2 variants in a population of lactating women. We also asked whether specific variants induce disturbances in intracellular Zn management or cause cellular dysfunction in mammary epithelial cells. Healthy, breastfeeding women were stratified into quartiles by milk [Zn] and exonic sequencing of SLC30A2 was performed. We found that 36% of women tested carried non-synonymous ZnT2 variants, all of whom had milk Zn levels that were distinctly above or below those in women without variants. We identified 12 novel heterozygous variants. Two variants (D(103)E and T(288)S) were identified with high frequency (9 and 16%, respectively) and expression of T(288)S was associated with a known hallmark of breast dysfunction (elevated milk sodium/potassium ratio). Select variants (A(28)D, K(66)N, Q(71)H, D(103)E, A(105)P, Q(137)H, T(288)S and T(312)K) were characterized in vitro. Compared with wild-type ZnT2, these variants were inappropriately localized, and most resulted in either 'loss-of-function' or 'gain-of-function', and altered sub-cellular Zn pools, Zn secretion, and cell cycle check-points. Our study indicates that SLC30A2 variants are common in this population, dysregulate Zn management and can lead to breast cell dysfunction. This suggests that genetic variation in ZnT2 could be an important modifier of infant growth/development and reproductive health/disease. Importantly, milk [Zn] level may serve as a bio-reporter of breast function during lactation.
authors: Department of Cellular and Molecular Physiology, The Pennsylvania State University Hershey College of Medicine, Hershey, PA, USA.|Department of Surgery, The Pennsylvania State University Hershey College of Medicine, Hershey, PA, USA.
authors: Samina
authors: S
authors: Alam
authors: Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA, USA.
authors: Stephen R
authors: SR
authors: Hennigar
authors: Department of Public Health Sciences, The Pennsylvania State University Hershey College of Medicine, Hershey, PA, USA.
authors: Carla
authors: C
authors: Gallagher
authors: Department of Cellular and Molecular Physiology, The Pennsylvania State University Hershey College of Medicine, Hershey, PA, USA.|Department of Surgery, The Pennsylvania State University Hershey College of Medicine, Hershey, PA, USA.
authors: David I
authors: DI
authors: Soybel
authors: Department of Cellular and Molecular Physiology, The Pennsylvania State University Hershey College of Medicine, Hershey, PA, USA. slk39@psu.edu.|Department of Pharmacology, The Pennsylvania State University Hershey College of Medicine, Hershey, PA, USA. slk39@psu.edu.|Department of Surgery, The Pennsylvania State University Hershey College of Medicine, Hershey, PA, USA. slk39@psu.edu.|Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA, USA. slk39@psu.edu.
authors: Shannon L
authors: SL
authors: Kelleher
mesh_terms: D000818:Animals; D001942:Breast Feeding; D027682:Cation Transport Proteins / Q000235:genetics*; D059447:Cell Cycle Checkpoints / Q000235:genetics; D002460:Cell Line; D004252:DNA Mutational Analysis; D004847:Epithelial Cells / Q000502:physiology*; D059472:Exome; D005260:Female; D006801:Humans; D007774:Lactation / Q000235:genetics*; D042361:Mammary Glands, Human / Q000503:physiopathology*; D051379:Mice; D008895:Milk, Human / Q000737:chemistry*; D009154:Mutation; D017422:Sequence Analysis, DNA; D015032:Zinc / Q000032:analysis / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; C486299:SLC30A2 protein, human; D015032:Zinc
keywords: Breast dysfunction; Breast milk zinc; Lactation; SLC30A2; Zinc secretion; ZnT2