Alternative titles; symbols
HGNC Approved Gene Symbol: SLC30A4
Cytogenetic location: 15q21.1 Genomic coordinates (GRCh38): 15:45,479,606-45,522,755 (from NCBI)
Zinc is the second most abundant trace metal in the human body. It is an essential element, serving both a structural role, as in the formation of zinc fingers in DNA-binding proteins, and a catalytic role in metalloenzymes, such as pancreatic carboxypeptidases (e.g., 114852), alkaline phosphatases (e.g., 171760), various dehydrogenases, and superoxide dismutases (e.g., 147450). SLC30A4, or ZNT4, belongs to the ZNT family of zinc transporters. ZNTs are involved in transporting zinc out of the cytoplasm and have similar structures, consisting of 6 transmembrane domains and a histidine-rich cytoplasmic loop (Huang and Gitschier, 1997).
During an effort to clone the gene for the mouse mutant 'pallid' (see 604310), which maps to mouse chromosome 2, Huang and Gitschier (1997) serendipitously cloned the gene responsible for 'lethal milk' (lm) (see ANIMAL MODEL), which was found to encode a novel ZNT family member, Znt4. The gene encodes a 430-amino acid protein that is homologous to Znt2 (SLC30A2; 609617) and Znt3 (SLC30A3; 602878). Znt4 was abundantly expressed in mammary epithelia and brain. Huang and Gitschier (1997) also isolated the human homolog of Znt4. The 429-amino acid human ZNT4 polypeptide shares 92% predicted identity with the mouse protein.
By EST database analysis, Seve et al. (2004) found evidence of moderate SLC30A4 expression in testis, with lower levels in amygdala, muscle, ovary, parathyroid, and stomach.
Huang and Gitschier (1997) found that mouse Znt4 conferred gene resistance to a zinc-sensitive yeast strain. Based on its involvement in the mouse lethal milk phenotype (see ANIMAL MODEL), Huang and Gitschier (1997) stated that Znt4 is presumably responsible for deposition of zinc into milk. Since adult lm/lm mice 8 months of age and older display zinc deficiency, they suggested that Znt4 may also participate in intestinal uptake of zinc. High expression of Znt4 in brain suggested that, like Znt2, it may have a role in accumulation of zinc into synaptic vesicles.
Huang et al. (2002) found that the intracellular localization of Znt4 in normal rat kidney cells was regulated by extracellular zinc in a concentration-dependent manner, with zinc causing Znt4 to diffuse from the perinuclear region toward cytoplasmic structures and the cell periphery.
The reduced concentration of zinc in the breast milk of mothers with zinc-deficient babies (608118) suggested that a defect similar to that found in the lm mouse mutant might be present (Piletz and Ganschow, 1978). Sharma et al. (1988) showed that the condition predisposing mothers to produce zinc-deficient breast milk is inherited. To investigate whether mutations or changes in expression of the human ZNT4 gene are responsible for this condition, Michalczyk et al. (2003) studied 2 unrelated mothers with low zinc milk levels whose babies had developed zinc deficiency. Sequence analysis of cDNA, RT-PCR, and Western blot analysis of the ZNT4 gene, performed on control cells and cells from the 2 mothers, showed no differences. The ZNT4 gene was highly expressed in mouthwash buccal cells compared with lymphoblasts and fibroblasts. The ZNT4 protein did not colocalize with intracellular free zinc pools, suggesting that ZNT4 is not involved in transport of zinc into vesicles destined for secretion into milk. This observation, combined with phenotypic differences between both the lm mouse and the human disorder, suggested that the lm mouse is not the corresponding model for the human zinc deficiency condition.
Kury et al. (2001) determined that the SLC30A4 gene contains 7 exons. Nakano et al. (2002) also characterized the exon/intron organization of the human ZNT4 gene. Seve et al. (2004) stated that the human SLC30A4 gene contains 8 exons.
Huang and Gitschier (1997) determined that the mouse Znt4 gene spans approximately 13 kb and consists of 7 exons.
Kury et al. (2001) localized the SLC30A4 gene to chromosome 15q15-q21 by fluorescence in situ hybridization. The localization was confirmed by comparison to BAC clones that map to 15q21.1, approximately 47 cM from the telomere.
Huang and Gitschier (1997) studied the only known mouse mutant of zinc metabolism, lethal milk (lm), an autosomal recessive condition so named because pups of any genotype suckled on lm/lm dams die before weaning. Before death, pups develop symptoms characteristic of nutritional zinc deficiency, including dermatitis, alopecia, and stunted growth. Symptoms can be reduced and survival improved by administration of zinc to either the mothers or the pups, or by fostering the pups on normal dams. Huang and Gitschier (1997) found that lm/lm mice over 8 months of age, even if fostered on normal dams, developed dermatitis, skin lesions, and hair loss, suggesting a systemic zinc deficiency in the adult mutant animals; lm/lm animals also have congenital absence of utricular otoconia (calcium carbonate crystals in the inner ear), which is not alleviated by maternal zinc supplementation or by growth on foster mothers. The absence of these otoconia may be the basis for some of the behavioral abnormalities in lethal milk animals, such as difficulty in righting, tail-spinning, and instability when swimming. The lethal milk mutation is located on mouse chromosome 2, approximately 10 cM from agouti (600201). Huang and Gitschier (1997) sequenced the genomic regions in the Znt4 gene of lethal milk mice and identified a single change, a C-to-T transition at nucleotide 934, resulting in a premature translation termination codon at arg297 (R297X). This mutation occurred at a CpG dinucleotide. Huang and Gitschier (1997) noted that development of otoconia requires carbonic anhydrase (e.g., 114800), a zinc-containing enzyme that generates carbonate ions. Maternal zinc administration leads to an alleviation of the saccular otolith defect, but not the utricular defect in lm/lm progeny. As the utricle is metabolically independent of the cochlea and the saccule, this absence of corrections suggests a primary role of Znt4 in delivery of zinc to the utricle.
Huang, L., Gitschier, J. A novel gene involved in zinc transport is deficient in the lethal milk mouse. Nature Genet. 17: 292-297, 1997. [PubMed: 9354792] [Full Text: https://doi.org/10.1038/ng1197-292]
Huang, L., Kirschke, C. P., Gitschier, J. Functional characterization of a novel mammalian zinc transporter, ZnT6. J. Biol. Chem. 277: 26389-26395, 2002. [PubMed: 11997387] [Full Text: https://doi.org/10.1074/jbc.M200462200]
Kury, S., Devilder, M.-C., Avet-Loiseau, H., Dreno, B., Moisan, J.-P. Expression pattern, genomic structure and evaluation of the human SLC30A4 gene as a candidate for acrodermatitis enteropathica. Hum. Genet. 109: 178-185, 2001. [PubMed: 11511923] [Full Text: https://doi.org/10.1007/s004390100539]
Michalczyk, A., Varigos, G., Catto-Smith, A., Blomeley, R. C., Ackland, M. L. Analysis of zinc transporter, hZnT4 (Slc30A4), gene expression in a mammary gland disorder leading to reduced zinc secretion into milk. Hum. Genet. 113: 202-210, 2003. [PubMed: 12743795] [Full Text: https://doi.org/10.1007/s00439-003-0952-2]
Nakano, A., Nakano, H., Hanada, K., Nomura, K., Uitto, J. ZNT4 gene is not responsible for acrodermatitis enteropathica in Japanese families. (Letter) Hum. Genet. 110: 201-202, 2002. [PubMed: 11935329] [Full Text: https://doi.org/10.1007/s00439-001-0661-7]
Piletz, J. E., Ganschow, R. E. Zinc deficiency in murine milk underlies expression of the 'lethal milk' (lm) mutation. Science 199: 181-183, 1978. [PubMed: 619449] [Full Text: https://doi.org/10.1126/science.619449]
Seve, M., Chimienti, F., Devergnas, S., Favier, A. In silico identification and expression of SLC30 family genes: an expressed sequence tag data mining strategy for the characterization of zinc transporters' tissue expression. BMC Genomics 5: 32, 2004. Note: Electronic Article. [PubMed: 15154973] [Full Text: https://doi.org/10.1186/1471-2164-5-32]
Sharma, N. L., Sharma, R. C., Gupta, K. R., Sharma, R. P. Self-limiting acrodermatitis enteropathica: a follow-up study of three interrelated families. Int. J. Derm. 27: 485-486, 1988. [PubMed: 3220631] [Full Text: https://doi.org/10.1111/j.1365-4362.1988.tb00926.x]