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First published online July 27, 2006
doi: 10.1242/10.1242/dev.02489
Correspondence |
Tenovus Centre for Cancer Research, Welsh School of Pharmacy, Cardiff University, Redwood Building, King Edward VIIth Avenue, Cardiff CF10 3XF, UK
* Author for correspondence (e-mail: Taylorkm{at}cardiff.ac.uk)
A recent paper in Development by Mathews and colleagues
demonstrates the essential role of Drosophila Fear of Intimacy (FOI) in gonad
morphogenesis (Mathews et al.,
2006
) that is linked to its ability to transport zinc. FOI is a
member of the LIV-1 subfamily of the Zrt, IRT-like protein (ZIP) family of ion
transporters. Given the increasing interest in this family of zinc
transporters, we wish to highlight certain points of nomenclature in the
Mathews et al. paper, which do not reflect on its conclusions.
The ZIP family of ion transporters divides into four subfamilies that
belong to solute carrier family 39 (SLC39A)
(Eide, 2003). LIV-1 is
designated SLC39A6 or ZIP6. FOI belongs to the LIV-1 subfamily
(Taylor and Nicholson, 2003),
which contains nine human sequences in total.
We question the designation of FOI as dSLC39A6/dZIP6, which suggests that
it is the Drosophila equivalent of LIV-1, which is already known as
SLC39A6 (Eide, 2003). There
appears to be no evidence to justify this, and an examination of the
phylogenetic tree of over 110 members of the SLC39A family
(Taylor and Nicholson, 2003)
clarifies this view. There are four Drosophila sequences in the LIV-1
subfamily termed Dm1-4. Dm4 represents FOI.
The section of the tree that includes both FOI and LIV-1 also contains
another Drosophila molecule and five human ones. The two
Drosophila sequences, Dm3 and Dm4 (FOI), are present in a different
branch to that containing the human sequences: ZIP10/SLC39A10, ZIP5/SLC39A5,
LIV-1/ZIP6/SLC39A6, ZIP14/SLC39A14 and ZIP8/SLC39A8. Additionally, when the
LIV-1 subfamily sequences alone are aligned
(Taylor et al., 2004), Dm3 and
FOI (Dm4) again locate in a separate branch, whereas LIV-1, ZIP10/SLC39A10 and
ZIP5/SLC39A5 locate in another. Furthermore, an alignment of the family
sequences across transmembrane domains IV and V
(Taylor and Nicholson, 2003),
containing the zinc transport active site, shows the FOI sequence to be
closest to ZIP5/SLC39A5 and ZIP10/SLC39A10, although there is also good
sequence similarity with LIV-1, ZIP12/SLC39A12, ZIP8/SLC39A8 and
ZIP14/SLC39A14. In light of this, it is our opinion that it is inappropriate
to assign FOI to any individual SLC39A family member, especially LIV-1, until
further research clarifies the situation.
REFERENCES
Eide, D. J. (2003). The SLC39 family of metal ion transporters. Pflügers Arch. 447,796 -800.
Mathews, W. R., Ong, D., Milutinovich, A. B. and Van Doren,
M. (2006). Zinc transport activity of Fear of Intimacy is
essential for proper gonad morphogenesis and DE-cadherin expression.
Development 133,1143
-1153.
Taylor, K. M. and Nicholson, R. I. (2003). The LZT proteins; the new LIV-1 subfamily of zinc transporters. Biochim. Biophys. Acta 1611,16 -30.[Medline]
Taylor, K. M., Morgan, H. E., Johnson, A. and Nicholson, R. I. (2004). Structure-function analysis of HKE4, a member of the new LIV-1 subfamily of zinc transporters. Biochem. J. 377,131 -139.[CrossRef][Medline]
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